From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:41164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751611AbdHPS7l (ORCPT ); Wed, 16 Aug 2017 14:59:41 -0400 Date: Wed, 16 Aug 2017 14:59:38 -0400 From: Steven Rostedt To: Waiman Long 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 Subject: Re: [PATCH] blktrace: Fix potentail deadlock between delete & sysfs ops Message-ID: <20170816145938.6cc7eaee@gandalf.local.home> In-Reply-To: <4841e079-c518-cdff-2fbd-661a9ef36722@redhat.com> References: <1502384553-14442-1-git-send-email-longman@redhat.com> <20170815191145.3c95680e@gandalf.local.home> <6fa9f560-e1c2-f164-779f-aeefc5aa7017@redhat.com> <20170816141749.6c11d14c@gandalf.local.home> <4841e079-c518-cdff-2fbd-661a9ef36722@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, 16 Aug 2017 14:46:42 -0400 Waiman Long wrote: > I haven't been thinking about RT tasks. You are right that it can be a > problem in this case. I think I will have to revert back to use > mutex_lock() if a RT task is running. Though in this case, the lock > inversion problem will still be there. However, it is highly unlikely > that a RT task will need to read write the block trace sysfs files. And it is highly unlikely that the lock inversion will happen. But let's not switch one bug with another. And with PREEMPT_RT coming, that can boost tasks into being RT, it can make the likelihood of RT tasks running normally non RT tasks higher. -- Steve