lkml.org 
[lkml]   [2004]   [Nov]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [Fwd: Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0.4]

    * Lee Revell <rlrevell@joe-job.com> wrote:

    > This was my conclusion as well. I have a patch sitting around to add
    > this to the emu10k1 ALSA driver, it's quite useful. It would be nice
    > if there were a facility in the kernel to easily identify missed
    > interrupts like this or (even better) unbalanced irq disable/enable -
    > AFAICT userspace alone cannot reliably distinguish lost interrupts
    > from scheduling problems (though you can get a lot of hints). Paul
    > mentioned trying to debug the unbalanced irq disable in his talk at
    > ZKM 2003, and said it's hard because the hardware will enable/disable
    > interrupts on its own and he could not identify all those places.
    > Ingo, is there an easy way to trace this like we do for unbalanced
    > preempt count?

    i wrote a cli/sti latency tracer a couple of years ago so it's possible.
    Note that an irqs-off condition is near impossible to 'leak' into
    userspace code though, since the x86 iret path restores flags to the
    previous value. Worst-case the irqs-off condition may leak into
    kernelspace, and that can still cause bad effects. X startup/shutdown
    can disable interrupts for a long time, was that excluded from your
    testing?

    Ingo
    -
    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 14:07    [W:4.082 / U:0.192 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site