Re: [patch 2/4] memcg: catch negative per-cpu sums in dirty info

[Minchan Kim]

On Mon, Nov 8, 2010 at 7:14 AM, Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> Folding the per-cpu counters can yield a negative value in case of
> accounting races between CPUs.
>
> When collecting the dirty info, the code would read those sums into an
> unsigned variable and then check for it being negative, which can not
> work.
>
> Instead, fold the counters into a signed local variable, make the
> check, and only then assign it.
>
> This way, the function signals correctly when there are insane values
> instead of leaking them out to the caller.
>
> Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>


-- 
Kind regards,
Minchan Kim
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