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

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Date:   Tue, 5 Dec 2017 15:54:09 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Petr Mladek <pmladek@...e.com>
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, 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.

-- Steve