Re: [patch] Real-Time Preemption, -RT-2.6.10-rc1-mm3-V0.7.25-1

From: Ingo Molnar
Date: Sun Nov 14 2004 - 08:47:32 EST



* Shane Shrybman <shrybman@xxxxxx> wrote:

> -#define IOAPIC_POSTFLUSH
> +//#define IOAPIC_POSTFLUSH

> -#if defined(CONFIG_PREEMPT_HARDIRQS) && defined(CONFIG_SMP)
> +#if defined(CONFIG_PREEMPT_HARDIRQS)

unfortunately the POST-flush is still needed. Without it i can see lots
of spurious interrupts on SMP systems. (most likely caused by the ACK
reaching the IO-APIC _before_ the mask-the-irq PCI-space write [which
gets delayed in the chipset due to write optimizations], so the IO-APIC
still thinks that the IRQ is enabled and for level-triggered IRQs this
means that another interrupt is sent to the CPU.)

Ingo
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