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    SubjectRe: [PATCH V6] powercap/drivers/idle_injection: Add an idle injection framework
    On Tue, Jun 12, 2018 at 03:02:14PM +0200, Daniel Lezcano wrote:
    > On 12/06/2018 14:52, Peter Zijlstra wrote:
    > > In this case, you can do:
    >
    > That is what we had before but we change the code to set the count
    > before waking up the task, so compute the cpumask_weight of the
    > resulting AND right before this loop.
    >
    > > + for_each_cpu_and(cpu, &ii_dev->cpumask, cpu_online_mask) {
    > > + iit = per_cpu_ptr(&idle_injection_thread, cpu);
    > > + iit->should_run = 1;
    > > + wake_up_process(iit->tsk);
    > > + }


    Ah, I see, but since you do:

    if (atomic_dec_and_test())
    last_man()

    where that last_man() thing will start a timer, there is no real problem
    with doing atomic_inc() with before wake_up_process().

    Yes, it allows doing last_man, too often, but repeated hrtimer_start()
    will DTRT and reprogram the timer.

    Also, last_man() uses @run_duration, but the way I read it, the timer is
    for waking things up again, this means it is in fact the sleep duration,
    no?

    Furthermore, should you not be using hrtimer_forward(&timer,
    idle_duration + run_duration) instead? AFAICT the current scheme is
    prone to drifting.

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