linux-kernel - Re: [Xen-devel] [patch 21/26] xen: Get rid of the last irq

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Date:	Mon, 24 Feb 2014 14:33:58 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Xen <xen-devel@...ts.xenproject.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [Xen-devel] [patch 21/26] xen: Get rid of the last irq_desc abuse

On 23/02/14 21:40, Thomas Gleixner wrote:
> I'd prefer to drop that completely but there seems to be some mystic
> value to the error printout and the allocation check.

    Warn if any PIRQ cannot be bound to an event channel.  Remove an
    unnecessary test for !desc in xen_destroy_irq() since the only caller
    will only do so if the irq was previously allocated.

> --- tip.orig/drivers/xen/events/events_base.c
> +++ tip/drivers/xen/events/events_base.c
[...]
> @@ -535,7 +528,7 @@ static unsigned int __startup_pirq(unsig
>  					BIND_PIRQ__WILL_SHARE : 0;
>  	rc = HYPERVISOR_event_channel_op(EVTCHNOP_bind_pirq, &bind_pirq);
>  	if (rc != 0) {
> -		if (!probing_irq(irq))
> +		if (!data || irqd_irq_has_action(data))
>  			pr_info("Failed to obtain physical IRQ %d\n", irq);

Remove this if and change the pr_info() to a pr_warn().

This hypercall never fails in practice, but it's still useful to have the
message in case on some systems it does.

>  		return 0;
>  	}
> @@ -769,15 +762,13 @@ error_irq:
>  
>  int xen_destroy_irq(int irq)
>  {
> -	struct irq_desc *desc;
>  	struct physdev_unmap_pirq unmap_irq;
>  	struct irq_info *info = info_for_irq(irq);
>  	int rc = -ENOENT;
>  
>  	mutex_lock(&irq_mapping_update_lock);
>  
> -	desc = irq_to_desc(irq);
> -	if (!desc)
> +	if (!irq_is_allocated(irq))
>  		goto out;

Remove this test.  The only caller of xen_destroy_irq() will only do
so if the irq was previously fully setup.

I think this means you don't need to introduce the irqd_irq_has_action()
and irq_is_allocated() helpers.

David
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