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 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.