1608 lines
40 KiB
C
1608 lines
40 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
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*
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* No idle tick implementation for low and high resolution timers
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*
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* Started by: Thomas Gleixner and Ingo Molnar
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/hrtimer.h>
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#include <linux/interrupt.h>
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#include <linux/kernel_stat.h>
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#include <linux/percpu.h>
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#include <linux/nmi.h>
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#include <linux/profile.h>
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#include <linux/sched/signal.h>
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#include <linux/sched/clock.h>
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#include <linux/sched/stat.h>
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#include <linux/sched/nohz.h>
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#include <linux/sched/loadavg.h>
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#include <linux/module.h>
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#include <linux/irq_work.h>
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#include <linux/posix-timers.h>
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#include <linux/context_tracking.h>
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#include <linux/mm.h>
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#include <asm/irq_regs.h>
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#include "tick-internal.h"
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#include <trace/events/timer.h>
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/*
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* Per-CPU nohz control structure
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*/
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static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
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struct tick_sched *tick_get_tick_sched(int cpu)
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{
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return &per_cpu(tick_cpu_sched, cpu);
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}
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#if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
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/*
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* The time, when the last jiffy update happened. Write access must hold
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* jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a
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* consistent view of jiffies and last_jiffies_update.
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*/
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static ktime_t last_jiffies_update;
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/*
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* Must be called with interrupts disabled !
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*/
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static void tick_do_update_jiffies64(ktime_t now)
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{
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unsigned long ticks = 1;
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ktime_t delta, nextp;
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/*
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* 64bit can do a quick check without holding jiffies lock and
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* without looking at the sequence count. The smp_load_acquire()
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* pairs with the update done later in this function.
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*
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* 32bit cannot do that because the store of tick_next_period
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* consists of two 32bit stores and the first store could move it
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* to a random point in the future.
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*/
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if (IS_ENABLED(CONFIG_64BIT)) {
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if (ktime_before(now, smp_load_acquire(&tick_next_period)))
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return;
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} else {
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unsigned int seq;
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/*
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* Avoid contention on jiffies_lock and protect the quick
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* check with the sequence count.
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*/
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do {
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seq = read_seqcount_begin(&jiffies_seq);
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nextp = tick_next_period;
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} while (read_seqcount_retry(&jiffies_seq, seq));
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if (ktime_before(now, nextp))
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return;
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}
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/* Quick check failed, i.e. update is required. */
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raw_spin_lock(&jiffies_lock);
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/*
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* Reevaluate with the lock held. Another CPU might have done the
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* update already.
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*/
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if (ktime_before(now, tick_next_period)) {
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raw_spin_unlock(&jiffies_lock);
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return;
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}
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write_seqcount_begin(&jiffies_seq);
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delta = ktime_sub(now, tick_next_period);
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if (unlikely(delta >= TICK_NSEC)) {
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/* Slow path for long idle sleep times */
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s64 incr = TICK_NSEC;
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ticks += ktime_divns(delta, incr);
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last_jiffies_update = ktime_add_ns(last_jiffies_update,
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incr * ticks);
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} else {
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last_jiffies_update = ktime_add_ns(last_jiffies_update,
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TICK_NSEC);
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}
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/* Advance jiffies to complete the jiffies_seq protected job */
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jiffies_64 += ticks;
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/*
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* Keep the tick_next_period variable up to date.
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*/
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nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
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if (IS_ENABLED(CONFIG_64BIT)) {
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/*
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* Pairs with smp_load_acquire() in the lockless quick
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* check above and ensures that the update to jiffies_64 is
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* not reordered vs. the store to tick_next_period, neither
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* by the compiler nor by the CPU.
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*/
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smp_store_release(&tick_next_period, nextp);
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} else {
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/*
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* A plain store is good enough on 32bit as the quick check
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* above is protected by the sequence count.
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*/
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tick_next_period = nextp;
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}
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/*
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* Release the sequence count. calc_global_load() below is not
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* protected by it, but jiffies_lock needs to be held to prevent
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* concurrent invocations.
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*/
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write_seqcount_end(&jiffies_seq);
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calc_global_load();
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raw_spin_unlock(&jiffies_lock);
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update_wall_time();
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}
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/*
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* Initialize and return retrieve the jiffies update.
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*/
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static ktime_t tick_init_jiffy_update(void)
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{
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ktime_t period;
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raw_spin_lock(&jiffies_lock);
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write_seqcount_begin(&jiffies_seq);
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/* Did we start the jiffies update yet ? */
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if (last_jiffies_update == 0) {
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u32 rem;
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/*
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* Ensure that the tick is aligned to a multiple of
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* TICK_NSEC.
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*/
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div_u64_rem(tick_next_period, TICK_NSEC, &rem);
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if (rem)
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tick_next_period += TICK_NSEC - rem;
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last_jiffies_update = tick_next_period;
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}
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period = last_jiffies_update;
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write_seqcount_end(&jiffies_seq);
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raw_spin_unlock(&jiffies_lock);
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return period;
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}
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#define MAX_STALLED_JIFFIES 5
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static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
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{
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int cpu = smp_processor_id();
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#ifdef CONFIG_NO_HZ_COMMON
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/*
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* Check if the do_timer duty was dropped. We don't care about
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* concurrency: This happens only when the CPU in charge went
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* into a long sleep. If two CPUs happen to assign themselves to
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* this duty, then the jiffies update is still serialized by
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* jiffies_lock.
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*
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* If nohz_full is enabled, this should not happen because the
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* tick_do_timer_cpu never relinquishes.
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*/
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if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
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#ifdef CONFIG_NO_HZ_FULL
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WARN_ON_ONCE(tick_nohz_full_running);
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#endif
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tick_do_timer_cpu = cpu;
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}
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#endif
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/* Check, if the jiffies need an update */
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if (tick_do_timer_cpu == cpu)
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tick_do_update_jiffies64(now);
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/*
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* If jiffies update stalled for too long (timekeeper in stop_machine()
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* or VMEXIT'ed for several msecs), force an update.
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*/
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if (ts->last_tick_jiffies != jiffies) {
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ts->stalled_jiffies = 0;
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ts->last_tick_jiffies = READ_ONCE(jiffies);
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} else {
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if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
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tick_do_update_jiffies64(now);
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ts->stalled_jiffies = 0;
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ts->last_tick_jiffies = READ_ONCE(jiffies);
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}
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}
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if (ts->inidle)
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ts->got_idle_tick = 1;
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}
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static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
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{
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#ifdef CONFIG_NO_HZ_COMMON
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/*
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* When we are idle and the tick is stopped, we have to touch
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* the watchdog as we might not schedule for a really long
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* time. This happens on complete idle SMP systems while
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* waiting on the login prompt. We also increment the "start of
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* idle" jiffy stamp so the idle accounting adjustment we do
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* when we go busy again does not account too much ticks.
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*/
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if (ts->tick_stopped) {
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touch_softlockup_watchdog_sched();
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if (is_idle_task(current))
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ts->idle_jiffies++;
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/*
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* In case the current tick fired too early past its expected
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* expiration, make sure we don't bypass the next clock reprogramming
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* to the same deadline.
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*/
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ts->next_tick = 0;
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}
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#endif
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update_process_times(user_mode(regs));
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profile_tick(CPU_PROFILING);
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}
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#endif
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#ifdef CONFIG_NO_HZ_FULL
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cpumask_var_t tick_nohz_full_mask;
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EXPORT_SYMBOL_GPL(tick_nohz_full_mask);
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bool tick_nohz_full_running;
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EXPORT_SYMBOL_GPL(tick_nohz_full_running);
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static atomic_t tick_dep_mask;
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static bool check_tick_dependency(atomic_t *dep)
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{
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int val = atomic_read(dep);
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if (val & TICK_DEP_MASK_POSIX_TIMER) {
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trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
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return true;
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}
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if (val & TICK_DEP_MASK_PERF_EVENTS) {
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trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
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return true;
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}
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if (val & TICK_DEP_MASK_SCHED) {
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trace_tick_stop(0, TICK_DEP_MASK_SCHED);
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return true;
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}
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if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
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trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
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return true;
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}
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if (val & TICK_DEP_MASK_RCU) {
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trace_tick_stop(0, TICK_DEP_MASK_RCU);
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return true;
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}
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if (val & TICK_DEP_MASK_RCU_EXP) {
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trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
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return true;
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}
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return false;
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}
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static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
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{
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lockdep_assert_irqs_disabled();
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if (unlikely(!cpu_online(cpu)))
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return false;
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if (check_tick_dependency(&tick_dep_mask))
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return false;
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if (check_tick_dependency(&ts->tick_dep_mask))
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return false;
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if (check_tick_dependency(¤t->tick_dep_mask))
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return false;
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if (check_tick_dependency(¤t->signal->tick_dep_mask))
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return false;
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return true;
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}
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static void nohz_full_kick_func(struct irq_work *work)
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{
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/* Empty, the tick restart happens on tick_nohz_irq_exit() */
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}
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static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) =
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IRQ_WORK_INIT_HARD(nohz_full_kick_func);
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/*
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* Kick this CPU if it's full dynticks in order to force it to
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* re-evaluate its dependency on the tick and restart it if necessary.
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* This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
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* is NMI safe.
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*/
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static void tick_nohz_full_kick(void)
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{
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if (!tick_nohz_full_cpu(smp_processor_id()))
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return;
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irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
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}
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/*
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* Kick the CPU if it's full dynticks in order to force it to
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* re-evaluate its dependency on the tick and restart it if necessary.
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*/
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void tick_nohz_full_kick_cpu(int cpu)
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{
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if (!tick_nohz_full_cpu(cpu))
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return;
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irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
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}
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static void tick_nohz_kick_task(struct task_struct *tsk)
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{
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int cpu;
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/*
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* If the task is not running, run_posix_cpu_timers()
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* has nothing to elapse, IPI can then be spared.
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*
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* activate_task() STORE p->tick_dep_mask
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* STORE p->on_rq
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* __schedule() (switch to task 'p') smp_mb() (atomic_fetch_or())
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* LOCK rq->lock LOAD p->on_rq
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* smp_mb__after_spin_lock()
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* tick_nohz_task_switch()
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* LOAD p->tick_dep_mask
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*/
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if (!sched_task_on_rq(tsk))
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return;
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/*
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* If the task concurrently migrates to another CPU,
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* we guarantee it sees the new tick dependency upon
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* schedule.
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*
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* set_task_cpu(p, cpu);
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* STORE p->cpu = @cpu
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* __schedule() (switch to task 'p')
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* LOCK rq->lock
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* smp_mb__after_spin_lock() STORE p->tick_dep_mask
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* tick_nohz_task_switch() smp_mb() (atomic_fetch_or())
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* LOAD p->tick_dep_mask LOAD p->cpu
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*/
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cpu = task_cpu(tsk);
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preempt_disable();
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if (cpu_online(cpu))
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tick_nohz_full_kick_cpu(cpu);
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preempt_enable();
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}
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/*
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* Kick all full dynticks CPUs in order to force these to re-evaluate
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* their dependency on the tick and restart it if necessary.
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*/
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static void tick_nohz_full_kick_all(void)
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{
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int cpu;
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if (!tick_nohz_full_running)
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return;
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preempt_disable();
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for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
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tick_nohz_full_kick_cpu(cpu);
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preempt_enable();
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}
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static void tick_nohz_dep_set_all(atomic_t *dep,
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enum tick_dep_bits bit)
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{
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int prev;
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prev = atomic_fetch_or(BIT(bit), dep);
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if (!prev)
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tick_nohz_full_kick_all();
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}
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/*
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* Set a global tick dependency. Used by perf events that rely on freq and
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* by unstable clock.
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*/
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void tick_nohz_dep_set(enum tick_dep_bits bit)
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{
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tick_nohz_dep_set_all(&tick_dep_mask, bit);
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}
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void tick_nohz_dep_clear(enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &tick_dep_mask);
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}
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/*
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* Set per-CPU tick dependency. Used by scheduler and perf events in order to
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* manage events throttling.
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*/
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void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
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{
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int prev;
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struct tick_sched *ts;
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ts = per_cpu_ptr(&tick_cpu_sched, cpu);
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prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
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if (!prev) {
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preempt_disable();
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/* Perf needs local kick that is NMI safe */
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if (cpu == smp_processor_id()) {
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tick_nohz_full_kick();
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} else {
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/* Remote irq work not NMI-safe */
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if (!WARN_ON_ONCE(in_nmi()))
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tick_nohz_full_kick_cpu(cpu);
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}
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preempt_enable();
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}
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
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void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
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{
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struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
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atomic_andnot(BIT(bit), &ts->tick_dep_mask);
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
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/*
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* Set a per-task tick dependency. RCU need this. Also posix CPU timers
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* in order to elapse per task timers.
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*/
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void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
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{
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if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
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tick_nohz_kick_task(tsk);
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
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void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
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}
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EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
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/*
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* Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
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* per process timers.
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*/
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void tick_nohz_dep_set_signal(struct task_struct *tsk,
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enum tick_dep_bits bit)
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{
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int prev;
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struct signal_struct *sig = tsk->signal;
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prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);
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if (!prev) {
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struct task_struct *t;
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lockdep_assert_held(&tsk->sighand->siglock);
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__for_each_thread(sig, t)
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tick_nohz_kick_task(t);
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}
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}
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void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
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{
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atomic_andnot(BIT(bit), &sig->tick_dep_mask);
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}
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/*
|
|
* Re-evaluate the need for the tick as we switch the current task.
|
|
* It might need the tick due to per task/process properties:
|
|
* perf events, posix CPU timers, ...
|
|
*/
|
|
void __tick_nohz_task_switch(void)
|
|
{
|
|
struct tick_sched *ts;
|
|
|
|
if (!tick_nohz_full_cpu(smp_processor_id()))
|
|
return;
|
|
|
|
ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
if (ts->tick_stopped) {
|
|
if (atomic_read(¤t->tick_dep_mask) ||
|
|
atomic_read(¤t->signal->tick_dep_mask))
|
|
tick_nohz_full_kick();
|
|
}
|
|
}
|
|
|
|
/* Get the boot-time nohz CPU list from the kernel parameters. */
|
|
void __init tick_nohz_full_setup(cpumask_var_t cpumask)
|
|
{
|
|
alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
|
|
cpumask_copy(tick_nohz_full_mask, cpumask);
|
|
tick_nohz_full_running = true;
|
|
}
|
|
|
|
bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
|
|
{
|
|
/*
|
|
* The tick_do_timer_cpu CPU handles housekeeping duty (unbound
|
|
* timers, workqueues, timekeeping, ...) on behalf of full dynticks
|
|
* CPUs. It must remain online when nohz full is enabled.
|
|
*/
|
|
if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
|
|
return false;
|
|
return true;
|
|
}
|
|
|
|
static int tick_nohz_cpu_down(unsigned int cpu)
|
|
{
|
|
return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
|
|
}
|
|
|
|
void __init tick_nohz_init(void)
|
|
{
|
|
int cpu, ret;
|
|
|
|
if (!tick_nohz_full_running)
|
|
return;
|
|
|
|
/*
|
|
* Full dynticks uses irq work to drive the tick rescheduling on safe
|
|
* locking contexts. But then we need irq work to raise its own
|
|
* interrupts to avoid circular dependency on the tick
|
|
*/
|
|
if (!arch_irq_work_has_interrupt()) {
|
|
pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
|
|
cpumask_clear(tick_nohz_full_mask);
|
|
tick_nohz_full_running = false;
|
|
return;
|
|
}
|
|
|
|
if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
|
|
!IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
|
|
cpu = smp_processor_id();
|
|
|
|
if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
|
|
pr_warn("NO_HZ: Clearing %d from nohz_full range "
|
|
"for timekeeping\n", cpu);
|
|
cpumask_clear_cpu(cpu, tick_nohz_full_mask);
|
|
}
|
|
}
|
|
|
|
for_each_cpu(cpu, tick_nohz_full_mask)
|
|
ct_cpu_track_user(cpu);
|
|
|
|
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
|
|
"kernel/nohz:predown", NULL,
|
|
tick_nohz_cpu_down);
|
|
WARN_ON(ret < 0);
|
|
pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
|
|
cpumask_pr_args(tick_nohz_full_mask));
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* NOHZ - aka dynamic tick functionality
|
|
*/
|
|
#ifdef CONFIG_NO_HZ_COMMON
|
|
/*
|
|
* NO HZ enabled ?
|
|
*/
|
|
bool tick_nohz_enabled __read_mostly = true;
|
|
unsigned long tick_nohz_active __read_mostly;
|
|
/*
|
|
* Enable / Disable tickless mode
|
|
*/
|
|
static int __init setup_tick_nohz(char *str)
|
|
{
|
|
return (kstrtobool(str, &tick_nohz_enabled) == 0);
|
|
}
|
|
|
|
__setup("nohz=", setup_tick_nohz);
|
|
|
|
bool tick_nohz_tick_stopped(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
return ts->tick_stopped;
|
|
}
|
|
|
|
bool tick_nohz_tick_stopped_cpu(int cpu)
|
|
{
|
|
struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
|
|
|
|
return ts->tick_stopped;
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_update_jiffies - update jiffies when idle was interrupted
|
|
*
|
|
* Called from interrupt entry when the CPU was idle
|
|
*
|
|
* In case the sched_tick was stopped on this CPU, we have to check if jiffies
|
|
* must be updated. Otherwise an interrupt handler could use a stale jiffy
|
|
* value. We do this unconditionally on any CPU, as we don't know whether the
|
|
* CPU, which has the update task assigned is in a long sleep.
|
|
*/
|
|
static void tick_nohz_update_jiffies(ktime_t now)
|
|
{
|
|
unsigned long flags;
|
|
|
|
__this_cpu_write(tick_cpu_sched.idle_waketime, now);
|
|
|
|
local_irq_save(flags);
|
|
tick_do_update_jiffies64(now);
|
|
local_irq_restore(flags);
|
|
|
|
touch_softlockup_watchdog_sched();
|
|
}
|
|
|
|
static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
|
|
{
|
|
ktime_t delta;
|
|
|
|
if (WARN_ON_ONCE(!ts->idle_active))
|
|
return;
|
|
|
|
delta = ktime_sub(now, ts->idle_entrytime);
|
|
|
|
write_seqcount_begin(&ts->idle_sleeptime_seq);
|
|
if (nr_iowait_cpu(smp_processor_id()) > 0)
|
|
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
|
|
else
|
|
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
|
|
|
|
ts->idle_entrytime = now;
|
|
ts->idle_active = 0;
|
|
write_seqcount_end(&ts->idle_sleeptime_seq);
|
|
|
|
sched_clock_idle_wakeup_event();
|
|
}
|
|
|
|
static void tick_nohz_start_idle(struct tick_sched *ts)
|
|
{
|
|
write_seqcount_begin(&ts->idle_sleeptime_seq);
|
|
ts->idle_entrytime = ktime_get();
|
|
ts->idle_active = 1;
|
|
write_seqcount_end(&ts->idle_sleeptime_seq);
|
|
|
|
sched_clock_idle_sleep_event();
|
|
}
|
|
|
|
static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
|
|
bool compute_delta, u64 *last_update_time)
|
|
{
|
|
ktime_t now, idle;
|
|
unsigned int seq;
|
|
|
|
if (!tick_nohz_active)
|
|
return -1;
|
|
|
|
now = ktime_get();
|
|
if (last_update_time)
|
|
*last_update_time = ktime_to_us(now);
|
|
|
|
do {
|
|
seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
|
|
|
|
if (ts->idle_active && compute_delta) {
|
|
ktime_t delta = ktime_sub(now, ts->idle_entrytime);
|
|
|
|
idle = ktime_add(*sleeptime, delta);
|
|
} else {
|
|
idle = *sleeptime;
|
|
}
|
|
} while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq));
|
|
|
|
return ktime_to_us(idle);
|
|
|
|
}
|
|
|
|
/**
|
|
* get_cpu_idle_time_us - get the total idle time of a CPU
|
|
* @cpu: CPU number to query
|
|
* @last_update_time: variable to store update time in. Do not update
|
|
* counters if NULL.
|
|
*
|
|
* Return the cumulative idle time (since boot) for a given
|
|
* CPU, in microseconds. Note this is partially broken due to
|
|
* the counter of iowait tasks that can be remotely updated without
|
|
* any synchronization. Therefore it is possible to observe backward
|
|
* values within two consecutive reads.
|
|
*
|
|
* This time is measured via accounting rather than sampling,
|
|
* and is as accurate as ktime_get() is.
|
|
*
|
|
* This function returns -1 if NOHZ is not enabled.
|
|
*/
|
|
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
|
|
{
|
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
|
return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime,
|
|
!nr_iowait_cpu(cpu), last_update_time);
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
|
|
|
|
/**
|
|
* get_cpu_iowait_time_us - get the total iowait time of a CPU
|
|
* @cpu: CPU number to query
|
|
* @last_update_time: variable to store update time in. Do not update
|
|
* counters if NULL.
|
|
*
|
|
* Return the cumulative iowait time (since boot) for a given
|
|
* CPU, in microseconds. Note this is partially broken due to
|
|
* the counter of iowait tasks that can be remotely updated without
|
|
* any synchronization. Therefore it is possible to observe backward
|
|
* values within two consecutive reads.
|
|
*
|
|
* This time is measured via accounting rather than sampling,
|
|
* and is as accurate as ktime_get() is.
|
|
*
|
|
* This function returns -1 if NOHZ is not enabled.
|
|
*/
|
|
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
|
|
{
|
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
|
return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime,
|
|
nr_iowait_cpu(cpu), last_update_time);
|
|
}
|
|
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
|
|
|
|
static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
|
|
{
|
|
hrtimer_cancel(&ts->sched_timer);
|
|
hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
|
|
|
|
/* Forward the time to expire in the future */
|
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
|
|
|
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
|
|
hrtimer_start_expires(&ts->sched_timer,
|
|
HRTIMER_MODE_ABS_PINNED_HARD);
|
|
} else {
|
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
|
|
}
|
|
|
|
/*
|
|
* Reset to make sure next tick stop doesn't get fooled by past
|
|
* cached clock deadline.
|
|
*/
|
|
ts->next_tick = 0;
|
|
}
|
|
|
|
static inline bool local_timer_softirq_pending(void)
|
|
{
|
|
return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
|
|
}
|
|
|
|
static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
|
|
{
|
|
u64 basemono, next_tick, delta, expires;
|
|
unsigned long basejiff;
|
|
unsigned int seq;
|
|
|
|
/* Read jiffies and the time when jiffies were updated last */
|
|
do {
|
|
seq = read_seqcount_begin(&jiffies_seq);
|
|
basemono = last_jiffies_update;
|
|
basejiff = jiffies;
|
|
} while (read_seqcount_retry(&jiffies_seq, seq));
|
|
ts->last_jiffies = basejiff;
|
|
ts->timer_expires_base = basemono;
|
|
|
|
/*
|
|
* Keep the periodic tick, when RCU, architecture or irq_work
|
|
* requests it.
|
|
* Aside of that check whether the local timer softirq is
|
|
* pending. If so its a bad idea to call get_next_timer_interrupt()
|
|
* because there is an already expired timer, so it will request
|
|
* immediate expiry, which rearms the hardware timer with a
|
|
* minimal delta which brings us back to this place
|
|
* immediately. Lather, rinse and repeat...
|
|
*/
|
|
if (rcu_needs_cpu() || arch_needs_cpu() ||
|
|
irq_work_needs_cpu() || local_timer_softirq_pending()) {
|
|
next_tick = basemono + TICK_NSEC;
|
|
} else {
|
|
/*
|
|
* Get the next pending timer. If high resolution
|
|
* timers are enabled this only takes the timer wheel
|
|
* timers into account. If high resolution timers are
|
|
* disabled this also looks at the next expiring
|
|
* hrtimer.
|
|
*/
|
|
next_tick = get_next_timer_interrupt(basejiff, basemono);
|
|
ts->next_timer = next_tick;
|
|
}
|
|
|
|
/*
|
|
* If the tick is due in the next period, keep it ticking or
|
|
* force prod the timer.
|
|
*/
|
|
delta = next_tick - basemono;
|
|
if (delta <= (u64)TICK_NSEC) {
|
|
/*
|
|
* Tell the timer code that the base is not idle, i.e. undo
|
|
* the effect of get_next_timer_interrupt():
|
|
*/
|
|
timer_clear_idle();
|
|
/*
|
|
* We've not stopped the tick yet, and there's a timer in the
|
|
* next period, so no point in stopping it either, bail.
|
|
*/
|
|
if (!ts->tick_stopped) {
|
|
ts->timer_expires = 0;
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* If this CPU is the one which had the do_timer() duty last, we limit
|
|
* the sleep time to the timekeeping max_deferment value.
|
|
* Otherwise we can sleep as long as we want.
|
|
*/
|
|
delta = timekeeping_max_deferment();
|
|
if (cpu != tick_do_timer_cpu &&
|
|
(tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last))
|
|
delta = KTIME_MAX;
|
|
|
|
/* Calculate the next expiry time */
|
|
if (delta < (KTIME_MAX - basemono))
|
|
expires = basemono + delta;
|
|
else
|
|
expires = KTIME_MAX;
|
|
|
|
ts->timer_expires = min_t(u64, expires, next_tick);
|
|
|
|
out:
|
|
return ts->timer_expires;
|
|
}
|
|
|
|
static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
|
|
{
|
|
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
|
|
u64 basemono = ts->timer_expires_base;
|
|
u64 expires = ts->timer_expires;
|
|
ktime_t tick = expires;
|
|
|
|
/* Make sure we won't be trying to stop it twice in a row. */
|
|
ts->timer_expires_base = 0;
|
|
|
|
/*
|
|
* If this CPU is the one which updates jiffies, then give up
|
|
* the assignment and let it be taken by the CPU which runs
|
|
* the tick timer next, which might be this CPU as well. If we
|
|
* don't drop this here the jiffies might be stale and
|
|
* do_timer() never invoked. Keep track of the fact that it
|
|
* was the one which had the do_timer() duty last.
|
|
*/
|
|
if (cpu == tick_do_timer_cpu) {
|
|
tick_do_timer_cpu = TICK_DO_TIMER_NONE;
|
|
ts->do_timer_last = 1;
|
|
} else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
|
|
ts->do_timer_last = 0;
|
|
}
|
|
|
|
/* Skip reprogram of event if its not changed */
|
|
if (ts->tick_stopped && (expires == ts->next_tick)) {
|
|
/* Sanity check: make sure clockevent is actually programmed */
|
|
if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer))
|
|
return;
|
|
|
|
WARN_ON_ONCE(1);
|
|
printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n",
|
|
basemono, ts->next_tick, dev->next_event,
|
|
hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer));
|
|
}
|
|
|
|
/*
|
|
* nohz_stop_sched_tick can be called several times before
|
|
* the nohz_restart_sched_tick is called. This happens when
|
|
* interrupts arrive which do not cause a reschedule. In the
|
|
* first call we save the current tick time, so we can restart
|
|
* the scheduler tick in nohz_restart_sched_tick.
|
|
*/
|
|
if (!ts->tick_stopped) {
|
|
calc_load_nohz_start();
|
|
quiet_vmstat();
|
|
|
|
ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
|
|
ts->tick_stopped = 1;
|
|
trace_tick_stop(1, TICK_DEP_MASK_NONE);
|
|
}
|
|
|
|
ts->next_tick = tick;
|
|
|
|
/*
|
|
* If the expiration time == KTIME_MAX, then we simply stop
|
|
* the tick timer.
|
|
*/
|
|
if (unlikely(expires == KTIME_MAX)) {
|
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
|
|
hrtimer_cancel(&ts->sched_timer);
|
|
else
|
|
tick_program_event(KTIME_MAX, 1);
|
|
return;
|
|
}
|
|
|
|
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
|
|
hrtimer_start(&ts->sched_timer, tick,
|
|
HRTIMER_MODE_ABS_PINNED_HARD);
|
|
} else {
|
|
hrtimer_set_expires(&ts->sched_timer, tick);
|
|
tick_program_event(tick, 1);
|
|
}
|
|
}
|
|
|
|
static void tick_nohz_retain_tick(struct tick_sched *ts)
|
|
{
|
|
ts->timer_expires_base = 0;
|
|
}
|
|
|
|
#ifdef CONFIG_NO_HZ_FULL
|
|
static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu)
|
|
{
|
|
if (tick_nohz_next_event(ts, cpu))
|
|
tick_nohz_stop_tick(ts, cpu);
|
|
else
|
|
tick_nohz_retain_tick(ts);
|
|
}
|
|
#endif /* CONFIG_NO_HZ_FULL */
|
|
|
|
static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
|
|
{
|
|
/* Update jiffies first */
|
|
tick_do_update_jiffies64(now);
|
|
|
|
/*
|
|
* Clear the timer idle flag, so we avoid IPIs on remote queueing and
|
|
* the clock forward checks in the enqueue path:
|
|
*/
|
|
timer_clear_idle();
|
|
|
|
calc_load_nohz_stop();
|
|
touch_softlockup_watchdog_sched();
|
|
/*
|
|
* Cancel the scheduled timer and restore the tick
|
|
*/
|
|
ts->tick_stopped = 0;
|
|
tick_nohz_restart(ts, now);
|
|
}
|
|
|
|
static void __tick_nohz_full_update_tick(struct tick_sched *ts,
|
|
ktime_t now)
|
|
{
|
|
#ifdef CONFIG_NO_HZ_FULL
|
|
int cpu = smp_processor_id();
|
|
|
|
if (can_stop_full_tick(cpu, ts))
|
|
tick_nohz_stop_sched_tick(ts, cpu);
|
|
else if (ts->tick_stopped)
|
|
tick_nohz_restart_sched_tick(ts, now);
|
|
#endif
|
|
}
|
|
|
|
static void tick_nohz_full_update_tick(struct tick_sched *ts)
|
|
{
|
|
if (!tick_nohz_full_cpu(smp_processor_id()))
|
|
return;
|
|
|
|
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
|
|
return;
|
|
|
|
__tick_nohz_full_update_tick(ts, ktime_get());
|
|
}
|
|
|
|
/*
|
|
* A pending softirq outside an IRQ (or softirq disabled section) context
|
|
* should be waiting for ksoftirqd to handle it. Therefore we shouldn't
|
|
* reach here due to the need_resched() early check in can_stop_idle_tick().
|
|
*
|
|
* However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the
|
|
* cpu_down() process, softirqs can still be raised while ksoftirqd is parked,
|
|
* triggering the below since wakep_softirqd() is ignored.
|
|
*
|
|
*/
|
|
static bool report_idle_softirq(void)
|
|
{
|
|
static int ratelimit;
|
|
unsigned int pending = local_softirq_pending();
|
|
|
|
if (likely(!pending))
|
|
return false;
|
|
|
|
/* Some softirqs claim to be safe against hotplug and ksoftirqd parking */
|
|
if (!cpu_active(smp_processor_id())) {
|
|
pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK;
|
|
if (!pending)
|
|
return false;
|
|
}
|
|
|
|
if (ratelimit >= 10)
|
|
return false;
|
|
|
|
/* On RT, softirqs handling may be waiting on some lock */
|
|
if (local_bh_blocked())
|
|
return false;
|
|
|
|
pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n",
|
|
pending);
|
|
ratelimit++;
|
|
|
|
return true;
|
|
}
|
|
|
|
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
|
|
{
|
|
/*
|
|
* If this CPU is offline and it is the one which updates
|
|
* jiffies, then give up the assignment and let it be taken by
|
|
* the CPU which runs the tick timer next. If we don't drop
|
|
* this here the jiffies might be stale and do_timer() never
|
|
* invoked.
|
|
*/
|
|
if (unlikely(!cpu_online(cpu))) {
|
|
if (cpu == tick_do_timer_cpu)
|
|
tick_do_timer_cpu = TICK_DO_TIMER_NONE;
|
|
/*
|
|
* Make sure the CPU doesn't get fooled by obsolete tick
|
|
* deadline if it comes back online later.
|
|
*/
|
|
ts->next_tick = 0;
|
|
return false;
|
|
}
|
|
|
|
if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
|
|
return false;
|
|
|
|
if (need_resched())
|
|
return false;
|
|
|
|
if (unlikely(report_idle_softirq()))
|
|
return false;
|
|
|
|
if (tick_nohz_full_enabled()) {
|
|
/*
|
|
* Keep the tick alive to guarantee timekeeping progression
|
|
* if there are full dynticks CPUs around
|
|
*/
|
|
if (tick_do_timer_cpu == cpu)
|
|
return false;
|
|
|
|
/* Should not happen for nohz-full */
|
|
if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_idle_stop_tick - stop the idle tick from the idle task
|
|
*
|
|
* When the next event is more than a tick into the future, stop the idle tick
|
|
*/
|
|
void tick_nohz_idle_stop_tick(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
int cpu = smp_processor_id();
|
|
ktime_t expires;
|
|
|
|
/*
|
|
* If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
|
|
* tick timer expiration time is known already.
|
|
*/
|
|
if (ts->timer_expires_base)
|
|
expires = ts->timer_expires;
|
|
else if (can_stop_idle_tick(cpu, ts))
|
|
expires = tick_nohz_next_event(ts, cpu);
|
|
else
|
|
return;
|
|
|
|
ts->idle_calls++;
|
|
|
|
if (expires > 0LL) {
|
|
int was_stopped = ts->tick_stopped;
|
|
|
|
tick_nohz_stop_tick(ts, cpu);
|
|
|
|
ts->idle_sleeps++;
|
|
ts->idle_expires = expires;
|
|
|
|
if (!was_stopped && ts->tick_stopped) {
|
|
ts->idle_jiffies = ts->last_jiffies;
|
|
nohz_balance_enter_idle(cpu);
|
|
}
|
|
} else {
|
|
tick_nohz_retain_tick(ts);
|
|
}
|
|
}
|
|
|
|
void tick_nohz_idle_retain_tick(void)
|
|
{
|
|
tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
|
|
/*
|
|
* Undo the effect of get_next_timer_interrupt() called from
|
|
* tick_nohz_next_event().
|
|
*/
|
|
timer_clear_idle();
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_idle_enter - prepare for entering idle on the current CPU
|
|
*
|
|
* Called when we start the idle loop.
|
|
*/
|
|
void tick_nohz_idle_enter(void)
|
|
{
|
|
struct tick_sched *ts;
|
|
|
|
lockdep_assert_irqs_enabled();
|
|
|
|
local_irq_disable();
|
|
|
|
ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
WARN_ON_ONCE(ts->timer_expires_base);
|
|
|
|
ts->inidle = 1;
|
|
tick_nohz_start_idle(ts);
|
|
|
|
local_irq_enable();
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_irq_exit - update next tick event from interrupt exit
|
|
*
|
|
* When an interrupt fires while we are idle and it doesn't cause
|
|
* a reschedule, it may still add, modify or delete a timer, enqueue
|
|
* an RCU callback, etc...
|
|
* So we need to re-calculate and reprogram the next tick event.
|
|
*/
|
|
void tick_nohz_irq_exit(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
if (ts->inidle)
|
|
tick_nohz_start_idle(ts);
|
|
else
|
|
tick_nohz_full_update_tick(ts);
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_idle_got_tick - Check whether or not the tick handler has run
|
|
*/
|
|
bool tick_nohz_idle_got_tick(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
if (ts->got_idle_tick) {
|
|
ts->got_idle_tick = 0;
|
|
return true;
|
|
}
|
|
return false;
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer
|
|
* or the tick, whatever that expires first. Note that, if the tick has been
|
|
* stopped, it returns the next hrtimer.
|
|
*
|
|
* Called from power state control code with interrupts disabled
|
|
*/
|
|
ktime_t tick_nohz_get_next_hrtimer(void)
|
|
{
|
|
return __this_cpu_read(tick_cpu_device.evtdev)->next_event;
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_get_sleep_length - return the expected length of the current sleep
|
|
* @delta_next: duration until the next event if the tick cannot be stopped
|
|
*
|
|
* Called from power state control code with interrupts disabled.
|
|
*
|
|
* The return value of this function and/or the value returned by it through the
|
|
* @delta_next pointer can be negative which must be taken into account by its
|
|
* callers.
|
|
*/
|
|
ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
|
|
{
|
|
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
int cpu = smp_processor_id();
|
|
/*
|
|
* The idle entry time is expected to be a sufficient approximation of
|
|
* the current time at this point.
|
|
*/
|
|
ktime_t now = ts->idle_entrytime;
|
|
ktime_t next_event;
|
|
|
|
WARN_ON_ONCE(!ts->inidle);
|
|
|
|
*delta_next = ktime_sub(dev->next_event, now);
|
|
|
|
if (!can_stop_idle_tick(cpu, ts))
|
|
return *delta_next;
|
|
|
|
next_event = tick_nohz_next_event(ts, cpu);
|
|
if (!next_event)
|
|
return *delta_next;
|
|
|
|
/*
|
|
* If the next highres timer to expire is earlier than next_event, the
|
|
* idle governor needs to know that.
|
|
*/
|
|
next_event = min_t(u64, next_event,
|
|
hrtimer_next_event_without(&ts->sched_timer));
|
|
|
|
return ktime_sub(next_event, now);
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
|
|
* for a particular CPU.
|
|
*
|
|
* Called from the schedutil frequency scaling governor in scheduler context.
|
|
*/
|
|
unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
|
|
{
|
|
struct tick_sched *ts = tick_get_tick_sched(cpu);
|
|
|
|
return ts->idle_calls;
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_get_idle_calls - return the current idle calls counter value
|
|
*
|
|
* Called from the schedutil frequency scaling governor in scheduler context.
|
|
*/
|
|
unsigned long tick_nohz_get_idle_calls(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
return ts->idle_calls;
|
|
}
|
|
|
|
static void tick_nohz_account_idle_time(struct tick_sched *ts,
|
|
ktime_t now)
|
|
{
|
|
unsigned long ticks;
|
|
|
|
ts->idle_exittime = now;
|
|
|
|
if (vtime_accounting_enabled_this_cpu())
|
|
return;
|
|
/*
|
|
* We stopped the tick in idle. Update process times would miss the
|
|
* time we slept as update_process_times does only a 1 tick
|
|
* accounting. Enforce that this is accounted to idle !
|
|
*/
|
|
ticks = jiffies - ts->idle_jiffies;
|
|
/*
|
|
* We might be one off. Do not randomly account a huge number of ticks!
|
|
*/
|
|
if (ticks && ticks < LONG_MAX)
|
|
account_idle_ticks(ticks);
|
|
}
|
|
|
|
void tick_nohz_idle_restart_tick(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
if (ts->tick_stopped) {
|
|
ktime_t now = ktime_get();
|
|
tick_nohz_restart_sched_tick(ts, now);
|
|
tick_nohz_account_idle_time(ts, now);
|
|
}
|
|
}
|
|
|
|
static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
|
|
{
|
|
if (tick_nohz_full_cpu(smp_processor_id()))
|
|
__tick_nohz_full_update_tick(ts, now);
|
|
else
|
|
tick_nohz_restart_sched_tick(ts, now);
|
|
|
|
tick_nohz_account_idle_time(ts, now);
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_idle_exit - restart the idle tick from the idle task
|
|
*
|
|
* Restart the idle tick when the CPU is woken up from idle
|
|
* This also exit the RCU extended quiescent state. The CPU
|
|
* can use RCU again after this function is called.
|
|
*/
|
|
void tick_nohz_idle_exit(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
bool idle_active, tick_stopped;
|
|
ktime_t now;
|
|
|
|
local_irq_disable();
|
|
|
|
WARN_ON_ONCE(!ts->inidle);
|
|
WARN_ON_ONCE(ts->timer_expires_base);
|
|
|
|
ts->inidle = 0;
|
|
idle_active = ts->idle_active;
|
|
tick_stopped = ts->tick_stopped;
|
|
|
|
if (idle_active || tick_stopped)
|
|
now = ktime_get();
|
|
|
|
if (idle_active)
|
|
tick_nohz_stop_idle(ts, now);
|
|
|
|
if (tick_stopped)
|
|
tick_nohz_idle_update_tick(ts, now);
|
|
|
|
local_irq_enable();
|
|
}
|
|
|
|
/*
|
|
* The nohz low res interrupt handler
|
|
*/
|
|
static void tick_nohz_handler(struct clock_event_device *dev)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
struct pt_regs *regs = get_irq_regs();
|
|
ktime_t now = ktime_get();
|
|
|
|
dev->next_event = KTIME_MAX;
|
|
|
|
tick_sched_do_timer(ts, now);
|
|
tick_sched_handle(ts, regs);
|
|
|
|
if (unlikely(ts->tick_stopped)) {
|
|
/*
|
|
* The clockevent device is not reprogrammed, so change the
|
|
* clock event device to ONESHOT_STOPPED to avoid spurious
|
|
* interrupts on devices which might not be truly one shot.
|
|
*/
|
|
tick_program_event(KTIME_MAX, 1);
|
|
return;
|
|
}
|
|
|
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
|
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
|
|
}
|
|
|
|
static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
|
|
{
|
|
if (!tick_nohz_enabled)
|
|
return;
|
|
ts->nohz_mode = mode;
|
|
/* One update is enough */
|
|
if (!test_and_set_bit(0, &tick_nohz_active))
|
|
timers_update_nohz();
|
|
}
|
|
|
|
/**
|
|
* tick_nohz_switch_to_nohz - switch to nohz mode
|
|
*/
|
|
static void tick_nohz_switch_to_nohz(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
ktime_t next;
|
|
|
|
if (!tick_nohz_enabled)
|
|
return;
|
|
|
|
if (tick_switch_to_oneshot(tick_nohz_handler))
|
|
return;
|
|
|
|
/*
|
|
* Recycle the hrtimer in ts, so we can share the
|
|
* hrtimer_forward with the highres code.
|
|
*/
|
|
hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
|
|
/* Get the next period */
|
|
next = tick_init_jiffy_update();
|
|
|
|
hrtimer_set_expires(&ts->sched_timer, next);
|
|
hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
|
|
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
|
|
tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
|
|
}
|
|
|
|
static inline void tick_nohz_irq_enter(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
ktime_t now;
|
|
|
|
if (!ts->idle_active && !ts->tick_stopped)
|
|
return;
|
|
now = ktime_get();
|
|
if (ts->idle_active)
|
|
tick_nohz_stop_idle(ts, now);
|
|
/*
|
|
* If all CPUs are idle. We may need to update a stale jiffies value.
|
|
* Note nohz_full is a special case: a timekeeper is guaranteed to stay
|
|
* alive but it might be busy looping with interrupts disabled in some
|
|
* rare case (typically stop machine). So we must make sure we have a
|
|
* last resort.
|
|
*/
|
|
if (ts->tick_stopped)
|
|
tick_nohz_update_jiffies(now);
|
|
}
|
|
|
|
#else
|
|
|
|
static inline void tick_nohz_switch_to_nohz(void) { }
|
|
static inline void tick_nohz_irq_enter(void) { }
|
|
static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
|
|
|
|
#endif /* CONFIG_NO_HZ_COMMON */
|
|
|
|
/*
|
|
* Called from irq_enter to notify about the possible interruption of idle()
|
|
*/
|
|
void tick_irq_enter(void)
|
|
{
|
|
tick_check_oneshot_broadcast_this_cpu();
|
|
tick_nohz_irq_enter();
|
|
}
|
|
|
|
/*
|
|
* High resolution timer specific code
|
|
*/
|
|
#ifdef CONFIG_HIGH_RES_TIMERS
|
|
/*
|
|
* We rearm the timer until we get disabled by the idle code.
|
|
* Called with interrupts disabled.
|
|
*/
|
|
static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
|
|
{
|
|
struct tick_sched *ts =
|
|
container_of(timer, struct tick_sched, sched_timer);
|
|
struct pt_regs *regs = get_irq_regs();
|
|
ktime_t now = ktime_get();
|
|
|
|
tick_sched_do_timer(ts, now);
|
|
|
|
/*
|
|
* Do not call, when we are not in irq context and have
|
|
* no valid regs pointer
|
|
*/
|
|
if (regs)
|
|
tick_sched_handle(ts, regs);
|
|
else
|
|
ts->next_tick = 0;
|
|
|
|
/* No need to reprogram if we are in idle or full dynticks mode */
|
|
if (unlikely(ts->tick_stopped))
|
|
return HRTIMER_NORESTART;
|
|
|
|
hrtimer_forward(timer, now, TICK_NSEC);
|
|
|
|
return HRTIMER_RESTART;
|
|
}
|
|
|
|
static int sched_skew_tick;
|
|
|
|
static int __init skew_tick(char *str)
|
|
{
|
|
get_option(&str, &sched_skew_tick);
|
|
|
|
return 0;
|
|
}
|
|
early_param("skew_tick", skew_tick);
|
|
|
|
/**
|
|
* tick_setup_sched_timer - setup the tick emulation timer
|
|
*/
|
|
void tick_setup_sched_timer(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
ktime_t now = ktime_get();
|
|
|
|
/*
|
|
* Emulate tick processing via per-CPU hrtimers:
|
|
*/
|
|
hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
|
|
ts->sched_timer.function = tick_sched_timer;
|
|
|
|
/* Get the next period (per-CPU) */
|
|
hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
|
|
|
|
/* Offset the tick to avert jiffies_lock contention. */
|
|
if (sched_skew_tick) {
|
|
u64 offset = TICK_NSEC >> 1;
|
|
do_div(offset, num_possible_cpus());
|
|
offset *= smp_processor_id();
|
|
hrtimer_add_expires_ns(&ts->sched_timer, offset);
|
|
}
|
|
|
|
hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
|
|
hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
|
|
tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
|
|
}
|
|
#endif /* HIGH_RES_TIMERS */
|
|
|
|
#if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
|
|
void tick_cancel_sched_timer(int cpu)
|
|
{
|
|
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
|
# ifdef CONFIG_HIGH_RES_TIMERS
|
|
if (ts->sched_timer.base)
|
|
hrtimer_cancel(&ts->sched_timer);
|
|
# endif
|
|
|
|
memset(ts, 0, sizeof(*ts));
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Async notification about clocksource changes
|
|
*/
|
|
void tick_clock_notify(void)
|
|
{
|
|
int cpu;
|
|
|
|
for_each_possible_cpu(cpu)
|
|
set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
|
|
}
|
|
|
|
/*
|
|
* Async notification about clock event changes
|
|
*/
|
|
void tick_oneshot_notify(void)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
set_bit(0, &ts->check_clocks);
|
|
}
|
|
|
|
/*
|
|
* Check, if a change happened, which makes oneshot possible.
|
|
*
|
|
* Called cyclic from the hrtimer softirq (driven by the timer
|
|
* softirq) allow_nohz signals, that we can switch into low-res nohz
|
|
* mode, because high resolution timers are disabled (either compile
|
|
* or runtime). Called with interrupts disabled.
|
|
*/
|
|
int tick_check_oneshot_change(int allow_nohz)
|
|
{
|
|
struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
|
|
|
|
if (!test_and_clear_bit(0, &ts->check_clocks))
|
|
return 0;
|
|
|
|
if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
|
|
return 0;
|
|
|
|
if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
|
|
return 0;
|
|
|
|
if (!allow_nohz)
|
|
return 1;
|
|
|
|
tick_nohz_switch_to_nohz();
|
|
return 0;
|
|
}
|