mac80211: fix station destruction in AP/mesh modes

Unfortunately, commit b22cfcfcae5b, intended to speed up roaming
by avoiding the synchronize_rcu() broke AP/mesh modes as it moved
some code into that work item that will still call into the driver
at a time where it's no longer expected to handle this: after the
AP or mesh has been stopped.

To fix this problem remove the per-station work struct, maintain a
station cleanup list instead and flush this list when stations are
flushed. To keep this patch smaller for stable, do this when the
stations are flushed (sta_info_flush()). This unfortunately brings
back the original roaming delay; I'll fix that again in a separate
patch.

Also, Ben reported that the original commit could sometimes (with
many interfaces) cause long delays when an interface is set down,
due to blocking on flush_workqueue(). Since we now maintain the
cleanup list, this particular change of the original patch can be
reverted.

Cc: stable@vger.kernel.org [3.7]
Reported-by: Ben Greear <greearb@candelatech.com>
Tested-by: Ben Greear <greearb@candelatech.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/mac80211/sta_info.h b/net/mac80211/sta_info.h
index 1489bca9ea9..37c1889afd3 100644
--- a/net/mac80211/sta_info.h
+++ b/net/mac80211/sta_info.h
@@ -299,7 +299,6 @@ struct sta_info {
 	spinlock_t lock;
 
 	struct work_struct drv_unblock_wk;
-	struct work_struct free_sta_wk;
 
 	u16 listen_interval;
 
@@ -563,4 +562,6 @@ void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta);
 void ieee80211_sta_ps_deliver_poll_response(struct sta_info *sta);
 void ieee80211_sta_ps_deliver_uapsd(struct sta_info *sta);
 
+void ieee80211_cleanup_sdata_stas(struct ieee80211_sub_if_data *sdata);
+
 #endif /* STA_INFO_H */