linux-kernel - Re: [PATCH v5 5/6] drm/log: Implement suspend/resume

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Message-ID: <84ikt3c8uy.fsf@jogness.linutronix.de>
Date: Mon, 04 Nov 2024 16:38:53 +0106
From: John Ogness <john.ogness@...utronix.de>
To: Petr Mladek <pmladek@...e.com>
Cc: Jocelyn Falempe <jfalempe@...hat.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>, Javier Martinez Canillas
 <javierm@...hat.com>, "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
 bluescreen_avenger@...izon.net, Caleb Connolly
 <caleb.connolly@...aro.org>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/6] drm/log: Implement suspend/resume

On 2024-11-04, Petr Mladek <pmladek@...e.com> wrote:
> I wonder whether console_start()/console_stop() should really
> manipulate CON_ENABLE flag. It might be historical solution when
> @console_suspended was a global variable.
>
> But it has changed with the commit 9e70a5e109a4a2336 ("printk: Add
> per-console suspended state").
>
> It might make more sense when console_start()/console_stop()
> manipulates CON_SUSPENDED flag. Then it would make sense
> to rename them suspend_this_console()/resume_this_console().

I worry about letting console drivers and printk.c both modify this flag
during normal runtime. One might clear CON_SUSPENDED too soon and cause
trouble.

CON_ENABLE and @console_suspended were always orthogonal. Moving
@console_suspended to CON_SUSPENDED did not change that relationship.

IMHO we should continue to keep them separate. But your point about the
console not being registered is a good one. We should update
console_stop()/console_start() to only operate on @console if it is
registered. Since those functions take the console_list_lock anyway, it
would be a simple change.

John