Michal Hocko wrote:
> > #define MAX_OOM_REAP_RETRIES 10
> > -static void oom_reap_task(struct task_struct *tsk)
> > +static void oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
> > {
> > int attempts = 0;
> > - struct mm_struct *mm = NULL;
> > - struct task_struct *p = find_lock_task_mm(tsk);
> >
> > /*
> > - * Make sure we find the associated mm_struct even when the particular
> > - * thread has already terminated and cleared its mm.
> > - * We might have race with exit path so consider our work done if there
> > - * is no mm.
> > + * Check MMF_OOM_REAPED in case oom_kill_process() found this mm
> > + * pinned.
> > */
> > - if (!p)
> > - goto done;
> > - mm = p->mm;
> > - atomic_inc(&mm->mm_count);
> > - task_unlock(p);
> > + if (test_bit(MMF_OOM_REAPED, &mm->flags))
> > + return;
> >
> > /* Retry the down_read_trylock(mmap_sem) a few times */
> > while (attempts++ < MAX_OOM_REAP_RETRIES && !__oom_reap_task(tsk, mm))
> > schedule_timeout_idle(HZ/10);
> >
> > if (attempts <= MAX_OOM_REAP_RETRIES)
> > - goto done;
> > + return;
> >
> > /* Ignore this mm because somebody can't call up_write(mmap_sem). */
> > set_bit(MMF_OOM_REAPED, &mm->flags);
>
> This seems unnecessary when oom_reaper always calls exit_oom_mm. The
> same applies to __oom_reap_task. Which then means that the flag is
> turning into a misnomer. MMF_SKIP_OOM would fit better its current
> meaning.
Large oom_score_adj value or being a child process of highest OOM score
might cause the same mm being selected again. I think these set_bit() are
necessary in order to avoid the same mm being selected again.
Other than that, I sent v3 patchset.
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