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    SubjectRe: [PATCH] net: sched: dev_deactivate_many(): use msleep(1) instead of yield() to wait for outstanding qdisc_run calls
    * Marc Kleine-Budde | 2014-03-06 22:39:58 [+0100]:

    >> Therefore it should allow lower priority threads to run, not just
    >> equal or higher priority ones.
    >
    >Yes, we need a call that does what you described, however I'm not sure
    >if yield() really does that. According to:
    >
    >http://lxr.free-electrons.com/source/kernel/sched/core.c#L3599
    >
    >> * Typical broken usage is:
    >> *
    >> * while (!event)
    >> * yield();
    >> *
    >> * where one assumes that yield() will let 'the other' process run that will
    >> * make event true. If the current task is a SCHED_FIFO task that will never
    >> * happen. Never use yield() as a progress guarantee!!
    >
    >My Process runs with SCHED_FIFO and prio > 50, with IRQ at default prio,
    >which is 50.
    >
    >Maybe the RT guys can comment on this. I found another interesting
    >function in the RT patch set: cpu_chill().

    If you boot mainline without -RT, use threadirqs, start your application
    do the same prio thing then you should end up with exactly the same
    outcome. Please say so :)

    msleep() is safe as long as it is used outside of the softirq. Nice that
    you found cpu_chill() but on non-RT it turns to cpu_relax() and you do
    not want this here.

    wait_event() would be nice in the end to have. For now I take that patch
    for -RT.

    >Marc

    Sebastian


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