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sched: more sanity checks on the bandwidth settings 

While playing around with it, I noticed we missed some sanity checks.
Also add some comments while we're there.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-09-23 15:33:44 +02:00 committed by Ingo Molnar
parent 78333cdd0e
commit 4653f803e6
1 changed files with 28 additions and 5 deletions
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33
kernel/sched.c
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@ -8866,11 +8866,29 @@ static int tg_schedulable(struct task_group *tg, void *data)
runtime = d->rt_runtime;
}
/*
* Cannot have more runtime than the period.
*/
if (runtime > period && runtime != RUNTIME_INF)
return -EINVAL;
/*
* Ensure we don't starve existing RT tasks.
*/
if (rt_bandwidth_enabled() && !runtime && tg_has_rt_tasks(tg))
return -EBUSY;
total = to_ratio(period, runtime);
/*
* Nobody can have more than the global setting allows.
*/
if (total > to_ratio(global_rt_period(), global_rt_runtime()))
return -EINVAL;
/*
* The sum of our children's runtime should not exceed our own.
*/
list_for_each_entry_rcu(child, &tg->children, siblings) {
period = ktime_to_ns(child->rt_bandwidth.rt_period);
runtime = child->rt_bandwidth.rt_runtime;
@ -8978,19 +8996,24 @@ long sched_group_rt_period(struct task_group *tg)
static int sched_rt_global_constraints(void)
{
struct task_group *tg = &root_task_group;
u64 rt_runtime, rt_period;
u64 runtime, period;
int ret = 0;
if (sysctl_sched_rt_period <= 0)
return -EINVAL;
rt_period = ktime_to_ns(tg->rt_bandwidth.rt_period);
rt_runtime = tg->rt_bandwidth.rt_runtime;
runtime = global_rt_runtime();
period = global_rt_period();
/*
* Sanity check on the sysctl variables.
*/
if (runtime > period && runtime != RUNTIME_INF)
return -EINVAL;
mutex_lock(&rt_constraints_mutex);
read_lock(&tasklist_lock);
ret = __rt_schedulable(tg, rt_period, rt_runtime);
ret = __rt_schedulable(NULL, 0, 0);
read_unlock(&tasklist_lock);
mutex_unlock(&rt_constraints_mutex);