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authorDavidlohr Bueso <dave@stgolabs.net>2016-04-20 20:09:24 -0700
committerThomas Gleixner <tglx@linutronix.de>2016-04-21 11:06:09 +0200
commitfe1bce9e2107ba3a8faffe572483b6974201a0e6 (patch)
treec7f1a4b8ab31d63aa79a7e130f8a65bbebfd3269
parent89e9e66ba1b3bde9d8ea90566c2aee20697ad681 (diff)
downloadlinux-sh-fe1bce9e2107ba3a8faffe572483b6974201a0e6.tar.gz
futex: Acknowledge a new waiter in counter before plist
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 <peterz@infradead.org> Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Cc: Davidlohr Bueso <dave@stgolabs.net> 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 <tglx@linutronix.de>
-rw-r--r--kernel/futex.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index fd204e1670c9..c20f06f38ef3 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1535,8 +1535,8 @@ 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);