Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754535AbZDHXpc (ORCPT ); Wed, 8 Apr 2009 19:45:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755617AbZDHXpV (ORCPT ); Wed, 8 Apr 2009 19:45:21 -0400 Received: from ozlabs.org ([203.10.76.45]:37930 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755269AbZDHXpU (ORCPT ); Wed, 8 Apr 2009 19:45:20 -0400 From: Rusty Russell To: Peter Zijlstra Subject: Re: pm-hibernate : possible circular locking dependency detected Date: Thu, 9 Apr 2009 09:15:17 +0930 User-Agent: KMail/1.11.2 (Linux/2.6.27-11-generic; KDE/4.2.2; i686; ; ) Cc: Ingo Molnar , "Rafael J. Wysocki" , Ming Lei , Andrew Morton , "Linux-pm mailing list" , Linux Kernel List , Gautham R Shenoy References: <200904081247.08712.rusty@rustcorp.com.au> <1239194906.13185.93.camel@twins> In-Reply-To: <1239194906.13185.93.camel@twins> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-15" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200904090915.18644.rusty@rustcorp.com.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1356 Lines: 34 On Wednesday 08 April 2009 22:18:26 Peter Zijlstra wrote: > On Wed, 2009-04-08 at 12:47 +0930, Rusty Russell wrote: > > On Tuesday 07 April 2009 16:35:53 Peter Zijlstra wrote: > > > On Tue, 2009-04-07 at 13:56 +0930, Rusty Russell wrote: > > > > Looks like this will be fixed by Andrew's work-on-cpu-in-own-thread > > > > patch which I just put out the pull request for. > > > > > > Would it make sense to teach it about a short-circuit like: > > > > > > work_on_cpu() { > > > > > > if (cpumask_weight(current->cpus_allowed) == 1 && > > > smp_processor_id() == cpu) > > > return do_work_right_here(); > > > > Does that happen much? I guess put a counter in and see? > > Ego spotted the case where cpufreq calls it from an cpu-affine > workqueue, it seems to me in that case its desirable to have the > short-cut, and currently that's needed for correctness too as it will > generate this circular lock thingy. Well, the correctness issue is fixed by Andrew's work_on_cpu-via-new-thread patch (hmm, which Linus hasn't taken, re-xmitting). So it's really a pure optimization. Cheers, Rusty. -- 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/