Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756630AbZKWJ5N (ORCPT ); Mon, 23 Nov 2009 04:57:13 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756450AbZKWJ5M (ORCPT ); Mon, 23 Nov 2009 04:57:12 -0500 Received: from mx1.redhat.com ([209.132.183.28]:19124 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756437AbZKWJ5M (ORCPT ); Mon, 23 Nov 2009 04:57:12 -0500 Date: Mon, 23 Nov 2009 10:52:46 +0100 From: Stanislaw Gruszka To: Hidetoshi Seto Cc: =?iso-8859-1?Q?Am=E9rico?= Wang , Peter Zijlstra , Spencer Candland , linux-kernel@vger.kernel.org, Ingo Molnar , Oleg Nesterov Subject: Re: [PATCH] fix granularity of task_u/stime(), v2 Message-ID: <20091123095246.GA25978@dhcp-lab-161.englab.brq.redhat.com> References: <1257778154.4108.341.camel@laptop> <4AF8FD3C.2090008@jp.fujitsu.com> <4AF8FE76.406@jp.fujitsu.com> <20091111121150.GA2549@dhcp-lab-161.englab.brq.redhat.com> <4AFB5019.7030901@jp.fujitsu.com> <4AFB77C2.8080705@jp.fujitsu.com> <2375c9f90911111855w20491a1er8d3400cf4e027855@mail.gmail.com> <4AFB8C21.6080404@jp.fujitsu.com> <4AFB9029.9000208@jp.fujitsu.com> <20091112144919.GA6218@dhcp-lab-161.englab.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091112144919.GA6218@dhcp-lab-161.englab.brq.redhat.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2408 Lines: 60 On Thu, Nov 12, 2009 at 03:49:19PM +0100, Stanislaw Gruszka wrote: > On Thu, Nov 12, 2009 at 01:33:45PM +0900, Hidetoshi Seto wrote: > > Originally task_s/utime() were designed to return clock_t but later > > changed to return cputime_t by following commit: > > > > commit efe567fc8281661524ffa75477a7c4ca9b466c63 > > Author: Christian Borntraeger > > Date: Thu Aug 23 15:18:02 2007 +0200 > > > > It only changed the type of return value, but not the implementation. > > As the result the granularity of task_s/utime() is still that of > > clock_t, not that of cputime_t. > > > > So using task_s/utime() in __exit_signal() makes values accumulated > > to the signal struct to be rounded and coarse grained. > > > > This patch removes casts to clock_t in task_u/stime(), to keep > > granularity of cputime_t over the calculation. > > > > v2: > > Use div_u64() to avoid error "undefined reference to `__udivdi3`" > > on some 32bit systems. > > > > Signed-off-by: Hidetoshi Seto > > --- > > kernel/sched.c | 22 +++++++++++++--------- > > 1 files changed, 13 insertions(+), 9 deletions(-) > > Patch not fix the issue on my system. I test it alone, together with > > posix-cpu-timers: avoid do_sys_times() races with __exit_signal( > > and (further) together with > > --- a/kernel/posix-cpu-timers.c > +++ b/kernel/posix-cpu-timers.c > @@ -248,8 +248,8 @@ void thread_group_cputime(struct task_struct *tsk, > struct task_cputime *times) > > t = tsk; > do { > - times->utime = cputime_add(times->utime, t->utime); > - times->stime = cputime_add(times->stime, t->stime); > + times->utime = cputime_add(times->utime, task_utime(t)); > + times->stime = cputime_add(times->stime, task_stime(t)); > times->sum_exec_runtime += t->se.sum_exec_runtime; > > t = next_thread(t); > > What only changed was probability to enter the issue. I was wrong here, that combination fix the problem on my system. I don't know how I was testing it before, perhaps I booted wrong kernel. Stanislaw -- 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/