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Subject[PATCH tip/core/rcu 10/30] locking/rtmutex: rcu: Add WRITE_ONCE() to rt_mutex ->owner
Date
From: "Paul E. McKenney" <paulmck@kernel.org>

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 <paulmck@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
---
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 851bbb1..c9f090d 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)
--
2.9.5
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