From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753349AbcBZGXy (ORCPT ); Fri, 26 Feb 2016 01:23:54 -0500 Received: from mail-pf0-f174.google.com ([209.85.192.174]:34722 "EHLO mail-pf0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750869AbcBZGXw (ORCPT ); Fri, 26 Feb 2016 01:23:52 -0500 Date: Fri, 26 Feb 2016 14:19:20 +0800 From: Peter Chen To: Tejun Heo Cc: Alan Stern , florian@mickler.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, usb-storage@lists.one-eyed-alien.net Subject: Re: Freezable workqueue blocks non-freezable workqueue during the system resume process Message-ID: <20160226061920.GA17288@shlinux2.ap.freescale.net> References: <20160223032056.GB12256@shlinux2.ap.freescale.net> <20160224072430.GC15452@shlinux2.ap.freescale.net> <20160225220112.GM6092@mtj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160225220112.GM6092@mtj.duckdns.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 25, 2016 at 05:01:12PM -0500, Tejun Heo wrote: > Hello, Peter. > > On Wed, Feb 24, 2016 at 03:24:30PM +0800, Peter Chen wrote: > > > You might want to complain to the block-layer people about this. I > > > don't know if anything can be done to fix it. > > > > > > Or maybe flush_work and flush_delayed_work can be changed to avoid > > > blocking if the workqueue is frozen. Tejun? > > > > > > > I have a patch to show the root cause of this issue. > > > > http://www.spinics.net/lists/linux-usb/msg136815.html > > I don't get it. Why would it deadlock? Shouldn't things get rolling > once the workqueues are thawed? > Hi Tejun, The workqueue writeback can't be thawed due to driver's resume (dpm_complete) is lock nested, and can't be finished. -- Best Regards, Peter Chen