mac80211: add interface list lock

Using only the RTNL has a number of problems, most notably that
ieee80211_iterate_active_interfaces() and other interface list
traversals cannot be done from the internal workqueue because it
needs to be flushed under the RTNL.

This patch introduces a new mutex that protects the interface list
against modifications. A more detailed explanation is part of the
code change.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index c1e8261e899e..8e65adf0a64c 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -928,9 +928,8 @@ enum ieee80211_hw_flags {
  * @workqueue: single threaded workqueue available for driver use,
  *      allocated by mac80211 on registration and flushed when an
  *      interface is removed.
- *      NOTICE: All work performed on this workqueue should NEVER
- *      acquire the RTNL lock (i.e. Don't use the function
- *      ieee80211_iterate_active_interfaces())
+ *      NOTICE: All work performed on this workqueue must not
+ *      acquire the RTNL lock.
  *
  * @priv: pointer to private area that was allocated for driver use
  *      along with this structure.