Commit 904ebd25 authored by Muchun Song's avatar Muchun Song Committed by Jens Axboe
Browse files

block: remove redundant explicit memory barrier from rq_qos waiter and waker 



The memory barriers in list_del_init_careful() and list_empty_careful()
in pairs already handle the proper ordering between data.got_token
and data.wq.entry. So remove the redundant explicit barriers. And also
change a "break" statement to "return" to avoid redundant calling of
finish_wait().

Signed-off-by: default avatarMuchun Song <songmuchun@bytedance.com>
Reviewed-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/20241021085251.73353-1-songmuchun@bytedance.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent fdad1a20

block/blk-rq-qos.c

+1 −3
Original line number Diff line number Diff line
@@ -218,7 +218,6 @@ static int rq_qos_wake_function(struct wait_queue_entry *curr, 
		return -1;



	data->got_token = true;

	smp_wmb();

	wake_up_process(data->task);

	list_del_init_careful(&curr->entry);

	return 1;
@@ -274,10 +273,9 @@ void rq_qos_wait(struct rq_wait *rqw, void *private_data, 
			 * which means we now have two. Put our local token

			 * and wake anyone else potentially waiting for one.

			 */

			smp_rmb();

			if (data.got_token)

				cleanup_cb(rqw, private_data);

			break;

			return;

		}

		io_schedule();

		has_sleeper = true;