Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753957AbZAFRCq (ORCPT ); Tue, 6 Jan 2009 12:02:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751287AbZAFRCf (ORCPT ); Tue, 6 Jan 2009 12:02:35 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:52114 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751017AbZAFRCe (ORCPT ); Tue, 6 Jan 2009 12:02:34 -0500 Date: Tue, 6 Jan 2009 18:02:04 +0100 From: Ingo Molnar To: Linus Torvalds Cc: Peter Zijlstra , Matthew Wilcox , Andi Kleen , Chris Mason , Andrew Morton , linux-kernel@vger.kernel.org, linux-fsdevel , linux-btrfs , Thomas Gleixner , Steven Rostedt , Gregory Haskins , Nick Piggin Subject: Re: [PATCH][RFC]: mutex: adaptive spin Message-ID: <20090106170204.GB32608@elte.hu> References: <87r63ljzox.fsf@basil.nowhere.org> <20090103191706.GA2002@parisc-linux.org> <1231093310.27690.5.camel@twins> <20090104184103.GE2002@parisc-linux.org> <1231242031.11687.97.camel@twins> <20090106121052.GA27232@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1228 Lines: 31 * Linus Torvalds wrote: > On Tue, 6 Jan 2009, Linus Torvalds wrote: > > > > Right now, if some process deadlocks on a mutex, we get hung process, > > but with a nice backtrace and hopefully other things (that don't need > > that lock) still continue to work. > > Clarification: the "nice backtrace" we only get with something like > sysrq-W, of course. We don't get a backtrace _automatically_, but with > an otherwise live machine, there's a better chance that people do get > wchan or other info. IOW, it's at least a fairly debuggable situation. btw., the softlockup watchdog detects non-progressing uninterruptible tasks (regardless of whether they locked up due to mutexes or any other reason). This does occasionally help in debugging deadlocks: http://marc.info/?l=linux-mm&m=122889587725061&w=2 but it would indeed be also good to have the most common self-deadlock case checked unconditionally in the mutex slowpath. Ingo -- 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/