mt76: avoid extra RCU synchronization on station removal

Use sta_pre_rcu_remove callback to clear wcid pointer earlier
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mac80211.c

@@ -984,9 +984,6 @@ void __mt76_sta_remove(struct mt76_dev *dev, struct ieee80211_vif *vif,
 	struct mt76_wcid *wcid = (struct mt76_wcid *)sta->drv_priv;
 	int i, idx = wcid->idx;
 
-	rcu_assign_pointer(dev->wcid[idx], NULL);
-	synchronize_rcu();
-
 	for (i = 0; i < ARRAY_SIZE(wcid->aggr); i++)
 		mt76_rx_aggr_stop(dev, wcid, i);
 
@@ -1036,6 +1033,19 @@ int mt76_sta_state(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 }
 EXPORT_SYMBOL_GPL(mt76_sta_state);
 
+void mt76_sta_pre_rcu_remove(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
+			     struct ieee80211_sta *sta)
+{
+	struct mt76_phy *phy = hw->priv;
+	struct mt76_dev *dev = phy->dev;
+	struct mt76_wcid *wcid = (struct mt76_wcid *)sta->drv_priv;
+
+	mutex_lock(&dev->mutex);
+	rcu_assign_pointer(dev->wcid[wcid->idx], NULL);
+	mutex_unlock(&dev->mutex);
+}
+EXPORT_SYMBOL_GPL(mt76_sta_pre_rcu_remove);
+
 int mt76_get_txpower(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		     int *dbm)
 {

drivers/net/wireless/mediatek/mt76/mt76.h

@@ -806,6 +806,8 @@ int mt76_sta_state(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 		   enum ieee80211_sta_state new_state);
 void __mt76_sta_remove(struct mt76_dev *dev, struct ieee80211_vif *vif,
 		       struct ieee80211_sta *sta);
+void mt76_sta_pre_rcu_remove(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
+			     struct ieee80211_sta *sta);
 
 int mt76_get_min_avg_rssi(struct mt76_dev *dev, bool ext_phy);
 

drivers/net/wireless/mediatek/mt76/mt7603/main.c

@@ -680,6 +680,7 @@ const struct ieee80211_ops mt7603_ops = {
 	.configure_filter = mt7603_configure_filter,
 	.bss_info_changed = mt7603_bss_info_changed,
 	.sta_state = mt76_sta_state,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt7603_set_key,
 	.conf_tx = mt7603_conf_tx,
 	.sw_scan_start = mt76_sw_scan,

drivers/net/wireless/mediatek/mt76/mt7615/main.c

@@ -712,6 +712,7 @@ const struct ieee80211_ops mt7615_ops = {
 	.bss_info_changed = mt7615_bss_info_changed,
 	.sta_add = mt7615_sta_add,
 	.sta_remove = mt7615_sta_remove,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt7615_set_key,
 	.ampdu_action = mt7615_ampdu_action,
 	.set_rts_threshold = mt7615_set_rts_threshold,

drivers/net/wireless/mediatek/mt76/mt76x0/pci.c

@@ -67,6 +67,7 @@ static const struct ieee80211_ops mt76x0e_ops = {
 	.configure_filter = mt76x02_configure_filter,
 	.bss_info_changed = mt76x02_bss_info_changed,
 	.sta_state = mt76_sta_state,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt76x02_set_key,
 	.conf_tx = mt76x02_conf_tx,
 	.sw_scan_start = mt76_sw_scan,

drivers/net/wireless/mediatek/mt76/mt76x0/usb.c

@@ -126,6 +126,7 @@ static const struct ieee80211_ops mt76x0u_ops = {
 	.configure_filter = mt76x02_configure_filter,
 	.bss_info_changed = mt76x02_bss_info_changed,
 	.sta_state = mt76_sta_state,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt76x02_set_key,
 	.conf_tx = mt76x02_conf_tx,
 	.sw_scan_start = mt76_sw_scan,

drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c

@@ -427,6 +427,8 @@ static void mt76x02_reset_state(struct mt76x02_dev *dev)
 		if (!wcid)
 			continue;
 
+		rcu_assign_pointer(dev->mt76.wcid[i], NULL);
+
 		priv = msta = container_of(wcid, struct mt76x02_sta, wcid);
 		sta = container_of(priv, struct ieee80211_sta, drv_priv);
 

drivers/net/wireless/mediatek/mt76/mt76x2/pci_main.c

@@ -145,6 +145,7 @@ const struct ieee80211_ops mt76x2_ops = {
 	.configure_filter = mt76x02_configure_filter,
 	.bss_info_changed = mt76x02_bss_info_changed,
 	.sta_state = mt76_sta_state,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt76x02_set_key,
 	.conf_tx = mt76x02_conf_tx,
 	.sw_scan_start = mt76_sw_scan,

drivers/net/wireless/mediatek/mt76/mt76x2/usb_main.c

@@ -105,6 +105,7 @@ const struct ieee80211_ops mt76x2u_ops = {
 	.add_interface = mt76x02_add_interface,
 	.remove_interface = mt76x02_remove_interface,
 	.sta_state = mt76_sta_state,
+	.sta_pre_rcu_remove = mt76_sta_pre_rcu_remove,
 	.set_key = mt76x02_set_key,
 	.ampdu_action = mt76x02_ampdu_action,
 	.config = mt76x2u_config,