linux-kernel - Re: [RFC PATCH] genirq: Avoid unnecessary low level irq function calls

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Date:   Mon, 26 Jun 2017 10:20:44 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
cc:     linux-kernel@...r.kernel.org, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org
Subject: Re: [RFC PATCH] genirq: Avoid unnecessary low level irq function
 calls

Jeffy,

On Mon, 26 Jun 2017, Jeffy Chen wrote:
>  void irq_enable(struct irq_desc *desc)
>  {
> -	irq_state_clr_disabled(desc);
> -	if (desc->irq_data.chip->irq_enable)
> -		desc->irq_data.chip->irq_enable(&desc->irq_data);
> -	else
> -		desc->irq_data.chip->irq_unmask(&desc->irq_data);
> -	irq_state_clr_masked(desc);
> +	if (irqd_is_started(&desc->irq_data) &&
> +	    !irqd_irq_disabled(&desc->irq_data)) {
> +		unmask_irq(desc);

I'm having a hard time to understand the logic here.

    if (started && !disabled)
    	unmask()

That does not make any sense. If you need that to work around a state
inconsistency then it needs to be addressed there and not worked around
here.

> +	} else {
> +		irq_state_clr_disabled(desc);
> +		if (desc->irq_data.chip->irq_enable) {
> +			desc->irq_data.chip->irq_enable(&desc->irq_data);
> +			irq_state_clr_masked(desc);
> +		} else {
> +			unmask_irq(desc);
> +		}
> +	}
>  }
>  
>  static void __irq_disable(struct irq_desc *desc, bool mask)
>  {
> -	irq_state_set_disabled(desc);
> -	if (desc->irq_data.chip->irq_disable) {
> -		desc->irq_data.chip->irq_disable(&desc->irq_data);
> -		irq_state_set_masked(desc);
> -	} else if (mask) {
> -		mask_irq(desc);
> +	if (irqd_irq_disabled(&desc->irq_data)) {
> +		if (mask)
> +			mask_irq(desc);
> +	} else {
> +		irq_state_set_disabled(desc);
> +		if (desc->irq_data.chip->irq_disable) {
> +			desc->irq_data.chip->irq_disable(&desc->irq_data);
> +			irq_state_set_masked(desc);
> +		} else if (mask) {
> +			mask_irq(desc);
> +		}
>  	}
>  }
>  
> @@ -311,18 +322,21 @@ void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu)
>  
>  static inline void mask_ack_irq(struct irq_desc *desc)
>  {
> -	if (desc->irq_data.chip->irq_mask_ack)
> +	if (desc->irq_data.chip->irq_mask_ack) {
>  		desc->irq_data.chip->irq_mask_ack(&desc->irq_data);
> -	else {
> -		desc->irq_data.chip->irq_mask(&desc->irq_data);
> +		irq_state_set_masked(desc);
> +	} else {
> +		mask_irq(desc);
>  		if (desc->irq_data.chip->irq_ack)
>  			desc->irq_data.chip->irq_ack(&desc->irq_data);
>  	}
> -	irq_state_set_masked(desc);
>  }
>  
>  void mask_irq(struct irq_desc *desc)
>  {
> +	if (irqd_irq_masked(&desc->irq_data))
> +		return;
> +
>  	if (desc->irq_data.chip->irq_mask) {
>  		desc->irq_data.chip->irq_mask(&desc->irq_data);
>  		irq_state_set_masked(desc);
> @@ -331,6 +345,10 @@ void mask_irq(struct irq_desc *desc)
>  
>  void unmask_irq(struct irq_desc *desc)
>  {
> +	if (irqd_is_started(&desc->irq_data) &&
> +	    !irqd_irq_masked(&desc->irq_data))
> +		return;

Ditto.

Thanks,

	tglx