net: hibmcge: fix rtnl deadlock issue

Currently, the hibmcge netdev acquires the rtnl_lock in
pci_error_handlers.reset_prepare() and releases it in
pci_error_handlers.reset_done().

However, in the PCI framework:
pci_reset_bus - __pci_reset_slot - pci_slot_save_and_disable_locked -
 pci_dev_save_and_disable - err_handler->reset_prepare(dev);

In pci_slot_save_and_disable_locked():
	list_for_each_entry(dev, &slot->bus->devices, bus_list) {
		if (!dev->slot || dev->slot!= slot)
			continue;
		pci_dev_save_and_disable(dev);
		if (dev->subordinate)
			pci_bus_save_and_disable_locked(dev->subordinate);
	}

This will iterate through all devices under the current bus and execute
err_handler->reset_prepare(), causing two devices of the hibmcge driver
to sequentially request the rtnl_lock, leading to a deadlock.

Since the driver now executes netif_device_detach()
before the reset process, it will not concurrently with
other netdev APIs, so there is no need to hold the rtnl_lock now.

Therefore, this patch removes the rtnl_lock during the reset process and
adjusts the position of HBG_NIC_STATE_RESETTING to ensure
that multiple resets are not executed concurrently.

Fixes: 3f5a61f ("net: hibmcge: Add reset supported in this module")
Signed-off-by: Jijie Shao <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Jijie Shao

drivers/net/ethernet/hisilicon/hibmcge/hbg_err.c

@@ -53,9 +53,11 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type)
 {
 	int ret;
 
-	ASSERT_RTNL();
+	if (test_and_set_bit(HBG_NIC_STATE_RESETTING, &priv->state))
+		return -EBUSY;
 
 	if (netif_running(priv->netdev)) {
+		clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 		dev_warn(&priv->pdev->dev,
 			 "failed to reset because port is up\n");
 		return -EBUSY;
@@ -64,7 +66,6 @@ static int hbg_reset_prepare(struct hbg_priv *priv, enum hbg_reset_type type)
 	netif_device_detach(priv->netdev);
 
 	priv->reset_type = type;
-	set_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 	clear_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state);
 	ret = hbg_hw_event_notify(priv, HBG_HW_EVENT_RESET);
 	if (ret) {
@@ -84,29 +85,26 @@ static int hbg_reset_done(struct hbg_priv *priv, enum hbg_reset_type type)
 	    type != priv->reset_type)
 		return 0;
 
-	ASSERT_RTNL();
-
-	clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 	ret = hbg_rebuild(priv);
 	if (ret) {
 		priv->stats.reset_fail_cnt++;
 		set_bit(HBG_NIC_STATE_RESET_FAIL, &priv->state);
+		clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 		dev_err(&priv->pdev->dev, "failed to rebuild after reset\n");
 		return ret;
 	}
 
 	netif_device_attach(priv->netdev);
+	clear_bit(HBG_NIC_STATE_RESETTING, &priv->state);
 
 	dev_info(&priv->pdev->dev, "reset done\n");
 	return ret;
 }
 
-/* must be protected by rtnl lock */
 int hbg_reset(struct hbg_priv *priv)
 {
 	int ret;
 
-	ASSERT_RTNL();
 	ret = hbg_reset_prepare(priv, HBG_RESET_TYPE_FUNCTION);
 	if (ret)
 		return ret;
@@ -171,7 +169,6 @@ static void hbg_pci_err_reset_prepare(struct pci_dev *pdev)
 	struct net_device *netdev = pci_get_drvdata(pdev);
 	struct hbg_priv *priv = netdev_priv(netdev);
 
-	rtnl_lock();
 	hbg_reset_prepare(priv, HBG_RESET_TYPE_FLR);
 }
 
@@ -181,7 +178,6 @@ static void hbg_pci_err_reset_done(struct pci_dev *pdev)
 	struct hbg_priv *priv = netdev_priv(netdev);
 
 	hbg_reset_done(priv, HBG_RESET_TYPE_FLR);
-	rtnl_unlock();
 }
 
 static const struct pci_error_handlers hbg_pci_err_handler = {