On Mon, 13 Mar 2023 10:08:38 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
> I suspect holding the lru lock when calling isolate_or_dissolve_huge_page was
> not considered. However, I wonder if this can really happen in practice?
>
> Before the code below, there is this:
>
> /*
> * Periodically drop the lock (if held) regardless of its
> * contention, to give chance to IRQs. Abort completely if
> * a fatal signal is pending.
> */
> if (!(low_pfn % COMPACT_CLUSTER_MAX)) {
> if (locked) {
> unlock_page_lruvec_irqrestore(locked, flags);
> locked = NULL;
> }
> ...
> }
>
> It would seem that the pfn of a hugetlb page would always be a multiple of
> COMPACT_CLUSTER_MAX so we would drop the lock. However, I am not sure if
> that is ALWAYS true and would prefer something like the code you suggested.
>
> Did you actually see this deadlock in practice?
Presumably the lack of lockdep reports about this tells us something?
