[PATCH -v4 04/10] futex: Use smp_store_release() in mark_wake_futex()

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	[PATCH -v4 04/10] futex: Use smp_store_release() in mark_wake_futex()
Date	2016-12-13 10:10 +0100
Message-ID	<sNRfX-7LI-7@gated-at.bofh.it> (permalink)
References	<sNRfX-7LI-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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) <peterz@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,

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[PATCH -v4 04/10] futex: Use smp_store_release() in mark_wake_futex() Peter Zijlstra <peterz@infradead.org> - 2016-12-13 10:10 +0100
  Re: [PATCH -v4 04/10] futex: Use smp_store_release() in  mark_wake_futex() Darren Hart <dvhart@infradead.org> - 2016-12-17 02:00 +0100

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