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

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Date:   Thu, 30 Jun 2022 12:35:43 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Michael Walle <michael@...le.cc>
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

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.

Cheers,
Nathan