[PATCH] kasan: avoid unnecessary quarantine lock cycling

[Hui Su]

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.

Suggested-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Hui Su <sh_def@xxxxxxx>
---
 mm/kasan/quarantine.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/mm/kasan/quarantine.c b/mm/kasan/quarantine.c
index 6958aa713c67..db7170f6f1b2 100644
--- a/mm/kasan/quarantine.c
+++ b/mm/kasan/quarantine.c
@@ -368,10 +368,12 @@ void kasan_quarantine_remove_cache(struct kmem_cache *cache)
 		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);
 
-- 
2.43.0