[PATCH 09/10] sched: rt: fix the bandwidth contraint computations

[Peter Zijlstra]

 - allow a subgroup to use all of its parent's bandwidth
 - contrain the global bandwidth to not be lower than the root group's

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/sched.c    |   11 ++++++++---
 kernel/sched_rt.c |    3 +++
 2 files changed, 11 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -8354,7 +8354,7 @@ static unsigned long to_ratio(u64 period
 #ifdef CONFIG_CGROUP_SCHED
 static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime)
 {
-	struct task_group *tgi, *parent = tg ? tg->parent : NULL;
+	struct task_group *tgi, *parent = tg->parent;
 	unsigned long total = 0;
 
 	if (!parent) {
@@ -8378,7 +8378,7 @@ static int __rt_schedulable(struct task_
 	}
 	rcu_read_unlock();
 
-	return total + to_ratio(period, runtime) <
+	return total + to_ratio(period, runtime) <=
 		to_ratio(ktime_to_ns(parent->rt_bandwidth.rt_period),
 				parent->rt_bandwidth.rt_runtime);
 }
@@ -8495,10 +8495,15 @@ long sched_group_rt_period(struct task_g
 
 static int sched_rt_global_constraints(void)
 {
+	struct task_group *tg = &root_task_group;
+	u64 rt_runtime, rt_period;
 	int ret = 0;
 
+	rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
+	rt_runtime = tg->rt_bandwidth.rt_runtime;
+
 	mutex_lock(&rt_constraints_mutex);
-	if (!__rt_schedulable(NULL, 1, 0))
+	if (!__rt_schedulable(tg, rt_period, rt_runtime))
 		ret = -EINVAL;
 	mutex_unlock(&rt_constraints_mutex);
 

-- 

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