lenovo R60 SMP/APIC_IO woes

Matthew Dillon dillon at apollo.backplane.com
Sun Apr 22 23:10:36 PDT 2007

:In the last few hours I've noted about 24 'stray interrupt 7' messages while
:running SMP (no IOAPIC) .. I'm guessing that these are incorrectly routed

    No, its probably a summary interrupt from the IOAPIC.  Because the BIOS
    is stupid, hardware chipsets are often able to route *ALL* of the masked
    IOAPIC interrupts to a single PIC interrupt.  It's usually IRQ 7 or
    IRQ 15.  Since the method to disable this routing is not usually
    documented, we have no way of turning it off short of hoping that the
    BIOS knows how to do it when we use the IOAPIC.  Some IOAPICs 
    automatically route this special interrupt if their pins are masked.
    Unfortunately, pin masking is a normal part of our interrupt handling
    code (linux does something nutty to try to avoid pin masking).

    The only real solution is for us to not use IRQ 7 at all and just
    mask it out on the PIC.

:>     kern.emergency_intr_enable	(default 0 = off)
:>     kern.emergency_intr_freq	(default 10 = 10hz)
:Do these need to be set by the bootloader, I suppose so, eh ?

    It can be set by the bootloader and/or at run-time with a sysctl.

:Thanks for all the info, Matt!  As always you're a great help!
:. any ideas about my other problem (previous message) wrt 1/2 speed kernel builds?

    All I can think of is that its having real problems routing interrupts.
    Are you using emergency interrupt polling or does it work without that?

					Matthew Dillon 
					<dillon at backplane.com>

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