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

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Date:   Thu, 30 Jun 2022 23:18:37 +0200
From:   Michael Walle <michael@...le.cc>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh@...nel.org>, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Guillaume Tucker <guillaume.tucker@...labora.com>,
        Imran Khan <imran.f.khan@...cle.com>,
        Petr Mladek <pmladek@...e.com>
Subject: Re: Regression for duplicate (?) console parameters on next-20220630

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://linux.kernelci.org/test/case/id/62bd840b330c4851eaa39c16/
>> 
>> 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.

-michael