[PATCH] igb: Use a sperate mutex insead of rtnl_lock()

[Kai-Heng Feng]

Commit 9474933caf21 ("igb: close/suspend race in netif_device_detach")
fixed race condition between close and power management ops by using
rtnl_lock().

This fix is a preparation for next patch, to prevent a dead lock under
rtnl_lock() when calling runtime resume routine.

However, we can't use device_lock() in igb_close() because when module
is getting removed, the lock is already held for igb_remove(), and
igb_close() gets called during unregistering the netdev, hence causing a
deadlock. So let's introduce a new mutex so we don't cause a deadlock
with driver core or netdev core.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index b46bff8fe056..dc7ed5dd216b 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -288,6 +288,8 @@ static const struct igb_reg_info igb_reg_info_tbl[] = {
 	{}
 };
 
+static DEFINE_MUTEX(igb_mutex);
+
 /* igb_regdump - register printout routine */
 static void igb_regdump(struct e1000_hw *hw, struct igb_reg_info *reginfo)
 {
@@ -4026,9 +4028,14 @@ static int __igb_close(struct net_device *netdev, bool suspending)
 
 int igb_close(struct net_device *netdev)
 {
+	int err = 0;
+
+	mutex_lock(&igb_mutex);
 	if (netif_device_present(netdev) || netdev->dismantle)
-		return __igb_close(netdev, false);
-	return 0;
+		err = __igb_close(netdev, false);
+	mutex_unlock(&igb_mutex);
+
+	return err;
 }
 
 /**
@@ -8760,7 +8767,7 @@ static int __igb_shutdown(struct pci_dev *pdev, bool *enable_wake,
 	u32 wufc = runtime ? E1000_WUFC_LNKC : adapter->wol;
 	bool wake;
 
-	rtnl_lock();
+	mutex_lock(&igb_mutex);
 	netif_device_detach(netdev);
 
 	if (netif_running(netdev))
@@ -8769,7 +8776,7 @@ static int __igb_shutdown(struct pci_dev *pdev, bool *enable_wake,
 	igb_ptp_suspend(adapter);
 
 	igb_clear_interrupt_scheme(adapter);
-	rtnl_unlock();
+	mutex_unlock(&igb_mutex);
 
 	status = rd32(E1000_STATUS);
 	if (status & E1000_STATUS_LU)
@@ -8897,13 +8904,13 @@ static int __maybe_unused igb_resume(struct device *dev)
 
 	wr32(E1000_WUS, ~0);
 
-	rtnl_lock();
+	mutex_lock(&igb_mutex);
 	if (!err && netif_running(netdev))
 		err = __igb_open(netdev, true);
 
 	if (!err)
 		netif_device_attach(netdev);
-	rtnl_unlock();
+	mutex_unlock(&igb_mutex);
 
 	return err;
 }
-- 
2.17.1