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

[Fengzhe Zhang <fengzhe.zhang@xxxxxxxxx>]

On 2011/2/16 22:53, Jan Beulich wrote:
> > > > 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
IRQ_PER_CPU switch is not found in current Kconfig. I'm not sure if this 
feature is going to be brought back in the short term. I remove the 
ifdef to set IRQ_PER_CPU flag in desc by default but still leave the IRQ 
handling logic unchanged. This is a temporary solution to fix system 
crash on poweroff. And this is the fix with minimum impact among the 
several solutions we tried.
-Fengzhe

> > +
> >                 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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