linux-kernel - Re: kernel hang during reboot when cmdline include a non-exist console device

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Message-ID: <87pmtudq3u.fsf@jogness.linutronix.de>
Date:   Tue, 31 Aug 2021 09:40:45 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     James Wang <jnwang@...ux.alibaba.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel hang during reboot when cmdline include a non-exist console device

Added the reporter to the discussion...

On 2021-08-31, Sergey Senozhatsky <senozhatsky@...omium.org> wrote:
>> There's a bugzilla for this, but let's just move it to reguilar email,
>> unless some of you want to track it that way.
>> 
>> The bugzilla entry says
>> 
>>   "When reboot， the capslock key of thinkpad x1 starts blinking"
>> 
>> which sounds like there's an oops that just isn't showing, quite
>> possibly because the console has already been shut down.

There is no console registered.

>> I didn't test this out, and would sincerely hope that somebody else is
>> willing to follow up on it since I'm in the busiest part of the merge
>> window.
>
> [..]
>
>> > https://bugzilla.kernel.org/show_bug.cgi?id=214201
>
> I think normally wrong/empty console boot argument should not cause
> problems. We have a huge number of devices that use console="", for
> instance. But on some hardware this triggers panic(), very early on.

@James: Is it possible that you can set up a crash kernel to capture the
dump?

If a crash kernel is not possible, another option would be to enable
kgdb+kdb for a serial port. This would allow you to dump the kernel log.

> I have the same symptoms on my laptop, and so far haven't been able to
> figure out how to track it down, but I need to re-start my
> investigation.

A crash kernel or kgdb/kdb on a serial port is the easiest way to debug
this.

John Ogness