Re: [PATCH 02/11] x86/mm/hotplug: Remove pgd_list use from the memory hotplug code

[Oleg Nesterov <oleg@redhat.com>]

On 09/29, Ingo Molnar wrote:
>
> * Oleg Nesterov <oleg@redhat.com> wrote:
>
> > 	struct task_struct *next_task_with_mm(struct task_struct *p)
> > 	{
> > 		struct task_struct *t;
> >
> > 		p = p->group_leader;
> > 		while ((p = next_task(p)) != &init_task) {
> > 			if (p->flags & PF_KTHREAD)
> > 				continue;
> >
> > 			t = find_lock_task_mm(p);
> > 			if (t)
> > 				return t;
> > 		}
> >
> > 		return NULL;
> > 	}
> >
> > 	#define for_each_task_lock_mm(p)
> > 		for (p = &init_task; (p = next_task_with_mm(p)); task_unlock(p))
> >
> >
> > So that you can do
> >
> > 	for_each_task_lock_mm(p) {
> > 		do_something_with(p->mm);
> >
> > 		if (some_condition()) {
> > 			// UNFORTUNATELY you can't just do "break"
> > 			task_unlock(p);
> > 			break;
> > 		}
> > 	}
> >
> > do you think it makes sense?
>
> Sure, I'm inclined to use the above code from you.
>
> > In fact it can't be simpler, we can move task_unlock() into next_task_with_mm(),
> > it can check ->mm != NULL or p != init_task.
>
> s/can't/can ?

yes, sorry,

> But even with that I'm not sure I can parse your suggestion. Got some (pseudo) code
> perhaps?

I meant

	struct task_struct *next_task_lock_mm(struct task_struct *p)
	{
		struct task_struct *t;

		if (p) {
			task_unlock(p);
			p = p->group_leader;
		} else {
			p = &init_task;
		}

		while ((p = next_task(p)) != &init_task) {
			if (p->flags & PF_KTHREAD)
				continue;

			t = find_lock_task_mm(p);
			if (t)
				return t;
		}

		return NULL;
	}

	#define for_each_task_lock_mm(p)
		for (p = NULL; (p = next_task_lock_mm(p)); )

Oleg.

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