"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