Re: [PATCH 2/2] x86, sched: Fix the undefined reference building error of init_freq_invariance_cppc

[Rafael J. Wysocki]

On Thu, Jan 6, 2022 at 6:12 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Thu, Jan 6, 2022 at 8:43 AM Huang Rui <ray.huang@xxxxxxx> wrote:
> >
> > The init_freq_invariance_cppc function is implemented in smpboot and depends on
> > CONFIG_SMP.
> >
> >   MODPOST vmlinux.symvers
> >   MODINFO modules.builtin.modinfo
> >   GEN     modules.builtin
> >   LD      .tmp_vmlinux.kallsyms1
> > ld: drivers/acpi/cppc_acpi.o: in function `acpi_cppc_processor_probe':
> > /home/ray/brahma3/linux/drivers/acpi/cppc_acpi.c:819: undefined reference to `init_freq_invariance_cppc'
> > make: *** [Makefile:1161: vmlinux] Error 1
> >
> > See https://lore.kernel.org/lkml/484af487-7511-647e-5c5b-33d4429acdec@xxxxxxxxxxxxx/.
> >
> > Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Reported-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
> > Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> > Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> >  arch/x86/include/asm/topology.h | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
> > index cc164777e661..2f0b6be8eaab 100644
> > --- a/arch/x86/include/asm/topology.h
> > +++ b/arch/x86/include/asm/topology.h
> > @@ -221,7 +221,7 @@ static inline void arch_set_max_freq_ratio(bool turbo_disabled)
> >  }
> >  #endif
> >
> > -#ifdef CONFIG_ACPI_CPPC_LIB
> > +#if defined(CONFIG_ACPI_CPPC_LIB) && defined(CONFIG_SMP)
> >  void init_freq_invariance_cppc(void);
> >  #define init_freq_invariance_cppc init_freq_invariance_cppc
>
> Why don't you check CONFIG_SMP instead of this symbol in cppc_acpi.c?
> That file depends on CONFIG_ACPI_CPPC_LIB anyway.

Scratch that, it needs to compile on non-x86 too.

The $subject patch is cleaner than all of the alternatives I have
considered, so I'm going to apply it.

However, I'm not really happy with the dependencies between CPPC and
smpboot.c going both ways.