From 4067196a52278156d18d8d6fa7f43970611b1b49 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Sat, 29 Mar 2025 19:10:29 +0200 Subject: 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 Reported-by: Srikanth Aithal Tested-by: Srikanth Aithal Cc: Dave Hansen Cc: Ashish Kalra Cc: David Hildenbrand Cc: "Edgecombe, Rick P" Cc: Mel Gorman Cc: "Mike Rapoport (IBM)" Cc: Thomas Lendacky Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/mmzone.h') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 25e80b2ca7f4..4c95fcc9e9df 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -967,6 +967,9 @@ struct zone { #ifdef CONFIG_UNACCEPTED_MEMORY /* Pages to be accepted. All pages on the list are MAX_PAGE_ORDER */ struct list_head unaccepted_pages; + + /* To be called once the last page in the zone is accepted */ + struct work_struct unaccepted_cleanup; #endif /* zone flags, see below */ -- cgit v1.2.3 From 38448181459e24257b40d5258afdbaa3565e8cfc Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Wed, 16 Apr 2025 09:45:39 -0400 Subject: mm: vmscan: restore high-cpu watermark safety in kswapd Vlastimil points out that commit a211c6550efc ("mm: page_alloc: defrag_mode kswapd/kcompactd watermarks") switched kswapd from zone_watermark_ok_safe() to the standard, percpu-cached version of reading free pages, thus dropping the watermark safety precautions for systems with high CPU counts (e.g. >212 cpus on 64G). Restore them. Since zone_watermark_ok_safe() is no longer the right interface, and this was the last caller of the function anyway, open-code the zone_page_state_snapshot() conditional and delete the function. Link: https://lkml.kernel.org/r/20250416135142.778933-2-hannes@cmpxchg.org Fixes: a211c6550efc ("mm: page_alloc: defrag_mode kswapd/kcompactd watermarks") Signed-off-by: Johannes Weiner Reported-by: Vlastimil Babka Reviewed-by: Vlastimil Babka Cc: Brendan Jackman Signed-off-by: Andrew Morton --- include/linux/mmzone.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include/linux/mmzone.h') diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 4c95fcc9e9df..6ccec1bf2896 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1502,8 +1502,6 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, bool zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, int highest_zoneidx, unsigned int alloc_flags); -bool zone_watermark_ok_safe(struct zone *z, unsigned int order, - unsigned long mark, int highest_zoneidx); /* * Memory initialization context, use to differentiate memory added by * the platform statically or via memory hotplug interface. -- cgit v1.2.3