Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751889Ab3D2FGx (ORCPT ); Mon, 29 Apr 2013 01:06:53 -0400 Received: from mail-qa0-f46.google.com ([209.85.216.46]:59923 "EHLO mail-qa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751639Ab3D2FGw (ORCPT ); Mon, 29 Apr 2013 01:06:52 -0400 Message-ID: <517DFFE9.4050808@gmail.com> Date: Mon, 29 Apr 2013 01:06:49 -0400 From: KOSAKI Motohiro User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20130328 Thunderbird/17.0.5 MIME-Version: 1.0 To: Olivier Langlois CC: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , schwidefsky@de.ibm.com, Steven Rostedt , Frederic Weisbecker , KOSAKI Motohiro , LKML Subject: Re: [PATCH v2 1/3] process cputimer is moving faster than its corresponding clock References: <1365184746.874.103.camel@Wailaba2> <1365593710.30071.52.camel@laptop> <1365608911.707.65.camel@Wailaba2> <1365763837.17140.52.camel@laptop> <1365782115.17140.68.camel@laptop> <1366951210.7911.28.camel@Wailaba2> <1366957639.7911.42.camel@Wailaba2> <517AD0AE.1030404@gmail.com> <1367037606.7911.66.camel@Wailaba2> In-Reply-To: <1367037606.7911.66.camel@Wailaba2> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2235 Lines: 55 (4/27/13 12:40 AM), Olivier Langlois wrote: > > > Forbids the cputimer to drift ahead of its process clock by > blocking its update when a tick occurs while a autoreaping task > is currently in do_exit() between the call to release_task() and > its final call to schedule(). > > Any task stats update after having called release_task() will > be lost because they are added to the global process stats located > in the signal struct from release_task(). > > Ideally, you should postpone the release_task() call after the > final context switch to get all the stats added but this is > more complex to achieve. > > In other words, this is slowing down the cputimer so it keep the same > pace than the process clock but in fact, what should be done is to > speed up the process clock by adding the missing stats to it. > > Signed-off-by: Olivier Langlois > --- > kernel/sched/fair.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 7a33e59..52d7b10 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -708,7 +708,15 @@ static void update_curr(struct cfs_rq *cfs_rq) > > trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime); > cpuacct_charge(curtask, delta_exec); > - account_group_exec_runtime(curtask, delta_exec); > + /* > + * Do not update the cputimer if the task is already released by > + * release_task(). > + * > + * it would preferable to defer the autoreap release_task > + * after the last context switch but harder to do. > + */ > + if (likely(curtask->sighand)) > + account_group_exec_runtime(curtask, delta_exec); > } I'm confused. glibc's rt/tst-cputimer1 doesn't have thread exiting code. I have no seen any issue in this accounting. -- 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/