From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751688AbdEASoM (ORCPT ); Mon, 1 May 2017 14:44:12 -0400 Received: from mail-yw0-f174.google.com ([209.85.161.174]:33578 "EHLO mail-yw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750957AbdEASoE (ORCPT ); Mon, 1 May 2017 14:44:04 -0400 Date: Mon, 1 May 2017 14:44:02 -0400 From: Tejun Heo To: "Paul E. McKenney" Cc: jiangshanlai@gmail.com, linux-kernel@vger.kernel.org Subject: Re: WARN_ON_ONCE() in process_one_work()? Message-ID: <20170501184402.GB8921@htj.duckdns.org> References: <20170501165747.GA993@linux.vnet.ibm.com> <20170501183807.GA7054@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170501183807.GA7054@linux.vnet.ibm.com> User-Agent: Mutt/1.8.0 (2017-02-23) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Paul. On Mon, May 01, 2017 at 11:38:07AM -0700, Paul E. McKenney wrote: > On Mon, May 01, 2017 at 09:57:47AM -0700, Paul E. McKenney wrote: > > Hello! > > > > I am hitting this WARN_ON_ONCE() in process_one_work() and am wondering > > what I did wrong to make this happen: > > Oh, wait... Rescuer, it says. Might this be due to the fact that RCU's > expedited grace periods block within a workqueue handler? Might this > in turn run the system out of workqueue kthreads? If this is the likely > cause, my approach would be to rework the expected-grace-period workqueue > handler to return when waiting for the grace period to complete, and to > replace the current wakeup with a schedule_work() or something similar. That should be completely fine. It could just be that the rescuer path has a bug around CPU hotplug handling. Can you please confirm either way on the cpuset usage? Thanks. -- tejun