267 lines
6.1 KiB
C
267 lines
6.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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#ifndef _ASM_POWERPC_SIMPLE_SPINLOCK_H
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#define _ASM_POWERPC_SIMPLE_SPINLOCK_H
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/*
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* Simple spin lock operations.
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*
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* Copyright (C) 2001-2004 Paul Mackerras <paulus@au.ibm.com>, IBM
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* Copyright (C) 2001 Anton Blanchard <anton@au.ibm.com>, IBM
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* Copyright (C) 2002 Dave Engebretsen <engebret@us.ibm.com>, IBM
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* Rework to support virtual processors
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*
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* Type of int is used as a full 64b word is not necessary.
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*
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* (the type definitions are in asm/simple_spinlock_types.h)
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*/
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#include <linux/irqflags.h>
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#include <asm/paravirt.h>
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#include <asm/paca.h>
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#include <asm/synch.h>
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#include <asm/ppc-opcode.h>
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#ifdef CONFIG_PPC64
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/* use 0x800000yy when locked, where yy == CPU number */
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#ifdef __BIG_ENDIAN__
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#define LOCK_TOKEN (*(u32 *)(&get_paca()->lock_token))
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#else
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#define LOCK_TOKEN (*(u32 *)(&get_paca()->paca_index))
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#endif
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#else
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#define LOCK_TOKEN 1
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#endif
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static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
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{
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return lock.slock == 0;
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}
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static inline int arch_spin_is_locked(arch_spinlock_t *lock)
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{
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return !arch_spin_value_unlocked(READ_ONCE(*lock));
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}
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/*
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* This returns the old value in the lock, so we succeeded
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* in getting the lock if the return value is 0.
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*/
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static inline unsigned long __arch_spin_trylock(arch_spinlock_t *lock)
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{
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unsigned long tmp, token;
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unsigned int eh = IS_ENABLED(CONFIG_PPC64);
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token = LOCK_TOKEN;
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__asm__ __volatile__(
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"1: lwarx %0,0,%2,%[eh]\n\
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cmpwi 0,%0,0\n\
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bne- 2f\n\
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stwcx. %1,0,%2\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:"
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: "=&r" (tmp)
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: "r" (token), "r" (&lock->slock), [eh] "n" (eh)
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: "cr0", "memory");
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return tmp;
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}
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static inline int arch_spin_trylock(arch_spinlock_t *lock)
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{
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return __arch_spin_trylock(lock) == 0;
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}
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/*
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* On a system with shared processors (that is, where a physical
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* processor is multiplexed between several virtual processors),
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* there is no point spinning on a lock if the holder of the lock
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* isn't currently scheduled on a physical processor. Instead
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* we detect this situation and ask the hypervisor to give the
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* rest of our timeslice to the lock holder.
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*
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* So that we can tell which virtual processor is holding a lock,
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* we put 0x80000000 | smp_processor_id() in the lock when it is
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* held. Conveniently, we have a word in the paca that holds this
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* value.
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*/
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#if defined(CONFIG_PPC_SPLPAR)
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/* We only yield to the hypervisor if we are in shared processor mode */
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void splpar_spin_yield(arch_spinlock_t *lock);
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void splpar_rw_yield(arch_rwlock_t *lock);
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#else /* SPLPAR */
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static inline void splpar_spin_yield(arch_spinlock_t *lock) {}
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static inline void splpar_rw_yield(arch_rwlock_t *lock) {}
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#endif
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static inline void spin_yield(arch_spinlock_t *lock)
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{
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if (is_shared_processor())
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splpar_spin_yield(lock);
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else
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barrier();
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}
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static inline void rw_yield(arch_rwlock_t *lock)
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{
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if (is_shared_processor())
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splpar_rw_yield(lock);
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else
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barrier();
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}
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static inline void arch_spin_lock(arch_spinlock_t *lock)
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{
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while (1) {
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if (likely(__arch_spin_trylock(lock) == 0))
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break;
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do {
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HMT_low();
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if (is_shared_processor())
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splpar_spin_yield(lock);
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} while (unlikely(lock->slock != 0));
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HMT_medium();
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}
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}
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static inline void arch_spin_unlock(arch_spinlock_t *lock)
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{
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__asm__ __volatile__("# arch_spin_unlock\n\t"
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PPC_RELEASE_BARRIER: : :"memory");
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lock->slock = 0;
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}
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/*
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* Read-write spinlocks, allowing multiple readers
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* but only one writer.
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*
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* NOTE! it is quite common to have readers in interrupts
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* but no interrupt writers. For those circumstances we
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* can "mix" irq-safe locks - any writer needs to get a
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* irq-safe write-lock, but readers can get non-irqsafe
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* read-locks.
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*/
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#ifdef CONFIG_PPC64
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#define __DO_SIGN_EXTEND "extsw %0,%0\n"
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#define WRLOCK_TOKEN LOCK_TOKEN /* it's negative */
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#else
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#define __DO_SIGN_EXTEND
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#define WRLOCK_TOKEN (-1)
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#endif
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/*
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* This returns the old value in the lock + 1,
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* so we got a read lock if the return value is > 0.
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*/
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static inline long __arch_read_trylock(arch_rwlock_t *rw)
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{
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long tmp;
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unsigned int eh = IS_ENABLED(CONFIG_PPC64);
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__asm__ __volatile__(
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"1: lwarx %0,0,%1,%[eh]\n"
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__DO_SIGN_EXTEND
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" addic. %0,%0,1\n\
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ble- 2f\n"
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" stwcx. %0,0,%1\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:" : "=&r" (tmp)
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: "r" (&rw->lock), [eh] "n" (eh)
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: "cr0", "xer", "memory");
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return tmp;
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}
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/*
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* This returns the old value in the lock,
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* so we got the write lock if the return value is 0.
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*/
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static inline long __arch_write_trylock(arch_rwlock_t *rw)
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{
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long tmp, token;
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unsigned int eh = IS_ENABLED(CONFIG_PPC64);
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token = WRLOCK_TOKEN;
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__asm__ __volatile__(
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"1: lwarx %0,0,%2,%[eh]\n\
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cmpwi 0,%0,0\n\
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bne- 2f\n"
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" stwcx. %1,0,%2\n\
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bne- 1b\n"
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PPC_ACQUIRE_BARRIER
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"2:" : "=&r" (tmp)
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: "r" (token), "r" (&rw->lock), [eh] "n" (eh)
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: "cr0", "memory");
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return tmp;
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}
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static inline void arch_read_lock(arch_rwlock_t *rw)
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{
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while (1) {
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if (likely(__arch_read_trylock(rw) > 0))
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break;
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do {
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HMT_low();
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if (is_shared_processor())
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splpar_rw_yield(rw);
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} while (unlikely(rw->lock < 0));
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HMT_medium();
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}
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}
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static inline void arch_write_lock(arch_rwlock_t *rw)
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{
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while (1) {
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if (likely(__arch_write_trylock(rw) == 0))
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break;
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do {
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HMT_low();
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if (is_shared_processor())
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splpar_rw_yield(rw);
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} while (unlikely(rw->lock != 0));
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HMT_medium();
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}
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}
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static inline int arch_read_trylock(arch_rwlock_t *rw)
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{
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return __arch_read_trylock(rw) > 0;
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}
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static inline int arch_write_trylock(arch_rwlock_t *rw)
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{
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return __arch_write_trylock(rw) == 0;
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}
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static inline void arch_read_unlock(arch_rwlock_t *rw)
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{
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long tmp;
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__asm__ __volatile__(
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"# read_unlock\n\t"
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PPC_RELEASE_BARRIER
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"1: lwarx %0,0,%1\n\
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addic %0,%0,-1\n"
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" stwcx. %0,0,%1\n\
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bne- 1b"
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: "=&r"(tmp)
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: "r"(&rw->lock)
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: "cr0", "xer", "memory");
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}
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static inline void arch_write_unlock(arch_rwlock_t *rw)
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{
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__asm__ __volatile__("# write_unlock\n\t"
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PPC_RELEASE_BARRIER: : :"memory");
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rw->lock = 0;
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}
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#define arch_spin_relax(lock) spin_yield(lock)
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#define arch_read_relax(lock) rw_yield(lock)
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#define arch_write_relax(lock) rw_yield(lock)
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#endif /* _ASM_POWERPC_SIMPLE_SPINLOCK_H */
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