linux-kernel - [PATCH] cputime: fix invalid gtime

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Date:	Thu, 3 Sep 2015 00:45:50 +0000
From:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] cputime: fix invalid gtime

From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>

/proc/stats shows invalid gtime when the thread is running in guest.
When vtime accounting is not enabled, we cannot get a valid delta.

Just return gtime when vtime accounting is not enabled in task_gtime().

Before
10987 (qemu-kvm) S 1 10923 10923 0 -1 138428608 7521 0 90 0 3776 460 0 0 20 0 24 0 11960 8090398720 151288 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 3554 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) S 1 10923 10923 0 -1 138428608 7521 0 90 0 3776 460 0 0 20 0 17 0 11960 8031649792 150268 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 3554 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) R 1 10923 10923 0 -1 138428624 7521 0 90 0 3843 460 0 0 20 0 17 0 11960 8031649792 150268 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 21415 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) R 1 10923 10923 0 -1 138428624 7521 0 90 0 3943 460 0 0 20 0 17 0 11960 8031649792 150268 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 21616 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) R 1 10923 10923 0 -1 138428624 7521 0 90 0 4044 460 0 0 20 0 17 0 11960 8031649792 150268 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 21816 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) R 1 10923 10923 0 -1 138428624 7521 0 90 0 4144 460 0 0 20 0 17 0 11960 8031649792 150268 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 22017 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) R 1 10923 10923 0 -1 138428624 7521 0 90 0 4245 460 0 0 20 0 11 0 11960 7981293568 149758 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 22218 0 0 0 0 0 0 0 0 0
10987 (qemu-kvm) S 1 10923 10923 0 -1 138428608 7521 0 90 0 4308 460 0 0 20 0 11 0 11960 7981293568 149758 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 9 0 0 0 4084 0 0 0 0 0 0 0 0 0

After
10845 (qemu-kvm) S 1 10792 10792 0 -1 138428608 202 0 0 0 2858 30 0 0 20 0 29 0 7676 8511279104 148187 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 2874 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) S 1 10792 10792 0 -1 138428608 202 0 0 0 2858 30 0 0 20 0 29 0 7676 8511279104 148187 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 2874 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) R 1 10792 10792 0 -1 138428624 203 0 0 0 2936 30 0 0 20 0 29 0 7676 8511279104 148187 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 2952 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) R 1 10792 10792 0 -1 138428624 203 0 0 0 3037 30 0 0 20 0 29 0 7676 8511279104 152184 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 3052 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) R 1 10792 10792 0 -1 138428624 203 0 0 0 3137 30 0 0 20 0 29 0 7676 8511279104 152184 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 3152 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) R 1 10792 10792 0 -1 138428624 203 0 0 0 3237 30 0 0 20 0 27 0 7676 8511279104 152188 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 3252 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) S 1 10792 10792 0 -1 138428608 203 0 0 0 3262 31 0 0 20 0 11 0 7676 8393781248 151156 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 3277 0 0 0 0 0 0 0 0 0
10845 (qemu-kvm) S 1 10792 10792 0 -1 138428608 203 0 0 0 3262 31 0 0 20 0 11 0 7676 8393781248 151156 18446744073709551615 1 1 0 0 0 0 2147220671 4096 25155 18446744073709551615 0 0 -1 3 0 0 0 3277 0 0 0 0 0 0 0 0 0

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
---
 kernel/sched/cputime.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 8cbc3db..f614ee9 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -786,6 +786,9 @@ cputime_t task_gtime(struct task_struct *t)
 	unsigned int seq;
 	cputime_t gtime;
 
+	if (!vtime_accounting_enabled())
+		return t->gtime;
+
 	do {
 		seq = read_seqbegin(&t->vtime_seqlock);
 
-- 
1.8.3.1

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