Hi Alasdair, I recently fixed a deadlock for a customer we have with the below patch. I have queued it up in my tree as not to lose it. Can I have an ack from you, or do you want to submit it yourself? I've marked it stable as well. >From 8ca211056519ac06bc96fb134dca1f8eb2141407 Mon Sep 17 00:00:00 2001 From: Jens Axboe <axboe@xxxxxxxxx> Date: Tue, 6 Nov 2012 12:24:26 +0100 Subject: [PATCH] dm: fix deadlock with request based dm and queue request_fn recursion Request based dm attempts to re-run the request queue off the request completion path. If used with a driver that potentially does end_io from its request_fn, we could deadlock trying to recurse back into request dispatch. Fix this by punting the request queue run to kblockd. Tested to fix a quickly reproducible deadlock in such a scenario. Cc: stable@xxxxxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- drivers/md/dm.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 02db918..77e6eff 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -740,8 +740,14 @@ static void rq_completed(struct mapped_device *md, int rw, int run_queue) if (!md_in_flight(md)) wake_up(&md->wait); + /* + * Run this off this callpath, as drivers could invoke end_io while + * inside their request_fn (and holding the queue lock). Calling + * back into ->request_fn() could deadlock attempting to grab the + * queue lock again. + */ if (run_queue) - blk_run_queue(md->queue); + blk_run_queue_async(md->queue); /* * dm_put() must be at the end of this function. See the comment above -- 1.7.12.rc3 -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
