Messages in this thread Patch in this message | | | Date | Mon, 08 Dec 2014 15:55:14 +0100 | From | Bart Van Assche <> | Subject | Re: [PATCH] blk-mq: Avoid that I/O hangs in bt_get() |
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On 11/06/14 14:41, Bart Van Assche wrote: > With kernel 3.18-rc3 and with can_queue=62 I can trigger a hang in > bt_get() easily.
(once more replying to my own e-mail)
Hello Jens,
Finally I found the time to look further into this. The patch below seems to be sufficient to prevent this hang. However, I'm not a block layer expert so it's not clear to me whether the patch below makes sense ?
Thanks,
Bart.
[PATCH] blk-mq: Fix bt_get() hang
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. --- block/blk-mq-tag.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 67ab88b..e88af88 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -256,6 +256,8 @@ static int bt_get(struct blk_mq_alloc_data *data, break; }
+ blk_mq_run_hw_queue(hctx, false); + blk_mq_put_ctx(data->ctx);
io_schedule();
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