Re: [PATCH v2] sched: fix user time incorrectly accounted assystem time on 32 bit

[Peter Zijlstra]

On Tue, 2010-09-14 at 16:35 +0200, Stanislaw Gruszka wrote:
> We have 32 bit variable overflow possibility when multiply in
> task_times() and thread_group_times() functions. If overflow happens
> calculated scaled utime value become wrongly small and scaled stime
> wrongly big.

Ah, right, (u64)foo * bar would have worked too I guess, but yeah, the
used (u64)(foo * bar) is wrong.

> Reported here:
> https://bugzilla.redhat.com/show_bug.cgi?id=633037
> https://bugzilla.kernel.org/show_bug.cgi?id=16559
> 
> Reported-by: Michael Chapman <redhat-bugzilla@xxxxxxxxxxxxxxxxx>
> Reported-by: Ciriaco Garcia de Celis <sysman@xxxxxxxxxxxxxx>
> Cc: Hidetoshi Seto <seto.hidetoshi@xxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxx>  # 2.6.32.19+ (partially) and 2.6.33+
> Signed-off-by: Stanislaw Gruszka <sgruszka@xxxxxxxxxx>

Thanks, got it.
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