lkml.org 
[lkml]   [2015]   [Nov]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 3.13.y-ckt 21/96] dm: fix AB-BA deadlock in __dm_destroy()
Date
3.13.11-ckt30 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Junichi Nomura <j-nomura@ce.jp.nec.com>

commit 2a708cff93f1845b9239bc7d6310aef54e716c6a upstream.

__dm_destroy() takes io_barrier SRCU lock (dm_get_live_table) and
suspend_lock in reverse order. Doing so can cause AB-BA deadlock:

__dm_destroy dm_swap_table
---------------------------------------------------
mutex_lock(suspend_lock)
dm_get_live_table()
srcu_read_lock(io_barrier)
dm_sync_table()
synchronize_srcu(io_barrier)
.. waiting for dm_put_live_table()
mutex_lock(suspend_lock)
.. waiting for suspend_lock

Fix this by taking the locks in proper order.

Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Fixes: ab7c7bb6f4ab ("dm: hold suspend_lock while suspending device during device deletion")
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
drivers/md/dm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 5489410..071b9ad 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2490,14 +2490,14 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
* do not race with internal suspend.
*/
mutex_lock(&md->suspend_lock);
+ map = dm_get_live_table(md, &srcu_idx);
if (!dm_suspended_md(md)) {
dm_table_presuspend_targets(map);
dm_table_postsuspend_targets(map);
}
- mutex_unlock(&md->suspend_lock);
-
/* dm_put_live_table must be before msleep, otherwise deadlock is possible */
dm_put_live_table(md, srcu_idx);
+ mutex_unlock(&md->suspend_lock);

/*
* Rare, but there may be I/O requests still going to complete,
--
1.9.1


\
 
 \ /
  Last update: 2015-11-13 23:21    [W:0.354 / U:0.160 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site