Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757164AbcDMCN0 (ORCPT ); Tue, 12 Apr 2016 22:13:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55058 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751181AbcDMCNY (ORCPT ); Tue, 12 Apr 2016 22:13:24 -0400 Reply-To: xlpang@redhat.com Subject: Re: [PATCH] sched/deadline/rtmutex: Fix a PI crash for deadline tasks References: <20160405091954.GI3448@twins.programming.kicks-ass.net> <20160405092954.GC24771@twins.programming.kicks-ass.net> <20160408122510.15978179@gandalf.local.home> <20160408173835.GC1087@worktop> <20160408145055.13c98a75@gandalf.local.home> <20160408185916.GQ3448@twins.programming.kicks-ass.net> <57087633.3020700@redhat.com> <20160409132935.GU3448@twins.programming.kicks-ass.net> <570A0D37.8080400@redhat.com> <570C6694.50803@redhat.com> <20160412155149.GJ1087@worktop> To: Peter Zijlstra Cc: Steven Rostedt , linux-kernel@vger.kernel.org, Juri Lelli , Ingo Molnar , Thomas Gleixner From: Xunlei Pang Message-ID: <570DAB3F.4030501@redhat.com> Date: Wed, 13 Apr 2016 10:13:19 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-Version: 1.0 In-Reply-To: <20160412155149.GJ1087@worktop> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 514 Lines: 12 On 2016/04/12 at 23:51, Peter Zijlstra wrote: > On Tue, Apr 12, 2016 at 11:08:04AM +0800, Xunlei Pang wrote: >> I spotted another issue, we access pi_task without any lock in enqueue_task_dl(), > OK, so I'm on the road and entirely jetlagged, but how can > enqueue_task_dl() not have rq->lock held? It held current's rq->lock, but not holding pi_task's any lock, so pi_task's attributes can change concurrently with subsequent pi_se->dl_runtime and pi_se->dl_period access, and result in issues. Regards, Xunlei