linux-kernel - Re: drivers/acpi/processor_thermal.c:66:1: warning: the frame size of 2160 bytes is larger than 2048 bytes

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Date:   Fri, 17 Jan 2020 16:51:21 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kbuild test robot <lkp@...el.com>,
        Linux PM list <linux-pm@...r.kernel.org>
Subject: Re: drivers/acpi/processor_thermal.c:66:1: warning: the frame size of
 2160 bytes is larger than 2048 bytes

Hi Rafael, Viresh,

On Fri, Nov 15, 2019 at 6:23 AM kbuild test robot <lkp@...el.com> wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   96b95eff4a591dbac582c2590d067e356a18aacb
> commit: 3000ce3c52f8b8db093e4dc649cd172390f71137 cpufreq: Use per-policy frequency QoS
> date:   4 weeks ago
> config: ia64-randconfig-a001-20191115 (attached as .config)
> compiler: ia64-linux-gcc (GCC) 7.4.0
> reproduce:
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout 3000ce3c52f8b8db093e4dc649cd172390f71137
>         # save the attached .config to linux build tree
>         GCC_VERSION=7.4.0 make.cross ARCH=ia64
>
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@...el.com>

Seeing similar warnings on arm64, so this triggered my attention.

> --
>    drivers/cpufreq/cpufreq.c: In function 'refresh_frequency_limits.part.33':
> >> drivers/cpufreq/cpufreq.c:1116:1: warning: the frame size of 2160 bytes is larger than 2048 bytes [-Wframe-larger-than=]

|       struct cpufreq_policy new_policy;

That's a large struct on the stack...

|       if (!policy_is_inactive(policy)) {
|               new_policy = *policy;

Let's make a copy?
How well does this work, given struct cpufreq_policy contains a
work_struct, list_head, kobject, completion, semaphore, spinlock_t,
wait_queue_head_t, and two notifier_blocks, which are all objects you
cannot just copy and reuse?

|               pr_debug("updating policy for CPU %u\n", policy->cpu);
|
|               cpufreq_set_policy(policy, &new_policy);

If cpufreq_set_policy() uses only a few fields from new_policy, it might
be a good idea to extract those into its own structure.

>     }
>     ^
>    drivers/cpufreq/cpufreq.c: In function 'store_scaling_governor':
>    drivers/cpufreq/cpufreq.c:789:1: warning: the frame size of 2176 bytes is larger than 2048 bytes [-Wframe-larger-than=]

|       struct cpufreq_policy new_policy;
|
|       memcpy(&new_policy, policy, sizeof(*policy));

Likewise.

>     }
>     ^
>    drivers/cpufreq/cpufreq.c: In function 'cpufreq_init_policy':
>    drivers/cpufreq/cpufreq.c:1081:1: warning: the frame size of 2160 bytes is larger than 2048 bytes [-Wframe-larger-than=]

|       struct cpufreq_policy new_policy;
|
|       memcpy(&new_policy, policy, sizeof(*policy));

One more.

>     }
>     ^

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds