[3.8.y.z extended stable] Patch "mac80211: fix scheduled scan rtnl deadlock" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    mac80211: fix scheduled scan rtnl deadlock

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.16.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 1fc1d556584d142ed4e7541b6560b47c92ab83c4 Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg at intel.com>
Date: Wed, 6 Nov 2013 10:34:36 +0100
Subject: mac80211: fix scheduled scan rtnl deadlock

commit 18db594a1005d908d995a2fc8f5a7bf4286fdca0 upstream.

When changing cfg80211 to use RTNL locking, this caused a
deadlock in mac80211 as it calls cfg80211_sched_scan_stopped()
from a work item that's on a workqueue that is flushed with
the RTNL held.

Fix this by simply using schedule_work(), the work only needs
to finish running before the wiphy is unregistered, no other
synchronisation (e.g. with suspend) is really required since
for suspend userspace is already blocked anyway when we flush
the workqueue so will only pick up the event after resume.

Fixes: 5fe231e87372 ("cfg80211: vastly simplify locking")
Reported-and-tested-by: Eliad Peller <eliadx.peller at intel.com>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/mac80211/main.c | 1 +
 net/mac80211/scan.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mac80211/main.c b/net/mac80211/main.c
index 1b087ff..e93d39d 100644
--- a/net/mac80211/main.c
+++ b/net/mac80211/main.c
@@ -1104,6 +1104,7 @@ void ieee80211_unregister_hw(struct ieee80211_hw *hw)

 	cancel_work_sync(&local->restart_work);
 	cancel_work_sync(&local->reconfig_filter);
+	flush_work(&local->sched_scan_stopped_work);

 	ieee80211_clear_tx_pending(local);
 	rate_control_deinitialize(local);
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 8d6ba43..49b5681 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -1049,6 +1049,6 @@ void ieee80211_sched_scan_stopped(struct ieee80211_hw *hw)

 	trace_api_sched_scan_stopped(local);

-	ieee80211_queue_work(&local->hw, &local->sched_scan_stopped_work);
+	schedule_work(&local->sched_scan_stopped_work);
 }
 EXPORT_SYMBOL(ieee80211_sched_scan_stopped);
--
1.8.3.2