From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758751Ab3EAKFm (ORCPT ); Wed, 1 May 2013 06:05:42 -0400 Received: from terminus.zytor.com ([198.137.202.10]:39018 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759472Ab3EAKFZ (ORCPT ); Wed, 1 May 2013 06:05:25 -0400 Date: Wed, 1 May 2013 03:04:50 -0700 From: tip-bot for Stanislaw Gruszka Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, dave@sr71.net, fweisbec@gmail.com, tglx@linutronix.de, sgruszka@redhat.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, peterz@infradead.org, dave@sr71.net, fweisbec@gmail.com, tglx@linutronix.de, sgruszka@redhat.com In-Reply-To: <1367314507-9728-2-git-send-email-sgruszka@redhat.com> References: <1367314507-9728-2-git-send-email-sgruszka@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched: Do not account bogus utime Git-Commit-ID: 772c808a252594692972773f6ee41c289b8e0b2a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 772c808a252594692972773f6ee41c289b8e0b2a Gitweb: http://git.kernel.org/tip/772c808a252594692972773f6ee41c289b8e0b2a Author: Stanislaw Gruszka AuthorDate: Tue, 30 Apr 2013 11:35:05 +0200 Committer: Ingo Molnar CommitDate: Tue, 30 Apr 2013 19:13:04 +0200 sched: Do not account bogus utime Due to rounding in scale_stime(), for big numbers, scaled stime values will grow in chunks. Since rtime grow in jiffies and we calculate utime like below: prev->stime = max(prev->stime, stime); prev->utime = max(prev->utime, rtime - prev->stime); we could erroneously account stime values as utime. To prevent that only update prev->{u,s}time values when they are smaller than current rtime. Signed-off-by: Stanislaw Gruszka Cc: Frederic Weisbecker Cc: rostedt@goodmis.org Cc: Linus Torvalds Cc: Dave Hansen Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1367314507-9728-2-git-send-email-sgruszka@redhat.com Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index e9198ab..1b7c216 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -581,6 +581,14 @@ static void cputime_adjust(struct task_cputime *curr, */ rtime = nsecs_to_cputime(curr->sum_exec_runtime); + /* + * Update userspace visible utime/stime values only if actual execution + * time is bigger than already exported. Note that can happen, that we + * provided bigger values due to scaling inaccuracy on big numbers. + */ + if (prev->stime + prev->utime >= rtime) + goto out; + if (!rtime) { stime = 0; } else if (!total) { @@ -598,6 +606,7 @@ static void cputime_adjust(struct task_cputime *curr, prev->stime = max(prev->stime, stime); prev->utime = max(prev->utime, rtime - prev->stime); +out: *ut = prev->utime; *st = prev->stime; }