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Subject[PATCH] igb: Use a sperate mutex insead of rtnl_lock()
Date
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@canonical.com>
---
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
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