Michal Hocko wrote:
> > > Anyway, would you be OK with the patch if I added the current->mm check
> > > and resolve its necessity in a separate patch?
> >
> > Please correct task_will_free_mem() in oom_kill_process() as well.
>
> We cannot hold task_lock over all task_will_free_mem I am even not sure
> we have to develop an elaborate way to make it raceless just for the nommu
> case. The current case is simple as we cannot race here. Is that
> sufficient for you?
We can use find_lock_task_mm() inside mark_oom_victim().
That is, call wake_oom_reaper() from mark_oom_victim() like
void mark_oom_victim(struct task_struct *tsk, bool can_use_oom_reaper)
{
WARN_ON(oom_killer_disabled);
/* OOM killer might race with memcg OOM */
tsk = find_lock_task_mm(tsk);
if (!tsk)
return;
if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) {
task_unlock(tsk);
return;
}
task_unlock(tsk);
atomic_inc(&tsk->signal->oom_victims);
/*
* Make sure that the task is woken up from uninterruptible sleep
* if it is frozen because OOM killer wouldn't be able to free
* any memory and livelock. freezing_slow_path will tell the freezer
* that TIF_MEMDIE tasks should be ignored.
*/
__thaw_task(tsk);
atomic_inc(&oom_victims);
if (can_use_oom_reaper)
wake_oom_reaper(tsk);
}
and move mark_oom_victim() by normal path to after task_unlock(victim).
do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
- mark_oom_victim(victim);
- if (can_oom_reap)
- wake_oom_reaper(victim);
+ wake_oom_reaper(victim, can_oom_reap);
If you don't like possibility of showing different pid for
pr_err("Killed process %d (%s)
and
pr_info("oom_reaper: reaped process %d (%s)
messages, you can defer the former till mark_oom_victim() locks that task.
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