Re: [PATCH] sched/rt: fix rt runtime corrupt when dl refuse a smaller bandwidth

Juri Lelli
2014-11-18T18:00:04Z

Hi,

On 13/11/14 08:47, Wanpeng Li wrote:
> Dl class will refuse the bandwidth being set to some value smaller
> than the currently allocated bandwidth in any of the root_domains
> through sched_rt_runtime_us and sched_rt_period_us. RT runtime will
> be set according to sched_rt_runtime_us before dl class verify if
> the new bandwidth is suitable in the case of !CONFIG_RT_GROUP_SCHED.
>
> However, rt runtime will be corrupt if dl refuse the new bandwidth
> since there is no undo to reset the rt runtime to the old value.
>

Can't we just move sched_dl_global_constraints() before
sched_rt_global_constraints(), and change the name of the
former to sched_dl_global_validate() ?

Thanks,

- Juri

> This patch fix it by setting rt runtime after all kinds of rational
> checking in the case of !CONFIG_RT_GROUP_SCHED.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
> ---
> kernel/sched/core.c | 30 ++++++++++++++++--------------
> 1 file changed, 16 insertions(+), 14 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 2e7578a..355dde3 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7795,20 +7795,7 @@ static int sched_rt_can_attach(struct task_group *tg, struct task_struct *tsk)
> #else /* !CONFIG_RT_GROUP_SCHED */
> static int sched_rt_global_constraints(void)
> {
> - unsigned long flags;
> - int i, ret = 0;
> -
> - raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
> - for_each_possible_cpu(i) {
> - struct rt_rq *rt_rq = &cpu_rq(i)->rt;
> -
> - raw_spin_lock(&rt_rq->rt_runtime_lock);
> - rt_rq->rt_runtime = global_rt_runtime();
> - raw_spin_unlock(&rt_rq->rt_runtime_lock);
> - }
> - raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
> -
> - return ret;
> + return 0;
> }
> #endif /* CONFIG_RT_GROUP_SCHED */
>
> @@ -7890,6 +7877,21 @@ static int sched_rt_global_validate(void)
>
> static void sched_rt_do_global(void)
> {
> +#ifndef CONFIG_RT_GROUP_SCHED
> + unsigned long flags;
> + int i;
> +
> + raw_spin_lock_irqsave(&def_rt_bandwidth.rt_runtime_lock, flags);
> + for_each_possible_cpu(i) {
> + struct rt_rq *rt_rq = &cpu_rq(i)->rt;
> +
> + raw_spin_lock(&rt_rq->rt_runtime_lock);
> + rt_rq->rt_runtime = global_rt_runtime();
> + raw_spin_unlock(&rt_rq->rt_runtime_lock);
> + }
> + raw_spin_unlock_irqrestore(&def_rt_bandwidth.rt_runtime_lock, flags);
> +#endif
> +
> def_rt_bandwidth.rt_runtime = global_rt_runtime();
> def_rt_bandwidth.rt_period = ns_to_ktime(global_rt_period());
> }
>