Re: [PATCH printk v6 26/30] printk: nbcon: Implement emergency sections

[Petr Mladek <pmladek@suse.com>]

On Mon 2024-05-27 08:43:45, John Ogness wrote:
> From: Thomas Gleixner <tglx@linutronix.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(). Each
> individual printk record has little meaning. It is the
> collection of printk messages that is most often needed by
> developers and users.
> 
> In order to help ensure that the collection of printk messages
> in an emergency situation are all stored to the ringbuffer as
> quickly as possible, disable console output for that CPU while
> it is in the emergency situation. The consoles need to be
> flushed when exiting the emergency situation.
> 
> 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.
> 
> Do not print if the current CPU is in an emergency state.
> 
> When exiting all emergency nesting, flush nbcon consoles
> directly using their atomic callback. Legacy consoles are
> flushed directly if safe, otherwise they are triggered for
> flushing via irq_work.
> 
> Note that the emergency state is not system-wide. While one CPU
> is in an emergency state, another CPU may continue to print
> console messages.
> 
> Co-developed-by: John Ogness <john.ogness@linutronix.de>
> Signed-off-by: John Ogness <john.ogness@linutronix.de>
> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de>

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

Best Regards,
Petr