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| author | Stanislaw Gruszka <sgruszka@redhat.com> | 2013-04-30 11:35:05 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-05-19 11:38:18 -0700 |
| commit | f25d7d1c9ba805c3d588ed3bbb336d05cfc1f1de (patch) | |
| tree | 303d413072ffd7e98219f2fa360a4488bbcb9f35 | |
| parent | 434c491303aff685d0b7246367d83a4833491146 (diff) | |
| download | lwn-f25d7d1c9ba805c3d588ed3bbb336d05cfc1f1de.tar.gz lwn-f25d7d1c9ba805c3d588ed3bbb336d05cfc1f1de.zip | |
sched: Do not account bogus utime
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 <sgruszka@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: rostedt@goodmis.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1367314507-9728-2-git-send-email-sgruszka@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/sched/cputime.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index a514a879e946..910d1f5be442 100644 --- a/kernel/sched/cputime.c +++ b/kernel/sched/cputime.c @@ -591,6 +591,14 @@ static void cputime_adjust(struct task_cputime *curr, */ 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_cputime *curr, prev->stime = max(prev->stime, stime); prev->utime = max(prev->utime, rtime - prev->stime); +out: *ut = prev->utime; *st = prev->stime; } |