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

[KAMEZAWA Hiroyuki]

On Sun,  7 Nov 2010 23:14:37 +0100
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>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/