linux-kernel - Re: [PATCH v1 0/2] x86/smp: Fix power regression introduced by commit 96040f7273e2

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Message-ID: <20250530080733.GH39944@noisy.programming.kicks-ass.net>
Date: Fri, 30 May 2025 10:07:33 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
	x86 Maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM <linux-pm@...r.kernel.org>, Len Brown <lenb@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...e.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
	"Gautham R. Shenoy" <gautham.shenoy@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Todd Brandt <todd.e.brandt@...ux.intel.com>
Subject: Re: [PATCH v1 0/2] x86/smp: Fix power regression introduced by
 commit 96040f7273e2

On Thu, May 29, 2025 at 11:38:05AM +0200, Rafael J. Wysocki wrote:

> First off, I'm not sure if all of the requisite things are ready then
> (sysfs etc.).

Pretty much everything is already running at early_initcall(). Sysfs
certainly is.

> We may end up doing this eventually, but it may not be straightforward.
> 
> More importantly, this is not a change for 6.15.y (y > 0).

Seriously, have you even tried? 

AFAICT the below is all that is needed.  That boots just fine on the one
randon system I tried, and seems to still work.

And this is plenty small enough to go into 6.15.y


diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 0835da449db8..0f25de8081af 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -814,4 +814,4 @@ static int __init cpuidle_init(void)
 
 module_param(off, int, 0444);
 module_param_string(governor, param_governor, CPUIDLE_NAME_LEN, 0444);
-core_initcall(cpuidle_init);
+early_initcall(cpuidle_init);