On Fri, Jan 15, 2021 at 08:49:41PM +0800, Muchun Song wrote:
> There is a race between isolate_huge_page() and __free_huge_page().
>
> CPU0: CPU1:
>
> if (PageHuge(page))
> put_page(page)
> __free_huge_page(page)
> spin_lock(&hugetlb_lock)
> update_and_free_page(page)
>
> set_compound_page_dtor(page,
> NULL_COMPOUND_DTOR)
> spin_unlock(&hugetlb_lock)
> isolate_huge_page(page)
> // trigger BUG_ON
> VM_BUG_ON_PAGE(!PageHead(page), page)
> spin_lock(&hugetlb_lock)
> page_huge_active(page)
> // trigger BUG_ON
> VM_BUG_ON_PAGE(!PageHuge(page), page)
> spin_unlock(&hugetlb_lock)
>
> When we isolate a HugeTLB page on CPU0. Meanwhile, we free it to the
> buddy allocator on CPU1. Then, we can trigger a BUG_ON on CPU0. Because
> it is already freed to the buddy allocator.
>
> Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle
> hugepage")
> Signed-off-by: Muchun Song <[email protected]>
> Reviewed-by: Mike Kravetz <[email protected]>
> Acked-by: Michal Hocko <[email protected]>
> Cc: [email protected]
Reviewed-by: Oscar Salvador <[email protected]>
--
Oscar Salvador
SUSE L3
