linux-kernel - Re: [PATCH printk v7 31/35] printk: nbcon: Implement emergency sections

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Message-ID: <ZrNuDAqRZsjvnjsT@pathway.suse.cz>
Date: Wed, 7 Aug 2024 14:52:28 +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 v7 31/35] printk: nbcon: Implement emergency
 sections

On Sun 2024-08-04 02:57:34, John Ogness wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> In emergency situations (something has gone wrong but the
> system continues to operate), usually important information
> (such as a backtrace) is generated via printk(). This
> information should be pushed out to the consoles ASAP.
> 
> Add per-CPU emergency nesting tracking because an emergency
> can arise while in an emergency situation.
> 
> Add functions to mark the beginning and end of emergency
> sections where the urgent messages are generated.
> 
> Perform direct console flushing at the emergency priority if
> the current CPU is in an emergency state and it is safe to do
> so.
> 
> Note that the emergency state is not system-wide. While one CPU
> is in an emergency state, another CPU may attempt to print
> console messages at normal priority.
> 
> Also note that printk() already attempts to flush consoles in
> the caller context for normal priority. However, follow-up
> changes will introduce printing kthreads, in which case the
> normal priority printk() calls will offload to the kthreads.
> 
> Co-developed-by: John Ogness <john.ogness@...utronix.de>
> Signed-off-by: John Ogness <john.ogness@...utronix.de>
> Signed-off-by: Thomas Gleixner (Intel) <tglx@...utronix.de>

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

Best Regards,
Petr