On 03/31, David Rientjes wrote:
>
> On Thu, 1 Apr 2010, Oleg Nesterov wrote:
>
> > > Why? You ignored this part:
> > >
> > > Say, right after exit_mm() we are doing acct_process(), and f_op->write()
> > > needs a page. So, you are saying that in this case __page_cache_alloc()
> > > can never trigger out_of_memory() ?
> > >
> > > why this is not possible?
> > >
> > > David, I am not arguing, I am asking.
> >
> > In case I wasn't clear...
> >
> > Yes, currently __oom_kill_task(p) is not possible if p->mm == NULL.
> >
> > But your patch adds
> >
> > if (fatal_signal_pending(current))
> > __oom_kill_task(current);
> >
> > into out_of_memory().
> >
>
> Ok, and it's possible during the tasklist scan if current is PF_EXITING
> and that gets passed to oom_kill_process(),
Yes, but this is harmless, afaics. The task is either current or it was
found by select_bad_process() under tasklist. This means it is safe to
use force_sig (but as I said, we should not use force_sig() anyway).
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -459,7 +459,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
> * its children or threads, just set TIF_MEMDIE so it can die quickly
> */
> if (p->flags & PF_EXITING) {
> - __oom_kill_task(p);
> + set_tsk_thread_flag(p, TIF_MEMDIE);
So, probably this makes sense anyway but not strictly necessary, up to you.
> if (fatal_signal_pending(current)) {
> - __oom_kill_task(current);
> + set_tsk_thread_flag(current, TIF_MEMDIE);
Yes, I think this fix is needed.
Oleg.
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