From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752613AbaBTBsI (ORCPT ); Wed, 19 Feb 2014 20:48:08 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:52918 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751752AbaBTBsF (ORCPT ); Wed, 19 Feb 2014 20:48:05 -0500 X-IronPort-AV: E=Sophos;i="4.97,509,1389715200"; d="scan'208";a="9563837" Message-ID: <53055F6F.6060909@cn.fujitsu.com> Date: Thu, 20 Feb 2014 09:50:39 +0800 From: Lai Jiangshan User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: Tejun Heo CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] workqueue: Fix possible unexpectedly worker wakeup before started References: <1392781678-31952-1-git-send-email-laijs@cn.fujitsu.com> <20140220001142.GV10134@htj.dyndns.org> In-Reply-To: <20140220001142.GV10134@htj.dyndns.org> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/20 09:45:49, Serialize by Router on mailserver/fnst(Release 8.5.3|September 15, 2011) at 2014/02/20 09:45:52, Serialize complete at 2014/02/20 09:45:52 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/20/2014 08:11 AM, Tejun Heo wrote: > Hello, Lai. > > On Wed, Feb 19, 2014 at 11:47:58AM +0800, Lai Jiangshan wrote: >> If a worker is wokenup unexpectedly, it will start to work incorretly. >> Although it hardly happen, we should catch it and wait for being started >> if it does happen. > > Can this actually happen? If so, how? I don't think it can happen. It depends on the system outside of workqueue. I'm afraid someone see the task and wake up it. workqueue protect itself. > >> Signed-off-by: Lai Jiangshan >> --- >> kernel/workqueue.c | 6 ++++++ >> 1 files changed, 6 insertions(+), 0 deletions(-) >> >> diff --git a/kernel/workqueue.c b/kernel/workqueue.c >> index 82ef9f3..bee5fe1 100644 >> --- a/kernel/workqueue.c >> +++ b/kernel/workqueue.c >> @@ -2284,6 +2284,12 @@ static int worker_thread(void *__worker) >> struct worker *worker = __worker; >> struct worker_pool *pool = worker->pool; >> >> + if (WARN_ON_ONCE(!(worker->flags & WORKER_STARTED))) { > > And if this is something which can legitimately happen, why are we > triggering WARN on it? If it happens, it means there is something wrong in the system. > >> + /* The worker is wokenup unexpectedly before started */ >> + mutex_lock(&pool->manager_mutex); >> + mutex_unlock(&pool->manager_mutex); > > And what does these mutex cycling achieve (they need comment)? Synchronize the manager to finish. > > Thanks. >