diff options
authorJens Axboe <axboe@kernel.dk>2012-11-06 12:24:26 +0100
committerJens Axboe <axboe@kernel.dk>2012-11-23 14:32:54 +0100
commita8c32a5c98943d370ea606a2e7dc04717eb92206 (patch)
parenteac7cc52c6b410e542af431b2ee93f3d7dbfb6af (diff)
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@kernel.org Acked-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 files changed, 7 insertions, 1 deletions
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 02db9183ca01..77e6eff41cae 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))
+ /*
+ * 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