[Xen-devel] Re: [PATCH] irq: Exclude percpu IRQs from being fixed up

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 16.02.11 at 15:26, "Zhang, Fengzhe" <fengzhe.zhang@xxxxxxxxx> wrote:
> irq: Exclude percpu IRQs from being fixed up
> 
> Xen spin unlock uses spurious ipi "lock_kicker_irq" to wake up blocked vCPUs 
> waiting on that lock. This irq should always be disabled. However, when Dom0 
> is shuting down, function fixup_irqs is called which unmasks all irqs. 
> Function unmask_irq effectively re-enables lock_kicker_irq and its irq 
> handler 
> is invoked which reports bug and crashes Dom0.
> 
> This patch sets IRQ_PER_CPU flag in irq desc and excludes percpu IRQs from 
> being fixed up when taking CPUs down.
> 
> Signed-off-by: Fengzhe Zhang <fengzhe.zhang@xxxxxxxxx>
> 
> diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
> index 977d8b4..f0f9450 100644
> --- a/arch/x86/kernel/irq_64.c
> +++ b/arch/x86/kernel/irq_64.c
> @@ -80,6 +80,9 @@ void fixup_irqs(void)
>               if (irq == 2)
>                       continue;
>  
> +             if (desc->status & IRQ_PER_CPU)
> +                     continue;
> +
>               /* interrupt's are disabled at this point */
>               spin_lock(&desc->lock);
>  
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index f34e231..26bc55a 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -727,10 +727,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, 
> struct irqaction *new)
>                               goto out_thread;
>               } else
>                       compat_irq_chip_set_default_handler(desc);
> -#if defined(CONFIG_IRQ_PER_CPU)

Why? XEN should select IRQ_PER_CPU instead in its Kconfig.

Jan

> +
>               if (new->flags & IRQF_PERCPU)
>                       desc->status |= IRQ_PER_CPU;
> -#endif
>  
>               desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
>                                 IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);



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