wireless: convert reg_regdb_search_lock to mutex

Stanse discovered that kmalloc is being called with GFP_KERNEL while
holding this spinlock.  The spinlock can be a mutex instead, which also
enables the removal of the unlock/lock around the lock/unlock of
cfg80211_mutex and the call to set_regdom.
Reported-by: Jiri Slaby <jirislaby@gmail.com>
Cc: stable@kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/wireless/reg.c

@@ -324,7 +324,7 @@ struct reg_regdb_search_request {
 };
 
 static LIST_HEAD(reg_regdb_search_list);
-static DEFINE_SPINLOCK(reg_regdb_search_lock);
+static DEFINE_MUTEX(reg_regdb_search_mutex);
 
 static void reg_regdb_search(struct work_struct *work)
 {
@@ -332,7 +332,7 @@ static void reg_regdb_search(struct work_struct *work)
 	const struct ieee80211_regdomain *curdom, *regdom;
 	int i, r;
 
-	spin_lock(&reg_regdb_search_lock);
+	mutex_lock(&reg_regdb_search_mutex);
 	while (!list_empty(&reg_regdb_search_list)) {
 		request = list_first_entry(&reg_regdb_search_list,
 					   struct reg_regdb_search_request,
@@ -346,18 +346,16 @@ static void reg_regdb_search(struct work_struct *work)
 				r = reg_copy_regd(&regdom, curdom);
 				if (r)
 					break;
-				spin_unlock(&reg_regdb_search_lock);
 				mutex_lock(&cfg80211_mutex);
 				set_regdom(regdom);
 				mutex_unlock(&cfg80211_mutex);
-				spin_lock(&reg_regdb_search_lock);
 				break;
 			}
 		}
 
 		kfree(request);
 	}
-	spin_unlock(&reg_regdb_search_lock);
+	mutex_unlock(&reg_regdb_search_mutex);
 }
 
 static DECLARE_WORK(reg_regdb_work, reg_regdb_search);
@@ -375,9 +373,9 @@ static void reg_regdb_query(const char *alpha2)
 
 	memcpy(request->alpha2, alpha2, 2);
 
-	spin_lock(&reg_regdb_search_lock);
+	mutex_lock(&reg_regdb_search_mutex);
 	list_add_tail(&request->list, &reg_regdb_search_list);
-	spin_unlock(&reg_regdb_search_lock);
+	mutex_unlock(&reg_regdb_search_mutex);
 
 	schedule_work(&reg_regdb_work);
 }