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    SubjectRe: RFC [patch] sched,cgroup_sched: convince RT_GROUP_SCHED throttle to work
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    On Sat, 2012-04-07 at 11:54 +0200, Mike Galbraith wrote:

    > With this patch, the thing appears to work perfectly, but it doesn't
    > look correct, since I'm futzing with ->rt_time where I should not.

    s/doesn't look/definitely isn't. This failed the "definitely works so
    may live on despite horrific appearance" test anyway, so how about just
    stop pretending root isn't global instead?

    sched,rt: fix isolated CPUs leaving root_task_group indefinitely throttled

    Root task group bandwidth replenishment must service all CPUs regardless of
    where it was last started.

    Signed-off-by: Mike Galbraith <efault@gmx.de>
    ---
    kernel/sched/rt.c | 13 +++++++++++++
    1 file changed, 13 insertions(+)

    --- a/kernel/sched/rt.c
    +++ b/kernel/sched/rt.c
    @@ -782,6 +782,19 @@ static int do_sched_rt_period_timer(stru
    const struct cpumask *span;

    span = sched_rt_period_mask();
    +#ifdef CONFIG_RT_GROUP_SCHED
    + /*
    + * FIXME: isolated CPUs should really leave the root task group,
    + * whether they are isolcpus or were isolated via cpusets, lest
    + * the timer run on a CPU which does not service all runqueues,
    + * potentially leaving other CPUs indefinitely throttled. If
    + * isolation is really required, the user will turn the throttle
    + * off to kill the perturbations it causes anyway. Meanwhile,
    + * this maintains functionality for boot and/or troubleshooting.
    + */
    + if (rt_b == &root_task_group.rt_bandwidth)
    + span = cpu_online_mask;
    +#endif
    for_each_cpu(i, span) {
    int enqueue = 0;
    struct rt_rq *rt_rq = sched_rt_period_rt_rq(rt_b, i);



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