Re: [PATCH resend 3/3] vmpressure: Make sure there are no eventsqueued after memcg is offlined

[Tejun Heo]

On Fri, Jul 19, 2013 at 06:51:11PM +0200, Michal Hocko wrote:
> vmpressure is called synchronously from the reclaim where the
> target_memcg is guaranteed to be alive but the eventfd is signaled from
> the work queue context. This means that memcg (along with vmpressure
> structure which is embedded into it) might go away while the work item
> is pending which would result in use-after-release bug.
> 
> We have two possible ways how to fix this. Either vmpressure pins memcg
> before it schedules vmpr->work and unpin it in vmpressure_work_fn or
> explicitely flush the work item from the css_offline context (as
> suggested by Tejun).
> 
> This patch implements the later one and it introduces vmpressure_cleanup
> which flushes the vmpressure work queue item item. It hooks into
> mem_cgroup_css_offline after the memcg itself is cleaned up.
> 
> Reported-by: Tejun Heo <tj@xxxxxxxxxx>
> Signed-off-by: Michal Hocko <mhocko@xxxxxxx>

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Thanks!

-- 
tejun
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