Messages in this thread | | | Subject | Re: [PATCH 0/7] Boot IRQ quirks and rerouting | From | Jon Masters <> | Date | Wed, 04 Jun 2008 14:44:00 -0400 |
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On Wed, 2008-06-04 at 11:49 +0200, Stefan Assmann wrote:
> On the chips (ICHx, ...) we saw, the interrupt lines on the PIC also go > to the first IO-APIC. So the boot interrupts go to both the PIC and the > first IO-APIC.
Yup, it's system dependent too, but it's a mess in many cases. I've seen numerous systems falling over - typically, the classical case will be some IO controller when under heavy load will stop doing interrupts. Another gotcha is that a lot of the time, these legacy interrupt (boot interrupts) happen to be shared between e.g. a disk controller and a USB host controller. On a server system running -RT, it's quite common that there won't be much going on with the other device, so the problem goes unnoticed for a long time...but it still bites you in the end.
> When running in APIC mode all PIC IRQs are disabled, except for the > timer maybe. Boot interrupts still arrive on the first IO-APIC and end > up as being counted as spurious interrupts.
Yup. I think the good thing is that both SuSE and Red Hat have identified the same problems, posited the same root cause, and contemplated similar workarounds...so I think we understand it.
Jon.
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