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

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Message-ID: <dbed42dc3bc05fa772e11b54e93526a66698401f.camel@surriel.com>
Date: Fri, 13 Sep 2024 13:25:33 -0400
From: Rik van Riel <riel@...riel.com>
To: Petr Mladek <pmladek@...e.com>, John Ogness <john.ogness@...utronix.de>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Omar Sandoval
 <osandov@...a.com>,  linux-kernel@...r.kernel.org, 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 Wed, 2024-07-24 at 17:08 +0200, Petr Mladek wrote:
> On Wed 2024-07-24 16:51:46, John Ogness wrote:
> 
> 
> I see. I agree that deferring printk on that CPU [0] is the right
> solution.
> 
> > [0]
> > https://lore.kernel.org/lkml/87plrcqyii.fsf@jogness.linutronix.de
> 
Hi Petr,

we have been running with John Ogness's fix (from the mail linked
above) for about a month now, and it has reduced the number of
deadlocks in the Linux kernel in our fleet by maybe 90%, comparing
a kernel with the fix, to a kernel without the fix.

Would it be possible to get John Ogness's fix queued up for merging
in the printk tree, and then later to Linus?

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