[Bug 215129] New: Linux kernel hangs during power down

[Heiner Kallweit]

On 25.11.2021 01:46, Jakub Kicinski wrote:
> Adding Kalle and Hainer.
> 
> On Wed, 24 Nov 2021 14:45:05 -0800 Stephen Hemminger wrote:
>> Begin forwarded message:
>>
>> Date: Wed, 24 Nov 2021 21:14:53 +0000
>> From: bugzilla-daemon at bugzilla.kernel.org
>> To: stephen at networkplumber.org
>> Subject: [Bug 215129] New: Linux kernel hangs during power down
>>
>>
>> https://bugzilla.kernel.org/show_bug.cgi?id=215129
>>
>>             Bug ID: 215129
>>            Summary: Linux kernel hangs during power down
>>            Product: Networking
>>            Version: 2.5
>>     Kernel Version: 5.15
>>           Hardware: All
>>                 OS: Linux
>>               Tree: Mainline
>>             Status: NEW
>>           Severity: normal
>>           Priority: P1
>>          Component: Other
>>           Assignee: stephen at networkplumber.org
>>           Reporter: martin.stolpe at gmail.com
>>         Regression: No
>>
>> Created attachment 299703
>>   --> https://bugzilla.kernel.org/attachment.cgi?id=299703&action=edit    
>> Kernel log after timeout occured
>>
>> On my system the kernel is waiting for a task during shutdown which doesn't
>> complete.
>>
>> The commit which causes this behavior is:
>> [f32a213765739f2a1db319346799f130a3d08820] ethtool: runtime-resume netdev
>> parent before ethtool ioctl ops
>>
>> This bug causes also that the system gets unresponsive after starting Steam:
>> https://steamcommunity.com/app/221410/discussions/2/3194736442566303600/
>>
> 

I think the reference to ath10k_pci is misleading, Kalle isn't needed here.
The actual issue is a RTNL deadlock in igb_resume(). See log snippet:

Nov 24 18:56:19 MartinsPc kernel:  igb_resume+0xff/0x1e0 [igb 21bf6a00cb1f20e9b0e8434f7f8748a0504e93f8]
Nov 24 18:56:19 MartinsPc kernel:  pci_pm_runtime_resume+0xa7/0xd0
Nov 24 18:56:19 MartinsPc kernel:  ? pci_pm_freeze_noirq+0x110/0x110
Nov 24 18:56:19 MartinsPc kernel:  __rpm_callback+0x41/0x120
Nov 24 18:56:19 MartinsPc kernel:  ? pci_pm_freeze_noirq+0x110/0x110
Nov 24 18:56:19 MartinsPc kernel:  rpm_callback+0x35/0x70
Nov 24 18:56:19 MartinsPc kernel:  rpm_resume+0x567/0x810
Nov 24 18:56:19 MartinsPc kernel:  __pm_runtime_resume+0x4a/0x80
Nov 24 18:56:19 MartinsPc kernel:  dev_ethtool+0xd4/0x2d80

We have at least two places in net core where runtime_resume() is called
under RTNL. This conflicts with the current structure in few Intel drivers
that have something like the following in their resume path.

	rtnl_lock();
	if (!err && netif_running(netdev))
		err = __igb_open(netdev, true);

	if (!err)
		netif_device_attach(netdev);
	rtnl_unlock();

Other drivers don't do this, so it's the question whether it's actually
needed here to take RTNL. Some discussion was started [0], but it ended
w/o tangible result and since then it has been surprisingly quiet.

[0] https://www.spinics.net/lists/netdev/msg736880.html