From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757531Ab1FIMe0 (ORCPT ); Thu, 9 Jun 2011 08:34:26 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:55736 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752336Ab1FIMeZ (ORCPT ); Thu, 9 Jun 2011 08:34:25 -0400 X-Authority-Analysis: v=1.1 cv=PfPQ8rIoTcZsncbPZjVSZ7K0hy8Zc4hmL68r4VPNpKE= c=1 sm=0 a=cWu3orRm09UA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=OPBmh+XkhLl+Enan7BmTLg==:17 a=pGLkceISAAAA:8 a=rQQHXOjxP4oWyp9PBsUA:9 a=PUjeQqilurYA:10 a=MSl-tDqOz04A:10 a=OPBmh+XkhLl+Enan7BmTLg==:117 X-Cloudmark-Score: 0 X-Originating-IP: 67.242.120.143 Subject: Re: [PATCH] sched: remove resetting exec_start in put_prev_task_rt() From: Steven Rostedt To: Yong Zhang Cc: Hillf Danton , LKML , Mike Galbraith , Peter Zijlstra , Ingo Molnar In-Reply-To: References: Content-Type: text/plain; charset="ISO-8859-15" Date: Thu, 09 Jun 2011 08:34:23 -0400 Message-ID: <1307622863.9218.40.camel@gandalf.stny.rr.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.2 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2011-06-02 at 16:04 +0800, Yong Zhang wrote: > On Wed, Jun 1, 2011 at 10:03 PM, Hillf Danton wrote: > > Resetting exec_start, after updated in update_curr_rt(), could open window for > > messing up the subsequent computations of delta_exec of the given task. > > I can't see how could this happen. what kind of 'subsequent computations' > do you mean? I still don't see a race. Hilf, if you still believe there's a race here, can you explain it in detail. Do something like: CPU0 CPU1 ---- ---- do_something; does_something_not_expected; continue_something; Obviously changing what those "somethings" are. That way we can visually see what you are trying to say. > > But because exec_start will be reset by _pick_next_task_rt()/set_curr_task_rt(), > you patch is ok. IMHO it is not critical, it's just cleanup instead. I disagree. Yes the exec_start is reset there, but I like the fact that it's 0 when not running. -- Steve