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Commit 521f1a24 authored by Dhaval Giani's avatar Dhaval Giani Committed by Ingo Molnar
Browse files

sched: don't allow rt_runtime_us to be zero for groups having rt tasks 



This patch checks if we can set the rt_runtime_us to 0. If there is a
realtime task in the group, we don't want to set the rt_runtime_us as 0
or bad things will happen. (that task wont get any CPU time despite
being TASK_RUNNNG)

Signed-off-by: default avatarDhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 2692a240

kernel/sched.c

+17 −0
Original line number Diff line number Diff line
@@ -7750,6 +7750,17 @@ static int __rt_schedulable(struct task_group *tg, u64 period, u64 runtime) 
	return total + to_ratio(period, runtime) < global_ratio;

}



/* Must be called with tasklist_lock held */

static inline int tg_has_rt_tasks(struct task_group *tg)

{

	struct task_struct *g, *p;

	do_each_thread(g, p) {

		if (rt_task(p) && rt_rq_of_se(&p->rt)->tg == tg)

			return 1;

	} while_each_thread(g, p);

	return 0;

}



int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)

{

	u64 rt_runtime, rt_period;
@@ -7761,12 +7772,18 @@ int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us) 
		rt_runtime = RUNTIME_INF;



	mutex_lock(&rt_constraints_mutex);

	read_lock(&tasklist_lock);

	if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) {

		err = -EBUSY;

		goto unlock;

	}

	if (!__rt_schedulable(tg, rt_period, rt_runtime)) {

		err = -EINVAL;

		goto unlock;

	}

	tg->rt_runtime = rt_runtime;

 unlock:

	read_unlock(&tasklist_lock);

	mutex_unlock(&rt_constraints_mutex);



	return err;