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

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Message-ID: <YS5CPGm4JENsFIem@alley>
Date:   Tue, 31 Aug 2021 16:52:44 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     James Wang <jnwang@...ux.alibaba.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        John Ogness <john.ogness@...utronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kernel hang during reboot when cmdline include a non-exist
 console device

On Tue 2021-08-31 22:38:42, James Wang wrote:
> 
> 在 2021/8/31 PM10:33, Petr Mladek 写道:
> > On Tue 2021-08-31 21:45:05, James Wang wrote:
> > > 在 2021/8/31 PM4:47, Sergey Senozhatsky 写道:
> > > > And may I ask, just in case, if James can revert a revert of Petr's commit:
> > > > 
> > > >          revert a91bd6223ecd46addc71ee6fcd432206d39365d2
> > > > 
> > > > boot with wrong console argument and see if the kernel reboots without
> > > > any problems.
> > > After test, revert Petr's commit can work; reboot without any problem;
> > Interesting, it looks like the panic() is really caused by missing
> > stdout, stdin, and stderr, for the init process.
> > 
> > Unfortunately, the fix is not easy, as described in the commit
> > a91bd6223ecd46addc71e ("Revert "init/console: Use ttynull as
> > a fallback when there is no console").
> 
> OK. But I suppose you could find a quick workaround to mitigate this issue.

You could either remove the invalid console=ttyUSB0,115200
parameter. As a result, tty0 will become the default console and
it will be used by the init process.

If you do not want any console, you could build the kernel with
CONFIG_NULL_TTY=y and use console=null on the commandline.

Best Regards,
Petr