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Commit 4653f803 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 78333cdd

kernel/sched.c

+28 −5
Original line number Diff line number Diff line
@@ -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);