[PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[Yue Hu]

From: Yue Hu <huyue2@yulong.com>

We observed warning about kzalloc() when register thermal cooling device
in backlight_device_register(). backlight display can be a cooling device
since reducing screen brightness will can help reduce temperature.

However, ->get_max_state of backlight will assign max brightness of 1024
to states. The memory size can be getting 1MB+ due to states * states.
That is so large to trigger kmalloc() warning.

So, let's use kvzalloc() to avoid the issue, also change kfree -> kvfree.

Suggested-by: Amit Kucheria <amitk@kernel.org>
Signed-off-by: Yue Hu <huyue2@yulong.com>
---
 drivers/thermal/thermal_sysfs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index aa99edb..d1703ee 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -16,6 +16,7 @@
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 #include <linux/string.h>
 #include <linux/jiffies.h>
 
@@ -919,7 +920,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
 	var += sizeof(*stats->time_in_state) * states;
 	var += sizeof(*stats->trans_table) * states * states;
 
-	stats = kzalloc(var, GFP_KERNEL);
+	stats = kvzalloc(var, GFP_KERNEL);
 	if (!stats)
 		return;
 
@@ -938,7 +939,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
 
 static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
 {
-	kfree(cdev->stats);
+	kvfree(cdev->stats);
 	cdev->stats = NULL;
 }
 
-- 
1.9.1

Re: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[Viresh Kumar]

On 21-08-20, 10:44, Yue Hu wrote:
> From: Yue Hu <huyue2@yulong.com>
> 
> We observed warning about kzalloc() when register thermal cooling device
> in backlight_device_register(). backlight display can be a cooling device
> since reducing screen brightness will can help reduce temperature.
> 
> However, ->get_max_state of backlight will assign max brightness of 1024
> to states. The memory size can be getting 1MB+ due to states * states.
> That is so large to trigger kmalloc() warning.
> 
> So, let's use kvzalloc() to avoid the issue, also change kfree -> kvfree.
> 
> Suggested-by: Amit Kucheria <amitk@kernel.org>
> Signed-off-by: Yue Hu <huyue2@yulong.com>
> ---
>  drivers/thermal/thermal_sysfs.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[Amit Kucheria]

On Fri, Aug 21, 2020 at 8:14 AM Yue Hu <zbestahu@gmail.com> wrote:
>
> From: Yue Hu <huyue2@yulong.com>
>
> We observed warning about kzalloc() when register thermal cooling device
> in backlight_device_register(). backlight display can be a cooling device
> since reducing screen brightness will can help reduce temperature.
>
> However, ->get_max_state of backlight will assign max brightness of 1024
> to states. The memory size can be getting 1MB+ due to states * states.
> That is so large to trigger kmalloc() warning.
>
> So, let's use kvzalloc() to avoid the issue, also change kfree -> kvfree.
>
> Suggested-by: Amit Kucheria <amitk@kernel.org>
> Signed-off-by: Yue Hu <huyue2@yulong.com>

 Reviewed-by: Amit Kucheria <amitk@kernel.org>

> ---
>  drivers/thermal/thermal_sysfs.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index aa99edb..d1703ee 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -16,6 +16,7 @@
>  #include <linux/device.h>
>  #include <linux/err.h>
>  #include <linux/slab.h>
> +#include <linux/mm.h>
>  #include <linux/string.h>
>  #include <linux/jiffies.h>
>
> @@ -919,7 +920,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
>         var += sizeof(*stats->time_in_state) * states;
>         var += sizeof(*stats->trans_table) * states * states;
>
> -       stats = kzalloc(var, GFP_KERNEL);
> +       stats = kvzalloc(var, GFP_KERNEL);
>         if (!stats)
>                 return;
>
> @@ -938,7 +939,7 @@ static void cooling_device_stats_setup(struct thermal_cooling_device *cdev)
>
>  static void cooling_device_stats_destroy(struct thermal_cooling_device *cdev)
>  {
> -       kfree(cdev->stats);
> +       kvfree(cdev->stats);
>         cdev->stats = NULL;
>  }
>
> --
> 1.9.1
>

RE: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[David Laight]

From: Yue Hu
> Sent: 21 August 2020 03:44
> 
> From: Yue Hu <huyue2@yulong.com>
> 
> We observed warning about kzalloc() when register thermal cooling device
> in backlight_device_register(). backlight display can be a cooling device
> since reducing screen brightness will can help reduce temperature.
> 
> However, ->get_max_state of backlight will assign max brightness of 1024
> to states. The memory size can be getting 1MB+ due to states * states.
> That is so large to trigger kmalloc() warning.

I can't help feeling that there is an 'adequate' implementation
that doesn't require anywhere near 1MB of memory.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)

Re: [PATCH] thermal: sysfs: Fall back to vmalloc() for cooling device's statistics

[Yue Hu]

On Fri, 21 Aug 2020 08:39:45 +0000
David Laight <David.Laight@ACULAB.COM> wrote:

> From: Yue Hu
> > Sent: 21 August 2020 03:44
> > 
> > From: Yue Hu <huyue2@yulong.com>
> > 
> > We observed warning about kzalloc() when register thermal cooling device
> > in backlight_device_register(). backlight display can be a cooling device
> > since reducing screen brightness will can help reduce temperature.
> > 
> > However, ->get_max_state of backlight will assign max brightness of 1024
> > to states. The memory size can be getting 1MB+ due to states * states.
> > That is so large to trigger kmalloc() warning.  
> 
> I can't help feeling that there is an 'adequate' implementation
> that doesn't require anywhere near 1MB of memory.

However, it should be a potential issue due to what i described above, rt?

Thx.

> 
> 	David
> 
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>