linux-kernel - [GIT PULL] cputime fix

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Message-ID: <20130905110952.GA23323@gmail.com>
Date:	Thu, 5 Sep 2013 13:09:52 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: [GIT PULL] cputime fix

Linus,

Please pull the latest timers-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers-urgent-for-linus

   HEAD: 5a8e01f8fa51f5cbce8f37acc050eb2319d12956 sched/cputime: Do not scale when utime == 0

This fixes a longer-standing cputime accounting bug that Stanislaw Gruszka 
finally managed to track down.

 Thanks,

	Ingo

------------------>
Stanislaw Gruszka (1):
      sched/cputime: Do not scale when utime == 0


 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;
 	}
 
 	/*
--
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