On 4/9/19 2:08 AM, Bob Liu wrote:
> void blk_freeze_queue_start(struct request_queue *q)
> {
> - int freeze_depth;
> -
> - freeze_depth = atomic_inc_return(&q->mq_freeze_depth);
> - if (freeze_depth == 1) {
> + mutex_lock(&q->mq_freeze_lock);
> + if (++q->mq_freeze_depth == 1) {
> percpu_ref_kill(&q->q_usage_counter);
> + mutex_unlock(&q->mq_freeze_lock);
> if (queue_is_mq(q))
> blk_mq_run_hw_queues(q, false);
> + } else {
> + mutex_unlock(&q->mq_freeze_lock);
> }
> }
Have you considered to move the mutex_unlock() call to the end of the function
such that there is only one mutex_unlock() call instead of two? In case you
would be worried about holding the mutex around the code that runs the queue,
how about changing the blk_mq_run_hw_queues() call such that the queues are
run async?
Bart.
