Use ifdef to guard reference to HOTPLUG_SMT symbols so HOTPLUG_PARALLEL
can be enabled without HOTPLUG_SMT being selected.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
 kernel/cpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 1209ddaec026..2ab3f68a1bb1 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1808,6 +1808,7 @@ static int __init parallel_bringup_parse_param(char *arg)
 }
 early_param("cpuhp.parallel", parallel_bringup_parse_param);
 
+#ifdef CONFIG_HOTPLUG_SMT
 static inline bool cpuhp_smt_aware(void)
 {
 	return cpu_smt_max_threads > 1;
@@ -1817,6 +1818,7 @@ static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
 {
 	return cpu_primary_thread_mask;
 }
+#endif
 
 /*
  * On architectures which have enabled parallel bringup this invokes all BP
@@ -1837,6 +1839,7 @@ static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
 	if (!__cpuhp_parallel_bringup)
 		return false;
 
+#ifdef CONFIG_HOTPLUG_SMT
 	if (cpuhp_smt_aware()) {
 		const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
 		static struct cpumask tmp_mask __initdata;
@@ -1857,6 +1860,7 @@ static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
 		cpumask_andnot(&tmp_mask, mask, pmask);
 		mask = &tmp_mask;
 	}
+#endif
 
 	/* Bring the not-yet started CPUs up */
 	cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);

-- 
2.45.2

On Fri, Jul 05 2024 at 11:29, Jiaxun Yang wrote:
>  
> +#ifdef CONFIG_HOTPLUG_SMT
>  static inline bool cpuhp_smt_aware(void)
>  {
>  	return cpu_smt_max_threads > 1;
> @@ -1817,6 +1818,7 @@ static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
>  {
>  	return cpu_primary_thread_mask;
>  }
> +#endif

Please provide stub functions in an #else clause

#else
static inline bool cpuhp_smt_aware(void) { return false; }
static inline cpumask *cpuhp_get_primary_thread_mask(void) { return NULL; }
#endif

or something to that effect.

>  /*
>   * On architectures which have enabled parallel bringup this invokes all BP
> @@ -1837,6 +1839,7 @@ static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
>  	if (!__cpuhp_parallel_bringup)
>  		return false;
>  
> +#ifdef CONFIG_HOTPLUG_SMT

That way you spare the ugly #ifdef here in the middle of the code and
the compiler can optimize it out.

>  	if (cpuhp_smt_aware()) {
>  		const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
>  		static struct cpumask tmp_mask __initdata;
> @@ -1857,6 +1860,7 @@ static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
>  		cpumask_andnot(&tmp_mask, mask, pmask);
>  		mask = &tmp_mask;
>  	}
> +#endif

Thanks,

        tglx