Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750730AbWC3OvX (ORCPT ); Thu, 30 Mar 2006 09:51:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750727AbWC3OvW (ORCPT ); Thu, 30 Mar 2006 09:51:22 -0500 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:56045 "EHLO ecfrec.frec.bull.fr") by vger.kernel.org with ESMTP id S1750718AbWC3OvV (ORCPT ); Thu, 30 Mar 2006 09:51:21 -0500 Message-ID: <442BF083.2070104@bull.net> Date: Thu, 30 Mar 2006 16:51:47 +0200 From: Pierre PEIFFER User-Agent: Thunderbird 1.5 (X11/20060313) MIME-Version: 1.0 To: Eric Dumazet Cc: linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: [PATCH] 2.6.16 - futex: small optimization (?) References: <4428E7B7.8040408@bull.net> <442A8933.6090408@bull.net> <442AA708.3030802@cosmosbay.com> In-Reply-To: <442AA708.3030802@cosmosbay.com> X-MIMETrack: Itemize by SMTP Server on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 30/03/2006 16:53:27, Serialize by Router on ECN002/FR/BULL(Release 5.0.12 |February 13, 2003) at 30/03/2006 16:53:27, Serialize complete at 30/03/2006 16:53:27 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=ISO-8859-1; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 975 Lines: 31 Eric Dumazet a ?crit : > I think your analysis is correct Pierre, but you speak of > 'task-switches', where there is only a spinlock involved : > > On UP case : a wake_up_all() wont preempt current thread : it will > task-switch only when current thread exits kernel mode. > > On PREEMPT case : wake_up_all() wont preempt current thread (because > current thread is holding bh->lock). > > On SMP : the awaken thread will spin some time on bh->lock, but not > task-switch again. Ok, yes, you're right, thanks. > > On RT kernel, this might be different of course... So, I confirm it only happens on RT kernel ... ... but my patch does not work on those kernels :-/ In fact, I don't really see what's wrong ? -- Pierre - 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/