linux-kernel - Re: [PATCH printk v4 01/17] printk: nbcon: Add function for printers to reacquire ownership

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Message-ID: <Zs2_OCqT_lFdPm8v@pathway.suse.cz>
Date: Tue, 27 Aug 2024 13:57:44 +0200
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH printk v4 01/17] printk: nbcon: Add function for printers
 to reacquire ownership

On Tue 2024-08-27 06:49:17, John Ogness wrote:
> Since ownership can be lost at any time due to handover or
> takeover, a printing context _must_ be prepared to back out
> immediately and carefully. However, there are scenarios where
> the printing context must reacquire ownership in order to
> finalize or revert hardware changes.
> 
> One such example is when interrupts are disabled during
> printing. No other context will automagically re-enable the
> interrupts. For this case, the disabling context _must_
> reacquire nbcon ownership so that it can re-enable the
> interrupts.
> 
> Provide nbcon_reacquire_nobuf() for exactly this purpose. It
> allows a printing context to reacquire ownership using the same
> priority as its previous ownership.
> 
> Note that after a successful reacquire the printing context
> will have no output buffer because that has been lost. This
> function cannot be used to resume printing.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr