Subject: Re: [PATCH] igc: Avoid possible deadlock during suspend/resume

From: Vinicius Costa Gomes <[email-masked]>
Date: Thu, 02 Dec 2021 14:34:21 -0800

Hi Stefan,

Stefan Dietrich <[email-masked]> writes:

> Hi Vinicius,
>
> thanks for the patch - unfortunately it did not solve the issue and I
> am still getting reboots/lockups.
>

Thanks for the test. We learned something, not a lot, but something: the
problem you are facing is PTM related and it's not the same bug as that
PM deadlock.

I am still trying to understand what's going on.

Are you able to send me the 'dmesg' output for the two kernel configs
(CONFIG_PCIE_PTM enabled and disabled)? (no need to bring the network
interface up or down). Your kernel .config would be useful as well.

>
> Cheers,
> Stefan
>
> On Wed, 2021-12-01 at 10:57 -0800, Vinicius Costa Gomes wrote:
>> Inspired by:
>> https://bugzilla.kernel.org/show_bug.cgi?id=215129
>>
>> Signed-off-by: Vinicius Costa Gomes <[email-masked]>
>> ---
>> Just to see if it's indeed the same problem as the bug report above.
>>
>>  drivers/net/ethernet/intel/igc/igc_main.c | 19 +++++++++++++------
>>  1 file changed, 13 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c
>> b/drivers/net/ethernet/intel/igc/igc_main.c
>> index 0e19b4d02e62..c58bf557a2a1 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_main.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
>> @@ -6619,7 +6619,7 @@ static void igc_deliver_wake_packet(struct
>> net_device *netdev)
>>  	netif_rx(skb);
>>  }
>>
>> -static int __maybe_unused igc_resume(struct device *dev)
>> +static int __maybe_unused __igc_resume(struct device *dev, bool rpm)
>>  {
>>  	struct pci_dev *pdev = to_pci_dev(dev);
>>  	struct net_device *netdev = pci_get_drvdata(pdev);
>> @@ -6661,20 +6661,27 @@ static int __maybe_unused igc_resume(struct
>> device *dev)
>>
>>  	wr32(IGC_WUS, ~0);
>>
>> -	rtnl_lock();
>> +	if (!rpm)
>> +		rtnl_lock();
>>  	if (!err && netif_running(netdev))
>>  		err = __igc_open(netdev, true);
>>
>>  	if (!err)
>>  		netif_device_attach(netdev);
>> -	rtnl_unlock();
>> +	if (!rpm)
>> +		rtnl_unlock();
>>
>>  	return err;
>>  }
>>
>>  static int __maybe_unused igc_runtime_resume(struct device *dev)
>>  {
>> -	return igc_resume(dev);
>> +	return __igc_resume(dev, true);
>> +}
>> +
>> +static int __maybe_unused igc_resume(struct device *dev)
>> +{
>> +	return __igc_resume(dev, false);
>>  }
>>
>>  static int __maybe_unused igc_suspend(struct device *dev)
>> @@ -6738,7 +6745,7 @@ static pci_ers_result_t
>> igc_io_error_detected(struct pci_dev *pdev,
>>   *  @pdev: Pointer to PCI device
>>   *
>>   *  Restart the card from scratch, as if from a cold-boot.
>> Implementation
>> - *  resembles the first-half of the igc_resume routine.
>> + *  resembles the first-half of the __igc_resume routine.
>>   **/
>>  static pci_ers_result_t igc_io_slot_reset(struct pci_dev *pdev)
>>  {
>> @@ -6777,7 +6784,7 @@ static pci_ers_result_t
>> igc_io_slot_reset(struct pci_dev *pdev)
>>   *
>>   *  This callback is called when the error recovery driver tells us
>> that
>>   *  its OK to resume normal operation. Implementation resembles the
>> - *  second-half of the igc_resume routine.
>> + *  second-half of the __igc_resume routine.
>>   */
>>  static void igc_io_resume(struct pci_dev *pdev)
>>  {
>

Cheers,
-- 
Vinicius