linux-kernel - Re: [PATCH v5 2/5] printk: nbcon: Introduce KDB helpers

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Message-ID: <aOPK_jgFJwM0TWTY@pathway.suse.cz>
Date: Mon, 6 Oct 2025 15:58:22 +0200
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Marcos Paulo de Souza <mpdesouza@...e.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jason Wessel <jason.wessel@...driver.com>,
	Daniel Thompson <danielt@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net
Subject: Re: [PATCH v5 2/5] printk: nbcon: Introduce KDB helpers

On Wed 2025-10-01 17:02:41, John Ogness wrote:
> On 2025-09-30, Marcos Paulo de Souza <mpdesouza@...e.com> wrote:
> > diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
> > index 558ef31779760340ce42608294d91d5401239f1d..c23abed5933527cb7c6bcc42057fadbb44a43446 100644
> > --- a/kernel/printk/nbcon.c
> > +++ b/kernel/printk/nbcon.c
> > +/**
> > + * nbcon_kdb_release - Exit unsafe section and release the nbcon console
> > + *
> > + * @wctxt:	The nbcon write context initialized by a successful
> > + *		nbcon_kdb_try_acquire()
> > + *
> > + * Context:	Under console_srcu_read_lock() for emiting a single kdb message
> 
>                                        emitting ---^^^^^^^
> 
> > + *		using the given con->write_atomic() callback. Can be called
> > + *		only when the console is usable at the moment.
> 
> I do not think the "Context" is relevant. It must be called if
> a previous call to nbcon_kdb_try_acquire() was successful.

Makes sense. I am fine with removing the "Context:" secion completely
from nbcon_kdb_release().

Just to be sure. I think that we do not need to mention that it can
be called only when nbcon_kdb_try_acquire() succeeded. It is kind
of obvious.

Best Regards,
Petr

> > + */
> > +void nbcon_kdb_release(struct nbcon_write_context *wctxt)
> > +{
> > +	struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt);
> > +
> > +	if (!nbcon_context_exit_unsafe(ctxt))
> > +		return;
> > +
> > +	nbcon_context_release(ctxt);
> > +
> > +	/*
> > +	 * Flush any new printk() messages added when the console was blocked.
> > +	 * Only the console used by the given write context was	blocked.
> > +	 * The console was locked only when the write_atomic() callback
> > +	 * was usable.
> > +	 */
> > +	__nbcon_atomic_flush_pending_con(ctxt->console,
> > +					 prb_next_reserve_seq(prb), false);
> 
> This can all be one line. 100 characters is the official limit for code.
> 
> > +}