Re: [PATCH] sched: don't allow rt_runtime_us to be zero for groupshaving rt tasks

From: Peter Zijlstra
Date: Wed Feb 27 2008 - 09:12:25 EST



On Wed, 2008-02-27 at 18:54 +0530, Dhaval Giani wrote:

> 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.
>
> Signed-off-by: Dhaval Giani <dhaval@xxxxxxxxxxxxxxxxxx>

Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

> ---
> kernel/sched.c | 17 +++++++++++++++++
> 1 files changed, 17 insertions(+)
>
> Index: linux-2.6.25-rc3/kernel/sched.c
> ===================================================================
> --- linux-2.6.25-rc3.orig/kernel/sched.c
> +++ linux-2.6.25-rc3/kernel/sched.c
> @@ -7960,6 +7960,17 @@ static int __rt_schedulable(struct task_
> 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 *p;
> + for_each_process(p) {
> + if (rt_task(p) && rt_rq_of_se(&p->rt)->tg == tg)
> + return 1;
> + }
> + return 0;
> +}
> +
> int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us)
> {
> u64 rt_runtime, rt_period;
> @@ -7971,6 +7982,11 @@ int sched_group_set_rt_runtime(struct ta
> rt_runtime = rt_period;
>
> mutex_lock(&rt_constraints_mutex);
> + read_lock(&tasklist_lock);
> + if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) {
> + err = -EINVAL;
> + goto unlock;
> + }
> if (!__rt_schedulable(tg, rt_period, rt_runtime)) {
> err = -EINVAL;
> goto unlock;
> @@ -7979,6 +7995,7 @@ int sched_group_set_rt_runtime(struct ta
> rt_runtime = RUNTIME_INF;
> tg->rt_runtime = rt_runtime;
> unlock:
> + read_unlock(&tasklist_lock);
> mutex_unlock(&rt_constraints_mutex);
>
> return err;

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