loop: release the lo_work_lock before queue_work

Zhaoyang Huang · axboe · commit 3bee991f2b68 · 2025-02-11T07:14:28.000-07:00
queue_work could spin on wq->cpu_pwq->pool->lock which could lead to concurrent loop_process_work failed on lo_work_lock contention and increase the request latency. Remove this combination by moving the lock release ahead of queue_work. Signed-off-by: Zhaoyang Huang <zhaoyang.huang@unisoc.com> Link: https://lore.kernel.org/r/20250207091942.3966756-1-zhaoyang.huang@unisoc.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
@@ -894,8 +894,8 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd)
 		cmd_list = &lo->rootcg_cmd_list;
 	}
 	list_add_tail(&cmd->list_entry, cmd_list);
-	queue_work(lo->workqueue, work);
 	spin_unlock_irq(&lo->lo_work_lock);
+	queue_work(lo->workqueue, work);
 }
 
 static void loop_set_timer(struct loop_device *lo)

Original file line number	Diff line number	Diff line change
`@@ -894,8 +894,8 @@ static void loop_queue_work(struct loop_device lo, struct loop_cmd cmd)`
`894`	`894`	`cmd_list = &lo->rootcg_cmd_list;`
`895`	`895`	`}`
`896`	`896`	`list_add_tail(&cmd->list_entry, cmd_list);`
`897`		`- queue_work(lo->workqueue, work);`
`898`	`897`	`spin_unlock_irq(&lo->lo_work_lock);`
	`898`	`+ queue_work(lo->workqueue, work);`
`899`	`899`	`}`
`900`	`900`
`901`	`901`	`static void loop_set_timer(struct loop_device *lo)`