diff options
| author | Kirill A. Shutemov <kirill.shutemov@linux.intel.com> | 2025-03-29 19:10:29 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-04-17 20:10:05 -0700 |
| commit | 4067196a52278156d18d8d6fa7f43970611b1b49 (patch) | |
| tree | 464b0163dce8eb858c664b79c21f74cb6d756336 /mm | |
| parent | fc96b232f8e7c0a6c282f47726b2ff6a5fb341d2 (diff) | |
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/20250329171030.3942298-1-kirill.shutemov@linux.intel.com
Fixes: 55ad43e8ba0f ("mm: add a helper to accept page")
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reported-by: Srikanth Aithal <sraithal@amd.com>
Tested-by: Srikanth Aithal <sraithal@amd.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ashish Kalra <ashish.kalra@amd.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: "Mike Rapoport (IBM)" <rppt@kernel.org>
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/internal.h | 1 | ||||
| -rw-r--r-- | mm/mm_init.c | 1 | ||||
| -rw-r--r-- | mm/page_alloc.c | 28 |
3 files changed, 28 insertions, 2 deletions
diff --git a/mm/internal.h b/mm/internal.h index 50c2f590b2d0..e9695baa5922 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -1595,6 +1595,7 @@ unsigned long move_page_tables(struct pagetable_move_control *pmc); #ifdef CONFIG_UNACCEPTED_MEMORY void accept_page(struct page *page); +void unaccepted_cleanup_work(struct work_struct *work); #else /* CONFIG_UNACCEPTED_MEMORY */ static inline void accept_page(struct page *page) { 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 } diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1715e34b91af..e506e365d6f1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7191,6 +7191,11 @@ static DEFINE_STATIC_KEY_FALSE(zones_with_unaccepted_pages); static bool lazy_accept = true; +void unaccepted_cleanup_work(struct work_struct *work) +{ + static_branch_dec(&zones_with_unaccepted_pages); +} + static int __init accept_memory_parse(char *p) { if (!strcmp(p, "lazy")) { @@ -7229,8 +7234,27 @@ static void __accept_page(struct zone *zone, unsigned long *flags, __free_pages_ok(page, MAX_PAGE_ORDER, FPI_TO_TAIL); - if (last) - static_branch_dec(&zones_with_unaccepted_pages); + if (last) { + /* + * There are two corner cases: + * + * - If allocation occurs during the CPU bring up, + * static_branch_dec() cannot be used directly as + * it causes a deadlock on cpu_hotplug_lock. + * + * Instead, use schedule_work() to prevent deadlock. + * + * - If allocation occurs before workqueues are initialized, + * static_branch_dec() should be called directly. + * + * Workqueues are initialized before CPU bring up, so this + * will not conflict with the first scenario. + */ + if (system_wq) + schedule_work(&zone->unaccepted_cleanup); + else + unaccepted_cleanup_work(&zone->unaccepted_cleanup); + } } void accept_page(struct page *page) |