Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751672AbcDUKHZ (ORCPT ); Thu, 21 Apr 2016 06:07:25 -0400 Received: from terminus.zytor.com ([198.137.202.10]:60030 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751041AbcDUKHX (ORCPT ); Thu, 21 Apr 2016 06:07:23 -0400 Date: Thu, 21 Apr 2016 03:06:38 -0700 From: tip-bot for Davidlohr Bueso Message-ID: Cc: hpa@zytor.com, dbueso@suse.de, linux-kernel@vger.kernel.org, mingo@kernel.org, dave@stgolabs.net, peterz@infradead.org, tglx@linutronix.de Reply-To: peterz@infradead.org, tglx@linutronix.de, dbueso@suse.de, dave@stgolabs.net, mingo@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com In-Reply-To: <1461208164-29150-1-git-send-email-dave@stgolabs.net> References: <1461208164-29150-1-git-send-email-dave@stgolabs.net> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/urgent] futex: Acknowledge a new waiter in counter before plist Git-Commit-ID: fe1bce9e2107ba3a8faffe572483b6974201a0e6 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1506 Lines: 41 Commit-ID: fe1bce9e2107ba3a8faffe572483b6974201a0e6 Gitweb: http://git.kernel.org/tip/fe1bce9e2107ba3a8faffe572483b6974201a0e6 Author: Davidlohr Bueso AuthorDate: Wed, 20 Apr 2016 20:09:24 -0700 Committer: Thomas Gleixner CommitDate: Thu, 21 Apr 2016 11:06:09 +0200 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 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 --- kernel/futex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index fd204e1..c20f06f 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);