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

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)

+               if (desc->status&  IRQ_PER_CPU)
+                       continue;
                /* interrupt's are disabled at this point */

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
-#if defined(CONFIG_IRQ_PER_CPU)

Why? XEN should select IRQ_PER_CPU instead in its Kconfig.


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.


                if (new->flags&  IRQF_PERCPU)
                        desc->status |= IRQ_PER_CPU;

                desc->status&= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
                                  IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);

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