linux-kernel - Re: kernel CI: printk loglevels in kernel boot logs?

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Date:   Wed, 6 Dec 2017 14:54:49 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Fengguang Wu <fengguang.wu@...el.com>,
        Kevin Hilman <khilman@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: kernel CI: printk loglevels in kernel boot logs?

On Tue 2017-12-05 15:54:09, Steven Rostedt wrote:
> On Tue, 5 Dec 2017 16:55:37 +0100
> Petr Mladek <pmladek@...e.com> wrote:
> 
> > I would have agreed with this argument few weeks ago but I do not get
> > it any longer. If there are tools depending on the message format
> > and people enable the extended format, the tools might stop working.
> > 
> > You might argue that these people are shooting into their legs.
> > But other people might argue that kernel changed ABI and broke
> > userspace tools. Note that these tools do not have any chance
> > to force kernel using the old format, they are consumers.
> > 
> > It might be especially annoying if these tools are part of some
> > complex infrastructure that is used to access the boot logs
> > and admins get blind. Then it might be hard for them to debug
> > the problem, especially if they got this feature as part of
> > a bigger system update.
> > 
> > Am I too paranoid? Steven? Linus?
> 
> Remember, an ABI is only broken if a tool breaks. If it proves to break
> userspace, then it can be reverted. But if there is no tool that
> depends on it, it's fine to change.
> 
> That said, I haven't had a chance to fully read this thread. Mostly
> because of the Turkey holiday which put me behind in other areas, and
> also I currently traveling, and will be taking PTO for the rest of the
> week.

OK, I feel relieved. I am not aware of any tool that depends on the
 format. I just could imagine that there might be some.

Otherwise, I agree that showing log levels on the console might be
useful. So I am going to review the RFC implementation, see
https://lkml.kernel.org/r/20171201104404.1885-1-sergey.senozhatsky@gmail.com

Best Regards,
Petr