On Tue, Apr 6, 2021 at 2:50 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>
> ---
> arch/x86/include/asm/smp.h | 2 +-
> arch/x86/kernel/smpboot.c | 15 ++++++++++-----
> drivers/acpi/processor_idle.c | 3 +--
> 3 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 57ef2094af93..6f79deb1f970 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 wakeup_cpu0_if_needed(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..9547d870ee27 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1659,7 +1659,7 @@ void play_dead_common(void)
> local_irq_disable();
> }
>
> -bool wakeup_cpu0(void)
> +static bool wakeup_cpu0(void)
> {
> if (smp_processor_id() == 0 && enable_start_cpu0)
> return true;
> @@ -1667,6 +1667,13 @@ bool wakeup_cpu0(void)
> return false;
> }
>
> +void wakeup_cpu0_if_needed(void)
> +{
> + if (wakeup_cpu0())
> + start_cpu0();
Note that all of the callers of wakeup_cpu0 do the above, so maybe
make them all use the new function?
In which case it can be rewritten in the following way
void cond_wakeup_cpu0(void)
{
if (smp_processor_id() == 0 && enable_start_cpu0)
start_cpu0();
}
EXPORT_SYMBOL_GPL(cond_wakeup_cpu0);
Also please add a proper kerneldoc comment to it and maybe drop the
comments at the call sites?
> +}
> +EXPORT_SYMBOL_GPL(wakeup_cpu0_if_needed);
> +
> /*
> * We need to flush the caches before going to sleep, lest we have
> * dirty data in our caches when we come back up.
> @@ -1737,8 +1744,7 @@ static inline void mwait_play_dead(void)
> /*
> * If NMI wants to wake up CPU0, start CPU0.
> */
> - if (wakeup_cpu0())
> - start_cpu0();
> + wakeup_cpu0_if_needed();
> }
> }
>
> @@ -1752,8 +1758,7 @@ void hlt_play_dead(void)
> /*
> * If NMI wants to wake up CPU0, start CPU0.
> */
> - if (wakeup_cpu0())
> - start_cpu0();
> + wakeup_cpu0_if_needed();
> }
> }
>
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 768a6b4d2368..de15116b754a 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -545,8 +545,7 @@ static int acpi_idle_play_dead(struct cpuidle_device *dev, int index)
>
> #if defined(CONFIG_X86) && defined(CONFIG_HOTPLUG_CPU)
> /* If NMI wants to wake up CPU0, start CPU0. */
> - if (wakeup_cpu0())
> - start_cpu0();
> + wakeup_cpu0_if_needed();
> #endif
> }
>
> --
> 2.30.2
>
