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

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Date:   Tue, 31 Aug 2021 10:14:29 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        James Wang <jnwang@...ux.alibaba.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel hang during reboot when cmdline include a non-exist
 console device

Adding the reporter into Cc.

On Tue 2021-08-31 12:17:59, Sergey Senozhatsky wrote:
> On (21/08/30 19:53), Linus Torvalds 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.
> > 
> > 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.
> 
> 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.

Sergey, I think that you talk about the crash where there is no registered
console and console_on_rootfs() fails to create stdin, stdout, and
stderr for the init process. As a result the kernel crashes
during boot.

But the bugreport says that the system booted. It crashed later during
reboot. It will likely be in the shutdown phase. It still might be still
be caused by the missing console. But we should rule out other
problems.

James, do you see the problem:

  1. When there is a real console registered. When you remove the
     wrong console= parameter.

  2. When using "reboot -f" so that the system reboots a dirty way
     without trying to shut down services.

Best Regards,
Petr