linux-kernel - Re: [PATCH] printk: handle blank console arguments passed in.

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Message-ID: <20201006160821.GA430@jagdpanzerIV.localdomain>
Date:   Wed, 7 Oct 2020 01:08:21 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Shreyas Joshi <shreyas.joshi@...mp.com>, rostedt@...dmis.org,
        shreyasjoshi15@...il.com, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] printk: handle blank console arguments passed in.

On (20/10/06 07:22), Guenter Roeck wrote:
> On 10/6/20 6:33 AM, Sergey Senozhatsky wrote:
> > On (20/10/06 11:54), Petr Mladek wrote:
> >> On Tue 2020-10-06 15:59:07, Sergey Senozhatsky wrote:
> >>> On (20/10/05 20:35), Guenter Roeck wrote:
> >>>> On a side note, I don't see the problem presumably fixed with this
> >>>> patch in any of my tests.
> >>>
> >>> Hmm. This is rather interesting. Empty console= certainly oops-es my laptop,
> >>
> >> Just by chance. Do you have any log with the Oops? Or does it die
> >> silently?
> > 
> > The laptop in question has fbdev and no serial. It dies with blank screen.
> > I'll try to dig it and get some backtrace or anything useful.
> > 
> 
> Some versions of systemd (and possibly other distributions) apparently
> react allergic if no console is present. See [1]. Maybe that is what
> happens with your laptop ?

Seems to be crashing before /init

> That exchange leads to the question what should be done with /dev/console
> if there is no console. On Chromebooks we see an error when trying
> to open it if I recall correctly.

A wild guess:

Devices that you test, do they have 'blah blah  console=  blah blah'
command line? If so, does anything change if you revert the patch in
question and change kernel boot command line to 'blah blah console='?

	-ss