cfg80211: vastly simplify locking

Virtually all code paths in cfg80211 already (need to) hold
the RTNL. As such, there's little point in having another
four mutexes for various parts of the code, they just cause
lock ordering issues (and much of the time, the RTNL and a
few of the others need thus be held.)

Simplify all this by getting rid of the extra four mutexes
and just use the RTNL throughout. Only a few code changes
were needed to do this and we can get rid of a work struct
for bonus points.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 12 insertions, 24 deletions

diff --git a/net/wireless/reg.c b/net/wireless/reg.c
index cc35fbaa4578..e76559618588 100644
--- a/net/wireless/reg.c
+++ b/net/wireless/reg.c
@@ -377,7 +377,7 @@ static void reg_regdb_search(struct work_struct *work)
         const struct ieee80211_regdomain *curdom, *regdom = NULL;
         int i;
 
-        mutex_lock(&cfg80211_mutex);
+        rtnl_lock();
 
         mutex_lock(&reg_regdb_search_mutex);
         while (!list_empty(&reg_regdb_search_list)) {
@@ -402,7 +402,7 @@ static void reg_regdb_search(struct work_struct *work)
         if (!IS_ERR_OR_NULL(regdom))
                 set_regdom(regdom);
 
-        mutex_unlock(&cfg80211_mutex);
+        rtnl_unlock();
 }
 
 static DECLARE_WORK(reg_regdb_work, reg_regdb_search);
@@ -1225,7 +1225,7 @@ static void update_all_wiphy_regulatory(enum nl80211_reg_initiator initiator)
         struct cfg80211_registered_device *rdev;
         struct wiphy *wiphy;
 
-        assert_cfg80211_lock();
+        ASSERT_RTNL();
 
         list_for_each_entry(rdev, &cfg80211_rdev_list, list) {
                 wiphy = &rdev->wiphy;
@@ -1570,21 +1570,19 @@ static void reg_process_pending_hints(void)
 {
         struct regulatory_request *reg_request, *lr;
 
-        mutex_lock(&cfg80211_mutex);
-        mutex_lock(&reg_mutex);
         lr = get_last_request();
 
         /* When last_request->processed becomes true this will be rescheduled */
         if (lr && !lr->processed) {
                 REG_DBG_PRINT("Pending regulatory request, waiting for it to be processed...\n");
-                goto out;
+                return;
         }
 
         spin_lock(&reg_requests_lock);
 
         if (list_empty(&reg_requests_list)) {
                 spin_unlock(&reg_requests_lock);
-                goto out;
+                return;
         }
 
         reg_request = list_first_entry(&reg_requests_list,
@@ -1595,10 +1593,6 @@ static void reg_process_pending_hints(void)
         spin_unlock(&reg_requests_lock);
 
         reg_process_hint(reg_request, reg_request->initiator);
-
-out:
-        mutex_unlock(&reg_mutex);
-        mutex_unlock(&cfg80211_mutex);
 }
 
 /* Processes beacon hints -- this has nothing to do with country IEs */
@@ -1607,9 +1601,6 @@ static void reg_process_pending_beacon_hints(void)
         struct cfg80211_registered_device *rdev;
         struct reg_beacon *pending_beacon, *tmp;
 
-        mutex_lock(&cfg80211_mutex);
-        mutex_lock(&reg_mutex);
-
         /* This goes through the _pending_ beacon list */
         spin_lock_bh(&reg_pending_beacons_lock);
 
@@ -1626,14 +1617,16 @@ static void reg_process_pending_beacon_hints(void)
         }
 
         spin_unlock_bh(&reg_pending_beacons_lock);
-        mutex_unlock(&reg_mutex);
-        mutex_unlock(&cfg80211_mutex);
 }
 
 static void reg_todo(struct work_struct *work)
 {
+        rtnl_lock();
+        mutex_lock(&reg_mutex);
         reg_process_pending_hints();
         reg_process_pending_beacon_hints();
+        mutex_unlock(&reg_mutex);
+        rtnl_unlock();
 }
 
 static void queue_regulatory_request(struct regulatory_request *request)
@@ -1717,10 +1710,6 @@ int regulatory_hint(struct wiphy *wiphy, const char *alpha2)
 }
 EXPORT_SYMBOL(regulatory_hint);
 
-/*
- * We hold wdev_lock() here so we cannot hold cfg80211_mutex() and
- * therefore cannot iterate over the rdev list here.
- */
 void regulatory_hint_11d(struct wiphy *wiphy, enum ieee80211_band band,
                          const u8 *country_ie, u8 country_ie_len)
 {
@@ -1752,7 +1741,7 @@ void regulatory_hint_11d(struct wiphy *wiphy, enum ieee80211_band band,
         /*
          * We will run this only upon a successful connection on cfg80211.
          * We leave conflict resolution to the workqueue, where can hold
-         * cfg80211_mutex.
+         * the RTNL.
          */
         if (lr->initiator == NL80211_REGDOM_SET_BY_COUNTRY_IE &&
             lr->wiphy_idx != WIPHY_IDX_INVALID)
@@ -1858,7 +1847,8 @@ static void restore_regulatory_settings(bool reset_user)
         LIST_HEAD(tmp_reg_req_list);
         struct cfg80211_registered_device *rdev;
 
-        mutex_lock(&cfg80211_mutex);
+        ASSERT_RTNL();
+
         mutex_lock(&reg_mutex);
 
         reset_regdomains(true, &world_regdom);
@@ -1915,7 +1905,6 @@ static void restore_regulatory_settings(bool reset_user)
         spin_unlock(&reg_requests_lock);
 
         mutex_unlock(&reg_mutex);
-        mutex_unlock(&cfg80211_mutex);
 
         REG_DBG_PRINT("Kicking the queue\n");
 
@@ -2297,7 +2286,6 @@ void wiphy_regulatory_register(struct wiphy *wiphy)
         mutex_unlock(&reg_mutex);
 }
 
-/* Caller must hold cfg80211_mutex */
 void wiphy_regulatory_deregister(struct wiphy *wiphy)
 {
         struct wiphy *request_wiphy = NULL;