From 5ee9beb33f0c40ee852400997794a81215b11e24 Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 20 Apr 2016 20:09:24 -0700 Subject: futex: Acknowledge a new waiter in counter before plist [ Upstream commit fe1bce9e2107ba3a8faffe572483b6974201a0e6 ] Otherwise an incoming waker on the dest hash bucket can miss the waiter adding itself to the plist during the lockless check optimization (small window but still the correct way of doing this); similarly to the decrement counterpart. Suggested-by: Peter Zijlstra Signed-off-by: Davidlohr Bueso Cc: Davidlohr Bueso Cc: bigeasy@linutronix.de Cc: dvhart@infradead.org Cc: stable@kernel.org Link: http://lkml.kernel.org/r/1461208164-29150-1-git-send-email-dave@stgolabs.net Signed-off-by: Thomas Gleixner Signed-off-by: Sasha Levin --- kernel/futex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index d58859d62b8b..8874a7b431e4 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1381,8 +1381,8 @@ void requeue_futex(struct futex_q *q, struct futex_hash_bucket *hb1, if (likely(&hb1->chain != &hb2->chain)) { plist_del(&q->list, &hb1->chain); hb_waiters_dec(hb1); - plist_add(&q->list, &hb2->chain); hb_waiters_inc(hb2); + plist_add(&q->list, &hb2->chain); q->lock_ptr = &hb2->lock; } get_futex_key_refs(key2); -- cgit v1.2.3