diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2016-11-30 21:04:42 +0000 |
|---|---|---|
| committer | Jiri Slaby <jslaby@suse.cz> | 2017-01-26 17:22:16 +0100 |
| commit | 15543c65c619ea88c8b3fdf97f2371ea13d4048f (patch) | |
| tree | bc0a13469e19b0306fb98088d641abc424485864 /kernel | |
| parent | a0346c3237a7f29b957190875ab6d65689fa191a (diff) | |
locking/rtmutex: Use READ_ONCE() in rt_mutex_owner()
commit 1be5d4fa0af34fb7bafa205aeb59f5c7cc7a089d upstream.
While debugging the rtmutex unlock vs. dequeue race Will suggested to use
READ_ONCE() in rt_mutex_owner() as it might race against the
cmpxchg_release() in unlock_rt_mutex_safe().
Will: "It's a minor thing which will most likely not matter in practice"
Careful search did not unearth an actual problem in todays code, but it's
better to be safe than surprised.
Suggested-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20161130210030.431379999@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/rtmutex_common.h | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/kernel/rtmutex_common.h b/kernel/rtmutex_common.h index 53a66c85261b..1823c094fe96 100644 --- a/kernel/rtmutex_common.h +++ b/kernel/rtmutex_common.h @@ -96,8 +96,9 @@ task_top_pi_waiter(struct task_struct *p) static inline struct task_struct *rt_mutex_owner(struct rt_mutex *lock) { - return (struct task_struct *) - ((unsigned long)lock->owner & ~RT_MUTEX_OWNER_MASKALL); + unsigned long owner = (unsigned long) READ_ONCE(lock->owner); + + return (struct task_struct *) (owner & ~RT_MUTEX_OWNER_MASKALL); } /* |