Re: [PATCH v2] vmpressure: make sure memcg stays alive until all users are signaled

[Tejun Heo <tj@kernel.org>]

Hello, Michal.

On Thu, Jul 11, 2013 at 11:33:00AM +0200, Michal Hocko wrote:
> +static inline
> +struct mem_cgroup *vmpressure_to_mem_cgroup(struct vmpressure *vmpr)
> +{
> +	return container_of(vmpr, struct mem_cgroup, vmpressure);
> +}
> +
> +void vmpressure_pin_memcg(struct vmpressure *vmpr)
> +{
> +	struct mem_cgroup *memcg = vmpressure_to_mem_cgroup(vmpr);
> +
> +	css_get(&memcg->css);
> +}
> +
> +void vmpressure_unpin_memcg(struct vmpressure *vmpr)
> +{
> +	struct mem_cgroup *memcg = vmpressure_to_mem_cgroup(vmpr);
> +
> +	css_put(&memcg->css);
> +}

So, while this *should* work, can't we just cancel/flush the work item
from offline?  There doesn't seem to be any possible deadlocks from my
shallow glance and those mutexes don't seem to be held for long (do
they actually need to be mutexes?  what blocks inside them?).

Also, while at it, can you please remove the work_pending() check?
They're almost always spurious or racy and should be avoided in
general.

Thanks.

-- 
tejun

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