Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754482AbaFJUpS (ORCPT ); Tue, 10 Jun 2014 16:45:18 -0400 Received: from www.linutronix.de ([62.245.132.108]:55340 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752736AbaFJUpP (ORCPT ); Tue, 10 Jun 2014 16:45:15 -0400 Date: Tue, 10 Jun 2014 22:45:11 +0200 (CEST) From: Thomas Gleixner To: Steven Rostedt cc: LKML , Peter Zijlstra , Ingo Molnar , Lai Jiangshan , Jason Low , Brad Mouring Subject: Re: [patch V3 7/7] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk In-Reply-To: <20140610134745.668c8a4e@gandalf.local.home> Message-ID: References: <20140609201118.387571774@linutronix.de> <20140609202336.506044876@linutronix.de> <20140609212033.1cff0999@gandalf.local.home> <20140610134745.668c8a4e@gandalf.local.home> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 10 Jun 2014, Steven Rostedt wrote: > On Tue, 10 Jun 2014 19:41:39 +0200 (CEST) > Thomas Gleixner wrote: > > > > > On the loop back around, have something like: > > > > > > if (top_waiter) { > > > if (!task_has_pi_waiters(task)) > > > goto out_unlock_pi; > > > > The task has at least one pi waiter. > > > > > if (!requeue && > > > top_waiter != task_top_pi_waiter(task)) { > > > if (!detect_deadlock) > > > goto out_unlock_pi; > > > else > > > requeue = false; > > > } > > > > Errm? if requeue is off we are in deadlock detection chainwalk > > mode. So all we care about is whether task is blocked on > > next_lock or not. > > Actually that was a typo on my part. That should have been: > > if (requeue && > ... > > As we don't need to read the task_top_pi_waiter() again. if (requeue ... is completely pointless as the code you were talking about is in the if (!requeue) { branch. So what? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/