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SubjectRe: [patch 2/4] memcg: catch negative per-cpu sums in dirty info
On Sun,  7 Nov 2010 23:14:37 +0100
Johannes Weiner <> 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 <>

Acked-by: KAMEZAWA Hiroyuki <>

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