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

From: Jacob Pan <[email-masked]>
Date: Thu, 9 Jun 2022 16:49:21 -0700

, Arnd Bergmann <[email-masked]>, [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], palmer@dab
 belt.com, [email-masked], [email-masked], [email-masked], [email-masked]
Errors-To: linuxppc-dev-bounces+linuxppc-dev=[email-masked]
Sender: "Linuxppc-dev" <linuxppc-dev-bounces+linuxppc-dev=[email-masked]>

Hi Peter,

On Wed, 08 Jun 2022 16:27:27 +0200, Peter Zijlstra <[email-masked]>
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) <[email-masked]>
> ---
>  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