Re: [PATCH v4 02/16] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups

Peter Zijlstra
2018-09-12T16:24:43Z

On Tue, Aug 28, 2018 at 02:53:10PM +0100, Patrick Bellasi wrote:
> static inline int __setscheduler_uclamp(struct task_struct *p,
> const struct sched_attr *attr)

But large for inline now.

> {
> + int group_id[UCLAMP_CNT] = { UCLAMP_NOT_VALID };
> + int lower_bound, upper_bound;
> + struct uclamp_se *uc_se;
> + int result = 0;

I think the thing would become much more readable if you set
lower/upper_bound right here.
>
> + mutex_lock(&uclamp_mutex);
>
> + /* Find a valid group_id for each required clamp value */
> + if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
> + upper_bound = (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX)
> + ? attr->sched_util_max
> + : p->uclamp[UCLAMP_MAX].value;
> +
> + if (upper_bound == UCLAMP_NOT_VALID)
> + upper_bound = SCHED_CAPACITY_SCALE;
> + if (attr->sched_util_min > upper_bound) {
> + result = -EINVAL;
> + goto done;
> + }
> +
> + result = uclamp_group_find(UCLAMP_MIN, attr->sched_util_min);
> + if (result == -ENOSPC) {
> + pr_err(UCLAMP_ENOSPC_FMT, "MIN");

AFAICT this is an unpriv part of the syscall; and you can spam the log
without limits. Not good.

> + goto done;
> + }
> + group_id[UCLAMP_MIN] = result;
> + }
> + if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
> + lower_bound = (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
> + ? attr->sched_util_min
> + : p->uclamp[UCLAMP_MIN].value;
> +
> + if (lower_bound == UCLAMP_NOT_VALID)
> + lower_bound = 0;
> + if (attr->sched_util_max < lower_bound ||
> + attr->sched_util_max > SCHED_CAPACITY_SCALE) {
> + result = -EINVAL;
> + goto done;
> + }
> +
> + result = uclamp_group_find(UCLAMP_MAX, attr->sched_util_max);
> + if (result == -ENOSPC) {
> + pr_err(UCLAMP_ENOSPC_FMT, "MAX");
> + goto done;
> + }
> + group_id[UCLAMP_MAX] = result;
> + }
> +
> + /* Update each required clamp group */
> + if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
> + uc_se = &p->uclamp[UCLAMP_MIN];
> + uclamp_group_get(UCLAMP_MIN, group_id[UCLAMP_MIN],
> + uc_se, attr->sched_util_min);
> + }
> + if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
> + uc_se = &p->uclamp[UCLAMP_MAX];
> + uclamp_group_get(UCLAMP_MAX, group_id[UCLAMP_MAX],
> + uc_se, attr->sched_util_max);
> + }
> +
> +done:
> + mutex_unlock(&uclamp_mutex);
> +
> + return result;
> +}