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Revert "sched/cputime: Refactor the cputime_adjust() code"

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This reverts commit 72298e5c92.

As Peter explains:

> Argh, no... That code was perfectly fine. The new code otoh is
> convoluted.
>
> The old code had the following form:
>
>         if (exception1)
>           deal with exception1
>
>         if (execption2)
>           deal with exception2
>
>         do normal stuff
>
> Which is as simple and straight forward as it gets.
>
> The new code otoh reads like:
>
>         if (!exception1) {
>                 if (exception2)
>                   deal with exception 2
>                 else
>                   do normal stuff
>         }

So restore the old form.

Also fix the comment describing the logic, as it was confusing.

Requested-by: Peter Zijlstra <peterz@infradead.org>
Cc: Gustavo A. R. Silva <garsilva@embeddedor.com>
Cc: Frans Klaver <fransklaver@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wanpeng Li <wanpeng.li@hotmail.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar 2017-07-04 11:53:40 +02:00
parent 4422d80ed7
commit 3b9c08ae3d
1 changed files with 14 additions and 8 deletions
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22
kernel/sched/cputime.c
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@ -611,17 +611,23 @@ static void cputime_adjust(struct task_cputime *curr,
utime = curr->utime;
/*
* If either stime or both stime and utime are 0, assume all runtime is
* userspace. Once a task gets some ticks, the monotonicy code at
* 'update' will ensure things converge to the observed ratio.
* If either stime or utime are 0, assume all runtime is userspace.
* Once a task gets some ticks, the monotonicy code at 'update:'
* will ensure things converge to the observed ratio.
*/
if (stime != 0) {
if (utime == 0)
stime = rtime;
else
stime = scale_stime(stime, rtime, stime + utime);
if (stime == 0) {
utime = rtime;
goto update;
}
if (utime == 0) {
stime = rtime;
goto update;
}
stime = scale_stime(stime, rtime, stime + utime);
update:
/*
* Make sure stime doesn't go backwards; this preserves monotonicity
* for utime because rtime is monotonic.