Re: Regression for duplicate (?) console parameters on next-20220630

[Imran Khan]

Hello Michael, Hello Nathan,

Thanks for sharing the test result.

On 1/7/22 7:18 am, Michael Walle wrote:
> Am 2022-06-30 21:35, schrieb Nathan Chancellor:
>> On Thu, Jun 30, 2022 at 03:11:58PM +0200, Michael Walle wrote:
>>> Hi,
>>>
>>> I'm not sure it these are the correct recipients, feel free to CC others.
>>>
>>> Since next-20220630 (or maybe also since next-20220629) I'm getting the
>>>
>>> [    3.707900] WARNING: CPU: 0 PID: 38 at fs/kernfs/dir.c:531
>>> kernfs_put.part.0+0x1a0/0x1d4
>>> [    3.716313] kernfs_put: console/active: released with incorrect
>>> active_ref 0
>>>
>>> on both arm and arm64 boards. See for example:
>>> https://urldefense.com/v3/__https://linux.kernelci.org/test/case/id/62bd840b330c4851eaa39c16/__;!!ACWV5N9M2RV99hQ!LGrYRXVZCYKcB-xmJ52QGhidx1F_PJNpJPqzVxrbFnprXCDPx0p8f7uqnH-_pc0KrO3alOkTJuvOm2q2qzA$
>>>
>>> I have the console set in the device tree as well as on the commandline.
>>> Up until recently that wasn't a problem and I guess that should be a valid
>>> configuration. That being said, the warn() will go away if I remove the
>>> console= parameter on the commandline.
>>>
>>> I haven't had time to do a bisect yet. That will probably my next step;
>>> or maybe kernelci will already do that for me, Guillaume? Unless someone
>>> has some more insights/ideas.
>>
>> I noticed this as well when booting ARCH=um defconfig.
>>
>> I ended up doing a bisect against next-20220630 and I landed on the
>> driver-core merge (5732b42edfd18ee888e127fa13d425ed3ed1bef3). I did two
>> more bisects to figure out that there is some sort of contextual
>> contlict between commit 5831788afb17 ("Revert "printk: add kthread
>> console printers"") and commit b8f35fa1188b ("kernfs: Change
>> kernfs_notify_list to llist."), as it is only when those two changes are
>> present that this issue occurs. I am happy to provide more information
>> if necessary.
> 
> Thanks for the info.
> 
> I can confirm that reverting b8f35fa1188b will fix the error. I couldn't
> revert 5831788afb17 though, didn't apply cleanly.
> 

I tried to reproduce this issue on a qemu ARM instance (-m vexpress-a15, rootfs
based on buildroot) but could not reproduce this issue.
If you could share some more details about test steps/setup it would be great.
In the meanwhile based on the stack trace seen in WARN message and reverted
change, I think following change should fix this issue: