Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754035AbZAFQ4t (ORCPT ); Tue, 6 Jan 2009 11:56:49 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751449AbZAFQ4j (ORCPT ); Tue, 6 Jan 2009 11:56:39 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:52684 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750746AbZAFQ4i (ORCPT ); Tue, 6 Jan 2009 11:56:38 -0500 Date: Tue, 6 Jan 2009 17:56:15 +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: <20090106165615.GA5168@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> <20090106165409.GA32608@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090106165409.GA32608@elte.hu> 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: 1132 Lines: 26 * Ingo Molnar wrote: > One thought: > > BUG_ON()'s do_exit() shows a slightly misleading failure pattern to > users: instead of a 'hanging' task, we'd get a misbehaving app due to > one of its tasks exiting spuriously. It can even go completely unnoticed > [users dont look at kernel logs normally] - while a hanging task > generally does get noticed. (because there's no progress in processing) > > So instead of the BUG_ON() we could emit a WARN_ONCE() perhaps, plus not > do any spinning and just block - resulting in an uninterruptible task > (that the user will probably notice) and a scary message in the syslog? > [all in the slowpath] And we'd strictly do an uninterruptible sleep here, unconditionally: even if this is within mutex_lock_interruptible() - we dont want a Ctrl-C or a SIGKILL to allow to 'break out' the app from the deadlock. 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/