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

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Date:   Thu, 13 Sep 2018 21:20:34 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v4 02/16] sched/core: uclamp: map TASK's clamp values
 into CPU's clamp groups

On Wed, Sep 12, 2018 at 06:42:09PM +0100, Patrick Bellasi wrote:
> On 12-Sep 18:24, Peter Zijlstra wrote:
> > On Tue, Aug 28, 2018 at 02:53:10PM +0100, Patrick Bellasi wrote:

> > >  {
> > > +	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.

> Actually it could also make sense to have them before the mutex ;)

Indeed.

+               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");
+                       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;
+               }

That would end up soething like:

	unsigned int lower_bound = p->uclamp[UCLAMP_MIN].value;
	unsigned int upper_bound = p->uclamp[UCLAMP_MAX].value;

	if (sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN)
		lower_bound = attr->sched_util_min;

	if (sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX)
		upper_bound = attr->sched_util_max;

	if (lower_bound > upper_bound ||
	    upper_bound > SCHED_CAPACITY_MAX)
		return -EINVAL;

	mutex_lock(...);