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    SubjectRe: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]
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    On Mon, 2004-11-01 at 12:55 -0500, Lee Revell wrote:
    > I think there might even be a _very_ rare errant irq disable in T3 even.
    > On my 2-day test runs with 100s of millions of samples, I got 2 or 3
    > outliers in each graph. Jow Gwinn from LKML (thanks Joe) ran a
    > statistical analysis that showed these to be independent from the 4 or 5
    > underlying exponential distributions (each corresponding to a known or
    > suspected nonpreemptible section). Our theory was that these were very
    > rare code paths or race conditions that left IRQs off. Unfortunately
    > this seems impossible to debug unless you have a way to make the machine
    > crash dump immediately when it detects the situation.
    >
    > Anyway, the clearest way to demonstrate the problem with the -V series
    > here is to run the version of Florian's tool that tells you how many
    > interrupts were missed. If I spin my (USB, not sharing irq with
    > soundcard) trackball as fast as I can I can get it up to 54 or 55 in a
    > row. If I move it just the right way I can see the humps appear - 2,
    > then 15, then 50 then 15 then 2 missed interrupts in a row. This is at
    > 1024Hz - at 2048 I can get it to miss several hundred IRQs, but this
    > inevitably locks the machine.
    >
    > I suspect the lockups and the latencies are same bug.

    Until now there was no output on lockup. No I got one.
    The command was: cat /proc/interrupts

    Hope that helps

    tglx

    cat/1488: BUG in down_mutex
    at /work/thomas/Linux/2.6.9-mm1-RT/lib/rwsem-generic.c:1059
    [<c01ca9e2>] down_mutex+0x72/0x80 (8)
    [<c012db9a>] __mutex_lock+0x2a/0x40 (36)
    [<c012dbc7>] _mutex_lock+0x17/0x20 (12)
    [<c013fd62>] kfree+0x52/0xf0 (8)
    [<c013fd62>] kfree+0x52/0xf0 (4)
    [<c01774a2>] single_release+0x32/0x40 (32)
    [<c01571ba>] __fput+0x13a/0x150 (20)
    [<c0155899>] filp_close+0x59/0x90 (32)
    [<c015593f>] sys_close+0x6f/0xa0 (24)
    [<c010603b>] syscall_call+0x7/0xb (28)


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