linux-kernel - Re: [PATCH 2/2] xen: implement IRQ_WORK

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Date:	Mon, 16 Apr 2012 16:32:10 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Lin Ming <mlin@...pku.edu.cn>
Cc:	linux-kernel@...r.kernel.org,
	Steven Noonan <steven@...inklabs.net>,
	Ben Guthro <ben@...hro.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Marcus Granado <marcus.granado@...rix.com>,
	xen-devel@...ts.xen.org
Subject: Re: [PATCH 2/2] xen: implement IRQ_WORK_VECTOR handler

On Sun, Apr 15, 2012 at 02:09:32PM +0800, Lin Ming wrote:
> Signed-off-by: Lin Ming <mlin@...pku.edu.cn>
> ---
>  arch/x86/include/asm/xen/events.h |    1 +
>  arch/x86/xen/smp.c                |   30 ++++++++++++++++++++++++++++++
>  2 files changed, 31 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/include/asm/xen/events.h b/arch/x86/include/asm/xen/events.h
> index 1df3541..cc146d5 100644
> --- a/arch/x86/include/asm/xen/events.h
> +++ b/arch/x86/include/asm/xen/events.h
> @@ -6,6 +6,7 @@ enum ipi_vector {
>  	XEN_CALL_FUNCTION_VECTOR,
>  	XEN_CALL_FUNCTION_SINGLE_VECTOR,
>  	XEN_SPIN_UNLOCK_VECTOR,
> +	XEN_IRQ_WORK_VECTOR,
>  
>  	XEN_NR_IPIS,
>  };
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 2dc6628..92ad12d 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -16,6 +16,7 @@
>  #include <linux/err.h>
>  #include <linux/slab.h>
>  #include <linux/smp.h>
> +#include <linux/irq_work.h>
>  
>  #include <asm/paravirt.h>
>  #include <asm/desc.h>
> @@ -41,10 +42,12 @@ cpumask_var_t xen_cpu_initialized_map;
>  static DEFINE_PER_CPU(int, xen_resched_irq);
>  static DEFINE_PER_CPU(int, xen_callfunc_irq);
>  static DEFINE_PER_CPU(int, xen_callfuncsingle_irq);
> +static DEFINE_PER_CPU(int, xen_irq_work);
>  static DEFINE_PER_CPU(int, xen_debug_irq) = -1;
>  
>  static irqreturn_t xen_call_function_interrupt(int irq, void *dev_id);
>  static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id);
> +static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id);
>  
>  /*
>   * Reschedule call back.
> @@ -143,6 +146,17 @@ static int xen_smp_intr_init(unsigned int cpu)
>  		goto fail;
>  	per_cpu(xen_callfuncsingle_irq, cpu) = rc;
>  
> +	callfunc_name = kasprintf(GFP_KERNEL, "irqwork%d", cpu);
> +	rc = bind_ipi_to_irqhandler(XEN_IRQ_WORK_VECTOR,
> +				    cpu,
> +				    xen_irq_work_interrupt,
> +				    IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
> +				    callfunc_name,
> +				    NULL);
> +	if (rc < 0)
> +		goto fail;
> +	per_cpu(xen_irq_work, cpu) = rc;
> +
>  	return 0;
>  
>   fail:
> @@ -155,6 +169,8 @@ static int xen_smp_intr_init(unsigned int cpu)
>  	if (per_cpu(xen_callfuncsingle_irq, cpu) >= 0)
>  		unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu),
>  				       NULL);
> +	if (per_cpu(xen_irq_work, cpu) >= 0)
> +		unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
>  
>  	return rc;
>  }
> @@ -509,6 +525,9 @@ static inline int xen_map_vector(int vector)
>  	case CALL_FUNCTION_SINGLE_VECTOR:
>  		xen_vector = XEN_CALL_FUNCTION_SINGLE_VECTOR;
>  		break;
> +	case IRQ_WORK_VECTOR:
> +		xen_vector = XEN_IRQ_WORK_VECTOR;
> +		break;
>  	default:
>  		xen_vector = -1;
>  		printk(KERN_ERR "xen: vector 0x%x is not implemented\n",
> @@ -588,6 +607,16 @@ static irqreturn_t xen_call_function_single_interrupt(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> +static irqreturn_t xen_irq_work_interrupt(int irq, void *dev_id)
> +{
> +	irq_enter();
> +	inc_irq_stat(apic_irq_work_irqs);
> +	irq_work_run();

I think this usually done the other way around:

irq_work_run()
inc_irq_stat(apic_irq_work_irqs)

Or is there an excellent reason for doing it this way?

> +	irq_exit();
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static const struct smp_ops xen_smp_ops __initconst = {
>  	.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu,
>  	.smp_prepare_cpus = xen_smp_prepare_cpus,
> @@ -634,6 +663,7 @@ static void xen_hvm_cpu_die(unsigned int cpu)
>  	unbind_from_irqhandler(per_cpu(xen_callfunc_irq, cpu), NULL);
>  	unbind_from_irqhandler(per_cpu(xen_debug_irq, cpu), NULL);
>  	unbind_from_irqhandler(per_cpu(xen_callfuncsingle_irq, cpu), NULL);
> +	unbind_from_irqhandler(per_cpu(xen_irq_work, cpu), NULL);
>  	native_cpu_die(cpu);
>  }
>  
> -- 
> 1.7.2.5
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