linux-kernel - Re: [PATCH printk v2 1/1] printk: nbcon: Allow unsafe write

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Message-ID: <87346z5u1l.fsf@jogness.linutronix.de>
Date: Fri, 31 Oct 2025 10:02:06 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>, Steven Rostedt
 <rostedt@...dmis.org>, Breno Leitao <leitao@...ian.org>, Mike Galbraith
 <efault@....de>, linux-kernel@...r.kernel.org, Greg Kroah-Hartman
 <gregkh@...uxfoundation.org>
Subject: Re: [PATCH printk v2 1/1] printk: nbcon: Allow unsafe
 write_atomic() for panic

On 2025-10-30, Petr Mladek <pmladek@...e.com> wrote:
> The patch looks good to me:
>
> Reviewed-by: Petr Mladek <pmladek@...e.com>

Thanks.

> That said, it needs one more hunk to fix build with the patchset
> adding support for nbcon into kdb which is
> in https://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git/

[...]

> Also there is one trivial conflict with the new branch which is
> preventing hardlockups in atomic flush which is
> https://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git/log/?h=rework/atomic-flush-hardlockup
>
> Namely, it is the last patch which moves nbcon_context_try_acquire()
> into to while cycle, see
> https://git.kernel.org/pub/scm/linux/kernel/git/printk/linux.git/commit/?h=rework/atomic-flush-hardlockup&id=d5d399efff65773ed82ddaf6c11a0fcfdb5eb029

I can send a new patch that takes all these underlying series into
account... assuming it is going through the printk tree.

> I am not sure how to move forward. IMHO, the original plan was to push
> this patch together with the other netconsole-related changes. In this
> case, the conflicts will need to be solved when merging pull requests
> from netconsole and printk trees. Well, the conflicts are trivial.
>
> Or I could push this patch via the printk tree and queue it for 6.19.
> But this might be too late for netconsole.

@Breno: This new feature only exists for netconsole at the moment, so I
am fine with it going through the netconsole tree. But we need to decide
this soon because there are a lot of printk-changes queued for 6.19 that
conflict with this patch and we should get those sorted out sooner
rather than later. (Note that the patch in its current form will also
conflict with the netconsole tree, so regardless of our decision I need
to submit a new version.)

John