architectures often have extra per-cpu work that needs doing before a CPU is registered, often to determine if a CPU is hotpluggable.
To allow more architectures to use GENERIC_CPU_DEVICES, wrap the call as a __weak arch_register_cpu(). This aligns with the way x86, ia64 and loongarch register hotplug CPUs when they become present.
ACPI's acpi_processor.c also has a __weak version of this symbol because arm64 doesn't define one. The duplicate __weak definitions are only a problem if arm64 selects GENERIC_CPU_DEVICES without defining one. This gets fixed up in later patches.
Signed-off-by: James Morse james.morse@arm.com --- arch/ia64/include/asm/cpu.h | 1 - arch/loongarch/include/asm/cpu.h | 1 - arch/x86/include/asm/cpu.h | 1 - drivers/base/cpu.c | 14 ++++++++++---- include/linux/cpu.h | 5 +++++ 5 files changed, 15 insertions(+), 7 deletions(-)
diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h index db125df9e088..a3e690e685e5 100644 --- a/arch/ia64/include/asm/cpu.h +++ b/arch/ia64/include/asm/cpu.h @@ -16,7 +16,6 @@ DECLARE_PER_CPU(struct ia64_cpu, cpu_devices); DECLARE_PER_CPU(int, cpu_state);
#ifdef CONFIG_HOTPLUG_CPU -extern int arch_register_cpu(int num); extern void arch_unregister_cpu(int); #endif
diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h index 96d006c59149..ee5703fa4121 100644 --- a/arch/loongarch/include/asm/cpu.h +++ b/arch/loongarch/include/asm/cpu.h @@ -126,7 +126,6 @@ enum cpu_type_enum {
#if !defined(__ASSEMBLY__) #ifdef CONFIG_HOTPLUG_CPU -int arch_register_cpu(int num); void arch_unregister_cpu(int num); #endif #endif /* ! __ASSEMBLY__ */ diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index 8cbf623f0ecf..f06b05843c45 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -28,7 +28,6 @@ struct x86_cpu { };
#ifdef CONFIG_HOTPLUG_CPU -extern int arch_register_cpu(int num); extern void arch_unregister_cpu(int); extern void start_cpu0(void); #ifdef CONFIG_DEBUG_HOTPLUG_CPU0 diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index cf6407c34ede..178936533d87 100644 --- a/drivers/base/cpu.c +++ b/drivers/base/cpu.c @@ -492,19 +492,25 @@ bool cpu_is_hotpluggable(unsigned int cpu) EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
#ifdef CONFIG_GENERIC_CPU_DEVICES -static DEFINE_PER_CPU(struct cpu, cpu_devices); +DEFINE_PER_CPU(struct cpu, cpu_devices); + +int __weak arch_register_cpu(int cpu) +{ + return register_cpu(&per_cpu(cpu_devices, cpu), cpu); +} #endif
static void __init cpu_dev_register_generic(void) { -#ifdef CONFIG_GENERIC_CPU_DEVICES int i;
+ if (!IS_ENABLED(CONFIG_GENERIC_CPU_DEVICES)) + return; + for_each_present_cpu(i) { - if (register_cpu(&per_cpu(cpu_devices, i), i)) + if (arch_register_cpu(i)) panic("Failed to register CPU device"); } -#endif }
#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 314802f98b9d..86e79e702325 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -75,12 +75,17 @@ extern __printf(4, 5) struct device *cpu_device_create(struct device *parent, void *drvdata, const struct attribute_group **groups, const char *fmt, ...); +extern int arch_register_cpu(int cpu); #ifdef CONFIG_HOTPLUG_CPU extern void unregister_cpu(struct cpu *cpu); extern ssize_t arch_cpu_probe(const char *, size_t); extern ssize_t arch_cpu_release(const char *, size_t); #endif
+#ifdef CONFIG_GENERIC_CPU_DEVICES +DECLARE_PER_CPU(struct cpu, cpu_devices); +#endif + /* * These states are not related to the core CPU hotplug mechanism. They are * used by various (sub)architectures to track internal state