From 626e5fbc14358901ddaa90ce510e0fbeab310432 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Thu, 26 Apr 2018 11:34:24 +0100 Subject: [PATCH] locking/qspinlock: Use smp_store_release() in queued_spin_unlock() 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 Acked-by: Peter Zijlstra (Intel) Acked-by: Waiman Long Cc: Linus Torvalds Cc: Thomas Gleixner 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 --- arch/x86/include/asm/qspinlock.h | 17 ++++++----------- include/asm-generic/qspinlock.h | 2 +- 2 files changed, 7 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index da1370ad206d..3e70bed8a978 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -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 diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h index b37b4ad7eb94..a8ed0a352d75 100644 --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -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 -- 2.11.0