From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757502Ab0IZQYL (ORCPT ); Sun, 26 Sep 2010 12:24:11 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40769 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752872Ab0IZQYK (ORCPT ); Sun, 26 Sep 2010 12:24:10 -0400 Date: Sun, 26 Sep 2010 18:23:49 +0200 From: Ingo Molnar To: Heiko Carstens Cc: Andrew Morton , Peter Zijlstra , Venkatesh Pallipadi , Suresh Siddha , linux-kernel@vger.kernel.org, Jens Axboe Subject: Re: [PATCH] generic-ipi: fix deadlock in __smp_call_function_single Message-ID: <20100926162349.GA21557@elte.hu> References: <20100909135050.GB2228@osiris.boeblingen.de.ibm.com> <1284116817.402.33.camel@laptop> <20100910172805.a4fe5c7f.akpm@linux-foundation.org> <20100926084233.GA28809@elte.hu> <20100926125945.GA2597@osiris.boeblingen.de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100926125945.GA2597@osiris.boeblingen.de.ibm.com> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0010] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Heiko Carstens wrote: > On Sun, Sep 26, 2010 at 10:42:33AM +0200, Ingo Molnar wrote: > > > > * Andrew Morton wrote: > > > > > Maybe. Or maybe it papers over a scheduler bug by gratuitously adding > > > additional code which no present callsites actually need. > > > > Hm, indeed. > > > > We now have the scheduler bug fixed upstream. Do we really need this > > patch? > > General consensus was that it is good if smp_call_function_single() > and __smp_call_function_single() would behave the same if remote cpu > == current cpu. > > If you're not applying this patch then at least at a WARN_ON() which > triggers when remote cpu == current cpu. I don't want to debug > something like this again. Would be nice to hear from Andrew whether he's still opposed to this patch. I've got the patch queued up, but dont want to send it to Linus against Andrew's objections. > > > The patch didn't update the __smp_call_function_single() > > > kerneldoc. Compare it with smp_call_function_single() and note the > > > subtle difference between "a specific CPU" and the now incorrect > > > "on another CPU". > > > > In any case this feedback didnt get addressed AFAICS. > > It did get addressed in an updated patch which is the one which you > applied: http://lkml.org/lkml/2010/9/10/245 Indeed :-) Thanks, Ingo