On 2021/10/15 7:02, Tejun Heo wrote:
On Wed, Oct 13, 2021 at 08:44:56PM +0800, Yu Kuai wrote:
@@ -1401,6 +1406,7 @@ void blkcg_deactivate_policy(struct request_queue *q,
if (queue_is_mq(q))
blk_mq_freeze_queue(q);
+ mutex_lock(&q->blkg_lock);
spin_lock_irq(&q->queue_lock);
Given that deactivation drains q_usage_counter through
blk_mq_freeze_queue(), can't the blkg_conf_prep() just pin the usage count?
In fact, the caller of blkcg_deactivate_policy() aready freeze the
queue, either from blk_cleanup_queue() or from elevator_switch().
Grab q_usage_counter in blk_conf_prep() can prevent concurrent with
blkcg_deactivate_policy(), I'm afraid will it be too much since it
will also be synchoronized with all the other freeze/unfreeze queues?
Thanks,
Kuai
