Re: [PATCH] mm,oom: use per signal_struct flag rather than clear TIF_MEMDIE

[Oleg Nesterov <oleg@redhat.com>]

On 06/28, Michal Hocko wrote:
>
> On Mon 27-06-16 22:40:17, Oleg Nesterov wrote:
> >
> > Ah, but this is clear, note the "Ignoring the obvious races" above.
> > Can't we fix this race? I am a bit lost, but iirc we want this anyway
> > to ensure that we do not set TIF_MEMDIE if ->mm == NULL ?
>
> This is not about a race it is about not reaching exit_oom_victim and
> unblock the oom killer from selecting another victim.

I understand. What I do not understand why we can't rely on MMF_OOM_REAPED
if we ensure that TIF_MEMDIE can only be set if the victim did not call
exit_oom_victim() yet.

OK, please forget, I already got lost and right now I don't even have the
uptodate -mm tree sources.

> > Hmm. Although I am not sure I really understand the "may block for
> > unbounded period ..." above. Do you mean khugepaged_exit?
>
> __mmput->exit_aio can wait for IO to complete and who knows what that
> might depend on.

Yes, but I was confused by "waiting for somebody else's memory allocation",
I do not this this apllies to exit_aio.

Nevermind,

> Who knows how many others are lurking there.

Yes, yes, I agree. Just I wrongly thought Tetsuo meant something particular.

Oleg.

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