From 0050c7b2d27c3cc126df59bd8094fb3d25b00ade Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 3 Jan 2020 15:59:12 -0800 Subject: [PATCH] locking/rtmutex: rcu: Add WRITE_ONCE() to rt_mutex ->owner The rt_mutex structure's ->owner field is read locklessly, so this commit adds the WRITE_ONCE() to an update in order to provide proper documentation and READ_ONCE()/WRITE_ONCE() pairing. This data race was reported by KCSAN. Not appropriate for backporting due to failure being unlikely. Signed-off-by: Paul E. McKenney Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon --- kernel/locking/rtmutex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c index 851bbb10819d..c9f090d64f00 100644 --- a/kernel/locking/rtmutex.c +++ b/kernel/locking/rtmutex.c @@ -57,7 +57,7 @@ rt_mutex_set_owner(struct rt_mutex *lock, struct task_struct *owner) if (rt_mutex_has_waiters(lock)) val |= RT_MUTEX_HAS_WAITERS; - lock->owner = (struct task_struct *)val; + WRITE_ONCE(lock->owner, (struct task_struct *)val); } static inline void clear_rt_mutex_waiters(struct rt_mutex *lock)