Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751561AbdGRLgW (ORCPT ); Tue, 18 Jul 2017 07:36:22 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:53082 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751441AbdGRLgU (ORCPT ); Tue, 18 Jul 2017 07:36:20 -0400 Date: Tue, 18 Jul 2017 13:36:17 +0200 From: Peter Zijlstra To: Prateek Sood Cc: mingo@redhat.com, sramana@codeaurora.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] osq_lock: avoid live-lock issue for RT task Message-ID: <20170718113617.d4mpsmyzbhz3nr2l@hirez.programming.kicks-ass.net> References: <1500040149-27971-1-git-send-email-prsood@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500040149-27971-1-git-send-email-prsood@codeaurora.org> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 635 Lines: 17 On Fri, Jul 14, 2017 at 07:19:09PM +0530, Prateek Sood wrote: > Live Lock due to task spinning while unqueue of CPU osq_node > from optimistic_spin_queue. Task T1 had decremented mutex count to > acquire the lock on CPU0. Before setting owner it got preempted. You've been working on ancient kernels... That can no longer happen. Please see if this is still an issue after: 3ca0ff571b09 ("locking/mutex: Rework mutex::owner") If so, please write an up-to-date Changelog and patch (it doesn't apply because of commit 5aff60a191e5 ("locking/osq: Break out of spin-wait busy waiting loop for a preempted vCPU in osq_lock()") )