From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933789AbdKAVVK (ORCPT ); Wed, 1 Nov 2017 17:21:10 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:35027 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933767AbdKAVVG (ORCPT ); Wed, 1 Nov 2017 17:21:06 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Tejun Heo , Willy Tarreau Subject: [PATCH 3.10 040/139] workqueue: restore WQ_UNBOUND/max_active==1 to be ordered Date: Wed, 1 Nov 2017 22:17:40 +0100 Message-Id: <1509571159-4405-41-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1509571159-4405-1-git-send-email-w@1wt.eu> References: <1509571159-4405-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tejun Heo commit 5c0338c68706be53b3dc472e4308961c36e4ece1 upstream. The combination of WQ_UNBOUND and max_active == 1 used to imply ordered execution. After NUMA affinity 4c16bd327c74 ("workqueue: implement NUMA affinity for unbound workqueues"), this is no longer true due to per-node worker pools. While the right way to create an ordered workqueue is alloc_ordered_workqueue(), the documentation has been misleading for a long time and people do use WQ_UNBOUND and max_active == 1 for ordered workqueues which can lead to subtle bugs which are very difficult to trigger. It's unlikely that we'd see noticeable performance impact by enforcing ordering on WQ_UNBOUND / max_active == 1 workqueues. Let's automatically set __WQ_ORDERED for those workqueues. Signed-off-by: Tejun Heo Reported-by: Christoph Hellwig Reported-by: Alexei Potashnik Fixes: 4c16bd327c74 ("workqueue: implement NUMA affinity for unbound workqueues") Cc: stable@vger.kernel.org Signed-off-by: Willy Tarreau --- kernel/workqueue.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 66972ac..3f8558f 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -4213,6 +4213,16 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt, struct workqueue_struct *wq; struct pool_workqueue *pwq; + /* + * Unbound && max_active == 1 used to imply ordered, which is no + * longer the case on NUMA machines due to per-node pools. While + * alloc_ordered_workqueue() is the right way to create an ordered + * workqueue, keep the previous behavior to avoid subtle breakages + * on NUMA. + */ + if ((flags & WQ_UNBOUND) && max_active == 1) + flags |= __WQ_ORDERED; + /* allocate wq and format name */ if (flags & WQ_UNBOUND) tbl_size = wq_numa_tbl_len * sizeof(wq->numa_pwq_tbl[0]); -- 2.8.0.rc2.1.gbe9624a