Re: [PATCH -tip] sched/cputime: do not scale when utime == 0

From: Ingo Molnar
Date: Wed Sep 04 2013 - 08:33:57 EST



* Stanislaw Gruszka <sgruszka@xxxxxxxxxx> wrote:

> scale_stime() silently assumes that stime < rtime, otherwise when
> stime == rtime and both values are big (operations on them do not fit
> in 32 bits), the resulting scaling stime can be bigger than rtime.
> In consequence utime = rtime - stime results in negative value.

Please also describe observed/expected symptoms of this bug in apps, so
that we can later on redirect bugreporters to this fix and filter out new
symptoms (if any).

Thanks,

Ingo
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