linux-kernel - Re: [PATCH RFC v3 04/21] ACPI: processor: Register all CPUs from acpi_processor_get

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Date: Mon, 22 Jan 2024 21:56:18 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-pm@...r.kernel.org, loongarch@...ts.linux.dev,
	linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-riscv@...ts.infradead.org, kvmarm@...ts.linux.dev,
	x86@...nel.org, acpica-devel@...ts.linuxfoundation.org,
	linux-csky@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-ia64@...r.kernel.org, linux-parisc@...r.kernel.org,
	Salil Mehta <salil.mehta@...wei.com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	jianyong.wu@....com, justin.he@....com,
	James Morse <james.morse@....com>
Subject: Re: [PATCH RFC v3 04/21] ACPI: processor: Register all CPUs from
 acpi_processor_get_info()

On Mon, Dec 18, 2023 at 09:30:50PM +0100, Rafael J. Wysocki wrote:
> On Wed, Dec 13, 2023 at 1:49 PM Russell King <rmk+kernel@...linux.org.uk> wrote:
> > Systems can still be booted with 'acpi=off', or not include an
> > ACPI description at all. For these, the CPUs continue to be
> > registered by cpu_dev_register_generic().
> >
> > This moves the CPU register logic back to a subsys_initcall(),
> > while the memory nodes will have been registered earlier.
> 
> Isn't this somewhat risky?

Not really. The earlier full series moved the registration of CPUs
from subsys (by the various architecture specific code) into the
driver core - thus moving it much earlier. This patch merely
restores it back to the subsys initialisation stage.

There is a low chance that something _could_ have become reliant
on that change - and the longer it takes for this change to be
merged, the more risk there is that something could become reliant
on CPUs being registered very early.

Maybe this ought to be spelt out more explicitly that it's merely
restoring the point at which CPUs are registered.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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