From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Jan Beulich" <JBeulich@novell.com>
Subject: Re: [PATCH] irq: Exclude percpu IRQs from being fixed up
Date: Wed, 16 Feb 2011 14:53:34 +0000
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To: Fengzhe Zhang <fengzhe.zhang@intel.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, xen-devel <xen-devel@lists.xensource.com>, Eddie Dong <eddie.dong@intel.com>, Xin Li <xin.li@intel.com>
List-Id: xen-devel@lists.xenproject.org

>>> On 16.02.11 at 15:26, "Zhang, Fengzhe" <fengzhe.zhang@intel.com> =
wrote:
> irq: Exclude percpu IRQs from being fixed up
>=20
> Xen spin unlock uses spurious ipi "lock_kicker_irq" to wake up blocked =
vCPUs=20
> waiting on that lock. This irq should always be disabled. However, when =
Dom0=20
> is shuting down, function fixup_irqs is called which unmasks all =
irqs.=20
> Function unmask_irq effectively re-enables lock_kicker_irq and its irq =
handler=20
> is invoked which reports bug and crashes Dom0.
>=20
> This patch sets IRQ_PER_CPU flag in irq desc and excludes percpu IRQs =
from=20
> being fixed up when taking CPUs down.
>=20
> Signed-off-by: Fengzhe Zhang <fengzhe.zhang@intel.com>
>=20
> 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 =3D=3D 2)
>  			continue;
> =20
> +		if (desc->status & IRQ_PER_CPU)
> +			continue;
> +
>  		/* interrupt's are disabled at this point */
>  		spin_lock(&desc->lock);
> =20
> 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,=20
> 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 |=3D IRQ_PER_CPU;
> -#endif
> =20
>  		desc->status &=3D ~(IRQ_AUTODETECT | IRQ_WAITING | =
IRQ_ONESHOT |
>  				  IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);