locking/mutex: Set and clear owner using WRITE_ONCE() (6e281474) · Commits · 戴 / test

The mutex owner can get read and written to locklessly. Use WRITE_ONCE when setting and clearing the owner field in order to avoid optimizations such as store tearing. This avoids situations where the owner field gets written to with multiple stores and another thread could concurrently read and use a partially written owner value. Signed-off-by:

Jason Low <jason.low2@hpe.com> Signed-off-by:

Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by:

Davidlohr Bueso <dave@stgolabs.net> Acked-by:

Waiman Long <Waiman.Long@hpe.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Scott J Norton <scott.norton@hpe.com> Cc: Terry Rudd <terry.rudd@hpe.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1463782776.2479.9.camel@j-VirtualBox Signed-off-by:

Ingo Molnar <mingo@kernel.org>

kernel/locking/mutex-debug.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -29,12 +29,12 @@ extern void debug_mutex_init(struct mutex lock, const char name,

		static inline void mutex_set_owner(struct mutex *lock)
		{
		lock->owner = current;
		WRITE_ONCE(lock->owner, current);
		}

		static inline void mutex_clear_owner(struct mutex *lock)
		{
		lock->owner = NULL;
		WRITE_ONCE(lock->owner, NULL);
		}

		#define spin_lock_mutex(lock, flags) \

kernel/locking/mutex.h

+8 −2

Original line number	Diff line number	Diff line
		@@ -17,14 +17,20 @@
		__list_del((waiter)->list.prev, (waiter)->list.next)

		#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
		/*
		* The mutex owner can get read and written to locklessly.
		* We should use WRITE_ONCE when writing the owner value to
		* avoid store tearing, otherwise, a thread could potentially
		* read a partially written and incomplete owner value.
		*/
		static inline void mutex_set_owner(struct mutex *lock)
		{
		lock->owner = current;
		WRITE_ONCE(lock->owner, current);
		}

		static inline void mutex_clear_owner(struct mutex *lock)
		{
		lock->owner = NULL;
		WRITE_ONCE(lock->owner, NULL);
		}
		#else
		static inline void mutex_set_owner(struct mutex *lock)

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