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SubjectRe: [PATCH] i386 reduce spurious interrupt noise
On Thu, 2 Sep 2004, Chris Wedgwood wrote:

> i386 hardware can (and does) see spurious interrupts from time to
> tome. Ideally I would like the printk removed completely but this is
> probably good enough for now.
>
> Singed-of-By: Chris Wedgwood <cw@f00f.org>
>
> ===== arch/i386/kernel/apic.c 1.58 vs edited =====
> --- 1.58/arch/i386/kernel/apic.c 2004-08-26 23:30:31 -07:00
> +++ edited/arch/i386/kernel/apic.c 2004-09-02 12:19:19 -07:00
> @@ -1190,7 +1190,7 @@
> 6: Received illegal vector
> 7: Illegal register address
> */
> - printk (KERN_INFO "APIC error on CPU%d: %02lx(%02lx)\n",
> + printk (KERN_DEBUG "APIC error on CPU%d: %02lx(%02lx)\n",
> smp_processor_id(), v , v1);
> irq_exit();
> }

This should probably be KERN_ERR even. This is a serious condition -- if
you ever get such a message, then inter-APIC messages get corrupted and
this affects system's stability. E.g. with a badly corrupted message you
may get one or more of your processors halted if the matching destinations
misinterpret the delivery mode as a result. You certainly want to know
about these errors and perhaps get your hardware replaced (starting with
the PSU as they've been repeatedly reported to be the causers).

> ===== arch/i386/kernel/i8259.c 1.36 vs edited =====
> --- 1.36/arch/i386/kernel/i8259.c 2004-08-23 12:48:32 -07:00
> +++ edited/arch/i386/kernel/i8259.c 2004-09-02 12:20:49 -07:00
> @@ -226,7 +226,7 @@
> * lets ACK and report it. [once per IRQ]
> */
> if (!(spurious_irq_mask & irqmask)) {
> - printk("spurious 8259A interrupt: IRQ%d.\n", irq);
> + printk(KERN_DEBUG "spurious 8259A interrupt: IRQ%d.\n", irq);
> spurious_irq_mask |= irqmask;
> }
> atomic_inc(&irq_err_count);

You may ever get a single message per system boot from this line. It
encourages to have a look at the ERR counter in /proc/interrupts to check
for possible problems, though admittedly the suggestion isn't especially
clear.

Maciej
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