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locking/qspinlock: Use smp_store_release() in queued_spin_unlock()

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A qspinlock can be unlocked simply by writing zero to the locked byte.
This can be implemented in the generic code, so do that and remove the
arch-specific override for x86 in the !PV case.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: boqun.feng@gmail.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/1524738868-31318-11-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Will Deacon 2018-04-26 11:34:24 +01:00 committed by Ingo Molnar
parent c131a198c4
commit 626e5fbc14
2 changed files with 7 additions and 12 deletions
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17
arch/x86/include/asm/qspinlock.h
View File

@ -9,6 +9,12 @@
#define _Q_PENDING_LOOPS (1 << 9)
#ifdef CONFIG_PARAVIRT_SPINLOCKS
extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
extern void __pv_init_lock_hash(void);
extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
#define queued_spin_unlock queued_spin_unlock
/**
* queued_spin_unlock - release a queued spinlock
@ -21,12 +27,6 @@ static inline void native_queued_spin_unlock(struct qspinlock *lock)
smp_store_release(&lock->locked, 0);
}
#ifdef CONFIG_PARAVIRT_SPINLOCKS
extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
extern void __pv_init_lock_hash(void);
extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
{
pv_queued_spin_lock_slowpath(lock, val);
@ -42,11 +42,6 @@ static inline bool vcpu_is_preempted(long cpu)
{
return pv_vcpu_is_preempted(cpu);
}
#else
static inline void queued_spin_unlock(struct qspinlock *lock)
{
native_queued_spin_unlock(lock);
}
#endif
#ifdef CONFIG_PARAVIRT

2
include/asm-generic/qspinlock.h
View File

@ -100,7 +100,7 @@ static __always_inline void queued_spin_unlock(struct qspinlock *lock)
/*
* unlock() needs release semantics:
*/
(void)atomic_sub_return_release(_Q_LOCKED_VAL, &lock->val);
smp_store_release(&lock->locked, 0);
}
#endif