Re: [patch v4] mm, oom: fix unnecessary killing of additional processes

[David Rientjes]

On Sat, 21 Jul 2018, Tetsuo Handa wrote:

> You can't apply "[patch v4] mm, oom: fix unnecessary killing of additional processes"
> because Michal's patch which removes oom_lock serialization was added to -mm tree.
> 

I've rebased the patch to linux-next and posted a v5.

> You might worry about situations where __oom_reap_task_mm() is a no-op.
> But that is not always true. There is no point with emitting
> 
>   pr_info("oom_reaper: unable to reap pid:%d (%s)\n", ...);
>   debug_show_all_locks();
> 
> noise and doing
> 
>   set_bit(MMF_OOM_SKIP, &mm->flags);
> 
> because exit_mmap() will not release oom_lock until __oom_reap_task_mm()
> completes. That is, except extra noise, there is no difference with
> current behavior which sets set_bit(MMF_OOM_SKIP, &mm->flags) after
> returning from __oom_reap_task_mm().
> 

v5 has restructured how exit_mmap() serializes its unmapping with the oom 
reaper.  It sets MMF_OOM_SKIP while holding mm->mmap_sem.