void blk_mq_quiesce_queue(struct request_queue *q)
{
- struct blk_mq_hw_ctx *hctx;
- unsigned int i;
- bool rcu = false;
+ bool blocking = !!(q->tag_set->flags & BLK_MQ_F_BLOCKING);
+ bool was_quiesced =__blk_mq_quiesce_queue_nowait(q);
- __blk_mq_quiesce_queue_nowait(q);
+ if (!was_quiesced && blocking)
+ percpu_ref_kill(&q->dispatch_counter);
- queue_for_each_hw_ctx(q, hctx, i) {
- if (hctx->flags & BLK_MQ_F_BLOCKING)
- synchronize_srcu(hctx->srcu);
- else
- rcu = true;
- }
- if (rcu)
+ if (blocking)
+ wait_event(q->mq_quiesce_wq,
+ percpu_ref_is_zero(&q->dispatch_counter));
+ else
synchronize_rcu();
}
In the previous version, you had ensured no thread can unquiesce a queue
while another is waiting for quiescence. Now that the locking is gone,
a thread could unquiesce the queue before percpu_ref reaches zero, so
the wait_event() may never complete on the resurrected percpu_ref.
Yea, where did that go?
