mm/page_alloc: fix deadlock on cpu_hotplug_lock in __accept_page()

When the last page in the zone is accepted, __accept_page() calls
static_branch_dec().  This function takes cpu_hotplug_lock, which can lead
to a deadlock if the allocation occurs during CPU bringup path as
_cpu_up() also takes the lock.

To prevent this deadlock, defer static_branch_dec() to a workqueue.

Call static_branch_dec() only when the workqueue is not yet initialized. 
Workqueues are initialized before CPU bring up, so this will not conflict
with the first scenario.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: 55ad43e8ba0f ("mm: add a helper to accept page")
Signed-off-by: Kirill A. Shutemov <[email protected]>
Reported-by: Srikanth Aithal <[email protected]>
Tested-by: Srikanth Aithal <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ashish Kalra <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "Edgecombe, Rick P" <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: "Mike Rapoport (IBM)" <[email protected]>
Cc: Thomas Lendacky <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

1 files changed, 1 insertions, 0 deletions

diff --git a/mm/mm_init.c b/mm/mm_init.c
index 84f14fa12d0d..9659689b8ace 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1441,6 +1441,7 @@ static void __meminit zone_init_free_lists(struct zone *zone)
 
 #ifdef CONFIG_UNACCEPTED_MEMORY
 	INIT_LIST_HEAD(&zone->unaccepted_pages);
+	INIT_WORK(&zone->unaccepted_cleanup, unaccepted_cleanup_work);
 #endif
 }