linux-kernel - Re: [RFC PATCH] nmi,printk: fix ABBA deadlock between nmi_backtrace and dump_stack

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Message-ID: <df98d9d179a87990498414a569fd1c094d5f5347.camel@surriel.com>
Date: Thu, 18 Jul 2024 11:23:46 -0400
From: Rik van Riel <riel@...riel.com>
To: John Ogness <john.ogness@...utronix.de>, Andrew Morton
	 <akpm@...ux-foundation.org>
Cc: Omar Sandoval <osandov@...a.com>, linux-kernel@...r.kernel.org, Petr
 Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, Sergey
 Senozhatsky <senozhatsky@...omium.org>, kernel-team <kernel-team@...a.com>
Subject: Re: [RFC PATCH] nmi,printk: fix ABBA deadlock between nmi_backtrace
 and dump_stack_lvl

On Thu, 2024-07-18 at 16:15 +0206, John Ogness wrote:
> 
> However, my first suggestion to defer whenever the cpu_sync is held
> really is the only option because console_unlock() will spin on the
> uart
> port lock, and that is also not allowed when holding the cpu_sync.
> 
Agreed, even with using only trylocks inside the printk code
and console code, there is no way to control what other locks
might be lurking in the device drivers the console uses.

I'll go try out your first suggestion.

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