linux-kernel - Re: [patch] cpufreq: ondemand: Use cpumask_var

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Date:   Mon, 25 Jul 2022 20:39:01 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Zhao Liu <zhao1.liu@...ux.intel.com>
Cc:     "Rafael J . Wysocki" <rafael@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jiri Kosina <trivial@...nel.org>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhao Liu <zhao1.liu@...el.com>
Subject: Re: [patch] cpufreq: ondemand: Use cpumask_var_t for on-stack cpu mask

On Mon, Jul 25, 2022 at 12:30 PM Viresh Kumar <viresh.kumar@...aro.org> wrote:
>
> On 22-07-22, 10:50, Zhao Liu wrote:
> > A cpumask structure on the stack can cause a warning with
> > CONFIG_NR_CPUS=8192 (e.g. Ubuntu 22.04 uses this):
> >
> > drivers/cpufreq/cpufreq_ondemand.c: In function 'od_set_powersave_bias':
> > drivers/cpufreq/cpufreq_ondemand.c:449:1: warning: the frame size of
> >       1032 bytes is larger than 1024 bytes [-Wframe-larger-than=]
> >   449 | }
> >       | ^
> >
> > CONFIG_CPUMASK_OFFSTACK=y is enabled by default for most distros, and
> > hence we can work around the warning by using cpumask_var_t.
> >
> > Signed-off-by: Zhao Liu <zhao1.liu@...ux.intel.com>
> > ---
> >  drivers/cpufreq/cpufreq_ondemand.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
> > index e8fbf970ff07..c52d19d67557 100644
> > --- a/drivers/cpufreq/cpufreq_ondemand.c
> > +++ b/drivers/cpufreq/cpufreq_ondemand.c
> > @@ -416,10 +416,13 @@ static struct dbs_governor od_dbs_gov = {
> >  static void od_set_powersave_bias(unsigned int powersave_bias)
> >  {
> >       unsigned int cpu;
> > -     cpumask_t done;
> > +     cpumask_var_t done;
> > +
> > +     if (!alloc_cpumask_var(&done, GFP_KERNEL))
> > +             return;
> >
> >       default_powersave_bias = powersave_bias;
> > -     cpumask_clear(&done);
> > +     cpumask_clear(done);
> >
> >       cpus_read_lock();
> >       for_each_online_cpu(cpu) {
> > @@ -428,7 +431,7 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
> >               struct dbs_data *dbs_data;
> >               struct od_dbs_tuners *od_tuners;
> >
> > -             if (cpumask_test_cpu(cpu, &done))
> > +             if (cpumask_test_cpu(cpu, done))
> >                       continue;
> >
> >               policy = cpufreq_cpu_get_raw(cpu);
> > @@ -439,13 +442,15 @@ static void od_set_powersave_bias(unsigned int powersave_bias)
> >               if (!policy_dbs)
> >                       continue;
> >
> > -             cpumask_or(&done, &done, policy->cpus);
> > +             cpumask_or(done, done, policy->cpus);
> >
> >               dbs_data = policy_dbs->dbs_data;
> >               od_tuners = dbs_data->tuners;
> >               od_tuners->powersave_bias = default_powersave_bias;
> >       }
> >       cpus_read_unlock();
> > +
> > +     free_cpumask_var(done);
> >  }
> >
> >  void od_register_powersave_bias_handler(unsigned int (*f)
>
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

Applied as 5.20 material, thanks!