From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756493AbZBJUym (ORCPT ); Tue, 10 Feb 2009 15:54:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754966AbZBJUyd (ORCPT ); Tue, 10 Feb 2009 15:54:33 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52555 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754729AbZBJUyc (ORCPT ); Tue, 10 Feb 2009 15:54:32 -0500 Date: Tue, 10 Feb 2009 12:53:44 -0800 From: Andrew Morton To: Lai Jiangshan Cc: peterz@infradead.org, mingo@elte.hu, fweisbec@gmail.com, oleg@tv-sign.ru, dada1@cosmosbay.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] workqueue: not allow recursion run_workqueue Message-Id: <20090210125344.6fc244a3.akpm@linux-foundation.org> In-Reply-To: <498B9675.3000202@cn.fujitsu.com> References: <497838F0.7020408@cn.fujitsu.com> <20090122093046.GC5891@nowhere> <20090122093649.GD24758@elte.hu> <1232622615.4890.114.camel@laptop> <498AA0F1.2030003@cn.fujitsu.com> <498B9675.3000202@cn.fujitsu.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 06 Feb 2009 09:46:29 +0800 Lai Jiangshan wrote: > Hi, Ingo > > This is new changelog, I didn't change the patch, > except use WARN_ON instead BUG_ON. > > Thanks, Lai > > From: Lai Jiangshan > > 1) lockdep will complain when recursion run_workqueue() > 2) The recursive implement of run_workqueue() makes flush_workqueue() > and it's doc are inconsistent. It may hide deadlock and other bugs. > 3) recursion run_workqueue() will poison cwq->current_work, > but flush_work() and __cancel_work_timer() ...etc. need > reliable cwq->current_work. > > Signed-off-by: Lai Jiangshan > --- > diff --git a/kernel/workqueue.c b/kernel/workqueue.c > index 2f44583..1129cde 100644 > --- a/kernel/workqueue.c > +++ b/kernel/workqueue.c > @@ -48,8 +48,6 @@ struct cpu_workqueue_struct { > > struct workqueue_struct *wq; > struct task_struct *thread; > - > - int run_depth; /* Detect run_workqueue() recursion depth */ > } ____cacheline_aligned; > > /* > @@ -262,13 +260,6 @@ EXPORT_SYMBOL_GPL(queue_delayed_work_on); > static void run_workqueue(struct cpu_workqueue_struct *cwq) > { > spin_lock_irq(&cwq->lock); > - cwq->run_depth++; > - if (cwq->run_depth > 3) { > - /* morton gets to eat his hat */ > - printk("%s: recursion depth exceeded: %d\n", > - __func__, cwq->run_depth); > - dump_stack(); > - } I never did get to eat my hat. Do we know of any cases where there was ever any recursion here? Even single-level recursion?