Re: [RFC PATCH v2 24/35] drivers: base: Implement weak arch_unregister_cpu()

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On 9/14/23 02:38, James Morse wrote:
Add arch_unregister_cpu() to allow the ACPI machinery to call
unregister_cpu(). This is enough for arm64, riscv and loongarch, but
needs to be overridden by x86 and ia64 who need to do more work.

CC: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
Signed-off-by: James Morse <james.morse@xxxxxxx>
---
Changes since v1:
  * Added CONFIG_HOTPLUG_CPU ifdeffery around unregister_cpu
---
  arch/ia64/include/asm/cpu.h      | 4 ----
  arch/loongarch/include/asm/cpu.h | 6 ------
  arch/x86/include/asm/cpu.h       | 1 -
  drivers/base/cpu.c               | 9 ++++++++-
  4 files changed, 8 insertions(+), 12 deletions(-)


I agree with Jonathan this patch needs to come early. Maybe move this
before the following one:

[RFC PATCH v2 19/35] ACPI: Move acpi_bus_trim_one() before acpi_scan_hot_remove()

diff --git a/arch/ia64/include/asm/cpu.h b/arch/ia64/include/asm/cpu.h
index a3e690e685e5..642d71675ddb 100644
--- a/arch/ia64/include/asm/cpu.h
+++ b/arch/ia64/include/asm/cpu.h
@@ -15,8 +15,4 @@ DECLARE_PER_CPU(struct ia64_cpu, cpu_devices);
DECLARE_PER_CPU(int, cpu_state); -#ifdef CONFIG_HOTPLUG_CPU
-extern void arch_unregister_cpu(int);
-#endif
-
  #endif /* _ASM_IA64_CPU_H_ */
diff --git a/arch/loongarch/include/asm/cpu.h b/arch/loongarch/include/asm/cpu.h
index b8568e637420..48b9f7168bcc 100644
--- a/arch/loongarch/include/asm/cpu.h
+++ b/arch/loongarch/include/asm/cpu.h
@@ -128,10 +128,4 @@ enum cpu_type_enum {
  #define LOONGARCH_CPU_HYPERVISOR	BIT_ULL(CPU_FEATURE_HYPERVISOR)
  #define LOONGARCH_CPU_PTW		BIT_ULL(CPU_FEATURE_PTW)
-#if !defined(__ASSEMBLY__)
-#ifdef CONFIG_HOTPLUG_CPU
-void arch_unregister_cpu(int cpu);
-#endif
-#endif /* ! __ASSEMBLY__ */
-
  #endif /* _ASM_CPU_H */
diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h
index f349c94510e8..91867a6a9f8e 100644
--- a/arch/x86/include/asm/cpu.h
+++ b/arch/x86/include/asm/cpu.h
@@ -24,7 +24,6 @@ static inline void prefill_possible_map(void) {}
  #endif /* CONFIG_SMP */
#ifdef CONFIG_HOTPLUG_CPU
-extern void arch_unregister_cpu(int);
  extern void soft_restart_cpu(void);
  #endif
diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 677f963e02ce..c709747c4a18 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -531,7 +531,14 @@ int __weak arch_register_cpu(int cpu)
  {
  	return register_cpu(&per_cpu(cpu_devices, cpu), cpu);
  }
-#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
+void __weak arch_unregister_cpu(int num)
+{
+	unregister_cpu(&per_cpu(cpu_devices, num));
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+#endif /* CONFIG_GENERIC_CPU_DEVICES */

It seems conflicting with its declaration in include/linux/cpu.h. Besides,
the function is still needed by drivers/acpi/acpi_processor.c::acpi_processor_make_not_present()
even both CONFIG_HOTPLUG_CPU and CONFIG_GENERIC_CPU_DEVICES are disabled?

  static void __init cpu_dev_register_generic(void)
  {

Thanks,
Gavin




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