commit 68aa8efcd1ab961e4684ef5af32f72a6ec1911de upstream. Backported for 3.9-stable. Adjusted context. From: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> Dave Hansen reported strange utime/stime values on his system: https://lkml.org/lkml/2013/4/4/435 This happens because prev->stime value is bigger than rtime value. Root of the problem are non-monotonic rtime values (i.e. current rtime is smaller than previous rtime) and that should be debugged and fixed. But since problem did not manifest itself before commit 62188451f0d63add7ad0cd2a1ae269d600c1663d "cputime: Avoid multiplication overflow on utime scaling", it should be threated as regression, which we can easily fixed on cputime_adjust() function. For now, let's apply this fix, but further work is needed to fix root of the problem. Reported-and-tested-by: Dave Hansen <dave@xxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> # 3.9+ Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx> Cc: rostedt@xxxxxxxxxxx Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave@xxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1367314507-9728-3-git-send-email-sgruszka@xxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Lingzhu Xiang <lxiang@xxxxxxxxxx> --- kernel/sched/cputime.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index 910d1f5..6af50ad 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -574,7 +574,7 @@ static void cputime_adjust(struct task_cputime *curr, struct cputime *prev, cputime_t *ut, cputime_t *st) { - cputime_t rtime, stime, total; + cputime_t rtime, stime, utime, total; stime = curr->stime; total = stime + curr->utime; @@ -599,13 +599,13 @@ static void cputime_adjust(struct task_cputime *curr, if (prev->stime + prev->utime >= rtime) goto out; - if (!rtime) { - stime = 0; - } else if (!total) { - stime = rtime; - } else { + if (total) { stime = scale_stime((__force u64)stime, (__force u64)rtime, (__force u64)total); + utime = rtime - stime; + } else { + stime = rtime; + utime = 0; } /* @@ -614,7 +614,7 @@ static void cputime_adjust(struct task_cputime *curr, * Let's enforce monotonicity. */ prev->stime = max(prev->stime, stime); - prev->utime = max(prev->utime, rtime - prev->stime); + prev->utime = max(prev->utime, utime); out: *ut = prev->utime; -- 1.7.11.7 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html