+ kasan-avoid-unnecessary-quarantine-lock-cycling.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kasan: avoid unnecessary quarantine lock cycling
has been added to the -mm mm-new branch.  Its filename is
     kasan-avoid-unnecessary-quarantine-lock-cycling.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-avoid-unnecessary-quarantine-lock-cycling.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Hui Su <sh_def@163.com>
Subject: kasan: avoid unnecessary quarantine lock cycling
Date: Sun, 9 Aug 2026 03:12:31 +0800

kasan_quarantine_remove_cache() drops quarantine_lock and restores
interrupts after scanning each non-empty quarantine batch so that
cond_resched() can schedule during a long scan.

When no reschedule is pending, the unlock/IRQ restore and subsequent IRQ
save/relock cycle is unnecessary.

Check need_resched() before cycling quarantine_lock to avoid this overhead
when rescheduling is not needed.

Link: https://lore.kernel.org/20260808191230.3345930-2-sh_def@163.com
Signed-off-by: Hui Su <sh_def@163.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/quarantine.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/mm/kasan/quarantine.c~kasan-avoid-unnecessary-quarantine-lock-cycling
+++ a/mm/kasan/quarantine.c
@@ -373,10 +373,12 @@ void kasan_quarantine_remove_cache(struc
 		if (qlist_empty(&global_quarantine[i]))
 			continue;
 		qlist_move_cache(&global_quarantine[i], &to_free, cache);
-		/* Scanning whole quarantine can take a while. */
-		raw_spin_unlock_irqrestore(&quarantine_lock, flags);
-		cond_resched();
-		raw_spin_lock_irqsave(&quarantine_lock, flags);
+		if (need_resched()) {
+			/* Scanning whole quarantine can take a while. */
+			raw_spin_unlock_irqrestore(&quarantine_lock, flags);
+			cond_resched();
+			raw_spin_lock_irqsave(&quarantine_lock, flags);
+		}
 	}
 	raw_spin_unlock_irqrestore(&quarantine_lock, flags);
 
_

Patches currently in -mm which might be from sh_def@163.com are

kasan-fix-cache-shrink-race-with-cpu-hotplug.patch
kasan-avoid-unnecessary-quarantine-lock-cycling.patch