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locking/mutex: Set and clear owner using WRITE_ONCE()

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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>
This commit is contained in:
Jason Low 2016-05-20 15:19:36 -07:00 committed by Ingo Molnar
parent c0fcb6c2d3
commit 6e2814745c
2 changed files with 10 additions and 4 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
kernel/locking/mutex-debug.h
View file

@ -29,12 +29,12 @@ extern void debug_mutex_init(struct mutex *lock, const char *name,
static inline void mutex_set_owner(struct mutex *lock) 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) static inline void mutex_clear_owner(struct mutex *lock)
{ {
lock->owner = NULL; WRITE_ONCE(lock->owner, NULL);
} }
#define spin_lock_mutex(lock, flags) \ #define spin_lock_mutex(lock, flags) \

10
kernel/locking/mutex.h
View file

@ -17,14 +17,20 @@
__list_del((waiter)->list.prev, (waiter)->list.next) __list_del((waiter)->list.prev, (waiter)->list.next)
#ifdef CONFIG_MUTEX_SPIN_ON_OWNER #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) 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) static inline void mutex_clear_owner(struct mutex *lock)
{ {
lock->owner = NULL; WRITE_ONCE(lock->owner, NULL);
} }
#else #else
static inline void mutex_set_owner(struct mutex *lock) static inline void mutex_set_owner(struct mutex *lock)