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authorJens Axboe <axboe@kernel.dk>2012-11-06 12:24:26 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-12-03 11:38:00 -0800
commit7a7c7aafc83b95909f3912bdf880f217acd69e31 (patch)
tree77fca89938847b79921bb79f17c056555f59d72c
parent1840c51ad1842d31d810a64425dc2b52492ba269 (diff)
dm: fix deadlock with request based dm and queue request_fn recursion
commit a8c32a5c98943d370ea606a2e7dc04717eb92206 upstream. 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. Acked-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/md/dm.c8
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 67ffa391edcf..425620058747 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -754,8 +754,14 @@ 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