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linux-zen-desktop/kernel/sched/alt_core.c

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/*
* kernel/sched/alt_core.c
*
* Core alternative kernel scheduler code and related syscalls
*
* Copyright (C) 1991-2002 Linus Torvalds
*
* 2009-08-13 Brainfuck deadline scheduling policy by Con Kolivas deletes
* a whole lot of those previous things.
* 2017-09-06 Priority and Deadline based Skip list multiple queue kernel
* scheduler by Alfred Chen.
* 2019-02-20 BMQ(BitMap Queue) kernel scheduler by Alfred Chen.
*/
#include <linux/sched/clock.h>
#include <linux/sched/cputime.h>
#include <linux/sched/debug.h>
#include <linux/sched/isolation.h>
#include <linux/sched/loadavg.h>
#include <linux/sched/mm.h>
#include <linux/sched/nohz.h>
#include <linux/sched/stat.h>
#include <linux/sched/wake_q.h>
#include <linux/blkdev.h>
#include <linux/context_tracking.h>
#include <linux/cpuset.h>
#include <linux/delayacct.h>
#include <linux/init_task.h>
#include <linux/kcov.h>
#include <linux/kprobes.h>
#include <linux/nmi.h>
#include <linux/scs.h>
#include <uapi/linux/sched/types.h>
#include <asm/irq_regs.h>
#include <asm/switch_to.h>
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
#include <trace/events/ipi.h>
#undef CREATE_TRACE_POINTS
#include "sched.h"
#include "pelt.h"
#include "../../io_uring/io-wq.h"
#include "../smpboot.h"
EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu);
EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask);
/*
* Export tracepoints that act as a bare tracehook (ie: have no trace event
* associated with them) to allow external modules to probe them.
*/
EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp);
#ifdef CONFIG_SCHED_DEBUG
#define sched_feat(x) (1)
/*
* Print a warning if need_resched is set for the given duration (if
* LATENCY_WARN is enabled).
*
* If sysctl_resched_latency_warn_once is set, only one warning will be shown
* per boot.
*/
__read_mostly int sysctl_resched_latency_warn_ms = 100;
__read_mostly int sysctl_resched_latency_warn_once = 1;
#else
#define sched_feat(x) (0)
#endif /* CONFIG_SCHED_DEBUG */
#define ALT_SCHED_VERSION "v6.5-r0"
/*
* Compile time debug macro
* #define ALT_SCHED_DEBUG
*/
/* rt_prio(prio) defined in include/linux/sched/rt.h */
#define rt_task(p) rt_prio((p)->prio)
#define rt_policy(policy) ((policy) == SCHED_FIFO || (policy) == SCHED_RR)
#define task_has_rt_policy(p) (rt_policy((p)->policy))
#define STOP_PRIO (MAX_RT_PRIO - 1)
/* Default time slice is 4 in ms, can be set via kernel parameter "sched_timeslice" */
#ifdef CONFIG_ZEN_INTERACTIVE
u64 sched_timeslice_ns __read_mostly = (2 << 20);
#else
u64 sched_timeslice_ns __read_mostly = (4 << 20);
#endif
static inline void requeue_task(struct task_struct *p, struct rq *rq, int idx);
#ifdef CONFIG_SCHED_BMQ
#include "bmq.h"
#endif
#ifdef CONFIG_SCHED_PDS
#include "pds.h"
#endif
struct affinity_context {
const struct cpumask *new_mask;
struct cpumask *user_mask;
unsigned int flags;
};
static int __init sched_timeslice(char *str)
{
int timeslice_ms;
get_option(&str, &timeslice_ms);
if (2 != timeslice_ms)
timeslice_ms = 4;
sched_timeslice_ns = timeslice_ms << 20;
sched_timeslice_imp(timeslice_ms);
return 0;
}
early_param("sched_timeslice", sched_timeslice);
/* Reschedule if less than this many μs left */
#define RESCHED_NS (100 << 10)
/**
* sched_yield_type - Choose what sort of yield sched_yield will perform.
* 0: No yield.
* 1: Deboost and requeue task. (default)
* 2: Set rq skip task.
*/
#ifdef CONFIG_ZEN_INTERACTIVE
int sched_yield_type __read_mostly = 0;
#else
int sched_yield_type __read_mostly = 1;
#endif
#ifdef CONFIG_SMP
static cpumask_t sched_rq_pending_mask ____cacheline_aligned_in_smp;
DEFINE_PER_CPU_ALIGNED(cpumask_t [NR_CPU_AFFINITY_LEVELS], sched_cpu_topo_masks);
DEFINE_PER_CPU_ALIGNED(cpumask_t *, sched_cpu_llc_mask);
DEFINE_PER_CPU_ALIGNED(cpumask_t *, sched_cpu_topo_end_mask);
#ifdef CONFIG_SCHED_SMT
DEFINE_STATIC_KEY_FALSE(sched_smt_present);
EXPORT_SYMBOL_GPL(sched_smt_present);
#endif
/*
* Keep a unique ID per domain (we use the first CPUs number in the cpumask of
* the domain), this allows us to quickly tell if two cpus are in the same cache
* domain, see cpus_share_cache().
*/
DEFINE_PER_CPU(int, sd_llc_id);
#endif /* CONFIG_SMP */
static DEFINE_MUTEX(sched_hotcpu_mutex);
DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
#endif
#ifndef finish_arch_post_lock_switch
# define finish_arch_post_lock_switch() do { } while (0)
#endif
#ifdef CONFIG_SCHED_SMT
static cpumask_t sched_sg_idle_mask ____cacheline_aligned_in_smp;
#endif
static cpumask_t sched_preempt_mask[SCHED_QUEUE_BITS] ____cacheline_aligned_in_smp;
static cpumask_t *const sched_idle_mask = &sched_preempt_mask[0];
/* task function */
static inline const struct cpumask *task_user_cpus(struct task_struct *p)
{
if (!p->user_cpus_ptr)
return cpu_possible_mask; /* &init_task.cpus_mask */
return p->user_cpus_ptr;
}
/* sched_queue related functions */
static inline void sched_queue_init(struct sched_queue *q)
{
int i;
bitmap_zero(q->bitmap, SCHED_QUEUE_BITS);
for(i = 0; i < SCHED_LEVELS; i++)
INIT_LIST_HEAD(&q->heads[i]);
}
/*
* Init idle task and put into queue structure of rq
* IMPORTANT: may be called multiple times for a single cpu
*/
static inline void sched_queue_init_idle(struct sched_queue *q,
struct task_struct *idle)
{
idle->sq_idx = IDLE_TASK_SCHED_PRIO;
INIT_LIST_HEAD(&q->heads[idle->sq_idx]);
list_add(&idle->sq_node, &q->heads[idle->sq_idx]);
}
static inline void
clear_recorded_preempt_mask(int pr, int low, int high, int cpu)
{
if (low < pr && pr <= high)
cpumask_clear_cpu(cpu, sched_preempt_mask + SCHED_QUEUE_BITS - pr);
}
static inline void
set_recorded_preempt_mask(int pr, int low, int high, int cpu)
{
if (low < pr && pr <= high)
cpumask_set_cpu(cpu, sched_preempt_mask + SCHED_QUEUE_BITS - pr);
}
static atomic_t sched_prio_record = ATOMIC_INIT(0);
/* water mark related functions */
static inline void update_sched_preempt_mask(struct rq *rq)
{
unsigned long prio = find_first_bit(rq->queue.bitmap, SCHED_QUEUE_BITS);
unsigned long last_prio = rq->prio;
int cpu, pr;
if (prio == last_prio)
return;
rq->prio = prio;
cpu = cpu_of(rq);
pr = atomic_read(&sched_prio_record);
if (prio < last_prio) {
if (IDLE_TASK_SCHED_PRIO == last_prio) {
#ifdef CONFIG_SCHED_SMT
if (static_branch_likely(&sched_smt_present))
cpumask_andnot(&sched_sg_idle_mask,
&sched_sg_idle_mask, cpu_smt_mask(cpu));
#endif
cpumask_clear_cpu(cpu, sched_idle_mask);
last_prio -= 2;
}
clear_recorded_preempt_mask(pr, prio, last_prio, cpu);
return;
}
/* last_prio < prio */
if (IDLE_TASK_SCHED_PRIO == prio) {
#ifdef CONFIG_SCHED_SMT
if (static_branch_likely(&sched_smt_present) &&
cpumask_intersects(cpu_smt_mask(cpu), sched_idle_mask))
cpumask_or(&sched_sg_idle_mask,
&sched_sg_idle_mask, cpu_smt_mask(cpu));
#endif
cpumask_set_cpu(cpu, sched_idle_mask);
prio -= 2;
}
set_recorded_preempt_mask(pr, last_prio, prio, cpu);
}
/*
* This routine assume that the idle task always in queue
*/
static inline struct task_struct *sched_rq_first_task(struct rq *rq)
{
const struct list_head *head = &rq->queue.heads[sched_prio2idx(rq->prio, rq)];
return list_first_entry(head, struct task_struct, sq_node);
}
static inline struct task_struct *
sched_rq_next_task(struct task_struct *p, struct rq *rq)
{
unsigned long idx = p->sq_idx;
struct list_head *head = &rq->queue.heads[idx];
if (list_is_last(&p->sq_node, head)) {
idx = find_next_bit(rq->queue.bitmap, SCHED_QUEUE_BITS,
sched_idx2prio(idx, rq) + 1);
head = &rq->queue.heads[sched_prio2idx(idx, rq)];
return list_first_entry(head, struct task_struct, sq_node);
}
return list_next_entry(p, sq_node);
}
static inline struct task_struct *rq_runnable_task(struct rq *rq)
{
struct task_struct *next = sched_rq_first_task(rq);
if (unlikely(next == rq->skip))
next = sched_rq_next_task(next, rq);
return next;
}
/*
* Serialization rules:
*
* Lock order:
*
* p->pi_lock
* rq->lock
* hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls)
*
* rq1->lock
* rq2->lock where: rq1 < rq2
*
* Regular state:
*
* Normal scheduling state is serialized by rq->lock. __schedule() takes the
* local CPU's rq->lock, it optionally removes the task from the runqueue and
* always looks at the local rq data structures to find the most eligible task
* to run next.
*
* Task enqueue is also under rq->lock, possibly taken from another CPU.
* Wakeups from another LLC domain might use an IPI to transfer the enqueue to
* the local CPU to avoid bouncing the runqueue state around [ see
* ttwu_queue_wakelist() ]
*
* Task wakeup, specifically wakeups that involve migration, are horribly
* complicated to avoid having to take two rq->locks.
*
* Special state:
*
* System-calls and anything external will use task_rq_lock() which acquires
* both p->pi_lock and rq->lock. As a consequence the state they change is
* stable while holding either lock:
*
* - sched_setaffinity()/
* set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed
* - set_user_nice(): p->se.load, p->*prio
* - __sched_setscheduler(): p->sched_class, p->policy, p->*prio,
* p->se.load, p->rt_priority,
* p->dl.dl_{runtime, deadline, period, flags, bw, density}
* - sched_setnuma(): p->numa_preferred_nid
* - sched_move_task(): p->sched_task_group
* - uclamp_update_active() p->uclamp*
*
* p->state <- TASK_*:
*
* is changed locklessly using set_current_state(), __set_current_state() or
* set_special_state(), see their respective comments, or by
* try_to_wake_up(). This latter uses p->pi_lock to serialize against
* concurrent self.
*
* p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }:
*
* is set by activate_task() and cleared by deactivate_task(), under
* rq->lock. Non-zero indicates the task is runnable, the special
* ON_RQ_MIGRATING state is used for migration without holding both
* rq->locks. It indicates task_cpu() is not stable, see task_rq_lock().
*
* p->on_cpu <- { 0, 1 }:
*
* is set by prepare_task() and cleared by finish_task() such that it will be
* set before p is scheduled-in and cleared after p is scheduled-out, both
* under rq->lock. Non-zero indicates the task is running on its CPU.
*
* [ The astute reader will observe that it is possible for two tasks on one
* CPU to have ->on_cpu = 1 at the same time. ]
*
* task_cpu(p): is changed by set_task_cpu(), the rules are:
*
* - Don't call set_task_cpu() on a blocked task:
*
* We don't care what CPU we're not running on, this simplifies hotplug,
* the CPU assignment of blocked tasks isn't required to be valid.
*
* - for try_to_wake_up(), called under p->pi_lock:
*
* This allows try_to_wake_up() to only take one rq->lock, see its comment.
*
* - for migration called under rq->lock:
* [ see task_on_rq_migrating() in task_rq_lock() ]
*
* o move_queued_task()
* o detach_task()
*
* - for migration called under double_rq_lock():
*
* o __migrate_swap_task()
* o push_rt_task() / pull_rt_task()
* o push_dl_task() / pull_dl_task()
* o dl_task_offline_migration()
*
*/
/*
* Context: p->pi_lock
*/
static inline struct rq
*__task_access_lock(struct task_struct *p, raw_spinlock_t **plock)
{
struct rq *rq;
for (;;) {
rq = task_rq(p);
if (p->on_cpu || task_on_rq_queued(p)) {
raw_spin_lock(&rq->lock);
if (likely((p->on_cpu || task_on_rq_queued(p))
&& rq == task_rq(p))) {
*plock = &rq->lock;
return rq;
}
raw_spin_unlock(&rq->lock);
} else if (task_on_rq_migrating(p)) {
do {
cpu_relax();
} while (unlikely(task_on_rq_migrating(p)));
} else {
*plock = NULL;
return rq;
}
}
}
static inline void
__task_access_unlock(struct task_struct *p, raw_spinlock_t *lock)
{
if (NULL != lock)
raw_spin_unlock(lock);
}
static inline struct rq
*task_access_lock_irqsave(struct task_struct *p, raw_spinlock_t **plock,
unsigned long *flags)
{
struct rq *rq;
for (;;) {
rq = task_rq(p);
if (p->on_cpu || task_on_rq_queued(p)) {
raw_spin_lock_irqsave(&rq->lock, *flags);
if (likely((p->on_cpu || task_on_rq_queued(p))
&& rq == task_rq(p))) {
*plock = &rq->lock;
return rq;
}
raw_spin_unlock_irqrestore(&rq->lock, *flags);
} else if (task_on_rq_migrating(p)) {
do {
cpu_relax();
} while (unlikely(task_on_rq_migrating(p)));
} else {
raw_spin_lock_irqsave(&p->pi_lock, *flags);
if (likely(!p->on_cpu && !p->on_rq &&
rq == task_rq(p))) {
*plock = &p->pi_lock;
return rq;
}
raw_spin_unlock_irqrestore(&p->pi_lock, *flags);
}
}
}
static inline void
task_access_unlock_irqrestore(struct task_struct *p, raw_spinlock_t *lock,
unsigned long *flags)
{
raw_spin_unlock_irqrestore(lock, *flags);
}
/*
* __task_rq_lock - lock the rq @p resides on.
*/
struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf)
__acquires(rq->lock)
{
struct rq *rq;
lockdep_assert_held(&p->pi_lock);
for (;;) {
rq = task_rq(p);
raw_spin_lock(&rq->lock);
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p)))
return rq;
raw_spin_unlock(&rq->lock);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
/*
* task_rq_lock - lock p->pi_lock and lock the rq @p resides on.
*/
struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf)
__acquires(p->pi_lock)
__acquires(rq->lock)
{
struct rq *rq;
for (;;) {
raw_spin_lock_irqsave(&p->pi_lock, rf->flags);
rq = task_rq(p);
raw_spin_lock(&rq->lock);
/*
* move_queued_task() task_rq_lock()
*
* ACQUIRE (rq->lock)
* [S] ->on_rq = MIGRATING [L] rq = task_rq()
* WMB (__set_task_cpu()) ACQUIRE (rq->lock);
* [S] ->cpu = new_cpu [L] task_rq()
* [L] ->on_rq
* RELEASE (rq->lock)
*
* If we observe the old CPU in task_rq_lock(), the acquire of
* the old rq->lock will fully serialize against the stores.
*
* If we observe the new CPU in task_rq_lock(), the address
* dependency headed by '[L] rq = task_rq()' and the acquire
* will pair with the WMB to ensure we then also see migrating.
*/
if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) {
return rq;
}
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags);
while (unlikely(task_on_rq_migrating(p)))
cpu_relax();
}
}
static inline void
rq_lock_irqsave(struct rq *rq, struct rq_flags *rf)
__acquires(rq->lock)
{
raw_spin_lock_irqsave(&rq->lock, rf->flags);
}
static inline void
rq_unlock_irqrestore(struct rq *rq, struct rq_flags *rf)
__releases(rq->lock)
{
raw_spin_unlock_irqrestore(&rq->lock, rf->flags);
}
void raw_spin_rq_lock_nested(struct rq *rq, int subclass)
{
raw_spinlock_t *lock;
/* Matches synchronize_rcu() in __sched_core_enable() */
preempt_disable();
for (;;) {
lock = __rq_lockp(rq);
raw_spin_lock_nested(lock, subclass);
if (likely(lock == __rq_lockp(rq))) {
/* preempt_count *MUST* be > 1 */
preempt_enable_no_resched();
return;
}
raw_spin_unlock(lock);
}
}
void raw_spin_rq_unlock(struct rq *rq)
{
raw_spin_unlock(rq_lockp(rq));
}
/*
* RQ-clock updating methods:
*/
static void update_rq_clock_task(struct rq *rq, s64 delta)
{
/*
* In theory, the compile should just see 0 here, and optimize out the call
* to sched_rt_avg_update. But I don't trust it...
*/
s64 __maybe_unused steal = 0, irq_delta = 0;
#ifdef CONFIG_IRQ_TIME_ACCOUNTING
irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time;
/*
* Since irq_time is only updated on {soft,}irq_exit, we might run into
* this case when a previous update_rq_clock() happened inside a
* {soft,}irq region.
*
* When this happens, we stop ->clock_task and only update the
* prev_irq_time stamp to account for the part that fit, so that a next
* update will consume the rest. This ensures ->clock_task is
* monotonic.
*
* It does however cause some slight miss-attribution of {soft,}irq
* time, a more accurate solution would be to update the irq_time using
* the current rq->clock timestamp, except that would require using
* atomic ops.
*/
if (irq_delta > delta)
irq_delta = delta;
rq->prev_irq_time += irq_delta;
delta -= irq_delta;
delayacct_irq(rq->curr, irq_delta);
#endif
#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
if (static_key_false((&paravirt_steal_rq_enabled))) {
steal = paravirt_steal_clock(cpu_of(rq));
steal -= rq->prev_steal_time_rq;
if (unlikely(steal > delta))
steal = delta;
rq->prev_steal_time_rq += steal;
delta -= steal;
}
#endif
rq->clock_task += delta;
#ifdef CONFIG_HAVE_SCHED_AVG_IRQ
if ((irq_delta + steal))
update_irq_load_avg(rq, irq_delta + steal);
#endif
}
static inline void update_rq_clock(struct rq *rq)
{
s64 delta = sched_clock_cpu(cpu_of(rq)) - rq->clock;
if (unlikely(delta <= 0))
return;
rq->clock += delta;
sched_update_rq_clock(rq);
update_rq_clock_task(rq, delta);
}
/*
* RQ Load update routine
*/
#define RQ_LOAD_HISTORY_BITS (sizeof(s32) * 8ULL)
#define RQ_UTIL_SHIFT (8)
#define RQ_LOAD_HISTORY_TO_UTIL(l) (((l) >> (RQ_LOAD_HISTORY_BITS - 1 - RQ_UTIL_SHIFT)) & 0xff)
#define LOAD_BLOCK(t) ((t) >> 17)
#define LOAD_HALF_BLOCK(t) ((t) >> 16)
#define BLOCK_MASK(t) ((t) & ((0x01 << 18) - 1))
#define LOAD_BLOCK_BIT(b) (1UL << (RQ_LOAD_HISTORY_BITS - 1 - (b)))
#define CURRENT_LOAD_BIT LOAD_BLOCK_BIT(0)
static inline void rq_load_update(struct rq *rq)
{
u64 time = rq->clock;
u64 delta = min(LOAD_BLOCK(time) - LOAD_BLOCK(rq->load_stamp),
RQ_LOAD_HISTORY_BITS - 1);
u64 prev = !!(rq->load_history & CURRENT_LOAD_BIT);
u64 curr = !!rq->nr_running;
if (delta) {
rq->load_history = rq->load_history >> delta;
if (delta < RQ_UTIL_SHIFT) {
rq->load_block += (~BLOCK_MASK(rq->load_stamp)) * prev;
if (!!LOAD_HALF_BLOCK(rq->load_block) ^ curr)
rq->load_history ^= LOAD_BLOCK_BIT(delta);
}
rq->load_block = BLOCK_MASK(time) * prev;
} else {
rq->load_block += (time - rq->load_stamp) * prev;
}
if (prev ^ curr)
rq->load_history ^= CURRENT_LOAD_BIT;
rq->load_stamp = time;
}
unsigned long rq_load_util(struct rq *rq, unsigned long max)
{
return RQ_LOAD_HISTORY_TO_UTIL(rq->load_history) * (max >> RQ_UTIL_SHIFT);
}
#ifdef CONFIG_SMP
unsigned long sched_cpu_util(int cpu)
{
return rq_load_util(cpu_rq(cpu), arch_scale_cpu_capacity(cpu));
}
#endif /* CONFIG_SMP */
#ifdef CONFIG_CPU_FREQ
/**
* cpufreq_update_util - Take a note about CPU utilization changes.
* @rq: Runqueue to carry out the update for.
* @flags: Update reason flags.
*
* This function is called by the scheduler on the CPU whose utilization is
* being updated.
*
* It can only be called from RCU-sched read-side critical sections.
*
* The way cpufreq is currently arranged requires it to evaluate the CPU
* performance state (frequency/voltage) on a regular basis to prevent it from
* being stuck in a completely inadequate performance level for too long.
* That is not guaranteed to happen if the updates are only triggered from CFS
* and DL, though, because they may not be coming in if only RT tasks are
* active all the time (or there are RT tasks only).
*
* As a workaround for that issue, this function is called periodically by the
* RT sched class to trigger extra cpufreq updates to prevent it from stalling,
* but that really is a band-aid. Going forward it should be replaced with
* solutions targeted more specifically at RT tasks.
*/
static inline void cpufreq_update_util(struct rq *rq, unsigned int flags)
{
struct update_util_data *data;
#ifdef CONFIG_SMP
rq_load_update(rq);
#endif
data = rcu_dereference_sched(*per_cpu_ptr(&cpufreq_update_util_data,
cpu_of(rq)));
if (data)
data->func(data, rq_clock(rq), flags);
}
#else
static inline void cpufreq_update_util(struct rq *rq, unsigned int flags)
{
#ifdef CONFIG_SMP
rq_load_update(rq);
#endif
}
#endif /* CONFIG_CPU_FREQ */
#ifdef CONFIG_NO_HZ_FULL
/*
* Tick may be needed by tasks in the runqueue depending on their policy and
* requirements. If tick is needed, lets send the target an IPI to kick it out
* of nohz mode if necessary.
*/
static inline void sched_update_tick_dependency(struct rq *rq)
{
int cpu = cpu_of(rq);
if (!tick_nohz_full_cpu(cpu))
return;
if (rq->nr_running < 2)
tick_nohz_dep_clear_cpu(cpu, TICK_DEP_BIT_SCHED);
else
tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED);
}
#else /* !CONFIG_NO_HZ_FULL */
static inline void sched_update_tick_dependency(struct rq *rq) { }
#endif
bool sched_task_on_rq(struct task_struct *p)
{
return task_on_rq_queued(p);
}
unsigned long get_wchan(struct task_struct *p)
{
unsigned long ip = 0;
unsigned int state;
if (!p || p == current)
return 0;
/* Only get wchan if task is blocked and we can keep it that way. */
raw_spin_lock_irq(&p->pi_lock);
state = READ_ONCE(p->__state);
smp_rmb(); /* see try_to_wake_up() */
if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq)
ip = __get_wchan(p);
raw_spin_unlock_irq(&p->pi_lock);
return ip;
}
/*
* Add/Remove/Requeue task to/from the runqueue routines
* Context: rq->lock
*/
#define __SCHED_DEQUEUE_TASK(p, rq, flags, func) \
sched_info_dequeue(rq, p); \
\
list_del(&p->sq_node); \
if (list_empty(&rq->queue.heads[p->sq_idx])) { \
clear_bit(sched_idx2prio(p->sq_idx, rq), rq->queue.bitmap); \
func; \
}
#define __SCHED_ENQUEUE_TASK(p, rq, flags) \
sched_info_enqueue(rq, p); \
\
p->sq_idx = task_sched_prio_idx(p, rq); \
list_add_tail(&p->sq_node, &rq->queue.heads[p->sq_idx]); \
set_bit(sched_idx2prio(p->sq_idx, rq), rq->queue.bitmap);
static inline void dequeue_task(struct task_struct *p, struct rq *rq, int flags)
{
#ifdef ALT_SCHED_DEBUG
lockdep_assert_held(&rq->lock);
/*printk(KERN_INFO "sched: dequeue(%d) %px %016llx\n", cpu_of(rq), p, p->deadline);*/
WARN_ONCE(task_rq(p) != rq, "sched: dequeue task reside on cpu%d from cpu%d\n",
task_cpu(p), cpu_of(rq));
#endif
__SCHED_DEQUEUE_TASK(p, rq, flags, update_sched_preempt_mask(rq));
--rq->nr_running;
#ifdef CONFIG_SMP
if (1 == rq->nr_running)
cpumask_clear_cpu(cpu_of(rq), &sched_rq_pending_mask);
#endif
sched_update_tick_dependency(rq);
}
static inline void enqueue_task(struct task_struct *p, struct rq *rq, int flags)
{
#ifdef ALT_SCHED_DEBUG
lockdep_assert_held(&rq->lock);
/*printk(KERN_INFO "sched: enqueue(%d) %px %d\n", cpu_of(rq), p, p->prio);*/
WARN_ONCE(task_rq(p) != rq, "sched: enqueue task reside on cpu%d to cpu%d\n",
task_cpu(p), cpu_of(rq));
#endif
__SCHED_ENQUEUE_TASK(p, rq, flags);
update_sched_preempt_mask(rq);
++rq->nr_running;
#ifdef CONFIG_SMP
if (2 == rq->nr_running)
cpumask_set_cpu(cpu_of(rq), &sched_rq_pending_mask);
#endif
sched_update_tick_dependency(rq);
}
static inline void requeue_task(struct task_struct *p, struct rq *rq, int idx)
{
#ifdef ALT_SCHED_DEBUG
lockdep_assert_held(&rq->lock);
/*printk(KERN_INFO "sched: requeue(%d) %px %016llx\n", cpu_of(rq), p, p->deadline);*/
WARN_ONCE(task_rq(p) != rq, "sched: cpu[%d] requeue task reside on cpu%d\n",
cpu_of(rq), task_cpu(p));
#endif
list_del(&p->sq_node);
list_add_tail(&p->sq_node, &rq->queue.heads[idx]);
if (idx != p->sq_idx) {
if (list_empty(&rq->queue.heads[p->sq_idx]))
clear_bit(sched_idx2prio(p->sq_idx, rq), rq->queue.bitmap);
p->sq_idx = idx;
set_bit(sched_idx2prio(p->sq_idx, rq), rq->queue.bitmap);
update_sched_preempt_mask(rq);
}
}
/*
* cmpxchg based fetch_or, macro so it works for different integer types
*/
#define fetch_or(ptr, mask) \
({ \
typeof(ptr) _ptr = (ptr); \
typeof(mask) _mask = (mask); \
typeof(*_ptr) _val = *_ptr; \
\
do { \
} while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \
_val; \
})
#if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG)
/*
* Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG,
* this avoids any races wrt polling state changes and thereby avoids
* spurious IPIs.
*/
static inline bool set_nr_and_not_polling(struct task_struct *p)
{
struct thread_info *ti = task_thread_info(p);
return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG);
}
/*
* Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set.
*
* If this returns true, then the idle task promises to call
* sched_ttwu_pending() and reschedule soon.
*/
static bool set_nr_if_polling(struct task_struct *p)
{
struct thread_info *ti = task_thread_info(p);
typeof(ti->flags) val = READ_ONCE(ti->flags);
for (;;) {
if (!(val & _TIF_POLLING_NRFLAG))
return false;
if (val & _TIF_NEED_RESCHED)
return true;
if (try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED))
break;
}
return true;
}
#else
static inline bool set_nr_and_not_polling(struct task_struct *p)
{
set_tsk_need_resched(p);
return true;
}
#ifdef CONFIG_SMP
static inline bool set_nr_if_polling(struct task_struct *p)
{
return false;
}
#endif
#endif
static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task)
{
struct wake_q_node *node = &task->wake_q;
/*
* Atomically grab the task, if ->wake_q is !nil already it means
* it's already queued (either by us or someone else) and will get the
* wakeup due to that.
*
* In order to ensure that a pending wakeup will observe our pending
* state, even in the failed case, an explicit smp_mb() must be used.
*/
smp_mb__before_atomic();
if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL)))
return false;
/*
* The head is context local, there can be no concurrency.
*/
*head->lastp = node;
head->lastp = &node->next;
return true;
}
/**
* wake_q_add() - queue a wakeup for 'later' waking.
* @head: the wake_q_head to add @task to
* @task: the task to queue for 'later' wakeup
*
* Queue a task for later wakeup, most likely by the wake_up_q() call in the
* same context, _HOWEVER_ this is not guaranteed, the wakeup can come
* instantly.
*
* This function must be used as-if it were wake_up_process(); IOW the task
* must be ready to be woken at this location.
*/
void wake_q_add(struct wake_q_head *head, struct task_struct *task)
{
if (__wake_q_add(head, task))
get_task_struct(task);
}
/**
* wake_q_add_safe() - safely queue a wakeup for 'later' waking.
* @head: the wake_q_head to add @task to
* @task: the task to queue for 'later' wakeup
*
* Queue a task for later wakeup, most likely by the wake_up_q() call in the
* same context, _HOWEVER_ this is not guaranteed, the wakeup can come
* instantly.
*
* This function must be used as-if it were wake_up_process(); IOW the task
* must be ready to be woken at this location.
*
* This function is essentially a task-safe equivalent to wake_q_add(). Callers
* that already hold reference to @task can call the 'safe' version and trust
* wake_q to do the right thing depending whether or not the @task is already
* queued for wakeup.
*/
void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task)
{
if (!__wake_q_add(head, task))
put_task_struct(task);
}
void wake_up_q(struct wake_q_head *head)
{
struct wake_q_node *node = head->first;
while (node != WAKE_Q_TAIL) {
struct task_struct *task;
task = container_of(node, struct task_struct, wake_q);
/* task can safely be re-inserted now: */
node = node->next;
task->wake_q.next = NULL;
/*
* wake_up_process() executes a full barrier, which pairs with
* the queueing in wake_q_add() so as not to miss wakeups.
*/
wake_up_process(task);
put_task_struct(task);
}
}
/*
* resched_curr - mark rq's current task 'to be rescheduled now'.
*
* On UP this means the setting of the need_resched flag, on SMP it
* might also involve a cross-CPU call to trigger the scheduler on
* the target CPU.
*/
void resched_curr(struct rq *rq)
{
struct task_struct *curr = rq->curr;
int cpu;
lockdep_assert_held(&rq->lock);
if (test_tsk_need_resched(curr))
return;
cpu = cpu_of(rq);
if (cpu == smp_processor_id()) {
set_tsk_need_resched(curr);
set_preempt_need_resched();
return;
}
if (set_nr_and_not_polling(curr))
smp_send_reschedule(cpu);
else
trace_sched_wake_idle_without_ipi(cpu);
}
void resched_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
raw_spin_lock_irqsave(&rq->lock, flags);
if (cpu_online(cpu) || cpu == smp_processor_id())
resched_curr(cpu_rq(cpu));
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ_COMMON
void nohz_balance_enter_idle(int cpu) {}
void select_nohz_load_balancer(int stop_tick) {}
void set_cpu_sd_state_idle(void) {}
/*
* In the semi idle case, use the nearest busy CPU for migrating timers
* from an idle CPU. This is good for power-savings.
*
* We don't do similar optimization for completely idle system, as
* selecting an idle CPU will add more delays to the timers than intended
* (as that CPU's timer base may not be uptodate wrt jiffies etc).
*/
int get_nohz_timer_target(void)
{
int i, cpu = smp_processor_id(), default_cpu = -1;
struct cpumask *mask;
const struct cpumask *hk_mask;
if (housekeeping_cpu(cpu, HK_TYPE_TIMER)) {
if (!idle_cpu(cpu))
return cpu;
default_cpu = cpu;
}
hk_mask = housekeeping_cpumask(HK_TYPE_TIMER);
for (mask = per_cpu(sched_cpu_topo_masks, cpu) + 1;
mask < per_cpu(sched_cpu_topo_end_mask, cpu); mask++)
for_each_cpu_and(i, mask, hk_mask)
if (!idle_cpu(i))
return i;
if (default_cpu == -1)
default_cpu = housekeeping_any_cpu(HK_TYPE_TIMER);
cpu = default_cpu;
return cpu;
}
/*
* When add_timer_on() enqueues a timer into the timer wheel of an
* idle CPU then this timer might expire before the next timer event
* which is scheduled to wake up that CPU. In case of a completely
* idle system the next event might even be infinite time into the
* future. wake_up_idle_cpu() ensures that the CPU is woken up and
* leaves the inner idle loop so the newly added timer is taken into
* account when the CPU goes back to idle and evaluates the timer
* wheel for the next timer event.
*/
static inline void wake_up_idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
if (cpu == smp_processor_id())
return;
if (set_nr_and_not_polling(rq->idle))
smp_send_reschedule(cpu);
else
trace_sched_wake_idle_without_ipi(cpu);
}
static inline bool wake_up_full_nohz_cpu(int cpu)
{
/*
* We just need the target to call irq_exit() and re-evaluate
* the next tick. The nohz full kick at least implies that.
* If needed we can still optimize that later with an
* empty IRQ.
*/
if (cpu_is_offline(cpu))
return true; /* Don't try to wake offline CPUs. */
if (tick_nohz_full_cpu(cpu)) {
if (cpu != smp_processor_id() ||
tick_nohz_tick_stopped())
tick_nohz_full_kick_cpu(cpu);
return true;
}
return false;
}
void wake_up_nohz_cpu(int cpu)
{
if (!wake_up_full_nohz_cpu(cpu))
wake_up_idle_cpu(cpu);
}
static void nohz_csd_func(void *info)
{
struct rq *rq = info;
int cpu = cpu_of(rq);
unsigned int flags;
/*
* Release the rq::nohz_csd.
*/
flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
WARN_ON(!(flags & NOHZ_KICK_MASK));
rq->idle_balance = idle_cpu(cpu);
if (rq->idle_balance && !need_resched()) {
rq->nohz_idle_balance = flags;
raise_softirq_irqoff(SCHED_SOFTIRQ);
}
}
#endif /* CONFIG_NO_HZ_COMMON */
#endif /* CONFIG_SMP */
static inline void check_preempt_curr(struct rq *rq)
{
if (sched_rq_first_task(rq) != rq->curr)
resched_curr(rq);
}
static __always_inline
int __task_state_match(struct task_struct *p, unsigned int state)
{
if (READ_ONCE(p->__state) & state)
return 1;
#ifdef CONFIG_PREEMPT_RT
if (READ_ONCE(p->saved_state) & state)
return -1;
#endif
return 0;
}
static __always_inline
int task_state_match(struct task_struct *p, unsigned int state)
{
#ifdef CONFIG_PREEMPT_RT
int match;
/*
* Serialize against current_save_and_set_rtlock_wait_state() and
* current_restore_rtlock_saved_state().
*/
raw_spin_lock_irq(&p->pi_lock);
match = __task_state_match(p, state);
raw_spin_unlock_irq(&p->pi_lock);
return match;
#else
return __task_state_match(p, state);
#endif
}
/*
* wait_task_inactive - wait for a thread to unschedule.
*
* Wait for the thread to block in any of the states set in @match_state.
* If it changes, i.e. @p might have woken up, then return zero. When we
* succeed in waiting for @p to be off its CPU, we return a positive number
* (its total switch count). If a second call a short while later returns the
* same number, the caller can be sure that @p has remained unscheduled the
* whole time.
*
* The caller must ensure that the task *will* unschedule sometime soon,
* else this function might spin for a *long* time. This function can't
* be called with interrupts off, or it may introduce deadlock with
* smp_call_function() if an IPI is sent by the same process we are
* waiting to become inactive.
*/
unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state)
{
unsigned long flags;
int running, queued, match;
unsigned long ncsw;
struct rq *rq;
raw_spinlock_t *lock;
for (;;) {
rq = task_rq(p);
/*
* If the task is actively running on another CPU
* still, just relax and busy-wait without holding
* any locks.
*
* NOTE! Since we don't hold any locks, it's not
* even sure that "rq" stays as the right runqueue!
* But we don't care, since this will return false
* if the runqueue has changed and p is actually now
* running somewhere else!
*/
while (task_on_cpu(p)) {
if (!task_state_match(p, match_state))
return 0;
cpu_relax();
}
/*
* Ok, time to look more closely! We need the rq
* lock now, to be *sure*. If we're wrong, we'll
* just go back and repeat.
*/
task_access_lock_irqsave(p, &lock, &flags);
trace_sched_wait_task(p);
running = task_on_cpu(p);
queued = p->on_rq;
ncsw = 0;
if ((match = __task_state_match(p, match_state))) {
/*
* When matching on p->saved_state, consider this task
* still queued so it will wait.
*/
if (match < 0)
queued = 1;
ncsw = p->nvcsw | LONG_MIN; /* sets MSB */
}
task_access_unlock_irqrestore(p, lock, &flags);
/*
* If it changed from the expected state, bail out now.
*/
if (unlikely(!ncsw))
break;
/*
* Was it really running after all now that we
* checked with the proper locks actually held?
*
* Oops. Go back and try again..
*/
if (unlikely(running)) {
cpu_relax();
continue;
}
/*
* It's not enough that it's not actively running,
* it must be off the runqueue _entirely_, and not
* preempted!
*
* So if it was still runnable (but just not actively
* running right now), it's preempted, and we should
* yield - it could be a while.
*/
if (unlikely(queued)) {
ktime_t to = NSEC_PER_SEC / HZ;
set_current_state(TASK_UNINTERRUPTIBLE);
schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD);
continue;
}
/*
* Ahh, all good. It wasn't running, and it wasn't
* runnable, which means that it will never become
* running in the future either. We're all done!
*/
break;
}
return ncsw;
}
#ifdef CONFIG_SCHED_HRTICK
/*
* Use HR-timers to deliver accurate preemption points.
*/
static void hrtick_clear(struct rq *rq)
{
if (hrtimer_active(&rq->hrtick_timer))
hrtimer_cancel(&rq->hrtick_timer);
}
/*
* High-resolution timer tick.
* Runs from hardirq context with interrupts disabled.
*/
static enum hrtimer_restart hrtick(struct hrtimer *timer)
{
struct rq *rq = container_of(timer, struct rq, hrtick_timer);
WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
raw_spin_lock(&rq->lock);
resched_curr(rq);
raw_spin_unlock(&rq->lock);
return HRTIMER_NORESTART;
}
/*
* Use hrtick when:
* - enabled by features
* - hrtimer is actually high res
*/
static inline int hrtick_enabled(struct rq *rq)
{
/**
* Alt schedule FW doesn't support sched_feat yet
if (!sched_feat(HRTICK))
return 0;
*/
if (!cpu_active(cpu_of(rq)))
return 0;
return hrtimer_is_hres_active(&rq->hrtick_timer);
}
#ifdef CONFIG_SMP
static void __hrtick_restart(struct rq *rq)
{
struct hrtimer *timer = &rq->hrtick_timer;
ktime_t time = rq->hrtick_time;
hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD);
}
/*
* called from hardirq (IPI) context
*/
static void __hrtick_start(void *arg)
{
struct rq *rq = arg;
raw_spin_lock(&rq->lock);
__hrtick_restart(rq);
raw_spin_unlock(&rq->lock);
}
/*
* Called to set the hrtick timer state.
*
* called with rq->lock held and irqs disabled
*/
void hrtick_start(struct rq *rq, u64 delay)
{
struct hrtimer *timer = &rq->hrtick_timer;
s64 delta;
/*
* Don't schedule slices shorter than 10000ns, that just
* doesn't make sense and can cause timer DoS.
*/
delta = max_t(s64, delay, 10000LL);
rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta);
if (rq == this_rq())
__hrtick_restart(rq);
else
smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd);
}
#else
/*
* Called to set the hrtick timer state.
*
* called with rq->lock held and irqs disabled
*/
void hrtick_start(struct rq *rq, u64 delay)
{
/*
* Don't schedule slices shorter than 10000ns, that just
* doesn't make sense. Rely on vruntime for fairness.
*/
delay = max_t(u64, delay, 10000LL);
hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay),
HRTIMER_MODE_REL_PINNED_HARD);
}
#endif /* CONFIG_SMP */
static void hrtick_rq_init(struct rq *rq)
{
#ifdef CONFIG_SMP
INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq);
#endif
hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD);
rq->hrtick_timer.function = hrtick;
}
#else /* CONFIG_SCHED_HRTICK */
static inline int hrtick_enabled(struct rq *rq)
{
return 0;
}
static inline void hrtick_clear(struct rq *rq)
{
}
static inline void hrtick_rq_init(struct rq *rq)
{
}
#endif /* CONFIG_SCHED_HRTICK */
static inline int __normal_prio(int policy, int rt_prio, int static_prio)
{
return rt_policy(policy) ? (MAX_RT_PRIO - 1 - rt_prio) :
static_prio + MAX_PRIORITY_ADJ;
}
/*
* Calculate the expected normal priority: i.e. priority
* without taking RT-inheritance into account. Might be
* boosted by interactivity modifiers. Changes upon fork,
* setprio syscalls, and whenever the interactivity
* estimator recalculates.
*/
static inline int normal_prio(struct task_struct *p)
{
return __normal_prio(p->policy, p->rt_priority, p->static_prio);
}
/*
* Calculate the current priority, i.e. the priority
* taken into account by the scheduler. This value might
* be boosted by RT tasks as it will be RT if the task got
* RT-boosted. If not then it returns p->normal_prio.
*/
static int effective_prio(struct task_struct *p)
{
p->normal_prio = normal_prio(p);
/*
* If we are RT tasks or we were boosted to RT priority,
* keep the priority unchanged. Otherwise, update priority
* to the normal priority:
*/
if (!rt_prio(p->prio))
return p->normal_prio;
return p->prio;
}
/*
* activate_task - move a task to the runqueue.
*
* Context: rq->lock
*/
static void activate_task(struct task_struct *p, struct rq *rq)
{
enqueue_task(p, rq, ENQUEUE_WAKEUP);
p->on_rq = TASK_ON_RQ_QUEUED;
/*
* If in_iowait is set, the code below may not trigger any cpufreq
* utilization updates, so do it here explicitly with the IOWAIT flag
* passed.
*/
cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT * p->in_iowait);
}
/*
* deactivate_task - remove a task from the runqueue.
*
* Context: rq->lock
*/
static inline void deactivate_task(struct task_struct *p, struct rq *rq)
{
dequeue_task(p, rq, DEQUEUE_SLEEP);
p->on_rq = 0;
cpufreq_update_util(rq, 0);
}
static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
{
#ifdef CONFIG_SMP
/*
* After ->cpu is set up to a new value, task_access_lock(p, ...) can be
* successfully executed on another CPU. We must ensure that updates of
* per-task data have been completed by this moment.
*/
smp_wmb();
WRITE_ONCE(task_thread_info(p)->cpu, cpu);
#endif
}
static inline bool is_migration_disabled(struct task_struct *p)
{
#ifdef CONFIG_SMP
return p->migration_disabled;
#else
return false;
#endif
}
#define SCA_CHECK 0x01
#define SCA_USER 0x08
#ifdef CONFIG_SMP
void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
{
#ifdef CONFIG_SCHED_DEBUG
unsigned int state = READ_ONCE(p->__state);
/*
* We should never call set_task_cpu() on a blocked task,
* ttwu() will sort out the placement.
*/
WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq);
#ifdef CONFIG_LOCKDEP
/*
* The caller should hold either p->pi_lock or rq->lock, when changing
* a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.
*
* sched_move_task() holds both and thus holding either pins the cgroup,
* see task_group().
*/
WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||
lockdep_is_held(&task_rq(p)->lock)));
#endif
/*
* Clearly, migrating tasks to offline CPUs is a fairly daft thing.
*/
WARN_ON_ONCE(!cpu_online(new_cpu));
WARN_ON_ONCE(is_migration_disabled(p));
#endif
trace_sched_migrate_task(p, new_cpu);
if (task_cpu(p) != new_cpu)
{
rseq_migrate(p);
perf_event_task_migrate(p);
}
__set_task_cpu(p, new_cpu);
}
#define MDF_FORCE_ENABLED 0x80
static void
__do_set_cpus_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
/*
* This here violates the locking rules for affinity, since we're only
* supposed to change these variables while holding both rq->lock and
* p->pi_lock.
*
* HOWEVER, it magically works, because ttwu() is the only code that
* accesses these variables under p->pi_lock and only does so after
* smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule()
* before finish_task().
*
* XXX do further audits, this smells like something putrid.
*/
SCHED_WARN_ON(!p->on_cpu);
p->cpus_ptr = new_mask;
}
void migrate_disable(void)
{
struct task_struct *p = current;
int cpu;
if (p->migration_disabled) {
p->migration_disabled++;
return;
}
preempt_disable();
cpu = smp_processor_id();
if (cpumask_test_cpu(cpu, &p->cpus_mask)) {
cpu_rq(cpu)->nr_pinned++;
p->migration_disabled = 1;
p->migration_flags &= ~MDF_FORCE_ENABLED;
/*
* Violates locking rules! see comment in __do_set_cpus_ptr().
*/
if (p->cpus_ptr == &p->cpus_mask)
__do_set_cpus_ptr(p, cpumask_of(cpu));
}
preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_disable);
void migrate_enable(void)
{
struct task_struct *p = current;
if (0 == p->migration_disabled)
return;
if (p->migration_disabled > 1) {
p->migration_disabled--;
return;
}
if (WARN_ON_ONCE(!p->migration_disabled))
return;
/*
* Ensure stop_task runs either before or after this, and that
* __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule().
*/
preempt_disable();
/*
* Assumption: current should be running on allowed cpu
*/
WARN_ON_ONCE(!cpumask_test_cpu(smp_processor_id(), &p->cpus_mask));
if (p->cpus_ptr != &p->cpus_mask)
__do_set_cpus_ptr(p, &p->cpus_mask);
/*
* Mustn't clear migration_disabled() until cpus_ptr points back at the
* regular cpus_mask, otherwise things that race (eg.
* select_fallback_rq) get confused.
*/
barrier();
p->migration_disabled = 0;
this_rq()->nr_pinned--;
preempt_enable();
}
EXPORT_SYMBOL_GPL(migrate_enable);
static inline bool rq_has_pinned_tasks(struct rq *rq)
{
return rq->nr_pinned;
}
/*
* Per-CPU kthreads are allowed to run on !active && online CPUs, see
* __set_cpus_allowed_ptr() and select_fallback_rq().
*/
static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
{
/* When not in the task's cpumask, no point in looking further. */
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
return false;
/* migrate_disabled() must be allowed to finish. */
if (is_migration_disabled(p))
return cpu_online(cpu);
/* Non kernel threads are not allowed during either online or offline. */
if (!(p->flags & PF_KTHREAD))
return cpu_active(cpu) && task_cpu_possible(cpu, p);
/* KTHREAD_IS_PER_CPU is always allowed. */
if (kthread_is_per_cpu(p))
return cpu_online(cpu);
/* Regular kernel threads don't get to stay during offline. */
if (cpu_dying(cpu))
return false;
/* But are allowed during online. */
return cpu_online(cpu);
}
/*
* This is how migration works:
*
* 1) we invoke migration_cpu_stop() on the target CPU using
* stop_one_cpu().
* 2) stopper starts to run (implicitly forcing the migrated thread
* off the CPU)
* 3) it checks whether the migrated task is still in the wrong runqueue.
* 4) if it's in the wrong runqueue then the migration thread removes
* it and puts it into the right queue.
* 5) stopper completes and stop_one_cpu() returns and the migration
* is done.
*/
/*
* move_queued_task - move a queued task to new rq.
*
* Returns (locked) new rq. Old rq's lock is released.
*/
static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int
new_cpu)
{
int src_cpu;
lockdep_assert_held(&rq->lock);
src_cpu = cpu_of(rq);
WRITE_ONCE(p->on_rq, TASK_ON_RQ_MIGRATING);
dequeue_task(p, rq, 0);
set_task_cpu(p, new_cpu);
raw_spin_unlock(&rq->lock);
rq = cpu_rq(new_cpu);
raw_spin_lock(&rq->lock);
WARN_ON_ONCE(task_cpu(p) != new_cpu);
sched_mm_cid_migrate_to(rq, p, src_cpu);
sched_task_sanity_check(p, rq);
enqueue_task(p, rq, 0);
p->on_rq = TASK_ON_RQ_QUEUED;
check_preempt_curr(rq);
return rq;
}
struct migration_arg {
struct task_struct *task;
int dest_cpu;
};
/*
* Move (not current) task off this CPU, onto the destination CPU. We're doing
* this because either it can't run here any more (set_cpus_allowed()
* away from this CPU, or CPU going down), or because we're
* attempting to rebalance this task on exec (sched_exec).
*
* So we race with normal scheduler movements, but that's OK, as long
* as the task is no longer on this CPU.
*/
static struct rq *__migrate_task(struct rq *rq, struct task_struct *p, int
dest_cpu)
{
/* Affinity changed (again). */
if (!is_cpu_allowed(p, dest_cpu))
return rq;
return move_queued_task(rq, p, dest_cpu);
}
/*
* migration_cpu_stop - this will be executed by a highprio stopper thread
* and performs thread migration by bumping thread off CPU then
* 'pushing' onto another runqueue.
*/
static int migration_cpu_stop(void *data)
{
struct migration_arg *arg = data;
struct task_struct *p = arg->task;
struct rq *rq = this_rq();
unsigned long flags;
/*
* The original target CPU might have gone down and we might
* be on another CPU but it doesn't matter.
*/
local_irq_save(flags);
/*
* We need to explicitly wake pending tasks before running
* __migrate_task() such that we will not miss enforcing cpus_ptr
* during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test.
*/
flush_smp_call_function_queue();
raw_spin_lock(&p->pi_lock);
raw_spin_lock(&rq->lock);
/*
* If task_rq(p) != rq, it cannot be migrated here, because we're
* holding rq->lock, if p->on_rq == 0 it cannot get enqueued because
* we're holding p->pi_lock.
*/
if (task_rq(p) == rq && task_on_rq_queued(p)) {
update_rq_clock(rq);
rq = __migrate_task(rq, p, arg->dest_cpu);
}
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
return 0;
}
static inline void
set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx)
{
cpumask_copy(&p->cpus_mask, ctx->new_mask);
p->nr_cpus_allowed = cpumask_weight(ctx->new_mask);
/*
* Swap in a new user_cpus_ptr if SCA_USER flag set
*/
if (ctx->flags & SCA_USER)
swap(p->user_cpus_ptr, ctx->user_mask);
}
static void
__do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx)
{
lockdep_assert_held(&p->pi_lock);
set_cpus_allowed_common(p, ctx);
}
/*
* Used for kthread_bind() and select_fallback_rq(), in both cases the user
* affinity (if any) should be destroyed too.
*/
void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask)
{
struct affinity_context ac = {
.new_mask = new_mask,
.user_mask = NULL,
.flags = SCA_USER, /* clear the user requested mask */
};
union cpumask_rcuhead {
cpumask_t cpumask;
struct rcu_head rcu;
};
__do_set_cpus_allowed(p, &ac);
/*
* Because this is called with p->pi_lock held, it is not possible
* to use kfree() here (when PREEMPT_RT=y), therefore punt to using
* kfree_rcu().
*/
kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu);
}
static cpumask_t *alloc_user_cpus_ptr(int node)
{
/*
* See do_set_cpus_allowed() above for the rcu_head usage.
*/
int size = max_t(int, cpumask_size(), sizeof(struct rcu_head));
return kmalloc_node(size, GFP_KERNEL, node);
}
int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src,
int node)
{
cpumask_t *user_mask;
unsigned long flags;
/*
* Always clear dst->user_cpus_ptr first as their user_cpus_ptr's
* may differ by now due to racing.
*/
dst->user_cpus_ptr = NULL;
/*
* This check is racy and losing the race is a valid situation.
* It is not worth the extra overhead of taking the pi_lock on
* every fork/clone.
*/
if (data_race(!src->user_cpus_ptr))
return 0;
user_mask = alloc_user_cpus_ptr(node);
if (!user_mask)
return -ENOMEM;
/*
* Use pi_lock to protect content of user_cpus_ptr
*
* Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent
* do_set_cpus_allowed().
*/
raw_spin_lock_irqsave(&src->pi_lock, flags);
if (src->user_cpus_ptr) {
swap(dst->user_cpus_ptr, user_mask);
cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr);
}
raw_spin_unlock_irqrestore(&src->pi_lock, flags);
if (unlikely(user_mask))
kfree(user_mask);
return 0;
}
static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p)
{
struct cpumask *user_mask = NULL;
swap(p->user_cpus_ptr, user_mask);
return user_mask;
}
void release_user_cpus_ptr(struct task_struct *p)
{
kfree(clear_user_cpus_ptr(p));
}
#endif
/**
* task_curr - is this task currently executing on a CPU?
* @p: the task in question.
*
* Return: 1 if the task is currently executing. 0 otherwise.
*/
inline int task_curr(const struct task_struct *p)
{
return cpu_curr(task_cpu(p)) == p;
}
#ifdef CONFIG_SMP
/***
* kick_process - kick a running thread to enter/exit the kernel
* @p: the to-be-kicked thread
*
* Cause a process which is running on another CPU to enter
* kernel-mode, without any delay. (to get signals handled.)
*
* NOTE: this function doesn't have to take the runqueue lock,
* because all it wants to ensure is that the remote task enters
* the kernel. If the IPI races and the task has been migrated
* to another CPU then no harm is done and the purpose has been
* achieved as well.
*/
void kick_process(struct task_struct *p)
{
int cpu;
preempt_disable();
cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
smp_send_reschedule(cpu);
preempt_enable();
}
EXPORT_SYMBOL_GPL(kick_process);
/*
* ->cpus_ptr is protected by both rq->lock and p->pi_lock
*
* A few notes on cpu_active vs cpu_online:
*
* - cpu_active must be a subset of cpu_online
*
* - on CPU-up we allow per-CPU kthreads on the online && !active CPU,
* see __set_cpus_allowed_ptr(). At this point the newly online
* CPU isn't yet part of the sched domains, and balancing will not
* see it.
*
* - on cpu-down we clear cpu_active() to mask the sched domains and
* avoid the load balancer to place new tasks on the to be removed
* CPU. Existing tasks will remain running there and will be taken
* off.
*
* This means that fallback selection must not select !active CPUs.
* And can assume that any active CPU must be online. Conversely
* select_task_rq() below may allow selection of !active CPUs in order
* to satisfy the above rules.
*/
static int select_fallback_rq(int cpu, struct task_struct *p)
{
int nid = cpu_to_node(cpu);
const struct cpumask *nodemask = NULL;
enum { cpuset, possible, fail } state = cpuset;
int dest_cpu;
/*
* If the node that the CPU is on has been offlined, cpu_to_node()
* will return -1. There is no CPU on the node, and we should
* select the CPU on the other node.
*/
if (nid != -1) {
nodemask = cpumask_of_node(nid);
/* Look for allowed, online CPU in same node. */
for_each_cpu(dest_cpu, nodemask) {
if (is_cpu_allowed(p, dest_cpu))
return dest_cpu;
}
}
for (;;) {
/* Any allowed, online CPU? */
for_each_cpu(dest_cpu, p->cpus_ptr) {
if (!is_cpu_allowed(p, dest_cpu))
continue;
goto out;
}
/* No more Mr. Nice Guy. */
switch (state) {
case cpuset:
if (cpuset_cpus_allowed_fallback(p)) {
state = possible;
break;
}
fallthrough;
case possible:
/*
* XXX When called from select_task_rq() we only
* hold p->pi_lock and again violate locking order.
*
* More yuck to audit.
*/
do_set_cpus_allowed(p, task_cpu_possible_mask(p));
state = fail;
break;
case fail:
BUG();
break;
}
}
out:
if (state != cpuset) {
/*
* Don't tell them about moving exiting tasks or
* kernel threads (both mm NULL), since they never
* leave kernel.
*/
if (p->mm && printk_ratelimit()) {
printk_deferred("process %d (%s) no longer affine to cpu%d\n",
task_pid_nr(p), p->comm, cpu);
}
}
return dest_cpu;
}
static inline void
sched_preempt_mask_flush(cpumask_t *mask, int prio)
{
int cpu;
cpumask_copy(mask, sched_idle_mask);
for_each_clear_bit(cpu, cpumask_bits(mask), nr_cpumask_bits) {
if (prio < cpu_rq(cpu)->prio)
cpumask_set_cpu(cpu, mask);
}
}
static inline int
preempt_mask_check(struct task_struct *p, cpumask_t *allow_mask, cpumask_t *preempt_mask)
{
int task_prio = task_sched_prio(p);
cpumask_t *mask = sched_preempt_mask + SCHED_QUEUE_BITS - 1 - task_prio;
int pr = atomic_read(&sched_prio_record);
if (pr != task_prio) {
sched_preempt_mask_flush(mask, task_prio);
atomic_set(&sched_prio_record, task_prio);
}
return cpumask_and(preempt_mask, allow_mask, mask);
}
static inline int select_task_rq(struct task_struct *p)
{
cpumask_t allow_mask, mask;
if (unlikely(!cpumask_and(&allow_mask, p->cpus_ptr, cpu_active_mask)))
return select_fallback_rq(task_cpu(p), p);
if (
#ifdef CONFIG_SCHED_SMT
cpumask_and(&mask, &allow_mask, &sched_sg_idle_mask) ||
#endif
cpumask_and(&mask, &allow_mask, sched_idle_mask) ||
preempt_mask_check(p, &allow_mask, &mask))
return best_mask_cpu(task_cpu(p), &mask);
return best_mask_cpu(task_cpu(p), &allow_mask);
}
void sched_set_stop_task(int cpu, struct task_struct *stop)
{
static struct lock_class_key stop_pi_lock;
struct sched_param stop_param = { .sched_priority = STOP_PRIO };
struct sched_param start_param = { .sched_priority = 0 };
struct task_struct *old_stop = cpu_rq(cpu)->stop;
if (stop) {
/*
* Make it appear like a SCHED_FIFO task, its something
* userspace knows about and won't get confused about.
*
* Also, it will make PI more or less work without too
* much confusion -- but then, stop work should not
* rely on PI working anyway.
*/
sched_setscheduler_nocheck(stop, SCHED_FIFO, &stop_param);
/*
* The PI code calls rt_mutex_setprio() with ->pi_lock held to
* adjust the effective priority of a task. As a result,
* rt_mutex_setprio() can trigger (RT) balancing operations,
* which can then trigger wakeups of the stop thread to push
* around the current task.
*
* The stop task itself will never be part of the PI-chain, it
* never blocks, therefore that ->pi_lock recursion is safe.
* Tell lockdep about this by placing the stop->pi_lock in its
* own class.
*/
lockdep_set_class(&stop->pi_lock, &stop_pi_lock);
}
cpu_rq(cpu)->stop = stop;
if (old_stop) {
/*
* Reset it back to a normal scheduling policy so that
* it can die in pieces.
*/
sched_setscheduler_nocheck(old_stop, SCHED_NORMAL, &start_param);
}
}
static int affine_move_task(struct rq *rq, struct task_struct *p, int dest_cpu,
raw_spinlock_t *lock, unsigned long irq_flags)
__releases(rq->lock)
__releases(p->pi_lock)
{
/* Can the task run on the task's current CPU? If so, we're done */
if (!cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) {
if (p->migration_disabled) {
if (likely(p->cpus_ptr != &p->cpus_mask))
__do_set_cpus_ptr(p, &p->cpus_mask);
p->migration_disabled = 0;
p->migration_flags |= MDF_FORCE_ENABLED;
/* When p is migrate_disabled, rq->lock should be held */
rq->nr_pinned--;
}
if (task_on_cpu(p) || READ_ONCE(p->__state) == TASK_WAKING) {
struct migration_arg arg = { p, dest_cpu };
/* Need help from migration thread: drop lock and wait. */
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, irq_flags);
stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg);
return 0;
}
if (task_on_rq_queued(p)) {
/*
* OK, since we're going to drop the lock immediately
* afterwards anyway.
*/
update_rq_clock(rq);
rq = move_queued_task(rq, p, dest_cpu);
lock = &rq->lock;
}
}
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, irq_flags);
return 0;
}
static int __set_cpus_allowed_ptr_locked(struct task_struct *p,
struct affinity_context *ctx,
struct rq *rq,
raw_spinlock_t *lock,
unsigned long irq_flags)
{
const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p);
const struct cpumask *cpu_valid_mask = cpu_active_mask;
bool kthread = p->flags & PF_KTHREAD;
int dest_cpu;
int ret = 0;
if (kthread || is_migration_disabled(p)) {
/*
* Kernel threads are allowed on online && !active CPUs,
* however, during cpu-hot-unplug, even these might get pushed
* away if not KTHREAD_IS_PER_CPU.
*
* Specifically, migration_disabled() tasks must not fail the
* cpumask_any_and_distribute() pick below, esp. so on
* SCA_MIGRATE_ENABLE, otherwise we'll not call
* set_cpus_allowed_common() and actually reset p->cpus_ptr.
*/
cpu_valid_mask = cpu_online_mask;
}
if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) {
ret = -EINVAL;
goto out;
}
/*
* Must re-check here, to close a race against __kthread_bind(),
* sched_setaffinity() is not guaranteed to observe the flag.
*/
if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) {
ret = -EINVAL;
goto out;
}
if (cpumask_equal(&p->cpus_mask, ctx->new_mask))
goto out;
dest_cpu = cpumask_any_and(cpu_valid_mask, ctx->new_mask);
if (dest_cpu >= nr_cpu_ids) {
ret = -EINVAL;
goto out;
}
__do_set_cpus_allowed(p, ctx);
return affine_move_task(rq, p, dest_cpu, lock, irq_flags);
out:
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, irq_flags);
return ret;
}
/*
* Change a given task's CPU affinity. Migrate the thread to a
* is removed from the allowed bitmask.
*
* NOTE: the caller must have a valid reference to the task, the
* task must not exit() & deallocate itself prematurely. The
* call is not atomic; no spinlocks may be held.
*/
static int __set_cpus_allowed_ptr(struct task_struct *p,
struct affinity_context *ctx)
{
unsigned long irq_flags;
struct rq *rq;
raw_spinlock_t *lock;
raw_spin_lock_irqsave(&p->pi_lock, irq_flags);
rq = __task_access_lock(p, &lock);
/*
* Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_*
* flags are set.
*/
if (p->user_cpus_ptr &&
!(ctx->flags & SCA_USER) &&
cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr))
ctx->new_mask = rq->scratch_mask;
return __set_cpus_allowed_ptr_locked(p, ctx, rq, lock, irq_flags);
}
int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
{
struct affinity_context ac = {
.new_mask = new_mask,
.flags = 0,
};
return __set_cpus_allowed_ptr(p, &ac);
}
EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr);
/*
* Change a given task's CPU affinity to the intersection of its current
* affinity mask and @subset_mask, writing the resulting mask to @new_mask.
* If user_cpus_ptr is defined, use it as the basis for restricting CPU
* affinity or use cpu_online_mask instead.
*
* If the resulting mask is empty, leave the affinity unchanged and return
* -EINVAL.
*/
static int restrict_cpus_allowed_ptr(struct task_struct *p,
struct cpumask *new_mask,
const struct cpumask *subset_mask)
{
struct affinity_context ac = {
.new_mask = new_mask,
.flags = 0,
};
unsigned long irq_flags;
raw_spinlock_t *lock;
struct rq *rq;
int err;
raw_spin_lock_irqsave(&p->pi_lock, irq_flags);
rq = __task_access_lock(p, &lock);
if (!cpumask_and(new_mask, task_user_cpus(p), subset_mask)) {
err = -EINVAL;
goto err_unlock;
}
return __set_cpus_allowed_ptr_locked(p, &ac, rq, lock, irq_flags);
err_unlock:
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, irq_flags);
return err;
}
/*
* Restrict the CPU affinity of task @p so that it is a subset of
* task_cpu_possible_mask() and point @p->user_cpus_ptr to a copy of the
* old affinity mask. If the resulting mask is empty, we warn and walk
* up the cpuset hierarchy until we find a suitable mask.
*/
void force_compatible_cpus_allowed_ptr(struct task_struct *p)
{
cpumask_var_t new_mask;
const struct cpumask *override_mask = task_cpu_possible_mask(p);
alloc_cpumask_var(&new_mask, GFP_KERNEL);
/*
* __migrate_task() can fail silently in the face of concurrent
* offlining of the chosen destination CPU, so take the hotplug
* lock to ensure that the migration succeeds.
*/
cpus_read_lock();
if (!cpumask_available(new_mask))
goto out_set_mask;
if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask))
goto out_free_mask;
/*
* We failed to find a valid subset of the affinity mask for the
* task, so override it based on its cpuset hierarchy.
*/
cpuset_cpus_allowed(p, new_mask);
override_mask = new_mask;
out_set_mask:
if (printk_ratelimit()) {
printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n",
task_pid_nr(p), p->comm,
cpumask_pr_args(override_mask));
}
WARN_ON(set_cpus_allowed_ptr(p, override_mask));
out_free_mask:
cpus_read_unlock();
free_cpumask_var(new_mask);
}
static int
__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx);
/*
* Restore the affinity of a task @p which was previously restricted by a
* call to force_compatible_cpus_allowed_ptr().
*
* It is the caller's responsibility to serialise this with any calls to
* force_compatible_cpus_allowed_ptr(@p).
*/
void relax_compatible_cpus_allowed_ptr(struct task_struct *p)
{
struct affinity_context ac = {
.new_mask = task_user_cpus(p),
.flags = 0,
};
int ret;
/*
* Try to restore the old affinity mask with __sched_setaffinity().
* Cpuset masking will be done there too.
*/
ret = __sched_setaffinity(p, &ac);
WARN_ON_ONCE(ret);
}
#else /* CONFIG_SMP */
static inline int select_task_rq(struct task_struct *p)
{
return 0;
}
static inline int
__set_cpus_allowed_ptr(struct task_struct *p,
struct affinity_context *ctx)
{
return set_cpus_allowed_ptr(p, ctx->new_mask);
}
static inline bool rq_has_pinned_tasks(struct rq *rq)
{
return false;
}
static inline cpumask_t *alloc_user_cpus_ptr(int node)
{
return NULL;
}
#endif /* !CONFIG_SMP */
static void
ttwu_stat(struct task_struct *p, int cpu, int wake_flags)
{
struct rq *rq;
if (!schedstat_enabled())
return;
rq = this_rq();
#ifdef CONFIG_SMP
if (cpu == rq->cpu) {
__schedstat_inc(rq->ttwu_local);
__schedstat_inc(p->stats.nr_wakeups_local);
} else {
/** Alt schedule FW ToDo:
* How to do ttwu_wake_remote
*/
}
#endif /* CONFIG_SMP */
__schedstat_inc(rq->ttwu_count);
__schedstat_inc(p->stats.nr_wakeups);
}
/*
* Mark the task runnable.
*/
static inline void ttwu_do_wakeup(struct task_struct *p)
{
WRITE_ONCE(p->__state, TASK_RUNNING);
trace_sched_wakeup(p);
}
static inline void
ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags)
{
if (p->sched_contributes_to_load)
rq->nr_uninterruptible--;
if (
#ifdef CONFIG_SMP
!(wake_flags & WF_MIGRATED) &&
#endif
p->in_iowait) {
delayacct_blkio_end(p);
atomic_dec(&task_rq(p)->nr_iowait);
}
activate_task(p, rq);
check_preempt_curr(rq);
ttwu_do_wakeup(p);
}
/*
* Consider @p being inside a wait loop:
*
* for (;;) {
* set_current_state(TASK_UNINTERRUPTIBLE);
*
* if (CONDITION)
* break;
*
* schedule();
* }
* __set_current_state(TASK_RUNNING);
*
* between set_current_state() and schedule(). In this case @p is still
* runnable, so all that needs doing is change p->state back to TASK_RUNNING in
* an atomic manner.
*
* By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq
* then schedule() must still happen and p->state can be changed to
* TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we
* need to do a full wakeup with enqueue.
*
* Returns: %true when the wakeup is done,
* %false otherwise.
*/
static int ttwu_runnable(struct task_struct *p, int wake_flags)
{
struct rq *rq;
raw_spinlock_t *lock;
int ret = 0;
rq = __task_access_lock(p, &lock);
if (task_on_rq_queued(p)) {
if (!task_on_cpu(p)) {
/*
* When on_rq && !on_cpu the task is preempted, see if
* it should preempt the task that is current now.
*/
update_rq_clock(rq);
check_preempt_curr(rq);
}
ttwu_do_wakeup(p);
ret = 1;
}
__task_access_unlock(p, lock);
return ret;
}
#ifdef CONFIG_SMP
void sched_ttwu_pending(void *arg)
{
struct llist_node *llist = arg;
struct rq *rq = this_rq();
struct task_struct *p, *t;
struct rq_flags rf;
if (!llist)
return;
rq_lock_irqsave(rq, &rf);
update_rq_clock(rq);
llist_for_each_entry_safe(p, t, llist, wake_entry.llist) {
if (WARN_ON_ONCE(p->on_cpu))
smp_cond_load_acquire(&p->on_cpu, !VAL);
if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq)))
set_task_cpu(p, cpu_of(rq));
ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0);
}
/*
* Must be after enqueueing at least once task such that
* idle_cpu() does not observe a false-negative -- if it does,
* it is possible for select_idle_siblings() to stack a number
* of tasks on this CPU during that window.
*
* It is ok to clear ttwu_pending when another task pending.
* We will receive IPI after local irq enabled and then enqueue it.
* Since now nr_running > 0, idle_cpu() will always get correct result.
*/
WRITE_ONCE(rq->ttwu_pending, 0);
rq_unlock_irqrestore(rq, &rf);
}
/*
* Prepare the scene for sending an IPI for a remote smp_call
*
* Returns true if the caller can proceed with sending the IPI.
* Returns false otherwise.
*/
bool call_function_single_prep_ipi(int cpu)
{
if (set_nr_if_polling(cpu_rq(cpu)->idle)) {
trace_sched_wake_idle_without_ipi(cpu);
return false;
}
return true;
}
/*
* Queue a task on the target CPUs wake_list and wake the CPU via IPI if
* necessary. The wakee CPU on receipt of the IPI will queue the task
* via sched_ttwu_wakeup() for activation so the wakee incurs the cost
* of the wakeup instead of the waker.
*/
static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
{
struct rq *rq = cpu_rq(cpu);
p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
WRITE_ONCE(rq->ttwu_pending, 1);
__smp_call_single_queue(cpu, &p->wake_entry.llist);
}
static inline bool ttwu_queue_cond(struct task_struct *p, int cpu)
{
/*
* Do not complicate things with the async wake_list while the CPU is
* in hotplug state.
*/
if (!cpu_active(cpu))
return false;
/* Ensure the task will still be allowed to run on the CPU. */
if (!cpumask_test_cpu(cpu, p->cpus_ptr))
return false;
/*
* If the CPU does not share cache, then queue the task on the
* remote rqs wakelist to avoid accessing remote data.
*/
if (!cpus_share_cache(smp_processor_id(), cpu))
return true;
if (cpu == smp_processor_id())
return false;
/*
* If the wakee cpu is idle, or the task is descheduling and the
* only running task on the CPU, then use the wakelist to offload
* the task activation to the idle (or soon-to-be-idle) CPU as
* the current CPU is likely busy. nr_running is checked to
* avoid unnecessary task stacking.
*
* Note that we can only get here with (wakee) p->on_rq=0,
* p->on_cpu can be whatever, we've done the dequeue, so
* the wakee has been accounted out of ->nr_running.
*/
if (!cpu_rq(cpu)->nr_running)
return true;
return false;
}
static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
{
if (__is_defined(ALT_SCHED_TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) {
sched_clock_cpu(cpu); /* Sync clocks across CPUs */
__ttwu_queue_wakelist(p, cpu, wake_flags);
return true;
}
return false;
}
void wake_up_if_idle(int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
rcu_read_lock();
if (!is_idle_task(rcu_dereference(rq->curr)))
goto out;
raw_spin_lock_irqsave(&rq->lock, flags);
if (is_idle_task(rq->curr))
resched_curr(rq);
/* Else CPU is not idle, do nothing here */
raw_spin_unlock_irqrestore(&rq->lock, flags);
out:
rcu_read_unlock();
}
bool cpus_share_cache(int this_cpu, int that_cpu)
{
if (this_cpu == that_cpu)
return true;
return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu);
}
#else /* !CONFIG_SMP */
static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags)
{
return false;
}
#endif /* CONFIG_SMP */
static inline void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
{
struct rq *rq = cpu_rq(cpu);
if (ttwu_queue_wakelist(p, cpu, wake_flags))
return;
raw_spin_lock(&rq->lock);
update_rq_clock(rq);
ttwu_do_activate(rq, p, wake_flags);
raw_spin_unlock(&rq->lock);
}
/*
* Invoked from try_to_wake_up() to check whether the task can be woken up.
*
* The caller holds p::pi_lock if p != current or has preemption
* disabled when p == current.
*
* The rules of PREEMPT_RT saved_state:
*
* The related locking code always holds p::pi_lock when updating
* p::saved_state, which means the code is fully serialized in both cases.
*
* The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other
* bits set. This allows to distinguish all wakeup scenarios.
*/
static __always_inline
bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
{
int match;
if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
state != TASK_RTLOCK_WAIT);
}
*success = !!(match = __task_state_match(p, state));
#ifdef CONFIG_PREEMPT_RT
/*
* Saved state preserves the task state across blocking on
* an RT lock. If the state matches, set p::saved_state to
* TASK_RUNNING, but do not wake the task because it waits
* for a lock wakeup. Also indicate success because from
* the regular waker's point of view this has succeeded.
*
* After acquiring the lock the task will restore p::__state
* from p::saved_state which ensures that the regular
* wakeup is not lost. The restore will also set
* p::saved_state to TASK_RUNNING so any further tests will
* not result in false positives vs. @success
*/
if (match < 0)
p->saved_state = TASK_RUNNING;
#endif
return match > 0;
}
/*
* Notes on Program-Order guarantees on SMP systems.
*
* MIGRATION
*
* The basic program-order guarantee on SMP systems is that when a task [t]
* migrates, all its activity on its old CPU [c0] happens-before any subsequent
* execution on its new CPU [c1].
*
* For migration (of runnable tasks) this is provided by the following means:
*
* A) UNLOCK of the rq(c0)->lock scheduling out task t
* B) migration for t is required to synchronize *both* rq(c0)->lock and
* rq(c1)->lock (if not at the same time, then in that order).
* C) LOCK of the rq(c1)->lock scheduling in task
*
* Transitivity guarantees that B happens after A and C after B.
* Note: we only require RCpc transitivity.
* Note: the CPU doing B need not be c0 or c1
*
* Example:
*
* CPU0 CPU1 CPU2
*
* LOCK rq(0)->lock
* sched-out X
* sched-in Y
* UNLOCK rq(0)->lock
*
* LOCK rq(0)->lock // orders against CPU0
* dequeue X
* UNLOCK rq(0)->lock
*
* LOCK rq(1)->lock
* enqueue X
* UNLOCK rq(1)->lock
*
* LOCK rq(1)->lock // orders against CPU2
* sched-out Z
* sched-in X
* UNLOCK rq(1)->lock
*
*
* BLOCKING -- aka. SLEEP + WAKEUP
*
* For blocking we (obviously) need to provide the same guarantee as for
* migration. However the means are completely different as there is no lock
* chain to provide order. Instead we do:
*
* 1) smp_store_release(X->on_cpu, 0) -- finish_task()
* 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up()
*
* Example:
*
* CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule)
*
* LOCK rq(0)->lock LOCK X->pi_lock
* dequeue X
* sched-out X
* smp_store_release(X->on_cpu, 0);
*
* smp_cond_load_acquire(&X->on_cpu, !VAL);
* X->state = WAKING
* set_task_cpu(X,2)
*
* LOCK rq(2)->lock
* enqueue X
* X->state = RUNNING
* UNLOCK rq(2)->lock
*
* LOCK rq(2)->lock // orders against CPU1
* sched-out Z
* sched-in X
* UNLOCK rq(2)->lock
*
* UNLOCK X->pi_lock
* UNLOCK rq(0)->lock
*
*
* However; for wakeups there is a second guarantee we must provide, namely we
* must observe the state that lead to our wakeup. That is, not only must our
* task observe its own prior state, it must also observe the stores prior to
* its wakeup.
*
* This means that any means of doing remote wakeups must order the CPU doing
* the wakeup against the CPU the task is going to end up running on. This,
* however, is already required for the regular Program-Order guarantee above,
* since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire).
*
*/
/**
* try_to_wake_up - wake up a thread
* @p: the thread to be awakened
* @state: the mask of task states that can be woken
* @wake_flags: wake modifier flags (WF_*)
*
* Conceptually does:
*
* If (@state & @p->state) @p->state = TASK_RUNNING.
*
* If the task was not queued/runnable, also place it back on a runqueue.
*
* This function is atomic against schedule() which would dequeue the task.
*
* It issues a full memory barrier before accessing @p->state, see the comment
* with set_current_state().
*
* Uses p->pi_lock to serialize against concurrent wake-ups.
*
* Relies on p->pi_lock stabilizing:
* - p->sched_class
* - p->cpus_ptr
* - p->sched_task_group
* in order to do migration, see its use of select_task_rq()/set_task_cpu().
*
* Tries really hard to only take one task_rq(p)->lock for performance.
* Takes rq->lock in:
* - ttwu_runnable() -- old rq, unavoidable, see comment there;
* - ttwu_queue() -- new rq, for enqueue of the task;
* - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us.
*
* As a consequence we race really badly with just about everything. See the
* many memory barriers and their comments for details.
*
* Return: %true if @p->state changes (an actual wakeup was done),
* %false otherwise.
*/
static int try_to_wake_up(struct task_struct *p, unsigned int state,
int wake_flags)
{
unsigned long flags;
int cpu, success = 0;
preempt_disable();
if (p == current) {
/*
* We're waking current, this means 'p->on_rq' and 'task_cpu(p)
* == smp_processor_id()'. Together this means we can special
* case the whole 'p->on_rq && ttwu_runnable()' case below
* without taking any locks.
*
* In particular:
* - we rely on Program-Order guarantees for all the ordering,
* - we're serialized against set_special_state() by virtue of
* it disabling IRQs (this allows not taking ->pi_lock).
*/
if (!ttwu_state_match(p, state, &success))
goto out;
trace_sched_waking(p);
ttwu_do_wakeup(p);
goto out;
}
/*
* If we are going to wake up a thread waiting for CONDITION we
* need to ensure that CONDITION=1 done by the caller can not be
* reordered with p->state check below. This pairs with smp_store_mb()
* in set_current_state() that the waiting thread does.
*/
raw_spin_lock_irqsave(&p->pi_lock, flags);
smp_mb__after_spinlock();
if (!ttwu_state_match(p, state, &success))
goto unlock;
trace_sched_waking(p);
/*
* Ensure we load p->on_rq _after_ p->state, otherwise it would
* be possible to, falsely, observe p->on_rq == 0 and get stuck
* in smp_cond_load_acquire() below.
*
* sched_ttwu_pending() try_to_wake_up()
* STORE p->on_rq = 1 LOAD p->state
* UNLOCK rq->lock
*
* __schedule() (switch to task 'p')
* LOCK rq->lock smp_rmb();
* smp_mb__after_spinlock();
* UNLOCK rq->lock
*
* [task p]
* STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq
*
* Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
* __schedule(). See the comment for smp_mb__after_spinlock().
*
* A similar smb_rmb() lives in try_invoke_on_locked_down_task().
*/
smp_rmb();
if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
goto unlock;
#ifdef CONFIG_SMP
/*
* Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be
* possible to, falsely, observe p->on_cpu == 0.
*
* One must be running (->on_cpu == 1) in order to remove oneself
* from the runqueue.
*
* __schedule() (switch to task 'p') try_to_wake_up()
* STORE p->on_cpu = 1 LOAD p->on_rq
* UNLOCK rq->lock
*
* __schedule() (put 'p' to sleep)
* LOCK rq->lock smp_rmb();
* smp_mb__after_spinlock();
* STORE p->on_rq = 0 LOAD p->on_cpu
*
* Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in
* __schedule(). See the comment for smp_mb__after_spinlock().
*
* Form a control-dep-acquire with p->on_rq == 0 above, to ensure
* schedule()'s deactivate_task() has 'happened' and p will no longer
* care about it's own p->state. See the comment in __schedule().
*/
smp_acquire__after_ctrl_dep();
/*
* We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq
* == 0), which means we need to do an enqueue, change p->state to
* TASK_WAKING such that we can unlock p->pi_lock before doing the
* enqueue, such as ttwu_queue_wakelist().
*/
WRITE_ONCE(p->__state, TASK_WAKING);
/*
* If the owning (remote) CPU is still in the middle of schedule() with
* this task as prev, considering queueing p on the remote CPUs wake_list
* which potentially sends an IPI instead of spinning on p->on_cpu to
* let the waker make forward progress. This is safe because IRQs are
* disabled and the IPI will deliver after on_cpu is cleared.
*
* Ensure we load task_cpu(p) after p->on_cpu:
*
* set_task_cpu(p, cpu);
* STORE p->cpu = @cpu
* __schedule() (switch to task 'p')
* LOCK rq->lock
* smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu)
* STORE p->on_cpu = 1 LOAD p->cpu
*
* to ensure we observe the correct CPU on which the task is currently
* scheduling.
*/
if (smp_load_acquire(&p->on_cpu) &&
ttwu_queue_wakelist(p, task_cpu(p), wake_flags))
goto unlock;
/*
* If the owning (remote) CPU is still in the middle of schedule() with
* this task as prev, wait until it's done referencing the task.
*
* Pairs with the smp_store_release() in finish_task().
*
* This ensures that tasks getting woken will be fully ordered against
* their previous state and preserve Program Order.
*/
smp_cond_load_acquire(&p->on_cpu, !VAL);
sched_task_ttwu(p);
cpu = select_task_rq(p);
if (cpu != task_cpu(p)) {
if (p->in_iowait) {
delayacct_blkio_end(p);
atomic_dec(&task_rq(p)->nr_iowait);
}
wake_flags |= WF_MIGRATED;
set_task_cpu(p, cpu);
}
#else
sched_task_ttwu(p);
cpu = task_cpu(p);
#endif /* CONFIG_SMP */
ttwu_queue(p, cpu, wake_flags);
unlock:
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
out:
if (success)
ttwu_stat(p, task_cpu(p), wake_flags);
preempt_enable();
return success;
}
static bool __task_needs_rq_lock(struct task_struct *p)
{
unsigned int state = READ_ONCE(p->__state);
/*
* Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when
* the task is blocked. Make sure to check @state since ttwu() can drop
* locks at the end, see ttwu_queue_wakelist().
*/
if (state == TASK_RUNNING || state == TASK_WAKING)
return true;
/*
* Ensure we load p->on_rq after p->__state, otherwise it would be
* possible to, falsely, observe p->on_rq == 0.
*
* See try_to_wake_up() for a longer comment.
*/
smp_rmb();
if (p->on_rq)
return true;
#ifdef CONFIG_SMP
/*
* Ensure the task has finished __schedule() and will not be referenced
* anymore. Again, see try_to_wake_up() for a longer comment.
*/
smp_rmb();
smp_cond_load_acquire(&p->on_cpu, !VAL);
#endif
return false;
}
/**
* task_call_func - Invoke a function on task in fixed state
* @p: Process for which the function is to be invoked, can be @current.
* @func: Function to invoke.
* @arg: Argument to function.
*
* Fix the task in it's current state by avoiding wakeups and or rq operations
* and call @func(@arg) on it. This function can use ->on_rq and task_curr()
* to work out what the state is, if required. Given that @func can be invoked
* with a runqueue lock held, it had better be quite lightweight.
*
* Returns:
* Whatever @func returns
*/
int task_call_func(struct task_struct *p, task_call_f func, void *arg)
{
struct rq *rq = NULL;
struct rq_flags rf;
int ret;
raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
if (__task_needs_rq_lock(p))
rq = __task_rq_lock(p, &rf);
/*
* At this point the task is pinned; either:
* - blocked and we're holding off wakeups (pi->lock)
* - woken, and we're holding off enqueue (rq->lock)
* - queued, and we're holding off schedule (rq->lock)
* - running, and we're holding off de-schedule (rq->lock)
*
* The called function (@func) can use: task_curr(), p->on_rq and
* p->__state to differentiate between these states.
*/
ret = func(p, arg);
if (rq)
__task_rq_unlock(rq, &rf);
raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
return ret;
}
/**
* cpu_curr_snapshot - Return a snapshot of the currently running task
* @cpu: The CPU on which to snapshot the task.
*
* Returns the task_struct pointer of the task "currently" running on
* the specified CPU. If the same task is running on that CPU throughout,
* the return value will be a pointer to that task's task_struct structure.
* If the CPU did any context switches even vaguely concurrently with the
* execution of this function, the return value will be a pointer to the
* task_struct structure of a randomly chosen task that was running on
* that CPU somewhere around the time that this function was executing.
*
* If the specified CPU was offline, the return value is whatever it
* is, perhaps a pointer to the task_struct structure of that CPU's idle
* task, but there is no guarantee. Callers wishing a useful return
* value must take some action to ensure that the specified CPU remains
* online throughout.
*
* This function executes full memory barriers before and after fetching
* the pointer, which permits the caller to confine this function's fetch
* with respect to the caller's accesses to other shared variables.
*/
struct task_struct *cpu_curr_snapshot(int cpu)
{
struct task_struct *t;
smp_mb(); /* Pairing determined by caller's synchronization design. */
t = rcu_dereference(cpu_curr(cpu));
smp_mb(); /* Pairing determined by caller's synchronization design. */
return t;
}
/**
* wake_up_process - Wake up a specific process
* @p: The process to be woken up.
*
* Attempt to wake up the nominated process and move it to the set of runnable
* processes.
*
* Return: 1 if the process was woken up, 0 if it was already running.
*
* This function executes a full memory barrier before accessing the task state.
*/
int wake_up_process(struct task_struct *p)
{
return try_to_wake_up(p, TASK_NORMAL, 0);
}
EXPORT_SYMBOL(wake_up_process);
int wake_up_state(struct task_struct *p, unsigned int state)
{
return try_to_wake_up(p, state, 0);
}
/*
* Perform scheduler related setup for a newly forked process p.
* p is forked by current.
*
* __sched_fork() is basic setup used by init_idle() too:
*/
static inline void __sched_fork(unsigned long clone_flags, struct task_struct *p)
{
p->on_rq = 0;
p->on_cpu = 0;
p->utime = 0;
p->stime = 0;
p->sched_time = 0;
#ifdef CONFIG_SCHEDSTATS
/* Even if schedstat is disabled, there should not be garbage */
memset(&p->stats, 0, sizeof(p->stats));
#endif
#ifdef CONFIG_PREEMPT_NOTIFIERS
INIT_HLIST_HEAD(&p->preempt_notifiers);
#endif
#ifdef CONFIG_COMPACTION
p->capture_control = NULL;
#endif
#ifdef CONFIG_SMP
p->wake_entry.u_flags = CSD_TYPE_TTWU;
#endif
init_sched_mm_cid(p);
}
/*
* fork()/clone()-time setup:
*/
int sched_fork(unsigned long clone_flags, struct task_struct *p)
{
__sched_fork(clone_flags, p);
/*
* We mark the process as NEW here. This guarantees that
* nobody will actually run it, and a signal or other external
* event cannot wake it up and insert it on the runqueue either.
*/
p->__state = TASK_NEW;
/*
* Make sure we do not leak PI boosting priority to the child.
*/
p->prio = current->normal_prio;
/*
* Revert to default priority/policy on fork if requested.
*/
if (unlikely(p->sched_reset_on_fork)) {
if (task_has_rt_policy(p)) {
p->policy = SCHED_NORMAL;
p->static_prio = NICE_TO_PRIO(0);
p->rt_priority = 0;
} else if (PRIO_TO_NICE(p->static_prio) < 0)
p->static_prio = NICE_TO_PRIO(0);
p->prio = p->normal_prio = p->static_prio;
/*
* We don't need the reset flag anymore after the fork. It has
* fulfilled its duty:
*/
p->sched_reset_on_fork = 0;
}
#ifdef CONFIG_SCHED_INFO
if (unlikely(sched_info_on()))
memset(&p->sched_info, 0, sizeof(p->sched_info));
#endif
init_task_preempt_count(p);
return 0;
}
void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs)
{
unsigned long flags;
struct rq *rq;
/*
* Because we're not yet on the pid-hash, p->pi_lock isn't strictly
* required yet, but lockdep gets upset if rules are violated.
*/
raw_spin_lock_irqsave(&p->pi_lock, flags);
/*
* Share the timeslice between parent and child, thus the
* total amount of pending timeslices in the system doesn't change,
* resulting in more scheduling fairness.
*/
rq = this_rq();
raw_spin_lock(&rq->lock);
rq->curr->time_slice /= 2;
p->time_slice = rq->curr->time_slice;
#ifdef CONFIG_SCHED_HRTICK
hrtick_start(rq, rq->curr->time_slice);
#endif
if (p->time_slice < RESCHED_NS) {
p->time_slice = sched_timeslice_ns;
resched_curr(rq);
}
sched_task_fork(p, rq);
raw_spin_unlock(&rq->lock);
rseq_migrate(p);
/*
* We're setting the CPU for the first time, we don't migrate,
* so use __set_task_cpu().
*/
__set_task_cpu(p, smp_processor_id());
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}
void sched_post_fork(struct task_struct *p)
{
}
#ifdef CONFIG_SCHEDSTATS
DEFINE_STATIC_KEY_FALSE(sched_schedstats);
static void set_schedstats(bool enabled)
{
if (enabled)
static_branch_enable(&sched_schedstats);
else
static_branch_disable(&sched_schedstats);
}
void force_schedstat_enabled(void)
{
if (!schedstat_enabled()) {
pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n");
static_branch_enable(&sched_schedstats);
}
}
static int __init setup_schedstats(char *str)
{
int ret = 0;
if (!str)
goto out;
if (!strcmp(str, "enable")) {
set_schedstats(true);
ret = 1;
} else if (!strcmp(str, "disable")) {
set_schedstats(false);
ret = 1;
}
out:
if (!ret)
pr_warn("Unable to parse schedstats=\n");
return ret;
}
__setup("schedstats=", setup_schedstats);
#ifdef CONFIG_PROC_SYSCTL
static int sysctl_schedstats(struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos)
{
struct ctl_table t;
int err;
int state = static_branch_likely(&sched_schedstats);
if (write && !capable(CAP_SYS_ADMIN))
return -EPERM;
t = *table;
t.data = &state;
err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
if (err < 0)
return err;
if (write)
set_schedstats(state);
return err;
}
static struct ctl_table sched_core_sysctls[] = {
{
.procname = "sched_schedstats",
.data = NULL,
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sysctl_schedstats,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_ONE,
},
{}
};
static int __init sched_core_sysctl_init(void)
{
register_sysctl_init("kernel", sched_core_sysctls);
return 0;
}
late_initcall(sched_core_sysctl_init);
#endif /* CONFIG_PROC_SYSCTL */
#endif /* CONFIG_SCHEDSTATS */
/*
* wake_up_new_task - wake up a newly created task for the first time.
*
* This function will do some initial scheduler statistics housekeeping
* that must be done for every newly created context, then puts the task
* on the runqueue and wakes it.
*/
void wake_up_new_task(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
raw_spin_lock_irqsave(&p->pi_lock, flags);
WRITE_ONCE(p->__state, TASK_RUNNING);
rq = cpu_rq(select_task_rq(p));
#ifdef CONFIG_SMP
rseq_migrate(p);
/*
* Fork balancing, do it here and not earlier because:
* - cpus_ptr can change in the fork path
* - any previously selected CPU might disappear through hotplug
*
* Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq,
* as we're not fully set-up yet.
*/
__set_task_cpu(p, cpu_of(rq));
#endif
raw_spin_lock(&rq->lock);
update_rq_clock(rq);
activate_task(p, rq);
trace_sched_wakeup_new(p);
check_preempt_curr(rq);
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}
#ifdef CONFIG_PREEMPT_NOTIFIERS
static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key);
void preempt_notifier_inc(void)
{
static_branch_inc(&preempt_notifier_key);
}
EXPORT_SYMBOL_GPL(preempt_notifier_inc);
void preempt_notifier_dec(void)
{
static_branch_dec(&preempt_notifier_key);
}
EXPORT_SYMBOL_GPL(preempt_notifier_dec);
/**
* preempt_notifier_register - tell me when current is being preempted & rescheduled
* @notifier: notifier struct to register
*/
void preempt_notifier_register(struct preempt_notifier *notifier)
{
if (!static_branch_unlikely(&preempt_notifier_key))
WARN(1, "registering preempt_notifier while notifiers disabled\n");
hlist_add_head(&notifier->link, &current->preempt_notifiers);
}
EXPORT_SYMBOL_GPL(preempt_notifier_register);
/**
* preempt_notifier_unregister - no longer interested in preemption notifications
* @notifier: notifier struct to unregister
*
* This is *not* safe to call from within a preemption notifier.
*/
void preempt_notifier_unregister(struct preempt_notifier *notifier)
{
hlist_del(&notifier->link);
}
EXPORT_SYMBOL_GPL(preempt_notifier_unregister);
static void __fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
struct preempt_notifier *notifier;
hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
notifier->ops->sched_in(notifier, raw_smp_processor_id());
}
static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
if (static_branch_unlikely(&preempt_notifier_key))
__fire_sched_in_preempt_notifiers(curr);
}
static void
__fire_sched_out_preempt_notifiers(struct task_struct *curr,
struct task_struct *next)
{
struct preempt_notifier *notifier;
hlist_for_each_entry(notifier, &curr->preempt_notifiers, link)
notifier->ops->sched_out(notifier, next);
}
static __always_inline void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
struct task_struct *next)
{
if (static_branch_unlikely(&preempt_notifier_key))
__fire_sched_out_preempt_notifiers(curr, next);
}
#else /* !CONFIG_PREEMPT_NOTIFIERS */
static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr)
{
}
static inline void
fire_sched_out_preempt_notifiers(struct task_struct *curr,
struct task_struct *next)
{
}
#endif /* CONFIG_PREEMPT_NOTIFIERS */
static inline void prepare_task(struct task_struct *next)
{
/*
* Claim the task as running, we do this before switching to it
* such that any running task will have this set.
*
* See the smp_load_acquire(&p->on_cpu) case in ttwu() and
* its ordering comment.
*/
WRITE_ONCE(next->on_cpu, 1);
}
static inline void finish_task(struct task_struct *prev)
{
#ifdef CONFIG_SMP
/*
* This must be the very last reference to @prev from this CPU. After
* p->on_cpu is cleared, the task can be moved to a different CPU. We
* must ensure this doesn't happen until the switch is completely
* finished.
*
* In particular, the load of prev->state in finish_task_switch() must
* happen before this.
*
* Pairs with the smp_cond_load_acquire() in try_to_wake_up().
*/
smp_store_release(&prev->on_cpu, 0);
#else
prev->on_cpu = 0;
#endif
}
#ifdef CONFIG_SMP
static void do_balance_callbacks(struct rq *rq, struct balance_callback *head)
{
void (*func)(struct rq *rq);
struct balance_callback *next;
lockdep_assert_held(&rq->lock);
while (head) {
func = (void (*)(struct rq *))head->func;
next = head->next;
head->next = NULL;
head = next;
func(rq);
}
}
static void balance_push(struct rq *rq);
/*
* balance_push_callback is a right abuse of the callback interface and plays
* by significantly different rules.
*
* Where the normal balance_callback's purpose is to be ran in the same context
* that queued it (only later, when it's safe to drop rq->lock again),
* balance_push_callback is specifically targeted at __schedule().
*
* This abuse is tolerated because it places all the unlikely/odd cases behind
* a single test, namely: rq->balance_callback == NULL.
*/
struct balance_callback balance_push_callback = {
.next = NULL,
.func = balance_push,
};
static inline struct balance_callback *
__splice_balance_callbacks(struct rq *rq, bool split)
{
struct balance_callback *head = rq->balance_callback;
if (likely(!head))
return NULL;
lockdep_assert_rq_held(rq);
/*
* Must not take balance_push_callback off the list when
* splice_balance_callbacks() and balance_callbacks() are not
* in the same rq->lock section.
*
* In that case it would be possible for __schedule() to interleave
* and observe the list empty.
*/
if (split && head == &balance_push_callback)
head = NULL;
else
rq->balance_callback = NULL;
return head;
}
static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
{
return __splice_balance_callbacks(rq, true);
}
static void __balance_callbacks(struct rq *rq)
{
do_balance_callbacks(rq, __splice_balance_callbacks(rq, false));
}
static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
{
unsigned long flags;
if (unlikely(head)) {
raw_spin_lock_irqsave(&rq->lock, flags);
do_balance_callbacks(rq, head);
raw_spin_unlock_irqrestore(&rq->lock, flags);
}
}
#else
static inline void __balance_callbacks(struct rq *rq)
{
}
static inline struct balance_callback *splice_balance_callbacks(struct rq *rq)
{
return NULL;
}
static inline void balance_callbacks(struct rq *rq, struct balance_callback *head)
{
}
#endif
static inline void
prepare_lock_switch(struct rq *rq, struct task_struct *next)
{
/*
* Since the runqueue lock will be released by the next
* task (which is an invalid locking op but in the case
* of the scheduler it's an obvious special-case), so we
* do an early lockdep release here:
*/
spin_release(&rq->lock.dep_map, _THIS_IP_);
#ifdef CONFIG_DEBUG_SPINLOCK
/* this is a valid case when another task releases the spinlock */
rq->lock.owner = next;
#endif
}
static inline void finish_lock_switch(struct rq *rq)
{
/*
* If we are tracking spinlock dependencies then we have to
* fix up the runqueue lock - which gets 'carried over' from
* prev into current:
*/
spin_acquire(&rq->lock.dep_map, 0, 0, _THIS_IP_);
__balance_callbacks(rq);
raw_spin_unlock_irq(&rq->lock);
}
/*
* NOP if the arch has not defined these:
*/
#ifndef prepare_arch_switch
# define prepare_arch_switch(next) do { } while (0)
#endif
#ifndef finish_arch_post_lock_switch
# define finish_arch_post_lock_switch() do { } while (0)
#endif
static inline void kmap_local_sched_out(void)
{
#ifdef CONFIG_KMAP_LOCAL
if (unlikely(current->kmap_ctrl.idx))
__kmap_local_sched_out();
#endif
}
static inline void kmap_local_sched_in(void)
{
#ifdef CONFIG_KMAP_LOCAL
if (unlikely(current->kmap_ctrl.idx))
__kmap_local_sched_in();
#endif
}
/**
* prepare_task_switch - prepare to switch tasks
* @rq: the runqueue preparing to switch
* @next: the task we are going to switch to.
*
* This is called with the rq lock held and interrupts off. It must
* be paired with a subsequent finish_task_switch after the context
* switch.
*
* prepare_task_switch sets up locking and calls architecture specific
* hooks.
*/
static inline void
prepare_task_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
kcov_prepare_switch(prev);
sched_info_switch(rq, prev, next);
perf_event_task_sched_out(prev, next);
rseq_preempt(prev);
fire_sched_out_preempt_notifiers(prev, next);
kmap_local_sched_out();
prepare_task(next);
prepare_arch_switch(next);
}
/**
* finish_task_switch - clean up after a task-switch
* @rq: runqueue associated with task-switch
* @prev: the thread we just switched away from.
*
* finish_task_switch must be called after the context switch, paired
* with a prepare_task_switch call before the context switch.
* finish_task_switch will reconcile locking set up by prepare_task_switch,
* and do any other architecture-specific cleanup actions.
*
* Note that we may have delayed dropping an mm in context_switch(). If
* so, we finish that here outside of the runqueue lock. (Doing it
* with the lock held can cause deadlocks; see schedule() for
* details.)
*
* The context switch have flipped the stack from under us and restored the
* local variables which were saved when this task called schedule() in the
* past. prev == current is still correct but we need to recalculate this_rq
* because prev may have moved to another CPU.
*/
static struct rq *finish_task_switch(struct task_struct *prev)
__releases(rq->lock)
{
struct rq *rq = this_rq();
struct mm_struct *mm = rq->prev_mm;
unsigned int prev_state;
/*
* The previous task will have left us with a preempt_count of 2
* because it left us after:
*
* schedule()
* preempt_disable(); // 1
* __schedule()
* raw_spin_lock_irq(&rq->lock) // 2
*
* Also, see FORK_PREEMPT_COUNT.
*/
if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET,
"corrupted preempt_count: %s/%d/0x%x\n",
current->comm, current->pid, preempt_count()))
preempt_count_set(FORK_PREEMPT_COUNT);
rq->prev_mm = NULL;
/*
* A task struct has one reference for the use as "current".
* If a task dies, then it sets TASK_DEAD in tsk->state and calls
* schedule one last time. The schedule call will never return, and
* the scheduled task must drop that reference.
*
* We must observe prev->state before clearing prev->on_cpu (in
* finish_task), otherwise a concurrent wakeup can get prev
* running on another CPU and we could rave with its RUNNING -> DEAD
* transition, resulting in a double drop.
*/
prev_state = READ_ONCE(prev->__state);
vtime_task_switch(prev);
perf_event_task_sched_in(prev, current);
finish_task(prev);
tick_nohz_task_switch();
finish_lock_switch(rq);
finish_arch_post_lock_switch();
kcov_finish_switch(current);
/*
* kmap_local_sched_out() is invoked with rq::lock held and
* interrupts disabled. There is no requirement for that, but the
* sched out code does not have an interrupt enabled section.
* Restoring the maps on sched in does not require interrupts being
* disabled either.
*/
kmap_local_sched_in();
fire_sched_in_preempt_notifiers(current);
/*
* When switching through a kernel thread, the loop in
* membarrier_{private,global}_expedited() may have observed that
* kernel thread and not issued an IPI. It is therefore possible to
* schedule between user->kernel->user threads without passing though
* switch_mm(). Membarrier requires a barrier after storing to
* rq->curr, before returning to userspace, so provide them here:
*
* - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly
* provided by mmdrop(),
* - a sync_core for SYNC_CORE.
*/
if (mm) {
membarrier_mm_sync_core_before_usermode(mm);
mmdrop_sched(mm);
}
if (unlikely(prev_state == TASK_DEAD)) {
/* Task is done with its stack. */
put_task_stack(prev);
put_task_struct_rcu_user(prev);
}
return rq;
}
/**
* schedule_tail - first thing a freshly forked thread must call.
* @prev: the thread we just switched away from.
*/
asmlinkage __visible void schedule_tail(struct task_struct *prev)
__releases(rq->lock)
{
/*
* New tasks start with FORK_PREEMPT_COUNT, see there and
* finish_task_switch() for details.
*
* finish_task_switch() will drop rq->lock() and lower preempt_count
* and the preempt_enable() will end up enabling preemption (on
* PREEMPT_COUNT kernels).
*/
finish_task_switch(prev);
preempt_enable();
if (current->set_child_tid)
put_user(task_pid_vnr(current), current->set_child_tid);
calculate_sigpending();
}
/*
* context_switch - switch to the new MM and the new thread's register state.
*/
static __always_inline struct rq *
context_switch(struct rq *rq, struct task_struct *prev,
struct task_struct *next)
{
prepare_task_switch(rq, prev, next);
/*
* For paravirt, this is coupled with an exit in switch_to to
* combine the page table reload and the switch backend into
* one hypercall.
*/
arch_start_context_switch(prev);
/*
* kernel -> kernel lazy + transfer active
* user -> kernel lazy + mmgrab() active
*
* kernel -> user switch + mmdrop() active
* user -> user switch
*
* switch_mm_cid() needs to be updated if the barriers provided
* by context_switch() are modified.
*/
if (!next->mm) { // to kernel
enter_lazy_tlb(prev->active_mm, next);
next->active_mm = prev->active_mm;
if (prev->mm) // from user
mmgrab(prev->active_mm);
else
prev->active_mm = NULL;
} else { // to user
membarrier_switch_mm(rq, prev->active_mm, next->mm);
/*
* sys_membarrier() requires an smp_mb() between setting
* rq->curr / membarrier_switch_mm() and returning to userspace.
*
* The below provides this either through switch_mm(), or in
* case 'prev->active_mm == next->mm' through
* finish_task_switch()'s mmdrop().
*/
switch_mm_irqs_off(prev->active_mm, next->mm, next);
lru_gen_use_mm(next->mm);
if (!prev->mm) { // from kernel
/* will mmdrop() in finish_task_switch(). */
rq->prev_mm = prev->active_mm;
prev->active_mm = NULL;
}
}
/* switch_mm_cid() requires the memory barriers above. */
switch_mm_cid(rq, prev, next);
prepare_lock_switch(rq, next);
/* Here we just switch the register state and the stack. */
switch_to(prev, next, prev);
barrier();
return finish_task_switch(prev);
}
/*
* nr_running, nr_uninterruptible and nr_context_switches:
*
* externally visible scheduler statistics: current number of runnable
* threads, total number of context switches performed since bootup.
*/
unsigned int nr_running(void)
{
unsigned int i, sum = 0;
for_each_online_cpu(i)
sum += cpu_rq(i)->nr_running;
return sum;
}
/*
* Check if only the current task is running on the CPU.
*
* Caution: this function does not check that the caller has disabled
* preemption, thus the result might have a time-of-check-to-time-of-use
* race. The caller is responsible to use it correctly, for example:
*
* - from a non-preemptible section (of course)
*
* - from a thread that is bound to a single CPU
*
* - in a loop with very short iterations (e.g. a polling loop)
*/
bool single_task_running(void)
{
return raw_rq()->nr_running == 1;
}
EXPORT_SYMBOL(single_task_running);
unsigned long long nr_context_switches_cpu(int cpu)
{
return cpu_rq(cpu)->nr_switches;
}
unsigned long long nr_context_switches(void)
{
int i;
unsigned long long sum = 0;
for_each_possible_cpu(i)
sum += cpu_rq(i)->nr_switches;
return sum;
}
/*
* Consumers of these two interfaces, like for example the cpuidle menu
* governor, are using nonsensical data. Preferring shallow idle state selection
* for a CPU that has IO-wait which might not even end up running the task when
* it does become runnable.
*/
unsigned int nr_iowait_cpu(int cpu)
{
return atomic_read(&cpu_rq(cpu)->nr_iowait);
}
/*
* IO-wait accounting, and how it's mostly bollocks (on SMP).
*
* The idea behind IO-wait account is to account the idle time that we could
* have spend running if it were not for IO. That is, if we were to improve the
* storage performance, we'd have a proportional reduction in IO-wait time.
*
* This all works nicely on UP, where, when a task blocks on IO, we account
* idle time as IO-wait, because if the storage were faster, it could've been
* running and we'd not be idle.
*
* This has been extended to SMP, by doing the same for each CPU. This however
* is broken.
*
* Imagine for instance the case where two tasks block on one CPU, only the one
* CPU will have IO-wait accounted, while the other has regular idle. Even
* though, if the storage were faster, both could've ran at the same time,
* utilising both CPUs.
*
* This means, that when looking globally, the current IO-wait accounting on
* SMP is a lower bound, by reason of under accounting.
*
* Worse, since the numbers are provided per CPU, they are sometimes
* interpreted per CPU, and that is nonsensical. A blocked task isn't strictly
* associated with any one particular CPU, it can wake to another CPU than it
* blocked on. This means the per CPU IO-wait number is meaningless.
*
* Task CPU affinities can make all that even more 'interesting'.
*/
unsigned int nr_iowait(void)
{
unsigned int i, sum = 0;
for_each_possible_cpu(i)
sum += nr_iowait_cpu(i);
return sum;
}
#ifdef CONFIG_SMP
/*
* sched_exec - execve() is a valuable balancing opportunity, because at
* this point the task has the smallest effective memory and cache
* footprint.
*/
void sched_exec(void)
{
}
#endif
DEFINE_PER_CPU(struct kernel_stat, kstat);
DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat);
EXPORT_PER_CPU_SYMBOL(kstat);
EXPORT_PER_CPU_SYMBOL(kernel_cpustat);
static inline void update_curr(struct rq *rq, struct task_struct *p)
{
s64 ns = rq->clock_task - p->last_ran;
p->sched_time += ns;
cgroup_account_cputime(p, ns);
account_group_exec_runtime(p, ns);
p->time_slice -= ns;
p->last_ran = rq->clock_task;
}
/*
* Return accounted runtime for the task.
* Return separately the current's pending runtime that have not been
* accounted yet.
*/
unsigned long long task_sched_runtime(struct task_struct *p)
{
unsigned long flags;
struct rq *rq;
raw_spinlock_t *lock;
u64 ns;
#if defined(CONFIG_64BIT) && defined(CONFIG_SMP)
/*
* 64-bit doesn't need locks to atomically read a 64-bit value.
* So we have a optimization chance when the task's delta_exec is 0.
* Reading ->on_cpu is racy, but this is ok.
*
* If we race with it leaving CPU, we'll take a lock. So we're correct.
* If we race with it entering CPU, unaccounted time is 0. This is
* indistinguishable from the read occurring a few cycles earlier.
* If we see ->on_cpu without ->on_rq, the task is leaving, and has
* been accounted, so we're correct here as well.
*/
if (!p->on_cpu || !task_on_rq_queued(p))
return tsk_seruntime(p);
#endif
rq = task_access_lock_irqsave(p, &lock, &flags);
/*
* Must be ->curr _and_ ->on_rq. If dequeued, we would
* project cycles that may never be accounted to this
* thread, breaking clock_gettime().
*/
if (p == rq->curr && task_on_rq_queued(p)) {
update_rq_clock(rq);
update_curr(rq, p);
}
ns = tsk_seruntime(p);
task_access_unlock_irqrestore(p, lock, &flags);
return ns;
}
/* This manages tasks that have run out of timeslice during a scheduler_tick */
static inline void scheduler_task_tick(struct rq *rq)
{
struct task_struct *p = rq->curr;
if (is_idle_task(p))
return;
update_curr(rq, p);
cpufreq_update_util(rq, 0);
/*
* Tasks have less than RESCHED_NS of time slice left they will be
* rescheduled.
*/
if (p->time_slice >= RESCHED_NS)
return;
set_tsk_need_resched(p);
set_preempt_need_resched();
}
#ifdef CONFIG_SCHED_DEBUG
static u64 cpu_resched_latency(struct rq *rq)
{
int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms);
u64 resched_latency, now = rq_clock(rq);
static bool warned_once;
if (sysctl_resched_latency_warn_once && warned_once)
return 0;
if (!need_resched() || !latency_warn_ms)
return 0;
if (system_state == SYSTEM_BOOTING)
return 0;
if (!rq->last_seen_need_resched_ns) {
rq->last_seen_need_resched_ns = now;
rq->ticks_without_resched = 0;
return 0;
}
rq->ticks_without_resched++;
resched_latency = now - rq->last_seen_need_resched_ns;
if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC)
return 0;
warned_once = true;
return resched_latency;
}
static int __init setup_resched_latency_warn_ms(char *str)
{
long val;
if ((kstrtol(str, 0, &val))) {
pr_warn("Unable to set resched_latency_warn_ms\n");
return 1;
}
sysctl_resched_latency_warn_ms = val;
return 1;
}
__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms);
#else
static inline u64 cpu_resched_latency(struct rq *rq) { return 0; }
#endif /* CONFIG_SCHED_DEBUG */
/*
* This function gets called by the timer code, with HZ frequency.
* We call it with interrupts disabled.
*/
void scheduler_tick(void)
{
int cpu __maybe_unused = smp_processor_id();
struct rq *rq = cpu_rq(cpu);
struct task_struct *curr = rq->curr;
u64 resched_latency;
if (housekeeping_cpu(cpu, HK_TYPE_TICK))
arch_scale_freq_tick();
sched_clock_tick();
raw_spin_lock(&rq->lock);
update_rq_clock(rq);
scheduler_task_tick(rq);
if (sched_feat(LATENCY_WARN))
resched_latency = cpu_resched_latency(rq);
calc_global_load_tick(rq);
task_tick_mm_cid(rq, rq->curr);
raw_spin_unlock(&rq->lock);
if (sched_feat(LATENCY_WARN) && resched_latency)
resched_latency_warn(cpu, resched_latency);
perf_event_task_tick();
if (curr->flags & PF_WQ_WORKER)
wq_worker_tick(curr);
}
#ifdef CONFIG_SCHED_SMT
static inline int sg_balance_cpu_stop(void *data)
{
struct rq *rq = this_rq();
struct task_struct *p = data;
cpumask_t tmp;
unsigned long flags;
local_irq_save(flags);
raw_spin_lock(&p->pi_lock);
raw_spin_lock(&rq->lock);
rq->active_balance = 0;
/* _something_ may have changed the task, double check again */
if (task_on_rq_queued(p) && task_rq(p) == rq &&
cpumask_and(&tmp, p->cpus_ptr, &sched_sg_idle_mask) &&
!is_migration_disabled(p)) {
int cpu = cpu_of(rq);
int dcpu = __best_mask_cpu(&tmp, per_cpu(sched_cpu_llc_mask, cpu));
rq = move_queued_task(rq, p, dcpu);
}
raw_spin_unlock(&rq->lock);
raw_spin_unlock(&p->pi_lock);
local_irq_restore(flags);
return 0;
}
/* sg_balance_trigger - trigger slibing group balance for @cpu */
static inline int sg_balance_trigger(const int cpu)
{
struct rq *rq= cpu_rq(cpu);
unsigned long flags;
struct task_struct *curr;
int res;
if (!raw_spin_trylock_irqsave(&rq->lock, flags))
return 0;
curr = rq->curr;
res = (!is_idle_task(curr)) && (1 == rq->nr_running) &&\
cpumask_intersects(curr->cpus_ptr, &sched_sg_idle_mask) &&\
!is_migration_disabled(curr) && (!rq->active_balance);
if (res)
rq->active_balance = 1;
raw_spin_unlock_irqrestore(&rq->lock, flags);
if (res)
stop_one_cpu_nowait(cpu, sg_balance_cpu_stop, curr,
&rq->active_balance_work);
return res;
}
/*
* sg_balance - slibing group balance check for run queue @rq
*/
static inline void sg_balance(struct rq *rq, int cpu)
{
cpumask_t chk;
/* exit when cpu is offline */
if (unlikely(!rq->online))
return;
/*
* Only cpu in slibing idle group will do the checking and then
* find potential cpus which can migrate the current running task
*/
if (cpumask_test_cpu(cpu, &sched_sg_idle_mask) &&
cpumask_andnot(&chk, cpu_online_mask, sched_idle_mask) &&
cpumask_andnot(&chk, &chk, &sched_rq_pending_mask)) {
int i;
for_each_cpu_wrap(i, &chk, cpu) {
if (!cpumask_intersects(cpu_smt_mask(i), sched_idle_mask) &&\
sg_balance_trigger(i))
return;
}
}
}
#endif /* CONFIG_SCHED_SMT */
#ifdef CONFIG_NO_HZ_FULL
struct tick_work {
int cpu;
atomic_t state;
struct delayed_work work;
};
/* Values for ->state, see diagram below. */
#define TICK_SCHED_REMOTE_OFFLINE 0
#define TICK_SCHED_REMOTE_OFFLINING 1
#define TICK_SCHED_REMOTE_RUNNING 2
/*
* State diagram for ->state:
*
*
* TICK_SCHED_REMOTE_OFFLINE
* | ^
* | |
* | | sched_tick_remote()
* | |
* | |
* +--TICK_SCHED_REMOTE_OFFLINING
* | ^
* | |
* sched_tick_start() | | sched_tick_stop()
* | |
* V |
* TICK_SCHED_REMOTE_RUNNING
*
*
* Other transitions get WARN_ON_ONCE(), except that sched_tick_remote()
* and sched_tick_start() are happy to leave the state in RUNNING.
*/
static struct tick_work __percpu *tick_work_cpu;
static void sched_tick_remote(struct work_struct *work)
{
struct delayed_work *dwork = to_delayed_work(work);
struct tick_work *twork = container_of(dwork, struct tick_work, work);
int cpu = twork->cpu;
struct rq *rq = cpu_rq(cpu);
struct task_struct *curr;
unsigned long flags;
u64 delta;
int os;
/*
* Handle the tick only if it appears the remote CPU is running in full
* dynticks mode. The check is racy by nature, but missing a tick or
* having one too much is no big deal because the scheduler tick updates
* statistics and checks timeslices in a time-independent way, regardless
* of when exactly it is running.
*/
if (!tick_nohz_tick_stopped_cpu(cpu))
goto out_requeue;
raw_spin_lock_irqsave(&rq->lock, flags);
curr = rq->curr;
if (cpu_is_offline(cpu))
goto out_unlock;
update_rq_clock(rq);
if (!is_idle_task(curr)) {
/*
* Make sure the next tick runs within a reasonable
* amount of time.
*/
delta = rq_clock_task(rq) - curr->last_ran;
WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3);
}
scheduler_task_tick(rq);
calc_load_nohz_remote(rq);
out_unlock:
raw_spin_unlock_irqrestore(&rq->lock, flags);
out_requeue:
/*
* Run the remote tick once per second (1Hz). This arbitrary
* frequency is large enough to avoid overload but short enough
* to keep scheduler internal stats reasonably up to date. But
* first update state to reflect hotplug activity if required.
*/
os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING);
WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE);
if (os == TICK_SCHED_REMOTE_RUNNING)
queue_delayed_work(system_unbound_wq, dwork, HZ);
}
static void sched_tick_start(int cpu)
{
int os;
struct tick_work *twork;
if (housekeeping_cpu(cpu, HK_TYPE_TICK))
return;
WARN_ON_ONCE(!tick_work_cpu);
twork = per_cpu_ptr(tick_work_cpu, cpu);
os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING);
WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING);
if (os == TICK_SCHED_REMOTE_OFFLINE) {
twork->cpu = cpu;
INIT_DELAYED_WORK(&twork->work, sched_tick_remote);
queue_delayed_work(system_unbound_wq, &twork->work, HZ);
}
}
#ifdef CONFIG_HOTPLUG_CPU
static void sched_tick_stop(int cpu)
{
struct tick_work *twork;
int os;
if (housekeeping_cpu(cpu, HK_TYPE_TICK))
return;
WARN_ON_ONCE(!tick_work_cpu);
twork = per_cpu_ptr(tick_work_cpu, cpu);
/* There cannot be competing actions, but don't rely on stop-machine. */
os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING);
WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING);
/* Don't cancel, as this would mess up the state machine. */
}
#endif /* CONFIG_HOTPLUG_CPU */
int __init sched_tick_offload_init(void)
{
tick_work_cpu = alloc_percpu(struct tick_work);
BUG_ON(!tick_work_cpu);
return 0;
}
#else /* !CONFIG_NO_HZ_FULL */
static inline void sched_tick_start(int cpu) { }
static inline void sched_tick_stop(int cpu) { }
#endif
#if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \
defined(CONFIG_PREEMPT_TRACER))
/*
* If the value passed in is equal to the current preempt count
* then we just disabled preemption. Start timing the latency.
*/
static inline void preempt_latency_start(int val)
{
if (preempt_count() == val) {
unsigned long ip = get_lock_parent_ip();
#ifdef CONFIG_DEBUG_PREEMPT
current->preempt_disable_ip = ip;
#endif
trace_preempt_off(CALLER_ADDR0, ip);
}
}
void preempt_count_add(int val)
{
#ifdef CONFIG_DEBUG_PREEMPT
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0)))
return;
#endif
__preempt_count_add(val);
#ifdef CONFIG_DEBUG_PREEMPT
/*
* Spinlock count overflowing soon?
*/
DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >=
PREEMPT_MASK - 10);
#endif
preempt_latency_start(val);
}
EXPORT_SYMBOL(preempt_count_add);
NOKPROBE_SYMBOL(preempt_count_add);
/*
* If the value passed in equals to the current preempt count
* then we just enabled preemption. Stop timing the latency.
*/
static inline void preempt_latency_stop(int val)
{
if (preempt_count() == val)
trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip());
}
void preempt_count_sub(int val)
{
#ifdef CONFIG_DEBUG_PREEMPT
/*
* Underflow?
*/
if (DEBUG_LOCKS_WARN_ON(val > preempt_count()))
return;
/*
* Is the spinlock portion underflowing?
*/
if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) &&
!(preempt_count() & PREEMPT_MASK)))
return;
#endif
preempt_latency_stop(val);
__preempt_count_sub(val);
}
EXPORT_SYMBOL(preempt_count_sub);
NOKPROBE_SYMBOL(preempt_count_sub);
#else
static inline void preempt_latency_start(int val) { }
static inline void preempt_latency_stop(int val) { }
#endif
static inline unsigned long get_preempt_disable_ip(struct task_struct *p)
{
#ifdef CONFIG_DEBUG_PREEMPT
return p->preempt_disable_ip;
#else
return 0;
#endif
}
/*
* Print scheduling while atomic bug:
*/
static noinline void __schedule_bug(struct task_struct *prev)
{
/* Save this before calling printk(), since that will clobber it */
unsigned long preempt_disable_ip = get_preempt_disable_ip(current);
if (oops_in_progress)
return;
printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n",
prev->comm, prev->pid, preempt_count());
debug_show_held_locks(prev);
print_modules();
if (irqs_disabled())
print_irqtrace_events(prev);
if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)
&& in_atomic_preempt_off()) {
pr_err("Preemption disabled at:");
print_ip_sym(KERN_ERR, preempt_disable_ip);
}
check_panic_on_warn("scheduling while atomic");
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
/*
* Various schedule()-time debugging checks and statistics:
*/
static inline void schedule_debug(struct task_struct *prev, bool preempt)
{
#ifdef CONFIG_SCHED_STACK_END_CHECK
if (task_stack_end_corrupted(prev))
panic("corrupted stack end detected inside scheduler\n");
if (task_scs_end_corrupted(prev))
panic("corrupted shadow stack detected inside scheduler\n");
#endif
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) {
printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n",
prev->comm, prev->pid, prev->non_block_count);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
#endif
if (unlikely(in_atomic_preempt_off())) {
__schedule_bug(prev);
preempt_count_set(PREEMPT_DISABLED);
}
rcu_sleep_check();
SCHED_WARN_ON(ct_state() == CONTEXT_USER);
profile_hit(SCHED_PROFILING, __builtin_return_address(0));
schedstat_inc(this_rq()->sched_count);
}
#ifdef ALT_SCHED_DEBUG
void alt_sched_debug(void)
{
printk(KERN_INFO "sched: pending: 0x%04lx, idle: 0x%04lx, sg_idle: 0x%04lx\n",
sched_rq_pending_mask.bits[0],
sched_idle_mask->bits[0],
sched_sg_idle_mask.bits[0]);
}
#else
inline void alt_sched_debug(void) {}
#endif
#ifdef CONFIG_SMP
#ifdef CONFIG_PREEMPT_RT
#define SCHED_NR_MIGRATE_BREAK 8
#else
#define SCHED_NR_MIGRATE_BREAK 32
#endif
const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK;
/*
* Migrate pending tasks in @rq to @dest_cpu
*/
static inline int
migrate_pending_tasks(struct rq *rq, struct rq *dest_rq, const int dest_cpu)
{
struct task_struct *p, *skip = rq->curr;
int nr_migrated = 0;
int nr_tries = min(rq->nr_running / 2, sysctl_sched_nr_migrate);
/* WA to check rq->curr is still on rq */
if (!task_on_rq_queued(skip))
return 0;
while (skip != rq->idle && nr_tries &&
(p = sched_rq_next_task(skip, rq)) != rq->idle) {
skip = sched_rq_next_task(p, rq);
if (cpumask_test_cpu(dest_cpu, p->cpus_ptr)) {
__SCHED_DEQUEUE_TASK(p, rq, 0, );
set_task_cpu(p, dest_cpu);
sched_task_sanity_check(p, dest_rq);
sched_mm_cid_migrate_to(dest_rq, p, cpu_of(rq));
__SCHED_ENQUEUE_TASK(p, dest_rq, 0);
nr_migrated++;
}
nr_tries--;
}
return nr_migrated;
}
static inline int take_other_rq_tasks(struct rq *rq, int cpu)
{
struct cpumask *topo_mask, *end_mask;
if (unlikely(!rq->online))
return 0;
if (cpumask_empty(&sched_rq_pending_mask))
return 0;
topo_mask = per_cpu(sched_cpu_topo_masks, cpu) + 1;
end_mask = per_cpu(sched_cpu_topo_end_mask, cpu);
do {
int i;
for_each_cpu_and(i, &sched_rq_pending_mask, topo_mask) {
int nr_migrated;
struct rq *src_rq;
src_rq = cpu_rq(i);
if (!do_raw_spin_trylock(&src_rq->lock))
continue;
spin_acquire(&src_rq->lock.dep_map,
SINGLE_DEPTH_NESTING, 1, _RET_IP_);
if ((nr_migrated = migrate_pending_tasks(src_rq, rq, cpu))) {
src_rq->nr_running -= nr_migrated;
if (src_rq->nr_running < 2)
cpumask_clear_cpu(i, &sched_rq_pending_mask);
spin_release(&src_rq->lock.dep_map, _RET_IP_);
do_raw_spin_unlock(&src_rq->lock);
rq->nr_running += nr_migrated;
if (rq->nr_running > 1)
cpumask_set_cpu(cpu, &sched_rq_pending_mask);
update_sched_preempt_mask(rq);
cpufreq_update_util(rq, 0);
return 1;
}
spin_release(&src_rq->lock.dep_map, _RET_IP_);
do_raw_spin_unlock(&src_rq->lock);
}
} while (++topo_mask < end_mask);
return 0;
}
#endif
static inline void time_slice_expired(struct task_struct *p, struct rq *rq)
{
p->time_slice = sched_timeslice_ns;
sched_task_renew(p, rq);
if (SCHED_FIFO != p->policy && task_on_rq_queued(p))
requeue_task(p, rq, task_sched_prio_idx(p, rq));
}
/*
* Timeslices below RESCHED_NS are considered as good as expired as there's no
* point rescheduling when there's so little time left.
*/
static inline void check_curr(struct task_struct *p, struct rq *rq)
{
if (unlikely(rq->idle == p))
return;
update_curr(rq, p);
if (p->time_slice < RESCHED_NS)
time_slice_expired(p, rq);
}
static inline struct task_struct *
choose_next_task(struct rq *rq, int cpu)
{
struct task_struct *next;
if (unlikely(rq->skip)) {
next = rq_runnable_task(rq);
if (next == rq->idle) {
#ifdef CONFIG_SMP
if (!take_other_rq_tasks(rq, cpu)) {
#endif
rq->skip = NULL;
schedstat_inc(rq->sched_goidle);
return next;
#ifdef CONFIG_SMP
}
next = rq_runnable_task(rq);
#endif
}
rq->skip = NULL;
#ifdef CONFIG_HIGH_RES_TIMERS
hrtick_start(rq, next->time_slice);
#endif
return next;
}
next = sched_rq_first_task(rq);
if (next == rq->idle) {
#ifdef CONFIG_SMP
if (!take_other_rq_tasks(rq, cpu)) {
#endif
schedstat_inc(rq->sched_goidle);
/*printk(KERN_INFO "sched: choose_next_task(%d) idle %px\n", cpu, next);*/
return next;
#ifdef CONFIG_SMP
}
next = sched_rq_first_task(rq);
#endif
}
#ifdef CONFIG_HIGH_RES_TIMERS
hrtick_start(rq, next->time_slice);
#endif
/*printk(KERN_INFO "sched: choose_next_task(%d) next %px\n", cpu, next);*/
return next;
}
/*
* Constants for the sched_mode argument of __schedule().
*
* The mode argument allows RT enabled kernels to differentiate a
* preemption from blocking on an 'sleeping' spin/rwlock. Note that
* SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
* optimize the AND operation out and just check for zero.
*/
#define SM_NONE 0x0
#define SM_PREEMPT 0x1
#define SM_RTLOCK_WAIT 0x2
#ifndef CONFIG_PREEMPT_RT
# define SM_MASK_PREEMPT (~0U)
#else
# define SM_MASK_PREEMPT SM_PREEMPT
#endif
/*
* schedule() is the main scheduler function.
*
* The main means of driving the scheduler and thus entering this function are:
*
* 1. Explicit blocking: mutex, semaphore, waitqueue, etc.
*
* 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return
* paths. For example, see arch/x86/entry_64.S.
*
* To drive preemption between tasks, the scheduler sets the flag in timer
* interrupt handler scheduler_tick().
*
* 3. Wakeups don't really cause entry into schedule(). They add a
* task to the run-queue and that's it.
*
* Now, if the new task added to the run-queue preempts the current
* task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets
* called on the nearest possible occasion:
*
* - If the kernel is preemptible (CONFIG_PREEMPTION=y):
*
* - in syscall or exception context, at the next outmost
* preempt_enable(). (this might be as soon as the wake_up()'s
* spin_unlock()!)
*
* - in IRQ context, return from interrupt-handler to
* preemptible context
*
* - If the kernel is not preemptible (CONFIG_PREEMPTION is not set)
* then at the next:
*
* - cond_resched() call
* - explicit schedule() call
* - return from syscall or exception to user-space
* - return from interrupt-handler to user-space
*
* WARNING: must be called with preemption disabled!
*/
static void __sched notrace __schedule(unsigned int sched_mode)
{
struct task_struct *prev, *next;
unsigned long *switch_count;
unsigned long prev_state;
struct rq *rq;
int cpu;
cpu = smp_processor_id();
rq = cpu_rq(cpu);
prev = rq->curr;
schedule_debug(prev, !!sched_mode);
/* by passing sched_feat(HRTICK) checking which Alt schedule FW doesn't support */
hrtick_clear(rq);
local_irq_disable();
rcu_note_context_switch(!!sched_mode);
/*
* Make sure that signal_pending_state()->signal_pending() below
* can't be reordered with __set_current_state(TASK_INTERRUPTIBLE)
* done by the caller to avoid the race with signal_wake_up():
*
* __set_current_state(@state) signal_wake_up()
* schedule() set_tsk_thread_flag(p, TIF_SIGPENDING)
* wake_up_state(p, state)
* LOCK rq->lock LOCK p->pi_state
* smp_mb__after_spinlock() smp_mb__after_spinlock()
* if (signal_pending_state()) if (p->state & @state)
*
* Also, the membarrier system call requires a full memory barrier
* after coming from user-space, before storing to rq->curr.
*/
raw_spin_lock(&rq->lock);
smp_mb__after_spinlock();
update_rq_clock(rq);
switch_count = &prev->nivcsw;
/*
* We must load prev->state once (task_struct::state is volatile), such
* that we form a control dependency vs deactivate_task() below.
*/
prev_state = READ_ONCE(prev->__state);
if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
if (signal_pending_state(prev_state, prev)) {
WRITE_ONCE(prev->__state, TASK_RUNNING);
} else {
prev->sched_contributes_to_load =
(prev_state & TASK_UNINTERRUPTIBLE) &&
!(prev_state & TASK_NOLOAD) &&
!(prev_state & TASK_FROZEN);
if (prev->sched_contributes_to_load)
rq->nr_uninterruptible++;
/*
* __schedule() ttwu()
* prev_state = prev->state; if (p->on_rq && ...)
* if (prev_state) goto out;
* p->on_rq = 0; smp_acquire__after_ctrl_dep();
* p->state = TASK_WAKING
*
* Where __schedule() and ttwu() have matching control dependencies.
*
* After this, schedule() must not care about p->state any more.
*/
sched_task_deactivate(prev, rq);
deactivate_task(prev, rq);
if (prev->in_iowait) {
atomic_inc(&rq->nr_iowait);
delayacct_blkio_start();
}
}
switch_count = &prev->nvcsw;
}
check_curr(prev, rq);
next = choose_next_task(rq, cpu);
clear_tsk_need_resched(prev);
clear_preempt_need_resched();
#ifdef CONFIG_SCHED_DEBUG
rq->last_seen_need_resched_ns = 0;
#endif
if (likely(prev != next)) {
#ifdef CONFIG_SCHED_BMQ
rq->last_ts_switch = rq->clock;
#endif
next->last_ran = rq->clock_task;
/*printk(KERN_INFO "sched: %px -> %px\n", prev, next);*/
rq->nr_switches++;
/*
* RCU users of rcu_dereference(rq->curr) may not see
* changes to task_struct made by pick_next_task().
*/
RCU_INIT_POINTER(rq->curr, next);
/*
* The membarrier system call requires each architecture
* to have a full memory barrier after updating
* rq->curr, before returning to user-space.
*
* Here are the schemes providing that barrier on the
* various architectures:
* - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC.
* switch_mm() rely on membarrier_arch_switch_mm() on PowerPC.
* - finish_lock_switch() for weakly-ordered
* architectures where spin_unlock is a full barrier,
* - switch_to() for arm64 (weakly-ordered, spin_unlock
* is a RELEASE barrier),
*/
++*switch_count;
trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state);
/* Also unlocks the rq: */
rq = context_switch(rq, prev, next);
cpu = cpu_of(rq);
} else {
__balance_callbacks(rq);
raw_spin_unlock_irq(&rq->lock);
}
#ifdef CONFIG_SCHED_SMT
sg_balance(rq, cpu);
#endif
}
void __noreturn do_task_dead(void)
{
/* Causes final put_task_struct in finish_task_switch(): */
set_special_state(TASK_DEAD);
/* Tell freezer to ignore us: */
current->flags |= PF_NOFREEZE;
__schedule(SM_NONE);
BUG();
/* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
for (;;)
cpu_relax();
}
static inline void sched_submit_work(struct task_struct *tsk)
{
unsigned int task_flags;
if (task_is_running(tsk))
return;
task_flags = tsk->flags;
/*
* If a worker goes to sleep, notify and ask workqueue whether it
* wants to wake up a task to maintain concurrency.
*/
if (task_flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
if (task_flags & PF_WQ_WORKER)
wq_worker_sleeping(tsk);
else
io_wq_worker_sleeping(tsk);
}
/*
* spinlock and rwlock must not flush block requests. This will
* deadlock if the callback attempts to acquire a lock which is
* already acquired.
*/
SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT);
/*
* If we are going to sleep and we have plugged IO queued,
* make sure to submit it to avoid deadlocks.
*/
blk_flush_plug(tsk->plug, true);
}
static void sched_update_worker(struct task_struct *tsk)
{
if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER)) {
if (tsk->flags & PF_WQ_WORKER)
wq_worker_running(tsk);
else
io_wq_worker_running(tsk);
}
}
asmlinkage __visible void __sched schedule(void)
{
struct task_struct *tsk = current;
sched_submit_work(tsk);
do {
preempt_disable();
__schedule(SM_NONE);
sched_preempt_enable_no_resched();
} while (need_resched());
sched_update_worker(tsk);
}
EXPORT_SYMBOL(schedule);
/*
* synchronize_rcu_tasks() makes sure that no task is stuck in preempted
* state (have scheduled out non-voluntarily) by making sure that all
* tasks have either left the run queue or have gone into user space.
* As idle tasks do not do either, they must not ever be preempted
* (schedule out non-voluntarily).
*
* schedule_idle() is similar to schedule_preempt_disable() except that it
* never enables preemption because it does not call sched_submit_work().
*/
void __sched schedule_idle(void)
{
/*
* As this skips calling sched_submit_work(), which the idle task does
* regardless because that function is a nop when the task is in a
* TASK_RUNNING state, make sure this isn't used someplace that the
* current task can be in any other state. Note, idle is always in the
* TASK_RUNNING state.
*/
WARN_ON_ONCE(current->__state);
do {
__schedule(SM_NONE);
} while (need_resched());
}
#if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK)
asmlinkage __visible void __sched schedule_user(void)
{
/*
* If we come here after a random call to set_need_resched(),
* or we have been woken up remotely but the IPI has not yet arrived,
* we haven't yet exited the RCU idle mode. Do it here manually until
* we find a better solution.
*
* NB: There are buggy callers of this function. Ideally we
* should warn if prev_state != CONTEXT_USER, but that will trigger
* too frequently to make sense yet.
*/
enum ctx_state prev_state = exception_enter();
schedule();
exception_exit(prev_state);
}
#endif
/**
* schedule_preempt_disabled - called with preemption disabled
*
* Returns with preemption disabled. Note: preempt_count must be 1
*/
void __sched schedule_preempt_disabled(void)
{
sched_preempt_enable_no_resched();
schedule();
preempt_disable();
}
#ifdef CONFIG_PREEMPT_RT
void __sched notrace schedule_rtlock(void)
{
do {
preempt_disable();
__schedule(SM_RTLOCK_WAIT);
sched_preempt_enable_no_resched();
} while (need_resched());
}
NOKPROBE_SYMBOL(schedule_rtlock);
#endif
static void __sched notrace preempt_schedule_common(void)
{
do {
/*
* Because the function tracer can trace preempt_count_sub()
* and it also uses preempt_enable/disable_notrace(), if
* NEED_RESCHED is set, the preempt_enable_notrace() called
* by the function tracer will call this function again and
* cause infinite recursion.
*
* Preemption must be disabled here before the function
* tracer can trace. Break up preempt_disable() into two
* calls. One to disable preemption without fear of being
* traced. The other to still record the preemption latency,
* which can also be traced by the function tracer.
*/
preempt_disable_notrace();
preempt_latency_start(1);
__schedule(SM_PREEMPT);
preempt_latency_stop(1);
preempt_enable_no_resched_notrace();
/*
* Check again in case we missed a preemption opportunity
* between schedule and now.
*/
} while (need_resched());
}
#ifdef CONFIG_PREEMPTION
/*
* This is the entry point to schedule() from in-kernel preemption
* off of preempt_enable.
*/
asmlinkage __visible void __sched notrace preempt_schedule(void)
{
/*
* If there is a non-zero preempt_count or interrupts are disabled,
* we do not want to preempt the current task. Just return..
*/
if (likely(!preemptible()))
return;
preempt_schedule_common();
}
NOKPROBE_SYMBOL(preempt_schedule);
EXPORT_SYMBOL(preempt_schedule);
#ifdef CONFIG_PREEMPT_DYNAMIC
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#ifndef preempt_schedule_dynamic_enabled
#define preempt_schedule_dynamic_enabled preempt_schedule
#define preempt_schedule_dynamic_disabled NULL
#endif
DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled);
EXPORT_STATIC_CALL_TRAMP(preempt_schedule);
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule);
void __sched notrace dynamic_preempt_schedule(void)
{
if (!static_branch_unlikely(&sk_dynamic_preempt_schedule))
return;
preempt_schedule();
}
NOKPROBE_SYMBOL(dynamic_preempt_schedule);
EXPORT_SYMBOL(dynamic_preempt_schedule);
#endif
#endif
/**
* preempt_schedule_notrace - preempt_schedule called by tracing
*
* The tracing infrastructure uses preempt_enable_notrace to prevent
* recursion and tracing preempt enabling caused by the tracing
* infrastructure itself. But as tracing can happen in areas coming
* from userspace or just about to enter userspace, a preempt enable
* can occur before user_exit() is called. This will cause the scheduler
* to be called when the system is still in usermode.
*
* To prevent this, the preempt_enable_notrace will use this function
* instead of preempt_schedule() to exit user context if needed before
* calling the scheduler.
*/
asmlinkage __visible void __sched notrace preempt_schedule_notrace(void)
{
enum ctx_state prev_ctx;
if (likely(!preemptible()))
return;
do {
/*
* Because the function tracer can trace preempt_count_sub()
* and it also uses preempt_enable/disable_notrace(), if
* NEED_RESCHED is set, the preempt_enable_notrace() called
* by the function tracer will call this function again and
* cause infinite recursion.
*
* Preemption must be disabled here before the function
* tracer can trace. Break up preempt_disable() into two
* calls. One to disable preemption without fear of being
* traced. The other to still record the preemption latency,
* which can also be traced by the function tracer.
*/
preempt_disable_notrace();
preempt_latency_start(1);
/*
* Needs preempt disabled in case user_exit() is traced
* and the tracer calls preempt_enable_notrace() causing
* an infinite recursion.
*/
prev_ctx = exception_enter();
__schedule(SM_PREEMPT);
exception_exit(prev_ctx);
preempt_latency_stop(1);
preempt_enable_no_resched_notrace();
} while (need_resched());
}
EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
#ifdef CONFIG_PREEMPT_DYNAMIC
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#ifndef preempt_schedule_notrace_dynamic_enabled
#define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace
#define preempt_schedule_notrace_dynamic_disabled NULL
#endif
DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled);
EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace);
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace);
void __sched notrace dynamic_preempt_schedule_notrace(void)
{
if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace))
return;
preempt_schedule_notrace();
}
NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace);
EXPORT_SYMBOL(dynamic_preempt_schedule_notrace);
#endif
#endif
#endif /* CONFIG_PREEMPTION */
/*
* This is the entry point to schedule() from kernel preemption
* off of irq context.
* Note, that this is called and return with irqs disabled. This will
* protect us against recursive calling from irq.
*/
asmlinkage __visible void __sched preempt_schedule_irq(void)
{
enum ctx_state prev_state;
/* Catch callers which need to be fixed */
BUG_ON(preempt_count() || !irqs_disabled());
prev_state = exception_enter();
do {
preempt_disable();
local_irq_enable();
__schedule(SM_PREEMPT);
local_irq_disable();
sched_preempt_enable_no_resched();
} while (need_resched());
exception_exit(prev_state);
}
int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags,
void *key)
{
WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~WF_SYNC);
return try_to_wake_up(curr->private, mode, wake_flags);
}
EXPORT_SYMBOL(default_wake_function);
static inline void check_task_changed(struct task_struct *p, struct rq *rq)
{
/* Trigger resched if task sched_prio has been modified. */
if (task_on_rq_queued(p)) {
int idx;
update_rq_clock(rq);
idx = task_sched_prio_idx(p, rq);
if (idx != p->sq_idx) {
requeue_task(p, rq, idx);
check_preempt_curr(rq);
}
}
}
static void __setscheduler_prio(struct task_struct *p, int prio)
{
p->prio = prio;
}
#ifdef CONFIG_RT_MUTEXES
static inline int __rt_effective_prio(struct task_struct *pi_task, int prio)
{
if (pi_task)
prio = min(prio, pi_task->prio);
return prio;
}
static inline int rt_effective_prio(struct task_struct *p, int prio)
{
struct task_struct *pi_task = rt_mutex_get_top_task(p);
return __rt_effective_prio(pi_task, prio);
}
/*
* rt_mutex_setprio - set the current priority of a task
* @p: task to boost
* @pi_task: donor task
*
* This function changes the 'effective' priority of a task. It does
* not touch ->normal_prio like __setscheduler().
*
* Used by the rt_mutex code to implement priority inheritance
* logic. Call site only calls if the priority of the task changed.
*/
void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task)
{
int prio;
struct rq *rq;
raw_spinlock_t *lock;
/* XXX used to be waiter->prio, not waiter->task->prio */
prio = __rt_effective_prio(pi_task, p->normal_prio);
/*
* If nothing changed; bail early.
*/
if (p->pi_top_task == pi_task && prio == p->prio)
return;
rq = __task_access_lock(p, &lock);
/*
* Set under pi_lock && rq->lock, such that the value can be used under
* either lock.
*
* Note that there is loads of tricky to make this pointer cache work
* right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to
* ensure a task is de-boosted (pi_task is set to NULL) before the
* task is allowed to run again (and can exit). This ensures the pointer
* points to a blocked task -- which guarantees the task is present.
*/
p->pi_top_task = pi_task;
/*
* For FIFO/RR we only need to set prio, if that matches we're done.
*/
if (prio == p->prio)
goto out_unlock;
/*
* Idle task boosting is a nono in general. There is one
* exception, when PREEMPT_RT and NOHZ is active:
*
* The idle task calls get_next_timer_interrupt() and holds
* the timer wheel base->lock on the CPU and another CPU wants
* to access the timer (probably to cancel it). We can safely
* ignore the boosting request, as the idle CPU runs this code
* with interrupts disabled and will complete the lock
* protected section without being interrupted. So there is no
* real need to boost.
*/
if (unlikely(p == rq->idle)) {
WARN_ON(p != rq->curr);
WARN_ON(p->pi_blocked_on);
goto out_unlock;
}
trace_sched_pi_setprio(p, pi_task);
__setscheduler_prio(p, prio);
check_task_changed(p, rq);
out_unlock:
/* Avoid rq from going away on us: */
preempt_disable();
__balance_callbacks(rq);
__task_access_unlock(p, lock);
preempt_enable();
}
#else
static inline int rt_effective_prio(struct task_struct *p, int prio)
{
return prio;
}
#endif
void set_user_nice(struct task_struct *p, long nice)
{
unsigned long flags;
struct rq *rq;
raw_spinlock_t *lock;
if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
return;
/*
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
raw_spin_lock_irqsave(&p->pi_lock, flags);
rq = __task_access_lock(p, &lock);
p->static_prio = NICE_TO_PRIO(nice);
/*
* The RT priorities are set via sched_setscheduler(), but we still
* allow the 'normal' nice value to be set - but as expected
* it won't have any effect on scheduling until the task is
* not SCHED_NORMAL/SCHED_BATCH:
*/
if (task_has_rt_policy(p))
goto out_unlock;
p->prio = effective_prio(p);
check_task_changed(p, rq);
out_unlock:
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}
EXPORT_SYMBOL(set_user_nice);
/*
* is_nice_reduction - check if nice value is an actual reduction
*
* Similar to can_nice() but does not perform a capability check.
*
* @p: task
* @nice: nice value
*/
static bool is_nice_reduction(const struct task_struct *p, const int nice)
{
/* Convert nice value [19,-20] to rlimit style value [1,40]: */
int nice_rlim = nice_to_rlimit(nice);
return (nice_rlim <= task_rlimit(p, RLIMIT_NICE));
}
/*
* can_nice - check if a task can reduce its nice value
* @p: task
* @nice: nice value
*/
int can_nice(const struct task_struct *p, const int nice)
{
return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE);
}
#ifdef __ARCH_WANT_SYS_NICE
/*
* sys_nice - change the priority of the current process.
* @increment: priority increment
*
* sys_setpriority is a more generic, but much slower function that
* does similar things.
*/
SYSCALL_DEFINE1(nice, int, increment)
{
long nice, retval;
/*
* Setpriority might change our priority at the same moment.
* We don't have to worry. Conceptually one call occurs first
* and we have a single winner.
*/
increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
nice = task_nice(current) + increment;
nice = clamp_val(nice, MIN_NICE, MAX_NICE);
if (increment < 0 && !can_nice(current, nice))
return -EPERM;
retval = security_task_setnice(current, nice);
if (retval)
return retval;
set_user_nice(current, nice);
return 0;
}
#endif
/**
* task_prio - return the priority value of a given task.
* @p: the task in question.
*
* Return: The priority value as seen by users in /proc.
*
* sched policy return value kernel prio user prio/nice
*
* (BMQ)normal, batch, idle[0 ... 53] [100 ... 139] 0/[-20 ... 19]/[-7 ... 7]
* (PDS)normal, batch, idle[0 ... 39] 100 0/[-20 ... 19]
* fifo, rr [-1 ... -100] [99 ... 0] [0 ... 99]
*/
int task_prio(const struct task_struct *p)
{
return (p->prio < MAX_RT_PRIO) ? p->prio - MAX_RT_PRIO :
task_sched_prio_normal(p, task_rq(p));
}
/**
* idle_cpu - is a given CPU idle currently?
* @cpu: the processor in question.
*
* Return: 1 if the CPU is currently idle. 0 otherwise.
*/
int idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
if (rq->curr != rq->idle)
return 0;
if (rq->nr_running)
return 0;
#ifdef CONFIG_SMP
if (rq->ttwu_pending)
return 0;
#endif
return 1;
}
/**
* idle_task - return the idle task for a given CPU.
* @cpu: the processor in question.
*
* Return: The idle task for the cpu @cpu.
*/
struct task_struct *idle_task(int cpu)
{
return cpu_rq(cpu)->idle;
}
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
*
* The task of @pid, if found. %NULL otherwise.
*/
static inline struct task_struct *find_process_by_pid(pid_t pid)
{
return pid ? find_task_by_vpid(pid) : current;
}
/*
* sched_setparam() passes in -1 for its policy, to let the functions
* it calls know not to change it.
*/
#define SETPARAM_POLICY -1
static void __setscheduler_params(struct task_struct *p,
const struct sched_attr *attr)
{
int policy = attr->sched_policy;
if (policy == SETPARAM_POLICY)
policy = p->policy;
p->policy = policy;
/*
* allow normal nice value to be set, but will not have any
* effect on scheduling until the task not SCHED_NORMAL/
* SCHED_BATCH
*/
p->static_prio = NICE_TO_PRIO(attr->sched_nice);
/*
* __sched_setscheduler() ensures attr->sched_priority == 0 when
* !rt_policy. Always setting this ensures that things like
* getparam()/getattr() don't report silly values for !rt tasks.
*/
p->rt_priority = attr->sched_priority;
p->normal_prio = normal_prio(p);
}
/*
* check the target process has a UID that matches the current process's
*/
static bool check_same_owner(struct task_struct *p)
{
const struct cred *cred = current_cred(), *pcred;
bool match;
rcu_read_lock();
pcred = __task_cred(p);
match = (uid_eq(cred->euid, pcred->euid) ||
uid_eq(cred->euid, pcred->uid));
rcu_read_unlock();
return match;
}
/*
* Allow unprivileged RT tasks to decrease priority.
* Only issue a capable test if needed and only once to avoid an audit
* event on permitted non-privileged operations:
*/
static int user_check_sched_setscheduler(struct task_struct *p,
const struct sched_attr *attr,
int policy, int reset_on_fork)
{
if (rt_policy(policy)) {
unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
/* Can't set/change the rt policy: */
if (policy != p->policy && !rlim_rtprio)
goto req_priv;
/* Can't increase priority: */
if (attr->sched_priority > p->rt_priority &&
attr->sched_priority > rlim_rtprio)
goto req_priv;
}
/* Can't change other user's priorities: */
if (!check_same_owner(p))
goto req_priv;
/* Normal users shall not reset the sched_reset_on_fork flag: */
if (p->sched_reset_on_fork && !reset_on_fork)
goto req_priv;
return 0;
req_priv:
if (!capable(CAP_SYS_NICE))
return -EPERM;
return 0;
}
static int __sched_setscheduler(struct task_struct *p,
const struct sched_attr *attr,
bool user, bool pi)
{
const struct sched_attr dl_squash_attr = {
.size = sizeof(struct sched_attr),
.sched_policy = SCHED_FIFO,
.sched_nice = 0,
.sched_priority = 99,
};
int oldpolicy = -1, policy = attr->sched_policy;
int retval, newprio;
struct balance_callback *head;
unsigned long flags;
struct rq *rq;
int reset_on_fork;
raw_spinlock_t *lock;
/* The pi code expects interrupts enabled */
BUG_ON(pi && in_interrupt());
/*
* Alt schedule FW supports SCHED_DEADLINE by squash it as prio 0 SCHED_FIFO
*/
if (unlikely(SCHED_DEADLINE == policy)) {
attr = &dl_squash_attr;
policy = attr->sched_policy;
}
recheck:
/* Double check policy once rq lock held */
if (policy < 0) {
reset_on_fork = p->sched_reset_on_fork;
policy = oldpolicy = p->policy;
} else {
reset_on_fork = !!(attr->sched_flags & SCHED_RESET_ON_FORK);
if (policy > SCHED_IDLE)
return -EINVAL;
}
if (attr->sched_flags & ~(SCHED_FLAG_ALL))
return -EINVAL;
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL and
* SCHED_BATCH and SCHED_IDLE is 0.
*/
if (attr->sched_priority < 0 ||
(p->mm && attr->sched_priority > MAX_RT_PRIO - 1) ||
(!p->mm && attr->sched_priority > MAX_RT_PRIO - 1))
return -EINVAL;
if ((SCHED_RR == policy || SCHED_FIFO == policy) !=
(attr->sched_priority != 0))
return -EINVAL;
if (user) {
retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork);
if (retval)
return retval;
retval = security_task_setscheduler(p);
if (retval)
return retval;
}
/*
* Make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
*/
raw_spin_lock_irqsave(&p->pi_lock, flags);
/*
* To be able to change p->policy safely, task_access_lock()
* must be called.
* IF use task_access_lock() here:
* For the task p which is not running, reading rq->stop is
* racy but acceptable as ->stop doesn't change much.
* An enhancemnet can be made to read rq->stop saftly.
*/
rq = __task_access_lock(p, &lock);
/*
* Changing the policy of the stop threads its a very bad idea
*/
if (p == rq->stop) {
retval = -EINVAL;
goto unlock;
}
/*
* If not changing anything there's no need to proceed further:
*/
if (unlikely(policy == p->policy)) {
if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
goto change;
if (!rt_policy(policy) &&
NICE_TO_PRIO(attr->sched_nice) != p->static_prio)
goto change;
p->sched_reset_on_fork = reset_on_fork;
retval = 0;
goto unlock;
}
change:
/* Re-check policy now with rq lock held */
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
goto recheck;
}
p->sched_reset_on_fork = reset_on_fork;
newprio = __normal_prio(policy, attr->sched_priority, NICE_TO_PRIO(attr->sched_nice));
if (pi) {
/*
* Take priority boosted tasks into account. If the new
* effective priority is unchanged, we just store the new
* normal parameters and do not touch the scheduler class and
* the runqueue. This will be done when the task deboost
* itself.
*/
newprio = rt_effective_prio(p, newprio);
}
if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
__setscheduler_params(p, attr);
__setscheduler_prio(p, newprio);
}
check_task_changed(p, rq);
/* Avoid rq from going away on us: */
preempt_disable();
head = splice_balance_callbacks(rq);
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
if (pi)
rt_mutex_adjust_pi(p);
/* Run balance callbacks after we've adjusted the PI chain: */
balance_callbacks(rq, head);
preempt_enable();
return 0;
unlock:
__task_access_unlock(p, lock);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
return retval;
}
static int _sched_setscheduler(struct task_struct *p, int policy,
const struct sched_param *param, bool check)
{
struct sched_attr attr = {
.sched_policy = policy,
.sched_priority = param->sched_priority,
.sched_nice = PRIO_TO_NICE(p->static_prio),
};
/* Fixup the legacy SCHED_RESET_ON_FORK hack. */
if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
policy &= ~SCHED_RESET_ON_FORK;
attr.sched_policy = policy;
}
return __sched_setscheduler(p, &attr, check, true);
}
/**
* sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* Use sched_set_fifo(), read its comment.
*
* Return: 0 on success. An error code otherwise.
*
* NOTE that the task may be already dead.
*/
int sched_setscheduler(struct task_struct *p, int policy,
const struct sched_param *param)
{
return _sched_setscheduler(p, policy, param, true);
}
int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
{
return __sched_setscheduler(p, attr, true, true);
}
int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
{
return __sched_setscheduler(p, attr, false, true);
}
EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
/**
* sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* Just like sched_setscheduler, only don't bother checking if the
* current context has permission. For example, this is needed in
* stop_machine(): we create temporary high priority worker threads,
* but our caller might not have that capability.
*
* Return: 0 on success. An error code otherwise.
*/
int sched_setscheduler_nocheck(struct task_struct *p, int policy,
const struct sched_param *param)
{
return _sched_setscheduler(p, policy, param, false);
}
/*
* SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
* incapable of resource management, which is the one thing an OS really should
* be doing.
*
* This is of course the reason it is limited to privileged users only.
*
* Worse still; it is fundamentally impossible to compose static priority
* workloads. You cannot take two correctly working static prio workloads
* and smash them together and still expect them to work.
*
* For this reason 'all' FIFO tasks the kernel creates are basically at:
*
* MAX_RT_PRIO / 2
*
* The administrator _MUST_ configure the system, the kernel simply doesn't
* know enough information to make a sensible choice.
*/
void sched_set_fifo(struct task_struct *p)
{
struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_fifo);
/*
* For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
*/
void sched_set_fifo_low(struct task_struct *p)
{
struct sched_param sp = { .sched_priority = 1 };
WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_fifo_low);
void sched_set_normal(struct task_struct *p, int nice)
{
struct sched_attr attr = {
.sched_policy = SCHED_NORMAL,
.sched_nice = nice,
};
WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_normal);
static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lparam;
struct task_struct *p;
int retval;
if (!param || pid < 0)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
if (likely(p))
get_task_struct(p);
rcu_read_unlock();
if (likely(p)) {
retval = sched_setscheduler(p, policy, &lparam);
put_task_struct(p);
}
return retval;
}
/*
* Mimics kernel/events/core.c perf_copy_attr().
*/
static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
{
u32 size;
int ret;
/* Zero the full structure, so that a short copy will be nice: */
memset(attr, 0, sizeof(*attr));
ret = get_user(size, &uattr->size);
if (ret)
return ret;
/* ABI compatibility quirk: */
if (!size)
size = SCHED_ATTR_SIZE_VER0;
if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
goto err_size;
ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
if (ret) {
if (ret == -E2BIG)
goto err_size;
return ret;
}
/*
* XXX: Do we want to be lenient like existing syscalls; or do we want
* to be strict and return an error on out-of-bounds values?
*/
attr->sched_nice = clamp(attr->sched_nice, -20, 19);
/* sched/core.c uses zero here but we already know ret is zero */
return 0;
err_size:
put_user(sizeof(*attr), &uattr->size);
return -E2BIG;
}
/**
* sys_sched_setscheduler - set/change the scheduler policy and RT priority
* @pid: the pid in question.
* @policy: new policy.
*
* Return: 0 on success. An error code otherwise.
* @param: structure containing the new RT priority.
*/
SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
{
if (policy < 0)
return -EINVAL;
return do_sched_setscheduler(pid, policy, param);
}
/**
* sys_sched_setparam - set/change the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the new RT priority.
*
* Return: 0 on success. An error code otherwise.
*/
SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
{
return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
}
/**
* sys_sched_setattr - same as above, but with extended sched_attr
* @pid: the pid in question.
* @uattr: structure containing the extended parameters.
*/
SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
unsigned int, flags)
{
struct sched_attr attr;
struct task_struct *p;
int retval;
if (!uattr || pid < 0 || flags)
return -EINVAL;
retval = sched_copy_attr(uattr, &attr);
if (retval)
return retval;
if ((int)attr.sched_policy < 0)
return -EINVAL;
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
if (likely(p))
get_task_struct(p);
rcu_read_unlock();
if (likely(p)) {
retval = sched_setattr(p, &attr);
put_task_struct(p);
}
return retval;
}
/**
* sys_sched_getscheduler - get the policy (scheduling class) of a thread
* @pid: the pid in question.
*
* Return: On success, the policy of the thread. Otherwise, a negative error
* code.
*/
SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
{
struct task_struct *p;
int retval = -EINVAL;
if (pid < 0)
goto out_nounlock;
retval = -ESRCH;
rcu_read_lock();
p = find_process_by_pid(pid);
if (p) {
retval = security_task_getscheduler(p);
if (!retval)
retval = p->policy;
}
rcu_read_unlock();
out_nounlock:
return retval;
}
/**
* sys_sched_getscheduler - get the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the RT priority.
*
* Return: On success, 0 and the RT priority is in @param. Otherwise, an error
* code.
*/
SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
{
struct sched_param lp = { .sched_priority = 0 };
struct task_struct *p;
int retval = -EINVAL;
if (!param || pid < 0)
goto out_nounlock;
rcu_read_lock();
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
if (task_has_rt_policy(p))
lp.sched_priority = p->rt_priority;
rcu_read_unlock();
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
retval = copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
out_nounlock:
return retval;
out_unlock:
rcu_read_unlock();
return retval;
}
/*
* Copy the kernel size attribute structure (which might be larger
* than what user-space knows about) to user-space.
*
* Note that all cases are valid: user-space buffer can be larger or
* smaller than the kernel-space buffer. The usual case is that both
* have the same size.
*/
static int
sched_attr_copy_to_user(struct sched_attr __user *uattr,
struct sched_attr *kattr,
unsigned int usize)
{
unsigned int ksize = sizeof(*kattr);
if (!access_ok(uattr, usize))
return -EFAULT;
/*
* sched_getattr() ABI forwards and backwards compatibility:
*
* If usize == ksize then we just copy everything to user-space and all is good.
*
* If usize < ksize then we only copy as much as user-space has space for,
* this keeps ABI compatibility as well. We skip the rest.
*
* If usize > ksize then user-space is using a newer version of the ABI,
* which part the kernel doesn't know about. Just ignore it - tooling can
* detect the kernel's knowledge of attributes from the attr->size value
* which is set to ksize in this case.
*/
kattr->size = min(usize, ksize);
if (copy_to_user(uattr, kattr, kattr->size))
return -EFAULT;
return 0;
}
/**
* sys_sched_getattr - similar to sched_getparam, but with sched_attr
* @pid: the pid in question.
* @uattr: structure containing the extended parameters.
* @usize: sizeof(attr) for fwd/bwd comp.
* @flags: for future extension.
*/
SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
unsigned int, usize, unsigned int, flags)
{
struct sched_attr kattr = { };
struct task_struct *p;
int retval;
if (!uattr || pid < 0 || usize > PAGE_SIZE ||
usize < SCHED_ATTR_SIZE_VER0 || flags)
return -EINVAL;
rcu_read_lock();
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
kattr.sched_policy = p->policy;
if (p->sched_reset_on_fork)
kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
if (task_has_rt_policy(p))
kattr.sched_priority = p->rt_priority;
else
kattr.sched_nice = task_nice(p);
kattr.sched_flags &= SCHED_FLAG_ALL;
#ifdef CONFIG_UCLAMP_TASK
kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
#endif
rcu_read_unlock();
return sched_attr_copy_to_user(uattr, &kattr, usize);
out_unlock:
rcu_read_unlock();
return retval;
}
#ifdef CONFIG_SMP
int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
{
return 0;
}
#endif
static int
__sched_setaffinity(struct task_struct *p, struct affinity_context *ctx)
{
int retval;
cpumask_var_t cpus_allowed, new_mask;
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
return -ENOMEM;
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
retval = -ENOMEM;
goto out_free_cpus_allowed;
}
cpuset_cpus_allowed(p, cpus_allowed);
cpumask_and(new_mask, ctx->new_mask, cpus_allowed);
ctx->new_mask = new_mask;
ctx->flags |= SCA_CHECK;
retval = __set_cpus_allowed_ptr(p, ctx);
if (retval)
goto out_free_new_mask;
cpuset_cpus_allowed(p, cpus_allowed);
if (!cpumask_subset(new_mask, cpus_allowed)) {
/*
* We must have raced with a concurrent cpuset
* update. Just reset the cpus_allowed to the
* cpuset's cpus_allowed
*/
cpumask_copy(new_mask, cpus_allowed);
/*
* If SCA_USER is set, a 2nd call to __set_cpus_allowed_ptr()
* will restore the previous user_cpus_ptr value.
*
* In the unlikely event a previous user_cpus_ptr exists,
* we need to further restrict the mask to what is allowed
* by that old user_cpus_ptr.
*/
if (unlikely((ctx->flags & SCA_USER) && ctx->user_mask)) {
bool empty = !cpumask_and(new_mask, new_mask,
ctx->user_mask);
if (WARN_ON_ONCE(empty))
cpumask_copy(new_mask, cpus_allowed);
}
__set_cpus_allowed_ptr(p, ctx);
retval = -EINVAL;
}
out_free_new_mask:
free_cpumask_var(new_mask);
out_free_cpus_allowed:
free_cpumask_var(cpus_allowed);
return retval;
}
long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
struct affinity_context ac;
struct cpumask *user_mask;
struct task_struct *p;
int retval;
rcu_read_lock();
p = find_process_by_pid(pid);
if (!p) {
rcu_read_unlock();
return -ESRCH;
}
/* Prevent p going away */
get_task_struct(p);
rcu_read_unlock();
if (p->flags & PF_NO_SETAFFINITY) {
retval = -EINVAL;
goto out_put_task;
}
if (!check_same_owner(p)) {
rcu_read_lock();
if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
rcu_read_unlock();
retval = -EPERM;
goto out_put_task;
}
rcu_read_unlock();
}
retval = security_task_setscheduler(p);
if (retval)
goto out_put_task;
/*
* With non-SMP configs, user_cpus_ptr/user_mask isn't used and
* alloc_user_cpus_ptr() returns NULL.
*/
user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE);
if (user_mask) {
cpumask_copy(user_mask, in_mask);
} else if (IS_ENABLED(CONFIG_SMP)) {
retval = -ENOMEM;
goto out_put_task;
}
ac = (struct affinity_context){
.new_mask = in_mask,
.user_mask = user_mask,
.flags = SCA_USER,
};
retval = __sched_setaffinity(p, &ac);
kfree(ac.user_mask);
out_put_task:
put_task_struct(p);
return retval;
}
static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
struct cpumask *new_mask)
{
if (len < cpumask_size())
cpumask_clear(new_mask);
else if (len > cpumask_size())
len = cpumask_size();
return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}
/**
* sys_sched_setaffinity - set the CPU affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to the new CPU mask
*
* Return: 0 on success. An error code otherwise.
*/
SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
unsigned long __user *, user_mask_ptr)
{
cpumask_var_t new_mask;
int retval;
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
return -ENOMEM;
retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
if (retval == 0)
retval = sched_setaffinity(pid, new_mask);
free_cpumask_var(new_mask);
return retval;
}
long sched_getaffinity(pid_t pid, cpumask_t *mask)
{
struct task_struct *p;
raw_spinlock_t *lock;
unsigned long flags;
int retval;
rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
task_access_lock_irqsave(p, &lock, &flags);
cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
task_access_unlock_irqrestore(p, lock, &flags);
out_unlock:
rcu_read_unlock();
return retval;
}
/**
* sys_sched_getaffinity - get the CPU affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to hold the current CPU mask
*
* Return: size of CPU mask copied to user_mask_ptr on success. An
* error code otherwise.
*/
SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
unsigned long __user *, user_mask_ptr)
{
int ret;
cpumask_var_t mask;
if ((len * BITS_PER_BYTE) < nr_cpu_ids)
return -EINVAL;
if (len & (sizeof(unsigned long)-1))
return -EINVAL;
if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
return -ENOMEM;
ret = sched_getaffinity(pid, mask);
if (ret == 0) {
unsigned int retlen = min(len, cpumask_size());
if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen))
ret = -EFAULT;
else
ret = retlen;
}
free_cpumask_var(mask);
return ret;
}
static void do_sched_yield(void)
{
struct rq *rq;
struct rq_flags rf;
if (!sched_yield_type)
return;
rq = this_rq_lock_irq(&rf);
schedstat_inc(rq->yld_count);
if (1 == sched_yield_type) {
if (!rt_task(current))
do_sched_yield_type_1(current, rq);
} else if (2 == sched_yield_type) {
if (rq->nr_running > 1)
rq->skip = current;
}
preempt_disable();
raw_spin_unlock_irq(&rq->lock);
sched_preempt_enable_no_resched();
schedule();
}
/**
* sys_sched_yield - yield the current processor to other threads.
*
* This function yields the current CPU to other tasks. If there are no
* other threads running on this CPU then this function will return.
*
* Return: 0.
*/
SYSCALL_DEFINE0(sched_yield)
{
do_sched_yield();
return 0;
}
#if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC)
int __sched __cond_resched(void)
{
if (should_resched(0)) {
preempt_schedule_common();
return 1;
}
/*
* In preemptible kernels, ->rcu_read_lock_nesting tells the tick
* whether the current CPU is in an RCU read-side critical section,
* so the tick can report quiescent states even for CPUs looping
* in kernel context. In contrast, in non-preemptible kernels,
* RCU readers leave no in-memory hints, which means that CPU-bound
* processes executing in kernel context might never report an
* RCU quiescent state. Therefore, the following code causes
* cond_resched() to report a quiescent state, but only when RCU
* is in urgent need of one.
*/
#ifndef CONFIG_PREEMPT_RCU
rcu_all_qs();
#endif
return 0;
}
EXPORT_SYMBOL(__cond_resched);
#endif
#ifdef CONFIG_PREEMPT_DYNAMIC
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#define cond_resched_dynamic_enabled __cond_resched
#define cond_resched_dynamic_disabled ((void *)&__static_call_return0)
DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched);
EXPORT_STATIC_CALL_TRAMP(cond_resched);
#define might_resched_dynamic_enabled __cond_resched
#define might_resched_dynamic_disabled ((void *)&__static_call_return0)
DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched);
EXPORT_STATIC_CALL_TRAMP(might_resched);
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched);
int __sched dynamic_cond_resched(void)
{
klp_sched_try_switch();
if (!static_branch_unlikely(&sk_dynamic_cond_resched))
return 0;
return __cond_resched();
}
EXPORT_SYMBOL(dynamic_cond_resched);
static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched);
int __sched dynamic_might_resched(void)
{
if (!static_branch_unlikely(&sk_dynamic_might_resched))
return 0;
return __cond_resched();
}
EXPORT_SYMBOL(dynamic_might_resched);
#endif
#endif
/*
* __cond_resched_lock() - if a reschedule is pending, drop the given lock,
* call schedule, and on return reacquire the lock.
*
* This works OK both with and without CONFIG_PREEMPTION. We do strange low-level
* operations here to prevent schedule() from being called twice (once via
* spin_unlock(), once by hand).
*/
int __cond_resched_lock(spinlock_t *lock)
{
int resched = should_resched(PREEMPT_LOCK_OFFSET);
int ret = 0;
lockdep_assert_held(lock);
if (spin_needbreak(lock) || resched) {
spin_unlock(lock);
if (!_cond_resched())
cpu_relax();
ret = 1;
spin_lock(lock);
}
return ret;
}
EXPORT_SYMBOL(__cond_resched_lock);
int __cond_resched_rwlock_read(rwlock_t *lock)
{
int resched = should_resched(PREEMPT_LOCK_OFFSET);
int ret = 0;
lockdep_assert_held_read(lock);
if (rwlock_needbreak(lock) || resched) {
read_unlock(lock);
if (!_cond_resched())
cpu_relax();
ret = 1;
read_lock(lock);
}
return ret;
}
EXPORT_SYMBOL(__cond_resched_rwlock_read);
int __cond_resched_rwlock_write(rwlock_t *lock)
{
int resched = should_resched(PREEMPT_LOCK_OFFSET);
int ret = 0;
lockdep_assert_held_write(lock);
if (rwlock_needbreak(lock) || resched) {
write_unlock(lock);
if (!_cond_resched())
cpu_relax();
ret = 1;
write_lock(lock);
}
return ret;
}
EXPORT_SYMBOL(__cond_resched_rwlock_write);
#ifdef CONFIG_PREEMPT_DYNAMIC
#ifdef CONFIG_GENERIC_ENTRY
#include <linux/entry-common.h>
#endif
/*
* SC:cond_resched
* SC:might_resched
* SC:preempt_schedule
* SC:preempt_schedule_notrace
* SC:irqentry_exit_cond_resched
*
*
* NONE:
* cond_resched <- __cond_resched
* might_resched <- RET0
* preempt_schedule <- NOP
* preempt_schedule_notrace <- NOP
* irqentry_exit_cond_resched <- NOP
*
* VOLUNTARY:
* cond_resched <- __cond_resched
* might_resched <- __cond_resched
* preempt_schedule <- NOP
* preempt_schedule_notrace <- NOP
* irqentry_exit_cond_resched <- NOP
*
* FULL:
* cond_resched <- RET0
* might_resched <- RET0
* preempt_schedule <- preempt_schedule
* preempt_schedule_notrace <- preempt_schedule_notrace
* irqentry_exit_cond_resched <- irqentry_exit_cond_resched
*/
enum {
preempt_dynamic_undefined = -1,
preempt_dynamic_none,
preempt_dynamic_voluntary,
preempt_dynamic_full,
};
int preempt_dynamic_mode = preempt_dynamic_undefined;
int sched_dynamic_mode(const char *str)
{
if (!strcmp(str, "none"))
return preempt_dynamic_none;
if (!strcmp(str, "voluntary"))
return preempt_dynamic_voluntary;
if (!strcmp(str, "full"))
return preempt_dynamic_full;
return -EINVAL;
}
#if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
#define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled)
#define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled)
#elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY)
#define preempt_dynamic_enable(f) static_key_enable(&sk_dynamic_##f.key)
#define preempt_dynamic_disable(f) static_key_disable(&sk_dynamic_##f.key)
#else
#error "Unsupported PREEMPT_DYNAMIC mechanism"
#endif
static DEFINE_MUTEX(sched_dynamic_mutex);
static bool klp_override;
static void __sched_dynamic_update(int mode)
{
/*
* Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in
* the ZERO state, which is invalid.
*/
if (!klp_override)
preempt_dynamic_enable(cond_resched);
preempt_dynamic_enable(cond_resched);
preempt_dynamic_enable(might_resched);
preempt_dynamic_enable(preempt_schedule);
preempt_dynamic_enable(preempt_schedule_notrace);
preempt_dynamic_enable(irqentry_exit_cond_resched);
switch (mode) {
case preempt_dynamic_none:
if (!klp_override)
preempt_dynamic_enable(cond_resched);
preempt_dynamic_disable(might_resched);
preempt_dynamic_disable(preempt_schedule);
preempt_dynamic_disable(preempt_schedule_notrace);
preempt_dynamic_disable(irqentry_exit_cond_resched);
if (mode != preempt_dynamic_mode)
pr_info("Dynamic Preempt: none\n");
break;
case preempt_dynamic_voluntary:
if (!klp_override)
preempt_dynamic_enable(cond_resched);
preempt_dynamic_enable(might_resched);
preempt_dynamic_disable(preempt_schedule);
preempt_dynamic_disable(preempt_schedule_notrace);
preempt_dynamic_disable(irqentry_exit_cond_resched);
if (mode != preempt_dynamic_mode)
pr_info("Dynamic Preempt: voluntary\n");
break;
case preempt_dynamic_full:
if (!klp_override)
preempt_dynamic_enable(cond_resched);
preempt_dynamic_disable(might_resched);
preempt_dynamic_enable(preempt_schedule);
preempt_dynamic_enable(preempt_schedule_notrace);
preempt_dynamic_enable(irqentry_exit_cond_resched);
if (mode != preempt_dynamic_mode)
pr_info("Dynamic Preempt: full\n");
break;
}
preempt_dynamic_mode = mode;
}
void sched_dynamic_update(int mode)
{
mutex_lock(&sched_dynamic_mutex);
__sched_dynamic_update(mode);
mutex_unlock(&sched_dynamic_mutex);
}
#ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL
static int klp_cond_resched(void)
{
__klp_sched_try_switch();
return __cond_resched();
}
void sched_dynamic_klp_enable(void)
{
mutex_lock(&sched_dynamic_mutex);
klp_override = true;
static_call_update(cond_resched, klp_cond_resched);
mutex_unlock(&sched_dynamic_mutex);
}
void sched_dynamic_klp_disable(void)
{
mutex_lock(&sched_dynamic_mutex);
klp_override = false;
__sched_dynamic_update(preempt_dynamic_mode);
mutex_unlock(&sched_dynamic_mutex);
}
#endif /* CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */
static int __init setup_preempt_mode(char *str)
{
int mode = sched_dynamic_mode(str);
if (mode < 0) {
pr_warn("Dynamic Preempt: unsupported mode: %s\n", str);
return 0;
}
sched_dynamic_update(mode);
return 1;
}
__setup("preempt=", setup_preempt_mode);
static void __init preempt_dynamic_init(void)
{
if (preempt_dynamic_mode == preempt_dynamic_undefined) {
if (IS_ENABLED(CONFIG_PREEMPT_NONE)) {
sched_dynamic_update(preempt_dynamic_none);
} else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) {
sched_dynamic_update(preempt_dynamic_voluntary);
} else {
/* Default static call setting, nothing to do */
WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT));
preempt_dynamic_mode = preempt_dynamic_full;
pr_info("Dynamic Preempt: full\n");
}
}
}
#define PREEMPT_MODEL_ACCESSOR(mode) \
bool preempt_model_##mode(void) \
{ \
WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \
return preempt_dynamic_mode == preempt_dynamic_##mode; \
} \
EXPORT_SYMBOL_GPL(preempt_model_##mode)
PREEMPT_MODEL_ACCESSOR(none);
PREEMPT_MODEL_ACCESSOR(voluntary);
PREEMPT_MODEL_ACCESSOR(full);
#else /* !CONFIG_PREEMPT_DYNAMIC */
static inline void preempt_dynamic_init(void) { }
#endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */
/**
* yield - yield the current processor to other threads.
*
* Do not ever use this function, there's a 99% chance you're doing it wrong.
*
* The scheduler is at all times free to pick the calling task as the most
* eligible task to run, if removing the yield() call from your code breaks
* it, it's already broken.
*
* Typical broken usage is:
*
* while (!event)
* yield();
*
* where one assumes that yield() will let 'the other' process run that will
* make event true. If the current task is a SCHED_FIFO task that will never
* happen. Never use yield() as a progress guarantee!!
*
* If you want to use yield() to wait for something, use wait_event().
* If you want to use yield() to be 'nice' for others, use cond_resched().
* If you still want to use yield(), do not!
*/
void __sched yield(void)
{
set_current_state(TASK_RUNNING);
do_sched_yield();
}
EXPORT_SYMBOL(yield);
/**
* yield_to - yield the current processor to another thread in
* your thread group, or accelerate that thread toward the
* processor it's on.
* @p: target task
* @preempt: whether task preemption is allowed or not
*
* It's the caller's job to ensure that the target task struct
* can't go away on us before we can do any checks.
*
* In Alt schedule FW, yield_to is not supported.
*
* Return:
* true (>0) if we indeed boosted the target task.
* false (0) if we failed to boost the target.
* -ESRCH if there's no task to yield to.
*/
int __sched yield_to(struct task_struct *p, bool preempt)
{
return 0;
}
EXPORT_SYMBOL_GPL(yield_to);
int io_schedule_prepare(void)
{
int old_iowait = current->in_iowait;
current->in_iowait = 1;
blk_flush_plug(current->plug, true);
return old_iowait;
}
void io_schedule_finish(int token)
{
current->in_iowait = token;
}
/*
* This task is about to go to sleep on IO. Increment rq->nr_iowait so
* that process accounting knows that this is a task in IO wait state.
*
* But don't do that if it is a deliberate, throttling IO wait (this task
* has set its backing_dev_info: the queue against which it should throttle)
*/
long __sched io_schedule_timeout(long timeout)
{
int token;
long ret;
token = io_schedule_prepare();
ret = schedule_timeout(timeout);
io_schedule_finish(token);
return ret;
}
EXPORT_SYMBOL(io_schedule_timeout);
void __sched io_schedule(void)
{
int token;
token = io_schedule_prepare();
schedule();
io_schedule_finish(token);
}
EXPORT_SYMBOL(io_schedule);
/**
* sys_sched_get_priority_max - return maximum RT priority.
* @policy: scheduling class.
*
* Return: On success, this syscall returns the maximum
* rt_priority that can be used by a given scheduling class.
* On failure, a negative error code is returned.
*/
SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = MAX_RT_PRIO - 1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
case SCHED_IDLE:
ret = 0;
break;
}
return ret;
}
/**
* sys_sched_get_priority_min - return minimum RT priority.
* @policy: scheduling class.
*
* Return: On success, this syscall returns the minimum
* rt_priority that can be used by a given scheduling class.
* On failure, a negative error code is returned.
*/
SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = 1;
break;
case SCHED_NORMAL:
case SCHED_BATCH:
case SCHED_IDLE:
ret = 0;
break;
}
return ret;
}
static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
{
struct task_struct *p;
int retval;
alt_sched_debug();
if (pid < 0)
return -EINVAL;
retval = -ESRCH;
rcu_read_lock();
p = find_process_by_pid(pid);
if (!p)
goto out_unlock;
retval = security_task_getscheduler(p);
if (retval)
goto out_unlock;
rcu_read_unlock();
*t = ns_to_timespec64(sched_timeslice_ns);
return 0;
out_unlock:
rcu_read_unlock();
return retval;
}
/**
* sys_sched_rr_get_interval - return the default timeslice of a process.
* @pid: pid of the process.
* @interval: userspace pointer to the timeslice value.
*
*
* Return: On success, 0 and the timeslice is in @interval. Otherwise,
* an error code.
*/
SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
struct __kernel_timespec __user *, interval)
{
struct timespec64 t;
int retval = sched_rr_get_interval(pid, &t);
if (retval == 0)
retval = put_timespec64(&t, interval);
return retval;
}
#ifdef CONFIG_COMPAT_32BIT_TIME
SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
struct old_timespec32 __user *, interval)
{
struct timespec64 t;
int retval = sched_rr_get_interval(pid, &t);
if (retval == 0)
retval = put_old_timespec32(&t, interval);
return retval;
}
#endif
void sched_show_task(struct task_struct *p)
{
unsigned long free = 0;
int ppid;
if (!try_get_task_stack(p))
return;
pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
if (task_is_running(p))
pr_cont(" running task ");
#ifdef CONFIG_DEBUG_STACK_USAGE
free = stack_not_used(p);
#endif
ppid = 0;
rcu_read_lock();
if (pid_alive(p))
ppid = task_pid_nr(rcu_dereference(p->real_parent));
rcu_read_unlock();
pr_cont(" stack:%-5lu pid:%-5d ppid:%-6d flags:0x%08lx\n",
free, task_pid_nr(p), ppid,
read_task_thread_flags(p));
print_worker_info(KERN_INFO, p);
print_stop_info(KERN_INFO, p);
show_stack(p, NULL, KERN_INFO);
put_task_stack(p);
}
EXPORT_SYMBOL_GPL(sched_show_task);
static inline bool
state_filter_match(unsigned long state_filter, struct task_struct *p)
{
unsigned int state = READ_ONCE(p->__state);
/* no filter, everything matches */
if (!state_filter)
return true;
/* filter, but doesn't match */
if (!(state & state_filter))
return false;
/*
* When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows
* TASK_KILLABLE).
*/
if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD))
return false;
return true;
}
void show_state_filter(unsigned int state_filter)
{
struct task_struct *g, *p;
rcu_read_lock();
for_each_process_thread(g, p) {
/*
* reset the NMI-timeout, listing all files on a slow
* console might take a lot of time:
* Also, reset softlockup watchdogs on all CPUs, because
* another CPU might be blocked waiting for us to process
* an IPI.
*/
touch_nmi_watchdog();
touch_all_softlockup_watchdogs();
if (state_filter_match(state_filter, p))
sched_show_task(p);
}
#ifdef CONFIG_SCHED_DEBUG
/* TODO: Alt schedule FW should support this
if (!state_filter)
sysrq_sched_debug_show();
*/
#endif
rcu_read_unlock();
/*
* Only show locks if all tasks are dumped:
*/
if (!state_filter)
debug_show_all_locks();
}
void dump_cpu_task(int cpu)
{
if (cpu == smp_processor_id() && in_hardirq()) {
struct pt_regs *regs;
regs = get_irq_regs();
if (regs) {
show_regs(regs);
return;
}
}
if (trigger_single_cpu_backtrace(cpu))
return;
pr_info("Task dump for CPU %d:\n", cpu);
sched_show_task(cpu_curr(cpu));
}
/**
* init_idle - set up an idle thread for a given CPU
* @idle: task in question
* @cpu: CPU the idle task belongs to
*
* NOTE: this function does not set the idle thread's NEED_RESCHED
* flag, to make booting more robust.
*/
void __init init_idle(struct task_struct *idle, int cpu)
{
#ifdef CONFIG_SMP
struct affinity_context ac = (struct affinity_context) {
.new_mask = cpumask_of(cpu),
.flags = 0,
};
#endif
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
__sched_fork(0, idle);
raw_spin_lock_irqsave(&idle->pi_lock, flags);
raw_spin_lock(&rq->lock);
idle->last_ran = rq->clock_task;
idle->__state = TASK_RUNNING;
/*
* PF_KTHREAD should already be set at this point; regardless, make it
* look like a proper per-CPU kthread.
*/
idle->flags |= PF_IDLE | PF_KTHREAD | PF_NO_SETAFFINITY;
kthread_set_per_cpu(idle, cpu);
sched_queue_init_idle(&rq->queue, idle);
#ifdef CONFIG_SMP
/*
* It's possible that init_idle() gets called multiple times on a task,
* in that case do_set_cpus_allowed() will not do the right thing.
*
* And since this is boot we can forgo the serialisation.
*/
set_cpus_allowed_common(idle, &ac);
#endif
/* Silence PROVE_RCU */
rcu_read_lock();
__set_task_cpu(idle, cpu);
rcu_read_unlock();
rq->idle = idle;
rcu_assign_pointer(rq->curr, idle);
idle->on_cpu = 1;
raw_spin_unlock(&rq->lock);
raw_spin_unlock_irqrestore(&idle->pi_lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
init_idle_preempt_count(idle, cpu);
ftrace_graph_init_idle_task(idle, cpu);
vtime_init_idle(idle, cpu);
#ifdef CONFIG_SMP
sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu);
#endif
}
#ifdef CONFIG_SMP
int cpuset_cpumask_can_shrink(const struct cpumask __maybe_unused *cur,
const struct cpumask __maybe_unused *trial)
{
return 1;
}
int task_can_attach(struct task_struct *p)
{
int ret = 0;
/*
* Kthreads which disallow setaffinity shouldn't be moved
* to a new cpuset; we don't want to change their CPU
* affinity and isolating such threads by their set of
* allowed nodes is unnecessary. Thus, cpusets are not
* applicable for such threads. This prevents checking for
* success of set_cpus_allowed_ptr() on all attached tasks
* before cpus_mask may be changed.
*/
if (p->flags & PF_NO_SETAFFINITY)
ret = -EINVAL;
return ret;
}
bool sched_smp_initialized __read_mostly;
#ifdef CONFIG_HOTPLUG_CPU
/*
* Ensures that the idle task is using init_mm right before its CPU goes
* offline.
*/
void idle_task_exit(void)
{
struct mm_struct *mm = current->active_mm;
BUG_ON(current != this_rq()->idle);
if (mm != &init_mm) {
switch_mm(mm, &init_mm, current);
finish_arch_post_lock_switch();
}
/* finish_cpu(), as ran on the BP, will clean up the active_mm state */
}
static int __balance_push_cpu_stop(void *arg)
{
struct task_struct *p = arg;
struct rq *rq = this_rq();
struct rq_flags rf;
int cpu;
raw_spin_lock_irq(&p->pi_lock);
rq_lock(rq, &rf);
update_rq_clock(rq);
if (task_rq(p) == rq && task_on_rq_queued(p)) {
cpu = select_fallback_rq(rq->cpu, p);
rq = __migrate_task(rq, p, cpu);
}
rq_unlock(rq, &rf);
raw_spin_unlock_irq(&p->pi_lock);
put_task_struct(p);
return 0;
}
static DEFINE_PER_CPU(struct cpu_stop_work, push_work);
/*
* This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only
* effective when the hotplug motion is down.
*/
static void balance_push(struct rq *rq)
{
struct task_struct *push_task = rq->curr;
lockdep_assert_held(&rq->lock);
/*
* Ensure the thing is persistent until balance_push_set(.on = false);
*/
rq->balance_callback = &balance_push_callback;
/*
* Only active while going offline and when invoked on the outgoing
* CPU.
*/
if (!cpu_dying(rq->cpu) || rq != this_rq())
return;
/*
* Both the cpu-hotplug and stop task are in this case and are
* required to complete the hotplug process.
*/
if (kthread_is_per_cpu(push_task) ||
is_migration_disabled(push_task)) {
/*
* If this is the idle task on the outgoing CPU try to wake
* up the hotplug control thread which might wait for the
* last task to vanish. The rcuwait_active() check is
* accurate here because the waiter is pinned on this CPU
* and can't obviously be running in parallel.
*
* On RT kernels this also has to check whether there are
* pinned and scheduled out tasks on the runqueue. They
* need to leave the migrate disabled section first.
*/
if (!rq->nr_running && !rq_has_pinned_tasks(rq) &&
rcuwait_active(&rq->hotplug_wait)) {
raw_spin_unlock(&rq->lock);
rcuwait_wake_up(&rq->hotplug_wait);
raw_spin_lock(&rq->lock);
}
return;
}
get_task_struct(push_task);
/*
* Temporarily drop rq->lock such that we can wake-up the stop task.
* Both preemption and IRQs are still disabled.
*/
raw_spin_unlock(&rq->lock);
stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task,
this_cpu_ptr(&push_work));
/*
* At this point need_resched() is true and we'll take the loop in
* schedule(). The next pick is obviously going to be the stop task
* which kthread_is_per_cpu() and will push this task away.
*/
raw_spin_lock(&rq->lock);
}
static void balance_push_set(int cpu, bool on)
{
struct rq *rq = cpu_rq(cpu);
struct rq_flags rf;
rq_lock_irqsave(rq, &rf);
if (on) {
WARN_ON_ONCE(rq->balance_callback);
rq->balance_callback = &balance_push_callback;
} else if (rq->balance_callback == &balance_push_callback) {
rq->balance_callback = NULL;
}
rq_unlock_irqrestore(rq, &rf);
}
/*
* Invoked from a CPUs hotplug control thread after the CPU has been marked
* inactive. All tasks which are not per CPU kernel threads are either
* pushed off this CPU now via balance_push() or placed on a different CPU
* during wakeup. Wait until the CPU is quiescent.
*/
static void balance_hotplug_wait(void)
{
struct rq *rq = this_rq();
rcuwait_wait_event(&rq->hotplug_wait,
rq->nr_running == 1 && !rq_has_pinned_tasks(rq),
TASK_UNINTERRUPTIBLE);
}
#else
static void balance_push(struct rq *rq)
{
}
static void balance_push_set(int cpu, bool on)
{
}
static inline void balance_hotplug_wait(void)
{
}
#endif /* CONFIG_HOTPLUG_CPU */
static void set_rq_offline(struct rq *rq)
{
if (rq->online) {
update_rq_clock(rq);
rq->online = false;
}
}
static void set_rq_online(struct rq *rq)
{
if (!rq->online)
rq->online = true;
}
/*
* used to mark begin/end of suspend/resume:
*/
static int num_cpus_frozen;
/*
* Update cpusets according to cpu_active mask. If cpusets are
* disabled, cpuset_update_active_cpus() becomes a simple wrapper
* around partition_sched_domains().
*
* If we come here as part of a suspend/resume, don't touch cpusets because we
* want to restore it back to its original state upon resume anyway.
*/
static void cpuset_cpu_active(void)
{
if (cpuhp_tasks_frozen) {
/*
* num_cpus_frozen tracks how many CPUs are involved in suspend
* resume sequence. As long as this is not the last online
* operation in the resume sequence, just build a single sched
* domain, ignoring cpusets.
*/
partition_sched_domains(1, NULL, NULL);
if (--num_cpus_frozen)
return;
/*
* This is the last CPU online operation. So fall through and
* restore the original sched domains by considering the
* cpuset configurations.
*/
cpuset_force_rebuild();
}
cpuset_update_active_cpus();
}
static int cpuset_cpu_inactive(unsigned int cpu)
{
if (!cpuhp_tasks_frozen) {
cpuset_update_active_cpus();
} else {
num_cpus_frozen++;
partition_sched_domains(1, NULL, NULL);
}
return 0;
}
int sched_cpu_activate(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
/*
* Clear the balance_push callback and prepare to schedule
* regular tasks.
*/
balance_push_set(cpu, false);
#ifdef CONFIG_SCHED_SMT
/*
* When going up, increment the number of cores with SMT present.
*/
if (cpumask_weight(cpu_smt_mask(cpu)) == 2)
static_branch_inc_cpuslocked(&sched_smt_present);
#endif
set_cpu_active(cpu, true);
if (sched_smp_initialized)
cpuset_cpu_active();
/*
* Put the rq online, if not already. This happens:
*
* 1) In the early boot process, because we build the real domains
* after all cpus have been brought up.
*
* 2) At runtime, if cpuset_cpu_active() fails to rebuild the
* domains.
*/
raw_spin_lock_irqsave(&rq->lock, flags);
set_rq_online(rq);
raw_spin_unlock_irqrestore(&rq->lock, flags);
return 0;
}
int sched_cpu_deactivate(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
int ret;
set_cpu_active(cpu, false);
/*
* From this point forward, this CPU will refuse to run any task that
* is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively
* push those tasks away until this gets cleared, see
* sched_cpu_dying().
*/
balance_push_set(cpu, true);
/*
* We've cleared cpu_active_mask, wait for all preempt-disabled and RCU
* users of this state to go away such that all new such users will
* observe it.
*
* Specifically, we rely on ttwu to no longer target this CPU, see
* ttwu_queue_cond() and is_cpu_allowed().
*
* Do sync before park smpboot threads to take care the rcu boost case.
*/
synchronize_rcu();
raw_spin_lock_irqsave(&rq->lock, flags);
set_rq_offline(rq);
raw_spin_unlock_irqrestore(&rq->lock, flags);
#ifdef CONFIG_SCHED_SMT
/*
* When going down, decrement the number of cores with SMT present.
*/
if (cpumask_weight(cpu_smt_mask(cpu)) == 2) {
static_branch_dec_cpuslocked(&sched_smt_present);
if (!static_branch_likely(&sched_smt_present))
cpumask_clear(&sched_sg_idle_mask);
}
#endif
if (!sched_smp_initialized)
return 0;
ret = cpuset_cpu_inactive(cpu);
if (ret) {
balance_push_set(cpu, false);
set_cpu_active(cpu, true);
return ret;
}
return 0;
}
static void sched_rq_cpu_starting(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
rq->calc_load_update = calc_load_update;
}
int sched_cpu_starting(unsigned int cpu)
{
sched_rq_cpu_starting(cpu);
sched_tick_start(cpu);
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Invoked immediately before the stopper thread is invoked to bring the
* CPU down completely. At this point all per CPU kthreads except the
* hotplug thread (current) and the stopper thread (inactive) have been
* either parked or have been unbound from the outgoing CPU. Ensure that
* any of those which might be on the way out are gone.
*
* If after this point a bound task is being woken on this CPU then the
* responsible hotplug callback has failed to do it's job.
* sched_cpu_dying() will catch it with the appropriate fireworks.
*/
int sched_cpu_wait_empty(unsigned int cpu)
{
balance_hotplug_wait();
return 0;
}
/*
* Since this CPU is going 'away' for a while, fold any nr_active delta we
* might have. Called from the CPU stopper task after ensuring that the
* stopper is the last running task on the CPU, so nr_active count is
* stable. We need to take the teardown thread which is calling this into
* account, so we hand in adjust = 1 to the load calculation.
*
* Also see the comment "Global load-average calculations".
*/
static void calc_load_migrate(struct rq *rq)
{
long delta = calc_load_fold_active(rq, 1);
if (delta)
atomic_long_add(delta, &calc_load_tasks);
}
static void dump_rq_tasks(struct rq *rq, const char *loglvl)
{
struct task_struct *g, *p;
int cpu = cpu_of(rq);
lockdep_assert_held(&rq->lock);
printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running);
for_each_process_thread(g, p) {
if (task_cpu(p) != cpu)
continue;
if (!task_on_rq_queued(p))
continue;
printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm);
}
}
int sched_cpu_dying(unsigned int cpu)
{
struct rq *rq = cpu_rq(cpu);
unsigned long flags;
/* Handle pending wakeups and then migrate everything off */
sched_tick_stop(cpu);
raw_spin_lock_irqsave(&rq->lock, flags);
if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) {
WARN(true, "Dying CPU not properly vacated!");
dump_rq_tasks(rq, KERN_WARNING);
}
raw_spin_unlock_irqrestore(&rq->lock, flags);
calc_load_migrate(rq);
hrtick_clear(rq);
return 0;
}
#endif
#ifdef CONFIG_SMP
static void sched_init_topology_cpumask_early(void)
{
int cpu;
cpumask_t *tmp;
for_each_possible_cpu(cpu) {
/* init topo masks */
tmp = per_cpu(sched_cpu_topo_masks, cpu);
cpumask_copy(tmp, cpumask_of(cpu));
tmp++;
cpumask_copy(tmp, cpu_possible_mask);
per_cpu(sched_cpu_llc_mask, cpu) = tmp;
per_cpu(sched_cpu_topo_end_mask, cpu) = ++tmp;
/*per_cpu(sd_llc_id, cpu) = cpu;*/
}
}
#define TOPOLOGY_CPUMASK(name, mask, last)\
if (cpumask_and(topo, topo, mask)) { \
cpumask_copy(topo, mask); \
printk(KERN_INFO "sched: cpu#%02d topo: 0x%08lx - "#name, \
cpu, (topo++)->bits[0]); \
} \
if (!last) \
bitmap_complement(cpumask_bits(topo), cpumask_bits(mask), \
nr_cpumask_bits);
static void sched_init_topology_cpumask(void)
{
int cpu;
cpumask_t *topo;
for_each_online_cpu(cpu) {
/* take chance to reset time slice for idle tasks */
cpu_rq(cpu)->idle->time_slice = sched_timeslice_ns;
topo = per_cpu(sched_cpu_topo_masks, cpu) + 1;
bitmap_complement(cpumask_bits(topo), cpumask_bits(cpumask_of(cpu)),
nr_cpumask_bits);
#ifdef CONFIG_SCHED_SMT
TOPOLOGY_CPUMASK(smt, topology_sibling_cpumask(cpu), false);
#endif
per_cpu(sd_llc_id, cpu) = cpumask_first(cpu_coregroup_mask(cpu));
per_cpu(sched_cpu_llc_mask, cpu) = topo;
TOPOLOGY_CPUMASK(coregroup, cpu_coregroup_mask(cpu), false);
TOPOLOGY_CPUMASK(core, topology_core_cpumask(cpu), false);
TOPOLOGY_CPUMASK(others, cpu_online_mask, true);
per_cpu(sched_cpu_topo_end_mask, cpu) = topo;
printk(KERN_INFO "sched: cpu#%02d llc_id = %d, llc_mask idx = %d\n",
cpu, per_cpu(sd_llc_id, cpu),
(int) (per_cpu(sched_cpu_llc_mask, cpu) -
per_cpu(sched_cpu_topo_masks, cpu)));
}
}
#endif
void __init sched_init_smp(void)
{
/* Move init over to a non-isolated CPU */
if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0)
BUG();
current->flags &= ~PF_NO_SETAFFINITY;
sched_init_topology_cpumask();
sched_smp_initialized = true;
}
static int __init migration_init(void)
{
sched_cpu_starting(smp_processor_id());
return 0;
}
early_initcall(migration_init);
#else
void __init sched_init_smp(void)
{
cpu_rq(0)->idle->time_slice = sched_timeslice_ns;
}
#endif /* CONFIG_SMP */
int in_sched_functions(unsigned long addr)
{
return in_lock_functions(addr) ||
(addr >= (unsigned long)__sched_text_start
&& addr < (unsigned long)__sched_text_end);
}
#ifdef CONFIG_CGROUP_SCHED
/* task group related information */
struct task_group {
struct cgroup_subsys_state css;
struct rcu_head rcu;
struct list_head list;
struct task_group *parent;
struct list_head siblings;
struct list_head children;
#ifdef CONFIG_FAIR_GROUP_SCHED
unsigned long shares;
#endif
};
/*
* Default task group.
* Every task in system belongs to this group at bootup.
*/
struct task_group root_task_group;
LIST_HEAD(task_groups);
/* Cacheline aligned slab cache for task_group */
static struct kmem_cache *task_group_cache __read_mostly;
#endif /* CONFIG_CGROUP_SCHED */
void __init sched_init(void)
{
int i;
struct rq *rq;
printk(KERN_INFO "sched/alt: "ALT_SCHED_NAME" CPU Scheduler "ALT_SCHED_VERSION\
" by Alfred Chen.\n");
wait_bit_init();
#ifdef CONFIG_SMP
for (i = 0; i < SCHED_QUEUE_BITS; i++)
cpumask_copy(sched_preempt_mask + i, cpu_present_mask);
#endif
#ifdef CONFIG_CGROUP_SCHED
task_group_cache = KMEM_CACHE(task_group, 0);
list_add(&root_task_group.list, &task_groups);
INIT_LIST_HEAD(&root_task_group.children);
INIT_LIST_HEAD(&root_task_group.siblings);
#endif /* CONFIG_CGROUP_SCHED */
for_each_possible_cpu(i) {
rq = cpu_rq(i);
sched_queue_init(&rq->queue);
rq->prio = IDLE_TASK_SCHED_PRIO;
rq->skip = NULL;
raw_spin_lock_init(&rq->lock);
rq->nr_running = rq->nr_uninterruptible = 0;
rq->calc_load_active = 0;
rq->calc_load_update = jiffies + LOAD_FREQ;
#ifdef CONFIG_SMP
rq->online = false;
rq->cpu = i;
#ifdef CONFIG_SCHED_SMT
rq->active_balance = 0;
#endif
#ifdef CONFIG_NO_HZ_COMMON
INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq);
#endif
rq->balance_callback = &balance_push_callback;
#ifdef CONFIG_HOTPLUG_CPU
rcuwait_init(&rq->hotplug_wait);
#endif
#endif /* CONFIG_SMP */
rq->nr_switches = 0;
hrtick_rq_init(rq);
atomic_set(&rq->nr_iowait, 0);
zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i));
}
#ifdef CONFIG_SMP
/* Set rq->online for cpu 0 */
cpu_rq(0)->online = true;
#endif
/*
* The boot idle thread does lazy MMU switching as well:
*/
mmgrab(&init_mm);
enter_lazy_tlb(&init_mm, current);
/*
* The idle task doesn't need the kthread struct to function, but it
* is dressed up as a per-CPU kthread and thus needs to play the part
* if we want to avoid special-casing it in code that deals with per-CPU
* kthreads.
*/
WARN_ON(!set_kthread_struct(current));
/*
* Make us the idle thread. Technically, schedule() should not be
* called from this thread, however somewhere below it might be,
* but because we are the idle thread, we just pick up running again
* when this runqueue becomes "idle".
*/
init_idle(current, smp_processor_id());
calc_load_update = jiffies + LOAD_FREQ;
#ifdef CONFIG_SMP
idle_thread_set_boot_cpu();
balance_push_set(smp_processor_id(), false);
sched_init_topology_cpumask_early();
#endif /* SMP */
preempt_dynamic_init();
}
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
void __might_sleep(const char *file, int line)
{
unsigned int state = get_current_state();
/*
* Blocking primitives will set (and therefore destroy) current->state,
* since we will exit with TASK_RUNNING make sure we enter with it,
* otherwise we will destroy state.
*/
WARN_ONCE(state != TASK_RUNNING && current->task_state_change,
"do not call blocking ops when !TASK_RUNNING; "
"state=%x set at [<%p>] %pS\n", state,
(void *)current->task_state_change,
(void *)current->task_state_change);
__might_resched(file, line, 0);
}
EXPORT_SYMBOL(__might_sleep);
static void print_preempt_disable_ip(int preempt_offset, unsigned long ip)
{
if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT))
return;
if (preempt_count() == preempt_offset)
return;
pr_err("Preemption disabled at:");
print_ip_sym(KERN_ERR, ip);
}
static inline bool resched_offsets_ok(unsigned int offsets)
{
unsigned int nested = preempt_count();
nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT;
return nested == offsets;
}
void __might_resched(const char *file, int line, unsigned int offsets)
{
/* Ratelimiting timestamp: */
static unsigned long prev_jiffy;
unsigned long preempt_disable_ip;
/* WARN_ON_ONCE() by default, no rate limit required: */
rcu_sleep_check();
if ((resched_offsets_ok(offsets) && !irqs_disabled() &&
!is_idle_task(current) && !current->non_block_count) ||
system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING ||
oops_in_progress)
return;
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
/* Save this before calling printk(), since that will clobber it: */
preempt_disable_ip = get_preempt_disable_ip(current);
pr_err("BUG: sleeping function called from invalid context at %s:%d\n",
file, line);
pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n",
in_atomic(), irqs_disabled(), current->non_block_count,
current->pid, current->comm);
pr_err("preempt_count: %x, expected: %x\n", preempt_count(),
offsets & MIGHT_RESCHED_PREEMPT_MASK);
if (IS_ENABLED(CONFIG_PREEMPT_RCU)) {
pr_err("RCU nest depth: %d, expected: %u\n",
rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT);
}
if (task_stack_end_corrupted(current))
pr_emerg("Thread overran stack, or stack corrupted\n");
debug_show_held_locks(current);
if (irqs_disabled())
print_irqtrace_events(current);
print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK,
preempt_disable_ip);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
EXPORT_SYMBOL(__might_resched);
void __cant_sleep(const char *file, int line, int preempt_offset)
{
static unsigned long prev_jiffy;
if (irqs_disabled())
return;
if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
return;
if (preempt_count() > preempt_offset)
return;
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line);
printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n",
in_atomic(), irqs_disabled(),
current->pid, current->comm);
debug_show_held_locks(current);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
EXPORT_SYMBOL_GPL(__cant_sleep);
#ifdef CONFIG_SMP
void __cant_migrate(const char *file, int line)
{
static unsigned long prev_jiffy;
if (irqs_disabled())
return;
if (is_migration_disabled(current))
return;
if (!IS_ENABLED(CONFIG_PREEMPT_COUNT))
return;
if (preempt_count() > 0)
return;
if (current->migration_flags & MDF_FORCE_ENABLED)
return;
if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy)
return;
prev_jiffy = jiffies;
pr_err("BUG: assuming non migratable context at %s:%d\n", file, line);
pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n",
in_atomic(), irqs_disabled(), is_migration_disabled(current),
current->pid, current->comm);
debug_show_held_locks(current);
dump_stack();
add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
}
EXPORT_SYMBOL_GPL(__cant_migrate);
#endif
#endif
#ifdef CONFIG_MAGIC_SYSRQ
void normalize_rt_tasks(void)
{
struct task_struct *g, *p;
struct sched_attr attr = {
.sched_policy = SCHED_NORMAL,
};
read_lock(&tasklist_lock);
for_each_process_thread(g, p) {
/*
* Only normalize user tasks:
*/
if (p->flags & PF_KTHREAD)
continue;
schedstat_set(p->stats.wait_start, 0);
schedstat_set(p->stats.sleep_start, 0);
schedstat_set(p->stats.block_start, 0);
if (!rt_task(p)) {
/*
* Renice negative nice level userspace
* tasks back to 0:
*/
if (task_nice(p) < 0)
set_user_nice(p, 0);
continue;
}
__sched_setscheduler(p, &attr, false, false);
}
read_unlock(&tasklist_lock);
}
#endif /* CONFIG_MAGIC_SYSRQ */
#if defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB)
/*
* These functions are only useful for the IA64 MCA handling, or kdb.
*
* They can only be called when the whole system has been
* stopped - every CPU needs to be quiescent, and no scheduling
* activity can take place. Using them for anything else would
* be a serious bug, and as a result, they aren't even visible
* under any other configuration.
*/
/**
* curr_task - return the current task for a given CPU.
* @cpu: the processor in question.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*
* Return: The current task for @cpu.
*/
struct task_struct *curr_task(int cpu)
{
return cpu_curr(cpu);
}
#endif /* defined(CONFIG_IA64) || defined(CONFIG_KGDB_KDB) */
#ifdef CONFIG_IA64
/**
* ia64_set_curr_task - set the current task for a given CPU.
* @cpu: the processor in question.
* @p: the task pointer to set.
*
* Description: This function must only be used when non-maskable interrupts
* are serviced on a separate stack. It allows the architecture to switch the
* notion of the current task on a CPU in a non-blocking manner. This function
* must be called with all CPU's synchronised, and interrupts disabled, the
* and caller must save the original value of the current task (see
* curr_task() above) and restore that value before reenabling interrupts and
* re-starting the system.
*
* ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED!
*/
void ia64_set_curr_task(int cpu, struct task_struct *p)
{
cpu_curr(cpu) = p;
}
#endif
#ifdef CONFIG_CGROUP_SCHED
static void sched_free_group(struct task_group *tg)
{
kmem_cache_free(task_group_cache, tg);
}
static void sched_free_group_rcu(struct rcu_head *rhp)
{
sched_free_group(container_of(rhp, struct task_group, rcu));
}
static void sched_unregister_group(struct task_group *tg)
{
/*
* We have to wait for yet another RCU grace period to expire, as
* print_cfs_stats() might run concurrently.
*/
call_rcu(&tg->rcu, sched_free_group_rcu);
}
/* allocate runqueue etc for a new task group */
struct task_group *sched_create_group(struct task_group *parent)
{
struct task_group *tg;
tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
if (!tg)
return ERR_PTR(-ENOMEM);
return tg;
}
void sched_online_group(struct task_group *tg, struct task_group *parent)
{
}
/* rcu callback to free various structures associated with a task group */
static void sched_unregister_group_rcu(struct rcu_head *rhp)
{
/* Now it should be safe to free those cfs_rqs: */
sched_unregister_group(container_of(rhp, struct task_group, rcu));
}
void sched_destroy_group(struct task_group *tg)
{
/* Wait for possible concurrent references to cfs_rqs complete: */
call_rcu(&tg->rcu, sched_unregister_group_rcu);
}
void sched_release_group(struct task_group *tg)
{
}
static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
{
return css ? container_of(css, struct task_group, css) : NULL;
}
static struct cgroup_subsys_state *
cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
{
struct task_group *parent = css_tg(parent_css);
struct task_group *tg;
if (!parent) {
/* This is early initialization for the top cgroup */
return &root_task_group.css;
}
tg = sched_create_group(parent);
if (IS_ERR(tg))
return ERR_PTR(-ENOMEM);
return &tg->css;
}
/* Expose task group only after completing cgroup initialization */
static int cpu_cgroup_css_online(struct cgroup_subsys_state *css)
{
struct task_group *tg = css_tg(css);
struct task_group *parent = css_tg(css->parent);
if (parent)
sched_online_group(tg, parent);
return 0;
}
static void cpu_cgroup_css_released(struct cgroup_subsys_state *css)
{
struct task_group *tg = css_tg(css);
sched_release_group(tg);
}
static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
{
struct task_group *tg = css_tg(css);
/*
* Relies on the RCU grace period between css_released() and this.
*/
sched_unregister_group(tg);
}
#ifdef CONFIG_RT_GROUP_SCHED
static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
{
return 0;
}
#endif
static void cpu_cgroup_attach(struct cgroup_taskset *tset)
{
}
#ifdef CONFIG_FAIR_GROUP_SCHED
static DEFINE_MUTEX(shares_mutex);
int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
/*
* We can't change the weight of the root cgroup.
*/
if (&root_task_group == tg)
return -EINVAL;
shares = clamp(shares, scale_load(MIN_SHARES), scale_load(MAX_SHARES));
mutex_lock(&shares_mutex);
if (tg->shares == shares)
goto done;
tg->shares = shares;
done:
mutex_unlock(&shares_mutex);
return 0;
}
static int cpu_shares_write_u64(struct cgroup_subsys_state *css,
struct cftype *cftype, u64 shareval)
{
if (shareval > scale_load_down(ULONG_MAX))
shareval = MAX_SHARES;
return sched_group_set_shares(css_tg(css), scale_load(shareval));
}
static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css,
struct cftype *cft)
{
struct task_group *tg = css_tg(css);
return (u64) scale_load_down(tg->shares);
}
#endif
static struct cftype cpu_legacy_files[] = {
#ifdef CONFIG_FAIR_GROUP_SCHED
{
.name = "shares",
.read_u64 = cpu_shares_read_u64,
.write_u64 = cpu_shares_write_u64,
},
#endif
{ } /* Terminate */
};
static struct cftype cpu_files[] = {
{ } /* terminate */
};
static int cpu_extra_stat_show(struct seq_file *sf,
struct cgroup_subsys_state *css)
{
return 0;
}
struct cgroup_subsys cpu_cgrp_subsys = {
.css_alloc = cpu_cgroup_css_alloc,
.css_online = cpu_cgroup_css_online,
.css_released = cpu_cgroup_css_released,
.css_free = cpu_cgroup_css_free,
.css_extra_stat_show = cpu_extra_stat_show,
#ifdef CONFIG_RT_GROUP_SCHED
.can_attach = cpu_cgroup_can_attach,
#endif
.attach = cpu_cgroup_attach,
.legacy_cftypes = cpu_files,
.legacy_cftypes = cpu_legacy_files,
.dfl_cftypes = cpu_files,
.early_init = true,
.threaded = true,
};
#endif /* CONFIG_CGROUP_SCHED */
#undef CREATE_TRACE_POINTS
#ifdef CONFIG_SCHED_MM_CID
#
/*
* @cid_lock: Guarantee forward-progress of cid allocation.
*
* Concurrency ID allocation within a bitmap is mostly lock-free. The cid_lock
* is only used when contention is detected by the lock-free allocation so
* forward progress can be guaranteed.
*/
DEFINE_RAW_SPINLOCK(cid_lock);
/*
* @use_cid_lock: Select cid allocation behavior: lock-free vs spinlock.
*
* When @use_cid_lock is 0, the cid allocation is lock-free. When contention is
* detected, it is set to 1 to ensure that all newly coming allocations are
* serialized by @cid_lock until the allocation which detected contention
* completes and sets @use_cid_lock back to 0. This guarantees forward progress
* of a cid allocation.
*/
int use_cid_lock;
/*
* mm_cid remote-clear implements a lock-free algorithm to clear per-mm/cpu cid
* concurrently with respect to the execution of the source runqueue context
* switch.
*
* There is one basic properties we want to guarantee here:
*
* (1) Remote-clear should _never_ mark a per-cpu cid UNSET when it is actively
* used by a task. That would lead to concurrent allocation of the cid and
* userspace corruption.
*
* Provide this guarantee by introducing a Dekker memory ordering to guarantee
* that a pair of loads observe at least one of a pair of stores, which can be
* shown as:
*
* X = Y = 0
*
* w[X]=1 w[Y]=1
* MB MB
* r[Y]=y r[X]=x
*
* Which guarantees that x==0 && y==0 is impossible. But rather than using
* values 0 and 1, this algorithm cares about specific state transitions of the
* runqueue current task (as updated by the scheduler context switch), and the
* per-mm/cpu cid value.
*
* Let's introduce task (Y) which has task->mm == mm and task (N) which has
* task->mm != mm for the rest of the discussion. There are two scheduler state
* transitions on context switch we care about:
*
* (TSA) Store to rq->curr with transition from (N) to (Y)
*
* (TSB) Store to rq->curr with transition from (Y) to (N)
*
* On the remote-clear side, there is one transition we care about:
*
* (TMA) cmpxchg to *pcpu_cid to set the LAZY flag
*
* There is also a transition to UNSET state which can be performed from all
* sides (scheduler, remote-clear). It is always performed with a cmpxchg which
* guarantees that only a single thread will succeed:
*
* (TMB) cmpxchg to *pcpu_cid to mark UNSET
*
* Just to be clear, what we do _not_ want to happen is a transition to UNSET
* when a thread is actively using the cid (property (1)).
*
* Let's looks at the relevant combinations of TSA/TSB, and TMA transitions.
*
* Scenario A) (TSA)+(TMA) (from next task perspective)
*
* CPU0 CPU1
*
* Context switch CS-1 Remote-clear
* - store to rq->curr: (N)->(Y) (TSA) - cmpxchg to *pcpu_id to LAZY (TMA)
* (implied barrier after cmpxchg)
* - switch_mm_cid()
* - memory barrier (see switch_mm_cid()
* comment explaining how this barrier
* is combined with other scheduler
* barriers)
* - mm_cid_get (next)
* - READ_ONCE(*pcpu_cid) - rcu_dereference(src_rq->curr)
*
* This Dekker ensures that either task (Y) is observed by the
* rcu_dereference() or the LAZY flag is observed by READ_ONCE(), or both are
* observed.
*
* If task (Y) store is observed by rcu_dereference(), it means that there is
* still an active task on the cpu. Remote-clear will therefore not transition
* to UNSET, which fulfills property (1).
*
* If task (Y) is not observed, but the lazy flag is observed by READ_ONCE(),
* it will move its state to UNSET, which clears the percpu cid perhaps
* uselessly (which is not an issue for correctness). Because task (Y) is not
* observed, CPU1 can move ahead to set the state to UNSET. Because moving
* state to UNSET is done with a cmpxchg expecting that the old state has the
* LAZY flag set, only one thread will successfully UNSET.
*
* If both states (LAZY flag and task (Y)) are observed, the thread on CPU0
* will observe the LAZY flag and transition to UNSET (perhaps uselessly), and
* CPU1 will observe task (Y) and do nothing more, which is fine.
*
* What we are effectively preventing with this Dekker is a scenario where
* neither LAZY flag nor store (Y) are observed, which would fail property (1)
* because this would UNSET a cid which is actively used.
*/
void sched_mm_cid_migrate_from(struct task_struct *t)
{
t->migrate_from_cpu = task_cpu(t);
}
static
int __sched_mm_cid_migrate_from_fetch_cid(struct rq *src_rq,
struct task_struct *t,
struct mm_cid *src_pcpu_cid)
{
struct mm_struct *mm = t->mm;
struct task_struct *src_task;
int src_cid, last_mm_cid;
if (!mm)
return -1;
last_mm_cid = t->last_mm_cid;
/*
* If the migrated task has no last cid, or if the current
* task on src rq uses the cid, it means the source cid does not need
* to be moved to the destination cpu.
*/
if (last_mm_cid == -1)
return -1;
src_cid = READ_ONCE(src_pcpu_cid->cid);
if (!mm_cid_is_valid(src_cid) || last_mm_cid != src_cid)
return -1;
/*
* If we observe an active task using the mm on this rq, it means we
* are not the last task to be migrated from this cpu for this mm, so
* there is no need to move src_cid to the destination cpu.
*/
rcu_read_lock();
src_task = rcu_dereference(src_rq->curr);
if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
rcu_read_unlock();
t->last_mm_cid = -1;
return -1;
}
rcu_read_unlock();
return src_cid;
}
static
int __sched_mm_cid_migrate_from_try_steal_cid(struct rq *src_rq,
struct task_struct *t,
struct mm_cid *src_pcpu_cid,
int src_cid)
{
struct task_struct *src_task;
struct mm_struct *mm = t->mm;
int lazy_cid;
if (src_cid == -1)
return -1;
/*
* Attempt to clear the source cpu cid to move it to the destination
* cpu.
*/
lazy_cid = mm_cid_set_lazy_put(src_cid);
if (!try_cmpxchg(&src_pcpu_cid->cid, &src_cid, lazy_cid))
return -1;
/*
* The implicit barrier after cmpxchg per-mm/cpu cid before loading
* rq->curr->mm matches the scheduler barrier in context_switch()
* between store to rq->curr and load of prev and next task's
* per-mm/cpu cid.
*
* The implicit barrier after cmpxchg per-mm/cpu cid before loading
* rq->curr->mm_cid_active matches the barrier in
* sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
* sched_mm_cid_after_execve() between store to t->mm_cid_active and
* load of per-mm/cpu cid.
*/
/*
* If we observe an active task using the mm on this rq after setting
* the lazy-put flag, this task will be responsible for transitioning
* from lazy-put flag set to MM_CID_UNSET.
*/
rcu_read_lock();
src_task = rcu_dereference(src_rq->curr);
if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) {
rcu_read_unlock();
/*
* We observed an active task for this mm, there is therefore
* no point in moving this cid to the destination cpu.
*/
t->last_mm_cid = -1;
return -1;
}
rcu_read_unlock();
/*
* The src_cid is unused, so it can be unset.
*/
if (!try_cmpxchg(&src_pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
return -1;
return src_cid;
}
/*
* Migration to dst cpu. Called with dst_rq lock held.
* Interrupts are disabled, which keeps the window of cid ownership without the
* source rq lock held small.
*/
void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t, int src_cpu)
{
struct mm_cid *src_pcpu_cid, *dst_pcpu_cid;
struct mm_struct *mm = t->mm;
int src_cid, dst_cid;
struct rq *src_rq;
lockdep_assert_rq_held(dst_rq);
if (!mm)
return;
if (src_cpu == -1) {
t->last_mm_cid = -1;
return;
}
/*
* Move the src cid if the dst cid is unset. This keeps id
* allocation closest to 0 in cases where few threads migrate around
* many cpus.
*
* If destination cid is already set, we may have to just clear
* the src cid to ensure compactness in frequent migrations
* scenarios.
*
* It is not useful to clear the src cid when the number of threads is
* greater or equal to the number of allowed cpus, because user-space
* can expect that the number of allowed cids can reach the number of
* allowed cpus.
*/
dst_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu_of(dst_rq));
dst_cid = READ_ONCE(dst_pcpu_cid->cid);
if (!mm_cid_is_unset(dst_cid) &&
atomic_read(&mm->mm_users) >= t->nr_cpus_allowed)
return;
src_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, src_cpu);
src_rq = cpu_rq(src_cpu);
src_cid = __sched_mm_cid_migrate_from_fetch_cid(src_rq, t, src_pcpu_cid);
if (src_cid == -1)
return;
src_cid = __sched_mm_cid_migrate_from_try_steal_cid(src_rq, t, src_pcpu_cid,
src_cid);
if (src_cid == -1)
return;
if (!mm_cid_is_unset(dst_cid)) {
__mm_cid_put(mm, src_cid);
return;
}
/* Move src_cid to dst cpu. */
mm_cid_snapshot_time(dst_rq, mm);
WRITE_ONCE(dst_pcpu_cid->cid, src_cid);
}
static void sched_mm_cid_remote_clear(struct mm_struct *mm, struct mm_cid *pcpu_cid,
int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct task_struct *t;
unsigned long flags;
int cid, lazy_cid;
cid = READ_ONCE(pcpu_cid->cid);
if (!mm_cid_is_valid(cid))
return;
/*
* Clear the cpu cid if it is set to keep cid allocation compact. If
* there happens to be other tasks left on the source cpu using this
* mm, the next task using this mm will reallocate its cid on context
* switch.
*/
lazy_cid = mm_cid_set_lazy_put(cid);
if (!try_cmpxchg(&pcpu_cid->cid, &cid, lazy_cid))
return;
/*
* The implicit barrier after cmpxchg per-mm/cpu cid before loading
* rq->curr->mm matches the scheduler barrier in context_switch()
* between store to rq->curr and load of prev and next task's
* per-mm/cpu cid.
*
* The implicit barrier after cmpxchg per-mm/cpu cid before loading
* rq->curr->mm_cid_active matches the barrier in
* sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and
* sched_mm_cid_after_execve() between store to t->mm_cid_active and
* load of per-mm/cpu cid.
*/
/*
* If we observe an active task using the mm on this rq after setting
* the lazy-put flag, that task will be responsible for transitioning
* from lazy-put flag set to MM_CID_UNSET.
*/
rcu_read_lock();
t = rcu_dereference(rq->curr);
if (READ_ONCE(t->mm_cid_active) && t->mm == mm) {
rcu_read_unlock();
return;
}
rcu_read_unlock();
/*
* The cid is unused, so it can be unset.
* Disable interrupts to keep the window of cid ownership without rq
* lock small.
*/
local_irq_save(flags);
if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET))
__mm_cid_put(mm, cid);
local_irq_restore(flags);
}
static void sched_mm_cid_remote_clear_old(struct mm_struct *mm, int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct mm_cid *pcpu_cid;
struct task_struct *curr;
u64 rq_clock;
/*
* rq->clock load is racy on 32-bit but one spurious clear once in a
* while is irrelevant.
*/
rq_clock = READ_ONCE(rq->clock);
pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
/*
* In order to take care of infrequently scheduled tasks, bump the time
* snapshot associated with this cid if an active task using the mm is
* observed on this rq.
*/
rcu_read_lock();
curr = rcu_dereference(rq->curr);
if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) {
WRITE_ONCE(pcpu_cid->time, rq_clock);
rcu_read_unlock();
return;
}
rcu_read_unlock();
if (rq_clock < pcpu_cid->time + SCHED_MM_CID_PERIOD_NS)
return;
sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
}
static void sched_mm_cid_remote_clear_weight(struct mm_struct *mm, int cpu,
int weight)
{
struct mm_cid *pcpu_cid;
int cid;
pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu);
cid = READ_ONCE(pcpu_cid->cid);
if (!mm_cid_is_valid(cid) || cid < weight)
return;
sched_mm_cid_remote_clear(mm, pcpu_cid, cpu);
}
static void task_mm_cid_work(struct callback_head *work)
{
unsigned long now = jiffies, old_scan, next_scan;
struct task_struct *t = current;
struct cpumask *cidmask;
struct mm_struct *mm;
int weight, cpu;
SCHED_WARN_ON(t != container_of(work, struct task_struct, cid_work));
work->next = work; /* Prevent double-add */
if (t->flags & PF_EXITING)
return;
mm = t->mm;
if (!mm)
return;
old_scan = READ_ONCE(mm->mm_cid_next_scan);
next_scan = now + msecs_to_jiffies(MM_CID_SCAN_DELAY);
if (!old_scan) {
unsigned long res;
res = cmpxchg(&mm->mm_cid_next_scan, old_scan, next_scan);
if (res != old_scan)
old_scan = res;
else
old_scan = next_scan;
}
if (time_before(now, old_scan))
return;
if (!try_cmpxchg(&mm->mm_cid_next_scan, &old_scan, next_scan))
return;
cidmask = mm_cidmask(mm);
/* Clear cids that were not recently used. */
for_each_possible_cpu(cpu)
sched_mm_cid_remote_clear_old(mm, cpu);
weight = cpumask_weight(cidmask);
/*
* Clear cids that are greater or equal to the cidmask weight to
* recompact it.
*/
for_each_possible_cpu(cpu)
sched_mm_cid_remote_clear_weight(mm, cpu, weight);
}
void init_sched_mm_cid(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
int mm_users = 0;
if (mm) {
mm_users = atomic_read(&mm->mm_users);
if (mm_users == 1)
mm->mm_cid_next_scan = jiffies + msecs_to_jiffies(MM_CID_SCAN_DELAY);
}
t->cid_work.next = &t->cid_work; /* Protect against double add */
init_task_work(&t->cid_work, task_mm_cid_work);
}
void task_tick_mm_cid(struct rq *rq, struct task_struct *curr)
{
struct callback_head *work = &curr->cid_work;
unsigned long now = jiffies;
if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) ||
work->next != work)
return;
if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan)))
return;
task_work_add(curr, work, TWA_RESUME);
}
void sched_mm_cid_exit_signals(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
struct rq_flags rf;
struct rq *rq;
if (!mm)
return;
preempt_disable();
rq = this_rq();
rq_lock_irqsave(rq, &rf);
preempt_enable_no_resched(); /* holding spinlock */
WRITE_ONCE(t->mm_cid_active, 0);
/*
* Store t->mm_cid_active before loading per-mm/cpu cid.
* Matches barrier in sched_mm_cid_remote_clear_old().
*/
smp_mb();
mm_cid_put(mm);
t->last_mm_cid = t->mm_cid = -1;
rq_unlock_irqrestore(rq, &rf);
}
void sched_mm_cid_before_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
struct rq_flags rf;
struct rq *rq;
if (!mm)
return;
preempt_disable();
rq = this_rq();
rq_lock_irqsave(rq, &rf);
preempt_enable_no_resched(); /* holding spinlock */
WRITE_ONCE(t->mm_cid_active, 0);
/*
* Store t->mm_cid_active before loading per-mm/cpu cid.
* Matches barrier in sched_mm_cid_remote_clear_old().
*/
smp_mb();
mm_cid_put(mm);
t->last_mm_cid = t->mm_cid = -1;
rq_unlock_irqrestore(rq, &rf);
}
void sched_mm_cid_after_execve(struct task_struct *t)
{
struct mm_struct *mm = t->mm;
struct rq_flags rf;
struct rq *rq;
if (!mm)
return;
preempt_disable();
rq = this_rq();
rq_lock_irqsave(rq, &rf);
preempt_enable_no_resched(); /* holding spinlock */
WRITE_ONCE(t->mm_cid_active, 1);
/*
* Store t->mm_cid_active before loading per-mm/cpu cid.
* Matches barrier in sched_mm_cid_remote_clear_old().
*/
smp_mb();
t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm);
rq_unlock_irqrestore(rq, &rf);
rseq_set_notify_resume(t);
}
void sched_mm_cid_fork(struct task_struct *t)
{
WARN_ON_ONCE(!t->mm || t->mm_cid != -1);
t->mm_cid_active = 1;
}
#endif
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