linux-kernel - Re: [PATCH v3 1/2] sched/uclamp: Fix a uninitialized variable warnings

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Date:   Fri, 13 Jan 2023 09:13:20 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Qais Yousef <qyousef@...alina.io>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Lukasz Luba <lukasz.luba@....com>, Wei Wang <wvw@...gle.com>,
        Xuewen Yan <xuewen.yan94@...il.com>,
        Hank <han.lin@...iatek.com>,
        Jonathan JMChen <Jonathan.JMChen@...iatek.com>,
        kernel test robot <lkp@...el.com>,
        Dan Carpenter <error27@...il.com>
Subject: Re: [PATCH v3 1/2] sched/uclamp: Fix a uninitialized variable warnings

On Thu, 12 Jan 2023 at 13:27, Qais Yousef <qyousef@...alina.io> wrote:
>
> Addresses the following warnings:
>
> > config: riscv-randconfig-m031-20221111
> > compiler: riscv64-linux-gcc (GCC) 12.1.0
> >
> > smatch warnings:
> > kernel/sched/fair.c:7263 find_energy_efficient_cpu() error: uninitialized symbol 'util_min'.
> > kernel/sched/fair.c:7263 find_energy_efficient_cpu() error: uninitialized symbol 'util_max'.
>
> Fixes: 244226035a1f ("sched/uclamp: Fix fits_capacity() check in feec()")
> Reported-by: kernel test robot <lkp@...el.com>
> Reported-by: Dan Carpenter <error27@...il.com>
> Signed-off-by: Qais Yousef (Google) <qyousef@...alina.io>

Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>

> ---
>  kernel/sched/fair.c | 35 ++++++++++++++++-------------------
>  1 file changed, 16 insertions(+), 19 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e9d906a9bba9..5a8e75d4a17b 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7353,10 +7353,10 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
>         eenv_task_busy_time(&eenv, p, prev_cpu);
>
>         for (; pd; pd = pd->next) {
> +               unsigned long util_min = p_util_min, util_max = p_util_max;
>                 unsigned long cpu_cap, cpu_thermal_cap, util;
>                 unsigned long cur_delta, max_spare_cap = 0;
>                 unsigned long rq_util_min, rq_util_max;
> -               unsigned long util_min, util_max;
>                 unsigned long prev_spare_cap = 0;
>                 int max_spare_cap_cpu = -1;
>                 unsigned long base_energy;
> @@ -7375,6 +7375,8 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
>                 eenv.pd_cap = 0;
>
>                 for_each_cpu(cpu, cpus) {
> +                       struct rq *rq = cpu_rq(cpu);
> +
>                         eenv.pd_cap += cpu_thermal_cap;
>
>                         if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
> @@ -7393,24 +7395,19 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
>                          * much capacity we can get out of the CPU; this is
>                          * aligned with sched_cpu_util().
>                          */
> -                       if (uclamp_is_used()) {
> -                               if (uclamp_rq_is_idle(cpu_rq(cpu))) {
> -                                       util_min = p_util_min;
> -                                       util_max = p_util_max;
> -                               } else {
> -                                       /*
> -                                        * Open code uclamp_rq_util_with() except for
> -                                        * the clamp() part. Ie: apply max aggregation
> -                                        * only. util_fits_cpu() logic requires to
> -                                        * operate on non clamped util but must use the
> -                                        * max-aggregated uclamp_{min, max}.
> -                                        */
> -                                       rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
> -                                       rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
> -
> -                                       util_min = max(rq_util_min, p_util_min);
> -                                       util_max = max(rq_util_max, p_util_max);
> -                               }
> +                       if (uclamp_is_used() && !uclamp_rq_is_idle(rq)) {
> +                               /*
> +                                * Open code uclamp_rq_util_with() except for
> +                                * the clamp() part. Ie: apply max aggregation
> +                                * only. util_fits_cpu() logic requires to
> +                                * operate on non clamped util but must use the
> +                                * max-aggregated uclamp_{min, max}.
> +                                */
> +                               rq_util_min = uclamp_rq_get(rq, UCLAMP_MIN);
> +                               rq_util_max = uclamp_rq_get(rq, UCLAMP_MAX);
> +
> +                               util_min = max(rq_util_min, p_util_min);
> +                               util_max = max(rq_util_max, p_util_max);
>                         }
>                         if (!util_fits_cpu(util, util_min, util_max, cpu))
>                                 continue;
> --
> 2.25.1
>