linux-kernel - Re: [PATCH 0/2] Avoid crashes by early (boot) consoles using init memory

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Message-ID: <956ce40c-1640-387a-0ec9-9045c7d8af4b@redhat.com>
Date:   Fri, 14 Jul 2017 14:57:45 +0200
From:   "Fabio M. Di Nitto" <fdinitto@...hat.com>
To:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Matt Redfearn <matt.redfearn@...tec.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        "David S. Miller" <davem@...emloft.net>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH 0/2] Avoid crashes by early (boot) consoles using init
 memory

Hi Petr,

On 7/14/2017 2:51 PM, Petr Mladek wrote:
> Some early consoles have code and data in the init section. It makes some
> sense but this might cause problems when they are not replaced by
> the real console in time. The two patches fix the safequard and
> help to avoid the problems.
> 
> I though about removing keep_bootcon option completely. But it is useful
> at least for now.

Let´s just keep in mind that keep_bootcon was introduced only to debug
issues (read crashes or hangs) that could happen between disabling
bootconsole and enabling the real console. It shouldn´t be used for
anything else really.

If the new code can replace keep_bootcon, by all mean, go for it :-)

Cheers
Fabio

> There is not an easy way to disable a particular bootconsole
> when the related real console is installed. Instead all bootconsoles are
> removed when the preferred (last on the commandline) console is registered.
> But this is a bit cumbersome and non-intuitive.
> 
> In addition, the same problems might happen when the real console is
> registered using a deferred probe or when it is not registered at all
> for some reason.
> 
> The patchset is based on and inspired by the original patch from
> Matt Redfearn, see the discussion starting by the mail
> https://lkml.kernel.org/r/1499337481-19397-1-git-send-email-matt.redfearn@imgtec.com
> 
> Matt Redfearn (1):
>   printk/console: Always disable boot consoles that use init memory
>     before it is freed
> 
> Petr Mladek (1):
>   printk/console: Enhance the check for consoles using init memory
> 
>  kernel/printk/printk.c | 28 +++++++++++++++++-----------
>  1 file changed, 17 insertions(+), 11 deletions(-)
>