[PATCH v2] ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

[PATCH v2] ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

[Vitaly Kuznetsov]

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@intel.com>
Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
Cc: <stable@vger.kernel.org> # 5.10+
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
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.
+ */
+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

Re: [PATCH v2] ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

[Rafael J. Wysocki]

On Tue, Apr 6, 2021 at 4:01 PM Vitaly Kuznetsov <vkuznets@redhat.com> 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@intel.com>
> Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
> Cc: <stable@vger.kernel.org> # 5.10+
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> 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?

A proper kerneldoc would be something like:

/**
 * cond_wakeup_cpu0 - Wake up CPU0 if needed.
 *
 * If NMI wants to wake up CPU0, start CPU0.
 */

> +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
>

Re: [PATCH v2] ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

[Vitaly Kuznetsov]

"Rafael J. Wysocki" <rafael@kernel.org> writes:

> On Tue, Apr 6, 2021 at 4:01 PM Vitaly Kuznetsov <vkuznets@redhat.com> 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@intel.com>
>> Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
>> Cc: <stable@vger.kernel.org> # 5.10+
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> ---
>> 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

Re: [PATCH v2] ACPI: processor: Fix build when CONFIG_ACPI_PROCESSOR=m

[Rafael J. Wysocki]

On Tue, Apr 6, 2021 at 5:39 PM Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> "Rafael J. Wysocki" <rafael@kernel.org> writes:
>
> > On Tue, Apr 6, 2021 at 4:01 PM Vitaly Kuznetsov <vkuznets@redhat.com> 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@intel.com>
> >> Fixes: 8cdddd182bd7 ("CPI: processor: Fix CPU0 wakeup in acpi_idle_play_dead()")
> >> Cc: <stable@vger.kernel.org> # 5.10+
> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> >> ---
> >> 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.

Yes, please.

Exported functions generally need proper kerneldoc comments.