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

		io_schedule();

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