linux-kernel - Re: [PATCH printk 1/1] printk: nbcon: do not require migration disabled for nbcon_get_cpu_emergency

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Message-ID: <Zp5lcOihG4d6SNjt@pathway.suse.cz>
Date: Mon, 22 Jul 2024 15:58:41 +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,
	Juri Lelli <juri.lelli@...hat.com>
Subject: Re: [PATCH printk 1/1] printk: nbcon: do not require migration
 disabled for nbcon_get_cpu_emergency_nesting()

On Fri 2024-07-19 15:54:18, John Ogness wrote:
> Since entering emergency state disables preemption, there is no
> need for nbcon_get_cpu_emergency_nesting() to explicitly require
> migration disasbled. Either the current CPU is in emergency state
> (and thus preemption is disabled and the nesting level is not
> zero) or the current CPU is not in emergency state and the nesting
> level must by definition be zero, even when migration is enabled
> and the current CPU could change. The current CPU could never
> change to a CPU that is in emergency state.
> 
> Reported-by: Juri Lelli <juri.lelli@...hat.com>
> Closes: https://lore.kernel.org/aqkcpca4vgadxc3yzcu74xwq3grslj5m43f3eb5fcs23yo2gy4@gcsnqcts5tos
> Fixes: 46a1379208b7 ("printk: nbcon: Implement emergency sections")
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

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

Best Regards,
Petr