wifi: mt76: mt7921s: fix potential hung tasks during chip recovery

During chip recovery (e.g. chip reset), there is a possible situation that
kernel worker reset_work is holding the lock and waiting for kernel thread
stat_worker to be parked, while stat_worker is waiting for the release of
the same lock.
It causes a deadlock resulting in the dumping of hung tasks messages and
possible rebooting of the device.

This patch prevents the execution of stat_worker during the chip recovery.
Signed-off-by: Leon Yen <leon.yen@mediatek.com>
Signed-off-by: Ming Yen Hsieh <MingYen.Hsieh@mediatek.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt7921/mac.c

@@ -663,6 +663,7 @@ void mt7921_mac_reset_work(struct work_struct *work)
 	int i, ret;
 
 	dev_dbg(dev->mt76.dev, "chip reset\n");
+	set_bit(MT76_RESET, &dev->mphy.state);
 	dev->hw_full_reset = true;
 	ieee80211_stop_queues(hw);
 
@@ -691,6 +692,7 @@ void mt7921_mac_reset_work(struct work_struct *work)
 	}
 
 	dev->hw_full_reset = false;
+	clear_bit(MT76_RESET, &dev->mphy.state);
 	pm->suspended = false;
 	ieee80211_wake_queues(hw);
 	ieee80211_iterate_active_interfaces(hw,

drivers/net/wireless/mediatek/mt76/mt7921/pci_mac.c

@@ -64,7 +64,6 @@ int mt7921e_mac_reset(struct mt792x_dev *dev)
 	mt76_wr(dev, dev->irq_map->host_irq_enable, 0);
 	mt76_wr(dev, MT_PCIE_MAC_INT_ENABLE, 0x0);
 
-	set_bit(MT76_RESET, &dev->mphy.state);
 	set_bit(MT76_MCU_RESET, &dev->mphy.state);
 	wake_up(&dev->mt76.mcu.wait);
 	skb_queue_purge(&dev->mt76.mcu.res_q);
@@ -115,7 +114,6 @@ int mt7921e_mac_reset(struct mt792x_dev *dev)
 
 	err = __mt7921_start(&dev->phy);
 out:
-	clear_bit(MT76_RESET, &dev->mphy.state);
 
 	local_bh_disable();
 	napi_enable(&dev->mt76.tx_napi);

drivers/net/wireless/mediatek/mt76/mt7921/sdio_mac.c

@@ -98,7 +98,6 @@ int mt7921s_mac_reset(struct mt792x_dev *dev)
 	mt76_connac_free_pending_tx_skbs(&dev->pm, NULL);
 	mt76_txq_schedule_all(&dev->mphy);
 	mt76_worker_disable(&dev->mt76.tx_worker);
-	set_bit(MT76_RESET, &dev->mphy.state);
 	set_bit(MT76_MCU_RESET, &dev->mphy.state);
 	wake_up(&dev->mt76.mcu.wait);
 	skb_queue_purge(&dev->mt76.mcu.res_q);
@@ -135,7 +134,6 @@ int mt7921s_mac_reset(struct mt792x_dev *dev)
 
 	err = __mt7921_start(&dev->phy);
 out:
-	clear_bit(MT76_RESET, &dev->mphy.state);
 
 	mt76_worker_enable(&dev->mt76.tx_worker);
 

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

@@ -499,7 +499,8 @@ static void mt76s_tx_status_data(struct mt76_worker *worker)
 	dev = container_of(sdio, struct mt76_dev, sdio);
 
 	while (true) {
-		if (test_bit(MT76_REMOVED, &dev->phy.state))
+		if (test_bit(MT76_RESET, &dev->phy.state) ||
+		    test_bit(MT76_REMOVED, &dev->phy.state))
 			break;
 
 		if (!dev->drv->tx_status_data(dev, &update))