Re: mm, oom_reaper: How to handle race with oom_killer_disable() ?

[Michal Hocko]

On Wed 22-06-16 19:57:17, Tetsuo Handa wrote:
> Michal Hocko wrote:
[...]
> > That being said I guess the patch to try_to_freeze_tasks after
> > oom_killer_disable should be simple enough to go for now and stable
> > trees and we can come up with something less hackish later. I do not
> > like the fact that oom_killer_disable doesn't act as a full "barrier"
> > anymore.
> > 
> > What do you think?
> 
> I'm OK with calling try_to_freeze_tasks(true) again for Linux 4.6 and 4.7 kernels.

OK, I will resend the patch CC Rafael and stable.
 
> But if free memory is little such that oom_killer_disable() can not expect TIF_MEMDIE
> threads to clear TIF_MEMDIE by themselves (and therefore has to depend on the OOM
> reaper to clear TIF_MEMDIE on behalf of them after the OOM reaper reaped some memory),
> subsequent operations would be as well blocked waiting for an operation which cannot
> make any forward progress because it cannot proceed with an allocation. Then,
> oom_killer_disable() returns false after some timeout (i.e. "do not try to suspend
> when the system is almost OOM") will be a safer reaction.

Yes that is exactly what I meant by "oom_killer_disable has to give up"
alternative. pm suspend already has a notion of timeout for back off
and oom_killer_disable can use wait_even_timeout. But let's do that
separately.

-- 
Michal Hocko
SUSE Labs