Duplicated hardware interrupts

Doug White dwhite at gumbysoft.com
Wed Mar 2 03:13:12 GMT 2005

On Tue, 1 Mar 2005, Peter Jeremy wrote:

> Whilst tracking down some interrupt latency problems, I've found that
> I'm getting duplicate interrupts from some, but not all, devices.  The
> double interrupts appear to always occur for some IRQs and never occur
> on others.  Based on those symptoms, I wonder if there's a hardware
> issue.

That sounds like interrupt routing problems. If you're running UP, try
running this in loader before booting:

set hint.apic.0.disabled=1

If things improve then your I/O APIC or routing information is bad, which
isn't unusual for UP systems.  Remove "device apic" from your kernel or
add the hint to device.hints or loader.conf.  I need this on my KT400 at

> The system is a GigaByte GA-7VRX-P motherboard (VIA KT333) with an
> Athlon XP-1800 running 5.3-RELEASE-p5 with APIC and ACPI:
> CPU: AMD Athlon(tm) XP 1800+ (1533.40-MHz 686-class CPU)
>   Origin = "AuthenticAMD"  Id = 0x662  Stepping = 2
>   AMD Features=0xc0480000<MP,AMIE,DSP,3DNow!>
> real memory  = 536805376 (511 MB)
> avail memory = 515629056 (491 MB)
> ioapic0 <Version 0.2> irqs 0-23 on motherboard
> ...
> acpi0: <AMIINT AMIINI09> on motherboard
> I'm not seeing duplicate interrupts on atkbd0, rtc, fdc0, psm0 and ata0.
> I am seeing duplicate interrupts on drm0, rl0 and my video capture card.
> FWIW, the kernel code I'm using to check the interrupts is attached.
> Userland just mmap's the buffer, converts it to ASCII and dumps it to
> disk for later processing.
> Has anyone else seen anything like this?

Doug White                    |  FreeBSD: The Power to Serve
dwhite at gumbysoft.com          |  www.FreeBSD.org

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