Re: [PATCH] mm: hugetlb: fix softlockup when a large number of hugepages are freed.

Hi,

When I decrease the value of nr_hugepage in procfs a lot, softlockup happens.
It is because there is no chance of context switch during this process.

On the other hand, when I allocate a large number of hugepages,
there is some chance of context switch. Hence softlockup doesn't happen
during this process. So it's necessary to add the context switch
in the freeing process as same as allocating process to avoid softlockup.

...

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c

@@ -1535,6 +1535,7 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
 	while (min_count < persistent_huge_pages(h)) {
 		if (!free_pool_huge_page(h, nodes_allowed, 0))
 			break;
+		cond_resched_lock(&hugetlb_lock);
 	}
 	while (count < persistent_huge_pages(h)) {
 		if (!adjust_pool_surplus(h, nodes_allowed, 1))