linux-kernel - Re: [PATCH RFC v2] cpu-hotplug: provide prototypes for arch CPU registration

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Date:   Mon, 18 Sep 2023 09:16:18 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-acpi@...r.kernel.org, James Morse <james.morse@....com>,
        loongarch@...ts.linux.dev, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        jianyong.wu@....com, justin.he@....com,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Salil Mehta <salil.mehta@...wei.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-ia64@...r.kernel.org
Subject: Re: [PATCH RFC v2] cpu-hotplug: provide prototypes for arch CPU
 registration

On Fri, Sep 15, 2023 at 09:09:10PM +0200, Thomas Gleixner wrote:
> On Thu, Sep 14 2023 at 15:51, Russell King wrote:
> > Provide common prototypes for arch_register_cpu() and
> > arch_unregister_cpu(). These are called by acpi_processor.c, with
> > weak versions, so the prototype for this is already set. It is
> > generally not necessary for function prototypes to be conditional
> > on preprocessor macros.
> >
> > Some architectures (e.g. Loongarch) are missing the prototype for this,
> > and rather than add it to Loongarch's asm/cpu.h, lets do the job once
> > for everyone.
> >
> > Since this covers everyone, remove the now unnecessary prototypes in
> > asm/cpu.h, and we also need to remove the 'static' from one of ia64's
> > arch_register_cpu() definitions.
> >
> > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> > ---
> > Spotted during the review of James Morse's patches, I think rather than
> > adding prototypes for loongarch to its asm/cpu.h, it would make more
> > sense to provide the prototypes in a non-arch specific header file so
> > everyone can benefit, rather than having each architecture do its own
> > thing.
> >
> > I'm sending this as RFC as James has yet to comment on my proposal, and
> > also to a wider audience, and although it makes a little more work for
> > James (to respin his series) it does mean that his series should get a
> > little smaller.
> 
> And it makes tons of sense.
> 
> > See:
> >  https://lore.kernel.org/r/20230913163823.7880-2-james.morse@arm.com
> >  https://lore.kernel.org/r/20230913163823.7880-4-james.morse@arm.com
> >  https://lore.kernel.org/r/20230913163823.7880-23-james.morse@arm.com
> >
> > v2: lets try not fat-fingering vim.
> 
> Yeah. I wondered how you managed to mangle that :)
> 
> >  arch/ia64/include/asm/cpu.h | 5 -----
> >  arch/ia64/kernel/topology.c | 2 +-
> 
> That's moot as ia64 is queued for removal :)

Okay, one less thing to worry about. Tomorrow, I'll re-spin without the
ia64 bits included.

I would really like to hear from James before we think about merging
this, as it will impact James' patch set and would add a dependency
for that. I wouldn't want this patch to become a reason to delay
James' patch set for another kernel cycle.

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