[lkml]   [2012]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH 138/241] dm: fix deadlock with request based dm and queue request_fn recursion
Date -stable review patch.  If anyone has any objections, please let me know.


From: Jens Axboe <>

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 <>
Signed-off-by: Jens Axboe <>
Signed-off-by: Herton Ronaldo Krzesinski <>
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 9ff3019..32370ea 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))

+ /*
+ * 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

 \ /
  Last update: 2012-12-13 15:21    [W:0.376 / U:5.740 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site