Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932804Ab0BPRFo (ORCPT ); Tue, 16 Feb 2010 12:05:44 -0500 Received: from tomts13-srv.bellnexxia.net ([209.226.175.34]:44385 "EHLO tomts13-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932449Ab0BPRFm (ORCPT ); Tue, 16 Feb 2010 12:05:42 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AvsEAIJfektGHl8d/2dsb2JhbACbGXW9f4RbBIMUGg Date: Tue, 16 Feb 2010 12:05:40 -0500 From: Mathieu Desnoyers To: Thomas Gleixner Cc: Steven Rostedt , ltt-dev@lists.casi.polymtl.ca, Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [ltt-dev] LTTng0.158 Linux-2629-RT kernel BUG: sleeping function called from invalid context at kernel/rtmutex.c:685 Message-ID: <20100216170540.GA28039@Krystal> References: <1266337450.24271.140.camel@gandalf.stny.rr.com> <20100216164744.GA25115@Krystal> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 12:03:31 up 62 days, 1:21, 6 users, load average: 0.42, 0.25, 0.14 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1733 Lines: 49 * Thomas Gleixner (tglx@linutronix.de) wrote: > On Tue, 16 Feb 2010, Mathieu Desnoyers wrote: > > > The function is called from an IPI. That's a LTTNG problem, not a RT one. > > > > I use del_timer in IPI to delete lttng per-cpu timers on all CPUs. I > > have to do this because timers created with add_timer_on are documented > > to be incompatible with del_timer_sync(): > > > > * Synchronization rules: Callers must prevent restarting of the timer, > > * otherwise this function is meaningless. It must not be called from > > * interrupt contexts. The caller must not hold locks which would prevent > > * completion of the timer's handler. The timer's handler must not call > > * add_timer_on(). Upon exit the timer is not queued and the handler is > > * not running on any CPU. > > Errm. The documentation says: > > "The timer's handler must not call add_timer_on()." > > It's not talking about a timer which was initialized with > add_timer_on(). > > And your per cpu timer handlers have no requirement to call > add_timer_on() simply because add/mod_timer() is requeueing the timer > on the same cpu on which the handler runs. > > So the IPI is just a solution for a non existing problem. Oh, right. Thanks for the explanation. I'll look into moving LTTng to a saner del_timer_sync() scheme to delete the timers. Thanks, Mathieu > > Thanks, > > tglx > -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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/