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    SubjectRe: [PATCH]sched: Isochronous class v2 for unprivileged soft rt scheduling
    utz lehmann wrote:
    > @@ -2406,6 +2489,10 @@ void scheduler_tick(void)
    > task_t *p = current;
    > rq->timestamp_last_tick = sched_clock();
    > + if (iso_task(p) && !rq->iso_refractory)
    > + inc_iso_ticks(rq, p);
    > + else
    > + dec_iso_ticks(rq, p);
    > scheduler_tick() is not only called by the timer interrupt but also form
    > the fork code. Is this intended? I think the accounting for

    The calling from fork code only occurs if there is one millisecond of
    time_slice left so it will only very rarely be hit. I dont think this
    accounting problem is worth worrying about.

    > iso_refractory is wrong. Isn't calling it from
    > timer.c::update_process_times() better?
    > And shouldn't real RT task also counted? If RT tasks use 40% cpu you can
    > lockup the system as unprivileged user with SCHED_ISO because it doesn't
    > reach the 70% cpu limit.

    Ah yes. Good point. Will add that to the equation.

    > Futher on i see a fundamental problem with this accounting for
    > iso_refractory. What if i manage as unprivileged user to run a SCHED_ISO
    > task which consumes all cpu and only sleeps very short during the timer
    > interrupt? I think this will nearly lockup or very slow down the system.
    > The iso_cpu limit can't guaranteed.

    Right you are. The cpu accounting uses primitive on-interrupt run time
    which as we know is not infallible. To extend this I'll have to keep a
    timer based on the sched_clock which is already implemented. That's
    something for me to work on.

    > sysrq-n causes a reboot.

    And that will need looking into.

    Thanks very much for your comments!

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      Last update: 2005-03-22 14:09    [W:0.021 / U:4.644 seconds]
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