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SubjectRe: [Intel-wired-lan] [PATCH] igb: Use a sperate mutex insead of rtnl_lock()
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Dear Kai-Heng,


Thank you.

There is a small typo in the commit summary: s*epa*rate.

Am 26.03.20 um 11:39 schrieb 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.

Do you refer with *this fix* to the referenced commit? Or do you mean
the patch you just sent?

How can the issue be reproduced?

> 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.

Is there a bug report with more details?

If this fixes a regression, please add the appropriate `Fixes:` tag.

> 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;
> }

The rest looks fine.


Kind regards,

Paul

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