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Date: Tue, 28 Jan 2014 11:13:15 -0800 From: Jason Low <jason.low2@...com> To: mingo@...hat.com, peterz@...radead.org, paulmck@...ux.vnet.ibm.com, Waiman.Long@...com, torvalds@...ux-foundation.org, tglx@...utronix.de, jason.low2@...com Cc: linux-kernel@...r.kernel.org, riel@...hat.com, akpm@...ux-foundation.org, davidlohr@...com, hpa@...or.com, andi@...stfloor.org, aswin@...com, scott.norton@...com, chegu_vinod@...com Subject: [RFC][PATCH v2 4/5] mutex: Disable preemtion between modifying lock->owner and locking/unlocking mutex This RFC patch disables preemption between modifying lock->owner and locking/unlocking the mutex lock. This prevents situations where the owner can preempt between those 2 operations, which causes optimistic spinners to be unable to check if lock->owner is not on CPU. As mentioned in the thread for this v1 patchset, disabling preemption is a cheap operation. Signed-off-by: Jason Low <jason.low2@...com> --- kernel/locking/mutex.c | 30 ++++++++++++++++++++++++++++-- 1 files changed, 28 insertions(+), 2 deletions(-) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index 6d85b08..cfaaf53 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -98,8 +98,10 @@ void __sched mutex_lock(struct mutex *lock) * The locking fastpath is the 1->0 transition from * 'unlocked' into 'locked' state. */ + preempt_disable(); __mutex_fastpath_lock(&lock->count, __mutex_lock_slowpath); mutex_set_owner(lock); + preempt_enable(); } EXPORT_SYMBOL(mutex_lock); @@ -253,9 +255,13 @@ void __sched mutex_unlock(struct mutex *lock) * the slow path will always be taken, and that clears the owner field * after verifying that it was indeed current. */ + preempt_disable(); mutex_clear_owner(lock); #endif __mutex_fastpath_unlock(&lock->count, __mutex_unlock_slowpath); +#ifndef CONFIG_DEBUG_MUTEXES + preempt_enable(); +#endif } EXPORT_SYMBOL(mutex_unlock); @@ -292,9 +298,13 @@ void __sched ww_mutex_unlock(struct ww_mutex *lock) * the slow path will always be taken, and that clears the owner field * after verifying that it was indeed current. */ + preempt_disable(); mutex_clear_owner(&lock->base); #endif __mutex_fastpath_unlock(&lock->base.count, __mutex_unlock_slowpath); +#ifndef CONFIG_DEBUG_MUTEXES + preempt_enable(); +#endif } EXPORT_SYMBOL(ww_mutex_unlock); @@ -780,12 +790,16 @@ int __sched mutex_lock_interruptible(struct mutex *lock) int ret; might_sleep(); + preempt_disable(); ret = __mutex_fastpath_lock_retval(&lock->count); if (likely(!ret)) { mutex_set_owner(lock); + preempt_enable(); return 0; - } else + } else { + preempt_enable(); return __mutex_lock_interruptible_slowpath(lock); + } } EXPORT_SYMBOL(mutex_lock_interruptible); @@ -795,12 +809,16 @@ int __sched mutex_lock_killable(struct mutex *lock) int ret; might_sleep(); + preempt_disable(); ret = __mutex_fastpath_lock_retval(&lock->count); if (likely(!ret)) { mutex_set_owner(lock); + preempt_enable(); return 0; - } else + } else { + preempt_enable(); return __mutex_lock_killable_slowpath(lock); + } } EXPORT_SYMBOL(mutex_lock_killable); @@ -889,9 +907,11 @@ int __sched mutex_trylock(struct mutex *lock) { int ret; + preempt_disable(); ret = __mutex_fastpath_trylock(&lock->count, __mutex_trylock_slowpath); if (ret) mutex_set_owner(lock); + preempt_enable(); return ret; } @@ -904,6 +924,7 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) int ret; might_sleep(); + preempt_disable(); ret = __mutex_fastpath_lock_retval(&lock->base.count); @@ -912,6 +933,8 @@ __ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) mutex_set_owner(&lock->base); } else ret = __ww_mutex_lock_slowpath(lock, ctx); + + preempt_enable(); return ret; } EXPORT_SYMBOL(__ww_mutex_lock); @@ -922,6 +945,7 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) int ret; might_sleep(); + preempt_disable(); ret = __mutex_fastpath_lock_retval(&lock->base.count); @@ -930,6 +954,8 @@ __ww_mutex_lock_interruptible(struct ww_mutex *lock, struct ww_acquire_ctx *ctx) mutex_set_owner(&lock->base); } else ret = __ww_mutex_lock_interruptible_slowpath(lock, ctx); + + preempt_enable(); return ret; } EXPORT_SYMBOL(__ww_mutex_lock_interruptible); -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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