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SubjectRe: [RFC PATCH] mm: thp: grab the lock before manipulation defer list
On Mon, Jan 06, 2020 at 06:07:29PM -0800, David Rientjes wrote:
>On Tue, 7 Jan 2020, Wei Yang wrote:
>
>> >One thing you might want to do is pull the "if (compound)" check out
>> >and place it outside of the spinlock check. It would then simplify
>> >this signficantly so it is something like
>> >if (compound) {
>> > spin_lock();
>> > list = page_deferred_list(page);
>> > if (!list_empty(list)) {
>> > list_del_init(list);
>> > from->..split_queue_len--;
>> > }
>> > spin_unlock();
>> >}
>> >
>> >Same for the block below. I would pull the check for compound outside
>> >of the spinlock call since it is a value that shouldn't change and
>> >would eliminate an unnecessary lock in the non-compound case.
>>
>> This is reasonable, if no objection from others, I would change this in v2.
>
>Looks fine to me; I don't see it as a necessary improvement but there's
>also no reason to object to it. It's definitely a patch that is needed,
>however, for the simple reason that with the existing code we can
>manipulate the deferred split queue incorrectly so either way works for
>me. Feel free to keep my acked-by.

Ah, thanks David. You are so supportive.

--
Wei Yang
Help you, Help me

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