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    SubjectRe: 2.6.35-rc3: System unresponsive under load
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    On Sat, Jun 26, 2010 at 5:47 PM, Manfred Spraul
    <manfred@colorfullife.com> wrote:
    > Hi Luca,
    >
    > On 06/26/2010 02:52 PM, Luca Tettamanti wrote:
    >>
    >> They don't seem really hung as before, I see two different behaviours:
    >> * Near the end of the run ab is frozen for a few seconds, but in the
    >> end all requests are processed; however I see a few "length" errors,
    >> meaning that the received page does not match the expected content
    >> (I'm testing a static page):
    >>
    >>
    >
    > That's consistent with what I see:
    > If I run:
    > #./semtimedop 100 100&
    > #./semtimedop 100 100&
    > #./semtimedop 100 100&
    > #./semtimedop 100 100&
    >
    > (i.e.: 4 times the attached test app concurrently), then the system
    > sometimes locks up for 10..20 seconds:
    > The keyboard is unresponsive, not even the numlock key is processed (i.e.:
    > the LED does not change anymore).
    > After 10 or 20 seconds, the keyboard reacts again (both to <enter> and to
    > Num Lock)
    > The stock Fedora 13 kernel (2.6.33.5) does not exhibit this behavior
    > The load average is 300 or so, that's expected.

    Confirmed here: your test program freezes the system for a while under
    2.6.35-rc3, while vanilla 2.6.34 copes fine.
    sysrq-t was responsive during the freeze, so I took a snapshot during
    it, file is attached.

    > I have no idea why and how to debug the behavior.
    > # CONFIG_PREEMPT_NONE is not set
    > CONFIG_PREEMPT_VOLUNTARY=y
    > # CONFIG_PREEMPT is not set

    My kernel has PREEMPT enabled.

    Luca
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