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SubjectRe: [PATCH 0/2 v8] oom: capture unreclaimable slab info in oom message
On Thu 28-09-17 13:36:57, Tetsuo Handa wrote:
> On 2017/09/28 6:46, Yang Shi wrote:
> > Changelog v7 —> v8:
> > * Adopted Michal’s suggestion to dump unreclaim slab info when unreclaimable slabs amount > total user memory. Not only in oom panic path.
>
> Holding slab_mutex inside dump_unreclaimable_slab() was refrained since V2
> because there are
>
> mutex_lock(&slab_mutex);
> kmalloc(GFP_KERNEL);
> mutex_unlock(&slab_mutex);
>
> users. If we call dump_unreclaimable_slab() for non OOM panic path, aren't we
> introducing a risk of crash (i.e. kernel panic) for regular OOM path?

yes we are

> We can try mutex_trylock() from dump_unreclaimable_slab() at best.
> But it is still remaining unsafe, isn't it?

using the trylock sounds like a reasonable compromise.
--
Michal Hocko
SUSE Labs

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