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authorDavidlohr Bueso <dave@stgolabs.net>2016-04-20 20:09:24 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-05-04 14:48:43 -0700
commitad4b209d192624e8587f4988171d624346913ddd (patch)
tree26bdee892c3fb8af37bbe2ed70ff4ff09b139ed1 /kernel/futex.c
parent61fc0ae42c498f8eb782733065d93da6817d28b4 (diff)
futex: Acknowledge a new waiter in counter before plist
commit fe1bce9e2107ba3a8faffe572483b6974201a0e6 upstream. 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 Link: http://lkml.kernel.org/r/1461208164-29150-1-git-send-email-dave@stgolabs.net Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel/futex.c')
-rw-r--r--kernel/futex.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index eaa3a8dfd345..9d8163afd87c 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1484,8 +1484,8 @@ 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);