mac80211: allow driver to return error from sched_scan_stop

In order to solve races with sched_scan_stop, it is necessary
for the driver to be able to return an error to propagate that
to cfg80211 so it doesn't send an event.
Reviewed-by: Alexander Bondar <alexander.bondar@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/mvm/mac80211.c

@@ -1746,7 +1746,7 @@ static int iwl_mvm_mac_sched_scan_start(struct ieee80211_hw *hw,
 	return ret;
 }
 
-static void iwl_mvm_mac_sched_scan_stop(struct ieee80211_hw *hw,
+static int iwl_mvm_mac_sched_scan_stop(struct ieee80211_hw *hw,
 				       struct ieee80211_vif *vif)
 {
 	struct iwl_mvm *mvm = IWL_MAC80211_GET_MVM(hw);
@@ -1754,6 +1754,8 @@ static void iwl_mvm_mac_sched_scan_stop(struct ieee80211_hw *hw,
 	mutex_lock(&mvm->mutex);
 	iwl_mvm_sched_scan_stop(mvm);
 	mutex_unlock(&mvm->mutex);
+
+	return 0;
 }
 
 static int iwl_mvm_mac_set_key(struct ieee80211_hw *hw,

drivers/net/wireless/ti/wlcore/main.c

@@ -3668,7 +3668,7 @@ static int wl1271_op_sched_scan_start(struct ieee80211_hw *hw,
 	return ret;
 }
 
-static void wl1271_op_sched_scan_stop(struct ieee80211_hw *hw,
+static int wl1271_op_sched_scan_stop(struct ieee80211_hw *hw,
 				     struct ieee80211_vif *vif)
 {
 	struct wl1271 *wl = hw->priv;
@@ -3691,6 +3691,8 @@ static void wl1271_op_sched_scan_stop(struct ieee80211_hw *hw,
 	wl1271_ps_elp_sleep(wl);
 out:
 	mutex_unlock(&wl->mutex);
+
+	return 0;
 }
 
 static int wl1271_op_set_frag_threshold(struct ieee80211_hw *hw, u32 value)

include/net/mac80211.h

@@ -2460,6 +2460,7 @@ enum ieee80211_roc_type {
  *	This process will continue until sched_scan_stop is called.
  *
  * @sched_scan_stop: Tell the hardware to stop an ongoing scheduled scan.
+ *	In this case, ieee80211_sched_scan_stopped() must not be called.
  *
  * @sw_scan_start: Notifier function that is called just before a software scan
  *	is started. Can be NULL, if the driver doesn't need this notification.
@@ -2807,7 +2808,7 @@ struct ieee80211_ops {
 				struct ieee80211_vif *vif,
 				struct cfg80211_sched_scan_request *req,
 				struct ieee80211_sched_scan_ies *ies);
-	void (*sched_scan_stop)(struct ieee80211_hw *hw,
+	int (*sched_scan_stop)(struct ieee80211_hw *hw,
 			       struct ieee80211_vif *vif);
 	void (*sw_scan_start)(struct ieee80211_hw *hw);
 	void (*sw_scan_complete)(struct ieee80211_hw *hw);

net/mac80211/driver-ops.h

@@ -354,16 +354,20 @@ drv_sched_scan_start(struct ieee80211_local *local,
 	return ret;
 }
 
-static inline void drv_sched_scan_stop(struct ieee80211_local *local,
+static inline int drv_sched_scan_stop(struct ieee80211_local *local,
 				      struct ieee80211_sub_if_data *sdata)
 {
+	int ret;
+
 	might_sleep();
 
 	check_sdata_in_driver(sdata);
 
 	trace_drv_sched_scan_stop(local, sdata);
-	local->ops->sched_scan_stop(&local->hw, &sdata->vif);
-	trace_drv_return_void(local);
+	ret = local->ops->sched_scan_stop(&local->hw, &sdata->vif);
+	trace_drv_return_int(local, ret);
+
+	return ret;
 }
 
 static inline void drv_sw_scan_start(struct ieee80211_local *local)

net/mac80211/scan.c

@@ -1056,7 +1056,7 @@ int ieee80211_request_sched_scan_stop(struct ieee80211_sub_if_data *sdata)
 	local->sched_scan_req = NULL;
 
 	if (rcu_access_pointer(local->sched_scan_sdata))
-		drv_sched_scan_stop(local, sdata);
+		ret = drv_sched_scan_stop(local, sdata);
 
 out:
 	mutex_unlock(&local->mtx);