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authorMikulas Patocka <mpatocka@redhat.com>2009-12-11 02:51:52 +0300
committerAlasdair G Kergon <agk@redhat.com>2009-12-11 02:51:52 +0300
commit6076905b5ef39e0ea58db32583c9e0036c05e47b (patch)
tree918a8da9778d93e8ff6aff6497eb698d7a45edab /drivers/md/dm-uevent.c
parent3067e02f8f3ae2f3f02ba76400d03b8bcb4942b0 (diff)
downloadlinux-6076905b5ef39e0ea58db32583c9e0036c05e47b.tar.xz
dm: avoid _hash_lock deadlock
Fix a reported deadlock if there are still unprocessed multipath events on a device that is being removed. _hash_lock is held during dev_remove while trying to send the outstanding events. Sending the events requests the _hash_lock again in dm_copy_name_and_uuid. This patch introduces a separate lock around regions that modify the link to the hash table (dm_set_mdptr) or the name or uuid so that dm_copy_name_and_uuid no longer needs _hash_lock. Additionally, dm_copy_name_and_uuid can only be called if md exists so we can drop the dm_get() and dm_put() which can lead to a BUG() while md is being freed. The deadlock: #0 [ffff8106298dfb48] schedule at ffffffff80063035 #1 [ffff8106298dfc20] __down_read at ffffffff8006475d #2 [ffff8106298dfc60] dm_copy_name_and_uuid at ffffffff8824f740 #3 [ffff8106298dfc90] dm_send_uevents at ffffffff88252685 #4 [ffff8106298dfcd0] event_callback at ffffffff8824c678 #5 [ffff8106298dfd00] dm_table_event at ffffffff8824dd01 #6 [ffff8106298dfd10] __hash_remove at ffffffff882507ad #7 [ffff8106298dfd30] dev_remove at ffffffff88250865 #8 [ffff8106298dfd60] ctl_ioctl at ffffffff88250d80 #9 [ffff8106298dfee0] do_ioctl at ffffffff800418c4 #10 [ffff8106298dff00] vfs_ioctl at ffffffff8002fab9 #11 [ffff8106298dff40] sys_ioctl at ffffffff8004bdaf #12 [ffff8106298dff80] tracesys at ffffffff8005d28d (via system_call) Cc: stable@kernel.org Reported-by: guy keren <choo@actcom.co.il> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md/dm-uevent.c')
-rw-r--r--drivers/md/dm-uevent.c9
1 files changed, 4 insertions, 5 deletions
diff --git a/drivers/md/dm-uevent.c b/drivers/md/dm-uevent.c
index 6f65883aef12..c7c555a8c7b2 100644
--- a/drivers/md/dm-uevent.c
+++ b/drivers/md/dm-uevent.c
@@ -139,14 +139,13 @@ void dm_send_uevents(struct list_head *events, struct kobject *kobj)
list_del_init(&event->elist);
/*
- * Need to call dm_copy_name_and_uuid from here for now.
- * Context of previous var adds and locking used for
- * hash_cell not compatable.
+ * When a device is being removed this copy fails and we
+ * discard these unsent events.
*/
if (dm_copy_name_and_uuid(event->md, event->name,
event->uuid)) {
- DMERR("%s: dm_copy_name_and_uuid() failed",
- __func__);
+ DMINFO("%s: skipping sending uevent for lost device",
+ __func__);
goto uevent_free;
}