"Rafael J. Wysocki" <rafael@xxxxxxxxxx> writes:
> On Tue, Apr 6, 2021 at 4:01 PM Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote:
>>
>> Commit 8cdddd182bd7 ("ACPI: processor: Fix CPU0 wakeup in
>> acpi_idle_play_dead()") tried to fix CPU0 hotplug breakage by copying
>> wakeup_cpu0() + start_cpu0() logic from hlt_play_dead()//mwait_play_dead()
>> into acpi_idle_play_dead(). The problem is that these functions are not
>> exported to modules so when CONFIG_ACPI_PROCESSOR=m build fails.
>>
>> The issue could've been fixed by exporting both wakeup_cpu0()/start_cpu0()
>> (the later from assembly) but it seems putting the whole pattern into a
>> new function and exporting it instead is better.
>>
>> Reported-by: kernel test robot <lkp@xxxxxxxxx>
>> Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
>> Cc: <stable@xxxxxxxxxxxxxxx> # 5.10+
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
>> ---
>> Changes since v1:
>> - Rename wakeup_cpu0() to cond_wakeup_cpu0() and fold wakeup_cpu0() in
>> as it has no other users [Rafael J. Wysocki]
>> ---
>> arch/x86/include/asm/smp.h | 2 +-
>> arch/x86/kernel/smpboot.c | 24 ++++++++++--------------
>> drivers/acpi/processor_idle.c | 4 +---
>> 3 files changed, 12 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
>> index 57ef2094af93..630ff08532be 100644
>> --- a/arch/x86/include/asm/smp.h
>> +++ b/arch/x86/include/asm/smp.h
>> @@ -132,7 +132,7 @@ void native_play_dead(void);
>> void play_dead_common(void);
>> void wbinvd_on_cpu(int cpu);
>> int wbinvd_on_all_cpus(void);
>> -bool wakeup_cpu0(void);
>> +void cond_wakeup_cpu0(void);
>>
>> void native_smp_send_reschedule(int cpu);
>> void native_send_call_func_ipi(const struct cpumask *mask);
>> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
>> index f877150a91da..147f1bba9736 100644
>> --- a/arch/x86/kernel/smpboot.c
>> +++ b/arch/x86/kernel/smpboot.c
>> @@ -1659,13 +1659,15 @@ void play_dead_common(void)
>> local_irq_disable();
>> }
>>
>> -bool wakeup_cpu0(void)
>> +/*
>> + * If NMI wants to wake up CPU0, start CPU0.
>> + */
>
> Hasn't checkpatch.pl complained about this?
>
No, it didn't.
> A proper kerneldoc would be something like:
>
> /**
> * cond_wakeup_cpu0 - Wake up CPU0 if needed.
> *
> * If NMI wants to wake up CPU0, start CPU0.
> */
Yea, I didn't do that partly because of my laziness but partly because
I don't see much usage of this format in arch/x86/kernel/[smpboot.c]. I
can certainly do v3 if it's prefered.
>
>> +void cond_wakeup_cpu0(void)
>> {
>> if (smp_processor_id() == 0 && enable_start_cpu0)
>> - return true;
>> -
>> - return false;
>> + start_cpu0();
>> }
>> +EXPORT_SYMBOL_GPL(cond_wakeup_cpu0);
>>
>> /*
>> * We need to flush the caches before going to sleep, lest we have
>> @@ -1734,11 +1736,8 @@ static inline void mwait_play_dead(void)
>> __monitor(mwait_ptr, 0, 0);
>> mb();
>> __mwait(eax, 0);
>> - /*
>> - * If NMI wants to wake up CPU0, start CPU0.
>> - */
>> - if (wakeup_cpu0())
>> - start_cpu0();
>> +
>> + cond_wakeup_cpu0();
>> }
>> }
>>
>> @@ -1749,11 +1748,8 @@ void hlt_play_dead(void)
>>
>> while (1) {
>> native_halt();
>> - /*
>> - * If NMI wants to wake up CPU0, start CPU0.
>> - */
>> - if (wakeup_cpu0())
>> - start_cpu0();
>> +
>> + cond_wakeup_cpu0();
>> }
>> }
>>
>> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
>> index 768a6b4d2368..4e2d76b8b697 100644
>> --- a/drivers/acpi/processor_idle.c
>> +++ b/drivers/acpi/processor_idle.c
>> @@ -544,9 +544,7 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
>> return -ENODEV;
>>
>> #if defined(CONFIG_X86) && defined(CONFIG_HOTPLUG_CPU)
>> - /* If NMI wants to wake up CPU0, start CPU0. */
>> - if (wakeup_cpu0())
>> - start_cpu0();
>> + cond_wakeup_cpu0();
>> #endif
>> }
>>
>> --
>> 2.30.2
>>
>
--
Vitaly
