[PATCH v2 5/6] debugobjects: Use hlist_splice_init() to reduce lock conflicts

[Zhen Lei]

The sub list can be prepared in advance outside the lock, so that the
operation time inside the lock can be reduced and the possibility of
lock conflict can be reduced.

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
 lib/debugobjects.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 4f64b5d4329c27d..9876e7ad5291492 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -171,23 +171,25 @@ static void fill_pool(void)
 		return;
 
 	while (READ_ONCE(obj_pool_free) < debug_objects_pool_min_level) {
-		struct debug_obj *new[ODEBUG_BATCH_SIZE];
+		struct debug_obj *new, *last = NULL;
+		HLIST_HEAD(freelist);
 		int cnt;
 
 		for (cnt = 0; cnt < ODEBUG_BATCH_SIZE; cnt++) {
-			new[cnt] = kmem_cache_zalloc(obj_cache, gfp);
-			if (!new[cnt])
+			new = kmem_cache_zalloc(obj_cache, gfp);
+			if (!new)
 				break;
+			hlist_add_head(&new->node, &freelist);
+			if (!last)
+				last = new;
 		}
 		if (!cnt)
 			return;
 
 		raw_spin_lock_irqsave(&pool_lock, flags);
-		while (cnt) {
-			hlist_add_head(&new[--cnt]->node, &obj_pool);
-			debug_objects_allocated++;
-			WRITE_ONCE(obj_pool_free, obj_pool_free + 1);
-		}
+		hlist_splice_init(&freelist, &last->node, &obj_pool);
+		debug_objects_allocated += cnt;
+		WRITE_ONCE(obj_pool_free, obj_pool_free + cnt);
 		raw_spin_unlock_irqrestore(&pool_lock, flags);
 	}
 }
-- 
2.34.1