[RFC][PATCH 2/4] futex: Use smp_store_release() in mark_wake_futex()

[Peter Zijlstra]

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) <pet...@infradead.org>
---
 kernel/futex.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1288,8 +1288,7 @@ 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);
 }
 
 static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q 
*top_waiter,