Re: [PATCH 04/36] cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE

[Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>]

Hi Peter,

On Wed, 08 Jun 2022 16:27:27 +0200, Peter Zijlstra <peterz@xxxxxxxxxxxxx>
wrote:

> Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
> Xeons") wrecked intel_idle in two ways:
> 
>  - must not have tracing in idle functions
>  - must return with IRQs disabled
> 
> Additionally, it added a branch for no good reason.
> 
> Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on Xeons")
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
>  drivers/idle/intel_idle.c |   48
> +++++++++++++++++++++++++++++++++++----------- 1 file changed, 37
> insertions(+), 11 deletions(-)
> 
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -129,21 +137,37 @@ static unsigned int mwait_substates __in
>   *
>   * Must be called under local_irq_disable().
>   */
nit: this comment is no long true, right?

> +
> -static __cpuidle int intel_idle(struct cpuidle_device *dev,
> -                             struct cpuidle_driver *drv, int index)
> +static __always_inline int __intel_idle(struct cpuidle_device *dev,
> +                                     struct cpuidle_driver *drv, int
> index) {
>       struct cpuidle_state *state = &drv->states[index];
>       unsigned long eax = flg2MWAIT(state->flags);
>       unsigned long ecx = 1; /* break on interrupt flag */
>  
> -     if (state->flags & CPUIDLE_FLAG_IRQ_ENABLE)
> -             local_irq_enable();
> -
>       mwait_idle_with_hints(eax, ecx);
>  
>       return index;
>  }
>  
> +static __cpuidle int intel_idle(struct cpuidle_device *dev,
> +                             struct cpuidle_driver *drv, int index)
> +{
> +     return __intel_idle(dev, drv, index);
> +}
> +
> +static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,
> +                                 struct cpuidle_driver *drv, int
> index) +{
> +     int ret;
> +
> +     raw_local_irq_enable();
> +     ret = __intel_idle(dev, drv, index);
> +     raw_local_irq_disable();
> +
> +     return ret;
> +}
> +
>  /**
>   * intel_idle_s2idle - Ask the processor to enter the given idle state.
>   * @dev: cpuidle device of the target CPU.
> @@ -1801,6 +1824,9 @@ static void __init intel_idle_init_cstat
>               /* Structure copy. */
>               drv->states[drv->state_count] =
> cpuidle_state_table[cstate]; 
> +             if (cpuidle_state_table[cstate].flags &
> CPUIDLE_FLAG_IRQ_ENABLE)
> +                     drv->states[drv->state_count].enter =
> intel_idle_irq; +
>               if ((disabled_states_mask & BIT(drv->state_count)) ||
>                   ((icpu->use_acpi || force_use_acpi) &&
>                    intel_idle_off_by_default(mwait_hint) &&
> 
> 


Thanks,

Jacob