Commit b3223207 authored Dec 08, 2014 by Bart Van Assche Committed by Jens Axboe Dec 08, 2014

blk-mq: fix hang in bt_get()



Avoid that if there are fewer hardware queues than CPU threads that
bt_get() can hang. The symptoms of the hang were as follows:

* All tags allocated for a particular hardware queue.
* (nr_tags) pending commands for that hardware queue.
* No pending commands for the software queues associated with that
  hardware queue.

Signed-off-by: Jens Axboe <axboe@fb.com>

parent 6637fadf

block/blk-mq-tag.c

+7 −0

Original line number	Original line	Diff line number	Diff line
	@@ -254,6 +254,13 @@ static int bt_get(struct blk_mq_alloc_data *data,
	if (tag != -1)		if (tag != -1)
	break;		break;

			/*
			* We're out of tags on this hardware queue, kick any
			* pending IO submits before going to sleep waiting for
			* some to complete.
			*/
			blk_mq_run_hw_queue(hctx, false);

	blk_mq_put_ctx(data->ctx);		blk_mq_put_ctx(data->ctx);

	io_schedule();		io_schedule();