linux-kernel - Re: [PATCH printk 0/1] alternate fix for nbcon_cpu_emergency

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Message-ID: <Zp5w8Z0DHJ8v9ORh@pathway.suse.cz>
Date: Mon, 22 Jul 2024 16:47:13 +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 0/1] alternate fix for nbcon_cpu_emergency_flush()

On Fri 2024-07-19 15:54:17, John Ogness wrote:
> Hi Petr,
> 
> Currently in linux-next we have commit b955f0eead54 ("printk: nbcon:
> Fix nbcon_cpu_emergency_flush() when preemptible"). But as you
> pointed out [0], there is no need to disable preemption at all if
> we only need to know if the current CPU is in emergency state.
> 
> Here is an alternative patch that correctly addresses the issue by
> avoiding the migration checks.
> 
> Since the previous patch is not yet mainline, perhaps you want to
> use this one instead in order to avoid a revert. Up to you.

Makes sense. I have replaced the commit b955f0eead54 ("printk: nbcon:
Fix nbcon_cpu_emergency_flush() when preemptible") with this new patch
in printk/linux.git, branch rework/write-atomic.

> [0] https://lore.kernel.org/lkml/Zn7b8g1HtuTIAwyi@pathway.suse.cz
> 
> John Ogness (1):
>   printk: nbcon: do not require migration disabled for
>     nbcon_get_cpu_emergency_nesting()
> 
>  kernel/printk/nbcon.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Best Regards,
Petr