From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:47288 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751728AbdHRN4A (ORCPT ); Fri, 18 Aug 2017 09:56:00 -0400 Subject: Re: [PATCH v2] blktrace: Fix potentail deadlock between delete & sysfs ops To: Steven Rostedt Cc: Jens Axboe , Jeff Layton , "J. Bruce Fields" , Ingo Molnar , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <1502916040-18067-1-git-send-email-longman@redhat.com> <20170817093444.3276f7ab@gandalf.local.home> <20170817171007.1ab33b8f@gandalf.local.home> <20170817173004.263d2891@gandalf.local.home> From: Waiman Long Message-ID: <5a5d0743-d2db-89c8-59cc-542835baeccf@redhat.com> Date: Fri, 18 Aug 2017 09:55:58 -0400 MIME-Version: 1.0 In-Reply-To: <20170817173004.263d2891@gandalf.local.home> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On 08/17/2017 05:30 PM, Steven Rostedt wrote: > On Thu, 17 Aug 2017 17:10:07 -0400 > Steven Rostedt wrote: > > >> Instead of playing games with taking the lock, the only way this race >> is hit, is if the partition is being deleted and the sysfs attribute is >> being read at the same time, correct? In that case, just return >> -ENODEV, and be done with it. > Nevermind that wont work. Too bad there's not a mutex_lock_timeout() > that we could use in a loop. It would solve the issue of forward > progress with RT tasks, and will break after a timeout in case of > deadlock. > > -- Steve I think it will be useful to have mutex_timed_lock(). RT-mutex does have a timed version, so I guess it shouldn't be hard to implement one for mutex. I can take a shot at trying to do that. Thanks, Longman