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在 2020/9/19 11:54, yangerkun 写道:
'f5bbbbe4d635 ("blk-mq: sync the update nr_hw_queues with
blk_mq_queue_tag_busy_iter")' introduce a bug what we may sleep between
rcu lock. Then '530ca2c9bd69 ("blk-mq: Allow blocking queue tag iter
callbacks")' fix it by get request_queue's ref. And 'a9a808084d6a ("block:
Remove the synchronize_rcu() call from __blk_mq_update_nr_hw_queues()")'
remove the synchronize_rcu in __blk_mq_update_nr_hw_queues. We need
update the confused comments in blk_mq_queue_tag_busy_iter.
Signed-off-by: yangerkun <yangerkun@xxxxxxxxxx>
---
block/blk-mq-tag.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 32d82e23b095..051227bd5a03 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -398,9 +398,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
/*
* __blk_mq_update_nr_hw_queues() updates nr_hw_queues and queue_hw_ctx
* while the queue is frozen. So we can use q_usage_counter to avoid
- * racing with it. __blk_mq_update_nr_hw_queues() uses
- * synchronize_rcu() to ensure this function left the critical section
- * below.
+ * racing with it.
*/
if (!percpu_ref_tryget(&q->q_usage_counter))
return;
