Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761167AbYFLXdS (ORCPT ); Thu, 12 Jun 2008 19:33:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758090AbYFLXcv (ORCPT ); Thu, 12 Jun 2008 19:32:51 -0400 Received: from www.tglx.de ([62.245.132.106]:42167 "EHLO www.tglx.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759089AbYFLXcu (ORCPT ); Thu, 12 Jun 2008 19:32:50 -0400 Date: Fri, 13 Jun 2008 01:30:58 +0200 (CEST) From: Thomas Gleixner To: Daniel Walker cc: LKML , Ulrich Drepper , Arjan van de Ven , Peter Zijlstra Subject: Re: [PATCH 5/5] futex: fix miss ordered wakeups In-Reply-To: <1213311963.16459.89.camel@localhost.localdomain> Message-ID: References: <20080611204916.271608740@mvista.com> <20080611204917.523866467@mvista.com> <1213277402.16459.25.camel@localhost.localdomain> <1213278286.16459.29.camel@localhost.localdomain> <1213286193.16459.53.camel@localhost.localdomain> <1213308598.16459.82.camel@localhost.localdomain> <1213311963.16459.89.camel@localhost.localdomain> User-Agent: Alpine 1.10 (LFD 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1780 Lines: 43 On Thu, 12 Jun 2008, Daniel Walker wrote: > On Fri, 2008-06-13 at 00:43 +0200, Thomas Gleixner wrote: > > On Thu, 12 Jun 2008, Daniel Walker wrote: > > > > > > > > On Thu, 2008-06-12 at 21:55 +0200, Thomas Gleixner wrote: > > > > Also your interpretation of the POSIX requirement is very > > > > questionable: > > > > > > > > "If there are threads blocked on the mutex object referenced by mutex > > > > when pthread_mutex_unlock() is called, resulting in the mutex > > > > becoming available, the scheduling policy shall determine which > > > > thread shall acquire the mutex." > > > > > > The key is "scheduling policy" .. When the mutex is un-blocked the next > > > task to run is the same as if the scheduler was selecting tasks from the > > > list of blocked tasks .. For Linux, that means the highest priority > > > tasks should be selected.. So it's no more acceptable for the scheduler > > > to priority invert some tasks than it is for the futex to do it. > > > > Sigh, when do you actually get a gripe that the default futex > > implementation does not and can not guarantee that at all and therefor > > your "correctness" patch is as important as a bag of rice which > > toopled over in China ? > > Well, the last email I got from Arjan said this, > > ".. Don't look at the release path... look at the acquire path. > If a thread sees the futex is free, it'll take it, without even going > to the kernel at all." > > And yes, I understand that fully. Great. Case closed, nothing to argue about. Thanks, tglx -- 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/