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

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Message-ID: <ZuhBymvNiB_8sWMu@pathway.suse.cz>
Date: Mon, 16 Sep 2024 16:33:46 +0200
From: Petr Mladek <pmladek@...e.com>
To: Rik van Riel <riel@...riel.com>
Cc: John Ogness <john.ogness@...utronix.de>,
	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 Fri 2024-09-13 13:25:33, Rik van Riel wrote:
> 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?

Sure. Thanks for reminder.

John, could you please send the fix as a proper patch with some
reasonable commit message?

Best Regards,
Petr