Re: [PATCH] mm,oom: use per signal_struct flag rather than clear TIF_MEMDIE

[Oleg Nesterov <oleg@redhat.com>]

On 06/27, Michal Hocko wrote:
>
> On Mon 27-06-16 17:51:20, Oleg Nesterov wrote:
> >
> > Yes I agree, it would be nice to remove find_lock_task_mm(). And in
> > fact it would be nice to kill task_struct->mm (but this needs a lot
> > of cleanups). We probably want signal_struct->mm, but this is a bit
> > complicated (locking).
>
> Is there any hard requirement to reset task_struct::mm in the first
> place?

Well, at least the scheduler needs this. And we need to audit every
->mm != NULL check.

> I mean I could have added oom_mm pointer into the task_struct and that
> would guarantee that we always have a valid pointer when it is needed
> but having yet another mm pointer there.

and add another mmdrop(oom_mm) into free_task() ? This would be bad, we
do not want to delay __mmdrop()... Look, we even want to make the
free_thread_info() synchronous, so that we could free ->stack before the
final put_task_struct ;)

But could you remind why do you want this right now? I mean, the ability
to find ->mm with mm_count != 0 even if the user memory was already freed?

Oleg.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>