Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935020Ab3IDOkt (ORCPT ); Wed, 4 Sep 2013 10:40:49 -0400 Received: from terminus.zytor.com ([198.137.202.10]:54688 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934439Ab3IDOkd (ORCPT ); Wed, 4 Sep 2013 10:40:33 -0400 Date: Wed, 4 Sep 2013 07:37:22 -0700 From: tip-bot for Stanislaw Gruszka Message-ID: Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org, peterz@infradead.org, sergey.senozhatsky@gmail.com, bp@alien8.de, paulmck@linux.vnet.ibm.com, fweisbec@gmail.com, tglx@linutronix.de, sgruszka@redhat.com Reply-To: mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org, sergey.senozhatsky@gmail.com, bp@alien8.de, paulmck@linux.vnet.ibm.com, fweisbec@gmail.com, tglx@linutronix.de, sgruszka@redhat.com In-Reply-To: <20130904131602.GC2564@redhat.com> References: <20130904131602.GC2564@redhat.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:timers/urgent] sched/cputime: Do not scale when utime == 0 Git-Commit-ID: 5a8e01f8fa51f5cbce8f37acc050eb2319d12956 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 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (terminus.zytor.com [127.0.0.1]); Wed, 04 Sep 2013 07:37:29 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3118 Lines: 90 Commit-ID: 5a8e01f8fa51f5cbce8f37acc050eb2319d12956 Gitweb: http://git.kernel.org/tip/5a8e01f8fa51f5cbce8f37acc050eb2319d12956 Author: Stanislaw Gruszka AuthorDate: Wed, 4 Sep 2013 15:16:03 +0200 Committer: Ingo Molnar CommitDate: Wed, 4 Sep 2013 16:31:25 +0200 sched/cputime: Do not scale when utime == 0 scale_stime() silently assumes that stime < rtime, otherwise when stime == rtime and both values are big enough (operations on them do not fit in 32 bits), the resulting scaling stime can be bigger than rtime. In consequence utime = rtime - stime results in negative value. User space visible symptoms of the bug are overflowed TIME values on ps/top, for example: $ ps aux | grep rcu root 8 0.0 0.0 0 0 ? S 12:42 0:00 [rcuc/0] root 9 0.0 0.0 0 0 ? S 12:42 0:00 [rcub/0] root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt] root 11 0.1 0.0 0 0 ? S 12:42 0:02 [rcuop/0] root 12 62422329 0.0 0 0 ? S 12:42 21114581:35 [rcuop/1] root 10 62422329 0.0 0 0 ? R 12:42 21114581:37 [rcu_preempt] or overflowed utime values read directly from /proc/$PID/stat Reference: https://lkml.org/lkml/2013/8/20/259 Reported-and-tested-by: Sergey Senozhatsky Signed-off-by: Stanislaw Gruszka Cc: stable@vger.kernel.org Cc: Frederic Weisbecker Cc: Peter Zijlstra Cc: Paul E. McKenney Cc: Borislav Petkov Link: http://lkml.kernel.org/r/20130904131602.GC2564@redhat.com Signed-off-by: Ingo Molnar --- kernel/sched/cputime.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index c1d7493..5b03f5b 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -551,10 +551,7 @@ static void cputime_adjust(struct task_cputime *curr, struct cputime *prev, cputime_t *ut, cputime_t *st) { - cputime_t rtime, stime, utime, total; - - stime = curr->stime; - total = stime + curr->utime; + cputime_t rtime, stime, utime; /* * Tick based cputime accounting depend on random scheduling @@ -576,13 +573,19 @@ static void cputime_adjust(struct task_cputime *curr, if (prev->stime + prev->utime >= rtime) goto out; - if (total) { + stime = curr->stime; + utime = curr->utime; + + if (utime == 0) { + stime = rtime; + } else if (stime == 0) { + utime = rtime; + } else { + cputime_t total = stime + utime; + stime = scale_stime((__force u64)stime, (__force u64)rtime, (__force u64)total); utime = rtime - stime; - } else { - stime = rtime; - utime = 0; } /* -- 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/