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Message-ID: <ZTbRKgxtiq9XQKBr@shell.armlinux.org.uk>
Date: Mon, 23 Oct 2023 21:01:46 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Gavin Shan <gshan@...hat.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
James Morse <james.morse@....com>, 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, Salil Mehta <salil.mehta@...wei.com>,
Jean-Philippe Brucker <jean-philippe@...aro.org>,
jianyong.wu@....com, justin.he@....com
Subject: Re: [RFC PATCH v2 20/35] ACPI: Rename acpi_processor_hotadd_init and
remove pre-processor guards
On Mon, Sep 18, 2023 at 03:50:09PM +1000, Gavin Shan wrote:
>
> On 9/15/23 00:17, Jonathan Cameron wrote:
> > On Wed, 13 Sep 2023 16:38:08 +0000
> > James Morse <james.morse@....com> wrote:
> >
> > > acpi_processor_hotadd_init() will make a CPU present by mapping it
> > > based on its hardware id.
> > >
> > > 'hotadd_init' is ambiguous once there are two different behaviours
> > > for cpu hotplug. This is for toggling the _STA present bit. Subsequent
> > > patches will add support for toggling the _STA enabled bit, named
> > > acpi_processor_make_enabled().
> > >
> > > Rename it acpi_processor_make_present() to make it clear this is
> > > for CPUs that were not previously present.
> > >
> > > Expose the function prototypes it uses to allow the preprocessor
> > > guards to be removed. The IS_ENABLED() check will let the compiler
> > > dead-code elimination pass remove this if it isn't going to be
> > > used.
> > >
> > > Signed-off-by: James Morse <james.morse@....com>
> > > ---
> > > drivers/acpi/acpi_processor.c | 14 +++++---------
> > > include/linux/acpi.h | 2 --
> > > 2 files changed, 5 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> > > index 75257fae10e7..22a15a614f95 100644
> > > --- a/drivers/acpi/acpi_processor.c
> > > +++ b/drivers/acpi/acpi_processor.c
> > > @@ -182,13 +182,15 @@ static void __init acpi_pcc_cpufreq_init(void) {}
> > > #endif /* CONFIG_X86 */
> > > /* Initialization */
> > > -#ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
> > > -static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> > > +static int acpi_processor_make_present(struct acpi_processor *pr)
> > > {
> > > unsigned long long sta;
> > > acpi_status status;
> > > int ret;
> > > + if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU))
> > > + return -ENODEV;
> > > +
> > > if (invalid_phys_cpuid(pr->phys_id))
> > > return -ENODEV;
> > > @@ -222,12 +224,6 @@ static int acpi_processor_hotadd_init(struct acpi_processor *pr)
> > > cpu_maps_update_done();
> > > return ret;
> > > }
> > > -#else
> > > -static inline int acpi_processor_hotadd_init(struct acpi_processor *pr)
> > > -{
> > > - return -ENODEV;
> > > -}
> > > -#endif /* CONFIG_ACPI_HOTPLUG_PRESENT_CPU */
> > > static int acpi_processor_get_info(struct acpi_device *device)
> > > {
> > > @@ -335,7 +331,7 @@ static int acpi_processor_get_info(struct acpi_device *device)
> > > * because cpuid <-> apicid mapping is persistent now.
> > > */
> > > if (invalid_logical_cpuid(pr->id) || !cpu_present(pr->id)) {
> > > - int ret = acpi_processor_hotadd_init(pr);
> > > + int ret = acpi_processor_make_present(pr);
> > > if (ret)
> > > return ret;
> > > diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> > > index 651dd43976a9..b7ab85857bb7 100644
> > > --- a/include/linux/acpi.h
> > > +++ b/include/linux/acpi.h
> > > @@ -316,12 +316,10 @@ static inline int acpi_processor_evaluate_cst(acpi_handle handle, u32 cpu,
> > > }
> > > #endif
> > > -#ifdef CONFIG_ACPI_HOTPLUG_PRESENT_CPU
> > > /* Arch dependent functions for cpu hotplug support */
> > > int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, u32 acpi_id,
> > > int *pcpu);
> > > int acpi_unmap_cpu(int cpu);
> >
> > I've lost track somewhat but I think the definitions of these are still under ifdefs
> > which is messy if nothing else and might cause build issues.
> >
>
> Yup, it's not safe to use 'if (!IS_ENABLED(CONFIG_ACPI_HOTPLUG_PRESENT_CPU))' in
> acpi_processor_make_present() until the ifdefs are removed for those two functions
> in individual architectures.
The same thing appears in a final patch that James seems to have added
to the repository:
ACPI: processor: Only call arch_unregister_cpu() if HOTPLUG_CPU is selected
in which acpi_processor_post_eject() has this change:
- if (!device)
+ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || !device)
I'm wondering if that's caused by a previous patch making the weak
definition of arch_unregister_cpu() dependent on HOTPLUG_CPU, and
whether dropping that ifdef around the function would be better. I
think I already asked that question, but this final patch seems to be
the confirmation that we need to provide a definition of it.
I think the reason James did it like that is because unregister_cpu()
is dependent upon CONFIG_HOTPLUG_CPU, but it's probably better to do:
#ifdef CONFIG_HOTPLUG_CPU
void __weak arch_unregister_cpu(int num)
{
unregister_cpu(&per_cpu(cpu_devices, num));
}
#else
void __weak arch_unregister_cpu(int num)
{
}
#endif
Agreed?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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