linux-kernel - Re: [PATCH next v4 1/2] lib/dump_stack: move cpu lock to printk.c

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Date:   Fri, 18 Jun 2021 12:25:41 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Alexander Potapenko <glider@...gle.com>
Subject: Re: [PATCH next v4 1/2] lib/dump_stack: move cpu lock to printk.c

On Fri, 18 Jun 2021 16:47:39 +0200
Petr Mladek <pmladek@...e.com> wrote:

> Good point! Just to be sure. Do you see the messed output with plain
> kernel? Or do you need the extra patches (from Peter Zijlstra) that
> redirect normal printk() to early_printk()?

I sometimes use this with Peter's patches, which also do basically the
same thing.

> 
> My understanding is that early_printk() is used only for very early
> boot message in plain kernel. And that there is not much concurrency
> at that time.

It will continue if you use ",keep" option. And that is something I
have done without Peter's patches, but then they become illegible when
there's a bug if more than one CPU triggers.

> 
> That said. I always wanted to upstream Peter's patchset. But I never
> found time to clean it up.

That would be great too!

-- Steve