From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753779AbaBGLaN (ORCPT ); Fri, 7 Feb 2014 06:30:13 -0500 Received: from www.linutronix.de ([62.245.132.108]:43290 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751734AbaBGLaI (ORCPT ); Fri, 7 Feb 2014 06:30:08 -0500 Date: Fri, 7 Feb 2014 12:30:06 +0100 From: Sebastian Andrzej Siewior To: Steven Rostedt Cc: LKML , linux-rt-users , Thomas Gleixner , Clark Williams , "Luis Claudio R. Goncalves" , John Kacur , Ulrich Obergfell Subject: Re: [PATCH RT] rt: Make cpu_chill() use hrtimer instead of msleep() Message-ID: <20140207113006.GD23668@linutronix.de> References: <20140205115125.3cc950ce@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20140205115125.3cc950ce@gandalf.local.home> X-Key-Id: 97C4700B X-Key-Fingerprint: 09E2 D1F3 9A3A FF13 C3D3 961C 0688 1C1E 97C4 700B User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt | 2014-02-05 11:51:25 [-0500]: >Ulrich Obergfell pointed out that cpu_chill() calls msleep() which is woken >up by the ksoftirqd running the TIMER softirq. But as the cpu_chill() is >called from softirq context, it may block the ksoftirqd() from running, in >which case, it may never wake up the msleep() causing the deadlock. > >I checked the vmcore, and irq/74-qla2xxx is stuck in the msleep() call, >running on CPU 8. The one ksoftirqd that is stuck, happens to be the one that >runs on CPU 8, and it is blocked on a lock held by irq/74-qla2xxx. As that >ksoftirqd is the one that will wake up irq/74-qla2xxx, and it happens to be >blocked on a lock that irq/74-qla2xxx holds, we have our deadlock. could you please tell me which two locks are invovled here? Sebastian