Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758896Ab3D2R4s (ORCPT ); Mon, 29 Apr 2013 13:56:48 -0400 Received: from mail-qe0-f41.google.com ([209.85.128.41]:32813 "EHLO mail-qe0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757448Ab3D2R4r (ORCPT ); Mon, 29 Apr 2013 13:56:47 -0400 Message-ID: <517EB45D.60007@gmail.com> Date: Mon, 29 Apr 2013 13:56:45 -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: KOSAKI Motohiro , Peter Zijlstra , Ingo Molnar , Thomas Gleixner , schwidefsky@de.ibm.com, Steven Rostedt , Frederic Weisbecker , 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> <517DFFE9.4050808@gmail.com> <1367255407.8833.4.camel@Wailaba2> In-Reply-To: <1367255407.8833.4.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: 2860 Lines: 71 (4/29/13 1:10 PM), Olivier Langlois wrote: > On Mon, 2013-04-29 at 01:06 -0400, KOSAKI Motohiro wrote: >> (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. > > glibc launch a helper thread to receive timer signal and will also > create a new thread upon signal reception when a timer is created with > sigev_notify = SIGEV_THREAD; > > please see: > > glibc-2.17/nptl/sysdeps/unix/sysv/linux/timer_create.c > glibc-2.17/nptl/sysdeps/unix/sysv/linux/timer_routines.c I know. I taled thread exiting. not thread creating. And, as far as I can see, only test sig1 can fail, not thr[12]. -- 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/