Re: [PATCH 07/12] x86/virt/guest/xen: Remove use of pgd_list from the Xen guest code

[Oleg Nesterov]

On 06/12, Ingo Molnar wrote:
>
> * Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> > So I think the only issue is that ->mm can become NULL when the thread group
> > leader dies - a non-NULL mm should always be shared among all threads.
>
> Indeed, we do that in exit_mm().

Yes,

> So we could add tsk->mm_leader or so,

No, no, please do not. Just do something like

	for_each_process(p) {

		for_each_thread(p, t) {
			if (t->mm) {
				do_something(t->mm);
				break;
			}
		}
	}

But either way I don't understand what protects this ->mm. Perhaps this needs
find_lock_task_mm().

Oleg.

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