From: Peter Zijlstra <[email protected]> commit 1b367ece0d7e696cab1c8501bab282cc6a538b3f upstream.
Since the futex_q can dissapear the instruction after assigning NULL, this really should be a RELEASE barrier. That stops loads from hitting dead memory too. Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Thomas Gleixner <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/futex.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1565,8 +1565,7 @@ static void mark_wake_futex(struct wake_ * memory barrier is required here to prevent the following * store to lock_ptr from getting ahead of the plist_del. */ - smp_wmb(); - q->lock_ptr = NULL; + smp_store_release(&q->lock_ptr, NULL); } /*
