linux-kernel - Re: [PATCH v7 01/15] sched/core: uclamp: Add CPU's clamp buckets refcounting

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Message-ID: <20190313172225.GG5996@hirez.programming.kicks-ass.net>
Date:   Wed, 13 Mar 2019 18:22:25 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...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 v7 01/15] sched/core: uclamp: Add CPU's clamp buckets
 refcounting

On Wed, Mar 13, 2019 at 04:12:29PM +0000, Patrick Bellasi wrote:
> Yes, the for looks better, but perhaps like that:
> 
> 	unsigned int bucket_id = UCLAMP_BUCKETS;
> 
>  	/*
>  	 * Both min and max clamps are MAX aggregated, thus the topmost
>  	 * bucket with some tasks defines the rq's clamp value.
>  	 */
> 	for (; bucket_id >= 0; --bucket_id) {

GCC will be clever and figure that unsigned will never be smaller than 0
and turn the above into an infinite loop or something daft.

That is; use 'int', not 'unsigned int' for bucket_id.