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sched: Fix sched rt group scheduling when hierachy is enabled

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The current sched rt code is broken when it comes to hierarchical
scheduling, this patch fixes two problems

1. It adds redundant enqueuing (harmless) when it finds a queue
   has tasks enqueued, but it has no run time and it is not
   throttled.

2. The most important change is in sched_rt_rq_enqueue/dequeue.
   The code just picks the rt_rq belonging to the current cpu
   on which the period timer runs, the patch fixes it, so that
   the correct rt_se is enqueued/dequeued.

Tested with a simple hierarchy

/c/d, c and d assigned similar runtimes of 50,000 and a while
1 loop runs within "d". Both c and d get throttled, without
the patch, the task just stops running and never runs (depends
on where the sched_rt b/w timer runs). With the patch, the
task is throttled and runs as expected.

[ bharata, suggestions on how to pick the rt_se belong to the
  rt_rq and correct cpu ]

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: stable@kernel.org
LKML-Reference: <20110303113435.GA2868@balbir.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Balbir Singh 2011-03-03 17:04:35 +05:30 committed by Ingo Molnar
parent b65a0e0c84
commit 0c3b916801
1 changed files with 9 additions and 5 deletions
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14
kernel/sched_rt.c
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@ -210,11 +210,12 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
{
int this_cpu = smp_processor_id();
struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
struct sched_rt_entity *rt_se;
rt_se = rt_rq->tg->rt_se[this_cpu];
int cpu = cpu_of(rq_of_rt_rq(rt_rq));
rt_se = rt_rq->tg->rt_se[cpu];
if (rt_rq->rt_nr_running) {
if (rt_se && !on_rt_rq(rt_se))
@ -226,10 +227,10 @@ static void sched_rt_rq_enqueue(struct rt_rq *rt_rq)
static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)
{
int this_cpu = smp_processor_id();
struct sched_rt_entity *rt_se;
int cpu = cpu_of(rq_of_rt_rq(rt_rq));
rt_se = rt_rq->tg->rt_se[this_cpu];
rt_se = rt_rq->tg->rt_se[cpu];
if (rt_se && on_rt_rq(rt_se))
dequeue_rt_entity(rt_se);
@ -565,8 +566,11 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun)
if (rt_rq->rt_time || rt_rq->rt_nr_running)
idle = 0;
raw_spin_unlock(&rt_rq->rt_runtime_lock);
} else if (rt_rq->rt_nr_running)
} else if (rt_rq->rt_nr_running) {
idle = 0;
if (!rt_rq_throttled(rt_rq))
enqueue = 1;
}
if (enqueue)
sched_rt_rq_enqueue(rt_rq);