From: Andrew Morton <akpm@linux-foundation.org>
Subject: kasan-prevent-cpu_quarantine-corruption-when-cpu-offline-and-cache-shrink-occur-at-same-time-fix

add comment, per Zqiang

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: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/kasan/quarantine.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/mm/kasan/quarantine.c~kasan-prevent-cpu_quarantine-corruption-when-cpu-offline-and-cache-shrink-occur-at-same-time-fix
+++ a/mm/kasan/quarantine.c
@@ -315,6 +315,11 @@ static void per_cpu_remove_cache(void *a
 	struct qlist_head *q;
 
 	q = this_cpu_ptr(&cpu_quarantine);
+	/*
+	 * Ensure the ordering between the writing to q->offline and
+	 * per_cpu_remove_cache.  Prevent cpu_quarantine from being corrupted
+	 * by interrupt.
+	 */
 	if (READ_ONCE(q->offline))
 		return;
 	qlist_move_cache(q, &to_free, cache);
_