linux-kernel - Re: [PATCH] prinkt/nbcon: Add a scheduling point to nbcon_kthread

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Date: Thu, 20 Jun 2024 14:34:07 -0400
From: Derek Barbosa <debarbos@...hat.com>
To: Andrew Halaney <ahalaney@...hat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	john.ogness@...utronix.de, pmladek@...e.com, rostedt@...dmis.org,
	senozhatsky@...omium.org, linux-rt-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, williams@...hat.com,
	jlelli@...hat.com, lgoncalv@...hat.com, jwyatt@...hat.com,
	aubaker@...hat.com
Subject: Re: [PATCH] prinkt/nbcon: Add a scheduling point to
 nbcon_kthread_func().

On Thu, Jun 20, 2024 at 12:18:37PM -0500, Andrew Halaney wrote:
> Acked-by: Andrew Halaney <ahalaney@...hat.com>
> Tested-by: Andrew Halaney <ahalaney@...hat.com>
> 
> This survived a bunch of tests that normally would cause some lockups
> etc in PREEMPT_VOLUNTARY systems. I can see that the nbcon thread successfully
> migrated NUMA nodes etc during periods of overwhelming the console backlog
> successfully, which without this would not work prior.
> 
> Thanks!

I'm going to second Andrew's observed results here. With the original
reproducer of calling LTP pty03 && pty06 in a while loop, plus invoking
stress-ng with --timeout 60000s && --numa 64, there were no problems with the
nbcon thread migrating NUMA nodes and no panic(s) with 
kernel.softlockup_panic = 1

This was observed on an nproc == 128 machine.

Thanks! :-) 

Acked-by: Derek Barbosa <debarbos@...hat.com>
Tested-by: Derek Barbosa <debarbos@...hat.com>