Re: [PATCH 8/8] mm,oom_reaper: Make OOM reaper use list of mm_struct.

[Oleg Nesterov <oleg@redhat.com>]

On 07/03, Tetsuo Handa wrote:
>
> +static void oom_reap_vmas(struct mm_struct *mm)
>  {
>  	int attempts = 0;
> -	struct mm_struct *mm = NULL;
> -	struct task_struct *p = find_lock_task_mm(tsk);
> +	bool ret;
>
>  	/*
> -	 * 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 after holding oom_lock because
> +	 * oom_kill_process() might find this mm pinned.
>  	 */
> -	if (!p)
> -		goto done;
> -	mm = p->mm;
> -	atomic_inc(&mm->mm_count);
> -	task_unlock(p);
> +	mutex_lock(&oom_lock);
> +	ret = test_bit(MMF_OOM_REAPED, &mm->flags);
> +	mutex_unlock(&oom_lock);

OK, but this looks strange...

Can't we instead move mark_oom_victim(victim) to the end of oom_kill_process(),
and change mark_oom_victim() to do nothing if MMF_OOM_REAPED is set? Or just
check this flag in oom_kill_process() before mark_oom_victim().

Oleg.

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