linux-kernel - Re: [PATCH 1/3] irq: Allow to pass the IRQF

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Date:   Thu, 22 Jun 2017 10:31:46 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org,
        Jens Axboe <axboe@...nel.dk>, Hannes Reinecke <hare@...e.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 1/3] irq: Allow to pass the IRQF_TIMER flag with percpu
 irq request

Hi Daniel,

On Tue, Jun 20, 2017 at 11:28:55PM +0200, Daniel Lezcano wrote:
> In the next changes, we track when the interrupts occur in order to
> statistically compute when is supposed to happen the next interrupt.
> 
> In all the interruptions, it does not make sense to store the timer interrupt
> occurences and try to predict the next interrupt as we know the expiration
> time.
> 
> The request_irq() has a irq flags parameter and the timer drivers use it to
> pass the IRQF_TIMER flag, letting us know the interrupt is coming from a timer.
> Based on this flag, we can discard these interrupts when tracking them.
> 
> But, the API request_percpu_irq does not allow to pass a flag, hence specifying
> if the interrupt type is a timer.
> 
> Add a function __request_percpu_irq() where we can specify the flags. The
> request_percpu_irq() function is changed to be a wrapper to
> __request_percpu_irq() passing a zero flag parameter.
> 
> For now, in order to prevent a misusage of this parameter, only the IRQF_TIMER
> flag (or zero) is a valid parameter to be passed to the
> __request_percpu_irq() function.
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Mark Rutland <mark.rutland@....com>

Sorry for leading you round the garden path on the naming.

FWIW:

Acked-by: Mark Rutland <mark.rutland@....com>

Thanks,
Mark.

> ---
> Changelog:
> 
>    V11:
> 	- Drop the changes in the timer drivers and rename the function
> 	  request_percpu_irq_flags to __request_percpu_irq.
>    V10:
> 	- Drop the change for arch arm virtual timer
> 	  https://lkml.org/lkml/2017/4/25/184
>    V9:
> 	- Clarified the patch description
> 	- Fixed EXPORT_SYMBOL_GPL(request_percpu_irq_flags)
> 
> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
> ---
>  include/linux/interrupt.h | 11 ++++++++++-
>  kernel/irq/manage.c       | 15 ++++++++++-----
>  2 files changed, 20 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index a6fba48..d4ae50e 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -152,8 +152,17 @@ request_any_context_irq(unsigned int irq, irq_handler_t handler,
>  			unsigned long flags, const char *name, void *dev_id);
>  
>  extern int __must_check
> +__request_percpu_irq(unsigned int irq, irq_handler_t handler,
> +		     unsigned long flags, const char *devname,
> +		     void __percpu *percpu_dev_id);
> +
> +static inline int __must_check
>  request_percpu_irq(unsigned int irq, irq_handler_t handler,
> -		   const char *devname, void __percpu *percpu_dev_id);
> +		   const char *devname, void __percpu *percpu_dev_id)
> +{
> +	return __request_percpu_irq(irq, handler, 0,
> +				    devname, percpu_dev_id);
> +}
>  
>  extern const void *free_irq(unsigned int, void *);
>  extern void free_percpu_irq(unsigned int, void __percpu *);
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 4c34696..5424cfb 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -1974,9 +1974,10 @@ int setup_percpu_irq(unsigned int irq, struct irqaction *act)
>  }
>  
>  /**
> - *	request_percpu_irq - allocate a percpu interrupt line
> + *	__request_percpu_irq - allocate a percpu interrupt line
>   *	@irq: Interrupt line to allocate
>   *	@handler: Function to be called when the IRQ occurs.
> + *	@flags: Interrupt type flags (IRQF_TIMER only)
>   *	@devname: An ascii name for the claiming device
>   *	@dev_id: A percpu cookie passed back to the handler function
>   *
> @@ -1989,8 +1990,9 @@ int setup_percpu_irq(unsigned int irq, struct irqaction *act)
>   *	the handler gets called with the interrupted CPU's instance of
>   *	that variable.
>   */
> -int request_percpu_irq(unsigned int irq, irq_handler_t handler,
> -		       const char *devname, void __percpu *dev_id)
> +int __request_percpu_irq(unsigned int irq, irq_handler_t handler,
> +			 unsigned long flags, const char *devname,
> +			 void __percpu *dev_id)
>  {
>  	struct irqaction *action;
>  	struct irq_desc *desc;
> @@ -2004,12 +2006,15 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
>  	    !irq_settings_is_per_cpu_devid(desc))
>  		return -EINVAL;
>  
> +	if (flags && flags != IRQF_TIMER)
> +		return -EINVAL;
> +
>  	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
>  	if (!action)
>  		return -ENOMEM;
>  
>  	action->handler = handler;
> -	action->flags = IRQF_PERCPU | IRQF_NO_SUSPEND;
> +	action->flags = flags | IRQF_PERCPU | IRQF_NO_SUSPEND;
>  	action->name = devname;
>  	action->percpu_dev_id = dev_id;
>  
> @@ -2030,7 +2035,7 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
>  
>  	return retval;
>  }
> -EXPORT_SYMBOL_GPL(request_percpu_irq);
> +EXPORT_SYMBOL_GPL(__request_percpu_irq);
>  
>  /**
>   *	irq_get_irqchip_state - returns the irqchip state of a interrupt.
> -- 
> 2.7.4
>