From 1e52892396c1d407ddccab6f7ebafaf14b26ae0b Mon Sep 17 00:00:00 2001 From: Davidlohr Bueso Date: Wed, 20 Apr 2016 20:09:24 -0700 Subject: [PATCH] futex: Acknowledge a new waiter in counter before plist Orabug: 25308063 [ 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 (cherry picked from commit 0ee1b6dbc57dc78541df83157e1251b983c51485) Signed-off-by: Dhaval Giani --- kernel/futex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index 46b168e19c98..2214b70f1910 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); -- 2.50.1