linux-kernel - Re: [PATCH v2] PM / devfreq: events: Fix excessive stack usage

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Date:   Mon, 11 Nov 2019 15:07:49 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     arnd@...db.de, myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
        krzk@...nel.org, kgene@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        chanwoo@...nel.org
Subject: Re: [PATCH v2] PM / devfreq: events: Fix excessive stack usage

On 11/11/19 3:05 PM, Chanwoo Choi wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Putting a 'struct devfreq_event_dev' object on the stack is generally
> a bad idea and here it leads to a warnig about potential stack overflow:
> 
> drivers/devfreq/event/exynos-ppmu.c:643:12: error: stack frame size of 1040 bytes in function 'exynos_ppmu_probe' [-Werror,-Wframe-larger-than=]
> 
> There is no real need for the device structure, only the string inside
> it, so add an internal helper function that simply takes the string
> as its argument and remove the device structure.
> 
> Fixes: 1dd62c66d345 ("PM / devfreq: events: extend events by type of counted data")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> [cw00.choi: Fix the issue from 'desc->name' to 'desc[j].name']
> Signed-off-by: Chanwoo Choi <cw00.choi@...sung.com>
> ---
> Changes from v1:
> - Fix the issue from 'desc->name' to 'desc[j].name'
> 
>  drivers/devfreq/event/exynos-ppmu.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/devfreq/event/exynos-ppmu.c b/drivers/devfreq/event/exynos-ppmu.c
> index 85c7a77bf3f0..055deea42c37 100644
> --- a/drivers/devfreq/event/exynos-ppmu.c
> +++ b/drivers/devfreq/event/exynos-ppmu.c
> @@ -101,17 +101,22 @@ static struct __exynos_ppmu_events {
>  	PPMU_EVENT(dmc1_1),
>  };
>  
> -static int exynos_ppmu_find_ppmu_id(struct devfreq_event_dev *edev)
> +static int __exynos_ppmu_find_ppmu_id(const char *edev_name)
>  {
>  	int i;
>  
>  	for (i = 0; i < ARRAY_SIZE(ppmu_events); i++)
> -		if (!strcmp(edev->desc->name, ppmu_events[i].name))
> +		if (!strcmp(edev_name, ppmu_events[i].name))
>  			return ppmu_events[i].id;
>  
>  	return -EINVAL;
>  }
>  
> +static int exynos_ppmu_find_ppmu_id(struct devfreq_event_dev *edev)
> +{
> +	return __exynos_ppmu_find_ppmu_id(edev->desc->name);
> +}
> +
>  /*
>   * The devfreq-event ops structure for PPMU v1.1
>   */
> @@ -556,13 +561,11 @@ static int of_get_devfreq_events(struct device_node *np,
>  			 * use default if not.
>  			 */
>  			if (info->ppmu_type == EXYNOS_TYPE_PPMU_V2) {
> -				struct devfreq_event_dev edev;
>  				int id;
>  				/* Not all registers take the same value for
>  				 * read+write data count.
>  				 */
> -				edev.desc = &desc[j];
> -				id = exynos_ppmu_find_ppmu_id(&edev);
> +				id = __exynos_ppmu_find_ppmu_id(desc[j].name);
>  
>  				switch (id) {
>  				case PPMU_PMNCNT0:
> 

Applied it. Thanks.

-- 
Best Regards,
Chanwoo Choi
Samsung Electronics