From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:60784 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933220AbcECAgw (ORCPT ); Mon, 2 May 2016 20:36:52 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Zijlstra , Davidlohr Bueso , Davidlohr Bueso , bigeasy@linutronix.de, dvhart@infradead.org, Thomas Gleixner Subject: [PATCH 4.5 047/200] futex: Acknowledge a new waiter in counter before plist Date: Mon, 2 May 2016 17:10:46 -0700 Message-Id: <20160503000556.141449591@linuxfoundation.org> In-Reply-To: <20160503000554.631204776@linuxfoundation.org> References: <20160503000554.631204776@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Davidlohr Bueso 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 Signed-off-by: Davidlohr Bueso Cc: Davidlohr Bueso 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 Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1452,8 +1452,8 @@ void requeue_futex(struct futex_q *q, st 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);