linux-kernel - Re: [PATCH] x86/nmi: Use trylock in __register_nmi_handler() when in

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Message-ID: <20241128092800.GB35539@noisy.programming.kicks-ass.net>
Date: Thu, 28 Nov 2024 10:28:00 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Waiman Long <longman@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/nmi: Use trylock in __register_nmi_handler() when
 in_nmi()

On Wed, Nov 27, 2024 at 06:34:55PM -0500, Waiman Long wrote:
> The __register_nmi_handler() function can be called in NMI context from
> nmi_shootdown_cpus() leading to a lockdep splat like the following.

This seems fundamentally insane. Why are we okay with this?