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SubjectRe: [PATCH] sched/uclamp: Avoid setting cpu.uclamp.min bigger than cpu.uclamp.max
On 06/08/21 23:01, Xuewen Yan wrote:
> Hi
>
> On Tue, Jun 8, 2021 at 10:25 PM Qais Yousef <qais.yousef@arm.com> wrote:
> >
> > --->8---
> >
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index 9e9a5be35cde..1d2d3e6648a6 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -1403,38 +1403,28 @@ static void uclamp_sync_util_min_rt_default(void)
> > static inline struct uclamp_se
> > uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id)
> > {
> > - struct uclamp_se uc_req = p->uclamp_req[clamp_id];
> > + /* Copy by value as we could modify it */
> > + struct uclamp_se uc_eff = p->uclamp_req[clamp_id];
> > #ifdef CONFIG_UCLAMP_TASK_GROUP
> > + unsigned long tg_min, tg_max, value;
> >
> > /*
> > * Tasks in autogroups or root task group will be
> > * restricted by system defaults.
> > */
> > if (task_group_is_autogroup(task_group(p)))
> > - return uc_req;
> > + return uc_eff;
> > if (task_group(p) == &root_task_group)
> > - return uc_req;
> > + return uc_eff;
> >
> > - switch (clamp_id) {
> > - case UCLAMP_MIN: {
> > - struct uclamp_se uc_min = task_group(p)->uclamp[clamp_id];
> > - if (uc_req.value < uc_min.value)
> > - return uc_min;
> > - break;
> > - }
> > - case UCLAMP_MAX: {
> > - struct uclamp_se uc_max = task_group(p)->uclamp[clamp_id];
> > - if (uc_req.value > uc_max.value)
> > - return uc_max;
> > - break;
> > - }
> > - default:
> > - WARN_ON_ONCE(1);
> > - break;
> > - }
> > + tg_min = task_group(p)->uclamp[UCLAMP_MIN].value;
> > + tg_max = task_group(p)->uclamp[UCLAMP_MAX].value;
> > + value = uc_eff.value;
> > + value = clamp(value, tg_min, tg_max);
> > + uclamp_se_set(&uc_eff, value, false);
>
> Is it reasonable to set user_defined to be false here?

Yep, it doesn't really matter for the effective value. It matters for the
actual task request.

>
> > #endif
> >
> > - return uc_req;
> > + return uc_eff;
> > }
> >
> > /*
> > @@ -1661,8 +1651,7 @@ uclamp_update_active(struct task_struct *p, enum uclamp_id clamp_id)
> >
> > #ifdef CONFIG_UCLAMP_TASK_GROUP
> > static inline void
> > -uclamp_update_active_tasks(struct cgroup_subsys_state *css,
> > - unsigned int clamps)
> > +uclamp_update_active_tasks(struct cgroup_subsys_state *css)
> > {
> > enum uclamp_id clamp_id;
> > struct css_task_iter it;
> > @@ -1670,10 +1659,8 @@ uclamp_update_active_tasks(struct cgroup_subsys_state *css,
> >
> > css_task_iter_start(css, 0, &it);
> > while ((p = css_task_iter_next(&it))) {
> > - for_each_clamp_id(clamp_id) {
> > - if ((0x1 << clamp_id) & clamps)
> > - uclamp_update_active(p, clamp_id);
> > - }
> > + for_each_clamp_id(clamp_id)
> > + uclamp_update_active(p, clamp_id);
> > }
> > css_task_iter_end(&it);
> > }
> > @@ -9626,7 +9613,7 @@ static void cpu_util_update_eff(struct cgroup_subsys_state *css)
> > }
> >
> > /* Immediately update descendants RUNNABLE tasks */
> > - uclamp_update_active_tasks(css, clamps);
> > + uclamp_update_active_tasks(css);
> > }
> > }
>
> Would you resend another email? maybe it would be better to resend an
> email with a new subject?

Yeah I will do a proper posting. But I need to stare at this a bit more then
will do.

Thanks

--
Qais Yousef

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