lkml.org 
[lkml]   [2004]   [Apr]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: IO-APIC on nforce2 [PATCH] + [PATCH] for nmi_debug=1 + [PATCH] for idle=C1halt, 2.6.5
    On Thu, 22 Apr 2004, Len Brown wrote:

    > date seems to gain 9sec/hour on my Shuttle/SN41G2/FN41 when using IOAPIC
    > timer.
    >
    > booted with "noapic" for XT-PIC timer, it stays locked
    > onto my wristwatch after an hour. If the workaround is disabled,
    > and XT-PIC timer is used, it matches the "noapic" behaviour -- no drift.
    >
    > I can't explain it. I think it is a timer problem independent of the
    > IRQ routing.
    >
    > -Len
    >
    > ps. when i ran in XT-PIC mode there were lots of ERR's registered in
    > /proc/interrupts -- doesn't look healthy.

    It looks like a noise on the timer IRQ line causing spurious interrupt
    edges. In the XT-PIC mode it gets ignored -- at the time the CPU issues
    an ack, the request is already gone and the PIC signals a spurious
    interrupt. In the APIC mode the interrupt is delivered as a regular one
    as edge interrupt events are persistent for the APICs -- if a falling edge
    happens before an interrupt is acked it's not assumed to be gone and is
    delivered as a real one.

    Another possibility is there's a bug in our APIC interrupt setup, leading
    to the timer interrupt being enabled both in the APIC and in the PIC.
    You can verify that by calling debug functions for dumping states of the
    controllers from io_apic.c. They are print_IO_APIC(), print_local_APIC()
    and print_PIC() -- you may call them from an ad-hoc written small module,
    although the first one is (accidentally?) marked __init, so you'd have to
    remove the mark first. You need to call all of them to get a complete
    view.

    Maciej

    --
    + Maciej W. Rozycki, Technical University of Gdansk, Poland +
    +--------------------------------------------------------------+
    + e-mail: macro@ds2.pg.gda.pl, PGP key available +
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2005-03-22 14:02    [W:0.023 / U:88.580 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site