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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: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Dhaval Giani 2008-02-28 15:21:56 +05:30 committed by Ingo Molnar
parent 2692a2406b
commit 521f1a2489
1 changed files with 17 additions and 0 deletions
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17
kernel/sched.c
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@ -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;