linux-kernel - Re: [BUG] printk/nbcon.c: watchdog BUG: softlockup

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Message-ID: <20240620093246.HE9XDWSZ@linutronix.de>
Date: Thu, 20 Jun 2024 11:32:46 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Derek Barbosa <debarbos@...hat.com>
Cc: pmladek@...e.com, rostedt@...dmis.org, john.ogness@...utronix.de,
	senozhatsky@...omium.org, linux-rt-users@...r.kernel.org,
	linux-kernel@...r.kernel.org, williams@...hat.com,
	jlelli@...hat.com, ahalaney@...hat.com, lgoncalv@...hat.com,
	jwyatt@...hat.com, aubaker@...hat.com
Subject: Re: [BUG] printk/nbcon.c: watchdog BUG: softlockup - CPU#x stuck for
 78s

On 2024-06-20 09:15:45 [+0200], To Derek Barbosa wrote:
> On 2024-06-18 13:37:42 [-0400], Derek Barbosa wrote:
> > Hi,
> Hi,
> 
> > We have a modicum of reasonable suspicion to believe that nbcon_reacquire, or
> > some other nbcon mechanism *may* be causing such behavior.
> 
> Does this help?
> 
> diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
> index bb9689f94d302..0813ce88a49c5 100644
> --- a/kernel/printk/nbcon.c
> +++ b/kernel/printk/nbcon.c
> @@ -1119,6 +1119,7 @@ static int nbcon_kthread_func(void *__console)
>  		}
>  
>  		console_srcu_read_unlock(cookie);
> +		cond_resched();
>  
>  	} while (backlog);
>  

Okay. Works here on a 144 CPU box without CONFIG_PREEMPT.

Sebastian