3.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Stanislaw Gruszka <[email protected]> commit 772c808a252594692972773f6ee41c289b8e0b2a upstream. 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 <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Peter Zijlstra <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- kernel/sched/cputime.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -591,6 +591,14 @@ static void cputime_adjust(struct task_c */ 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) { @@ -608,6 +616,7 @@ static void cputime_adjust(struct task_c prev->stime = max(prev->stime, stime); prev->utime = max(prev->utime, rtime - prev->stime); +out: *ut = prev->utime; *st = prev->stime; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
