linux-kernel - Re: [PATCH] sched: Make uclamp changes depend on CAP_SYS

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Date:   Thu, 10 Jun 2021 07:45:29 +0000
From:   Quentin Perret <qperret@...gle.com>
To:     Xuewen Yan <xuewen.yan94@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qais Yousef <qais.yousef@....com>, rickyiu@...gle.com,
        wvw@...gle.com, Patrick Bellasi <patrick.bellasi@...bug.net>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-team@...roid.com
Subject: Re: [PATCH] sched: Make uclamp changes depend on CAP_SYS_NICE

On Thursday 10 Jun 2021 at 11:33:04 (+0800), Xuewen Yan wrote:
> On Thu, Jun 10, 2021 at 2:16 AM Quentin Perret <qperret@...gle.com> wrote:
> > +static bool uclamp_reduce(struct task_struct *p, const struct sched_attr *attr)
> > +{
> > +       int util_min, util_max;
> > +
> > +       if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
> > +               util_min = p->uclamp_req[UCLAMP_MIN].value;
> > +               if (attr->sched_util_min > util_min)
> > +                       return false;
> > +       }
> > +
> > +       if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
> > +               util_max = p->uclamp_req[UCLAMP_MAX].value;
> > +               if (attr->sched_util_max > util_max)
> > +                       return false;
> 
> when the attr->sched_util_max = -1, and the util_max < 1024, here may
> should return false, but it would return ture.

Aha, indeed, I missed that -1 could be used to reset the clamps. I'll
send a v2.

Thanks!
Quentin