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SubjectRe: [PATCHv5 01/10] Thermal: Do kfree in _unregister functions
Hi Durgadoss,

On Fri, Jan 17, 2014 at 05:26:18AM +0530, Durgadoss R wrote:
> Currently the thermal_release function does
> kfree for all devices when they call device_unregister.
> This makes code scattering i.e whenever we add new
> devices (to thermal class) we need to add its
> corresponding kfree in thermal_release function.
> And the if-else is also growing lengthy.
>
> Instead, do all kfree() of devices in their own
> _unregister functions. This makes the code look
> clean and easy to maintain.
>
> Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> ---
> drivers/thermal/thermal_core.c | 17 +++++------------
> 1 file changed, 5 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 338a88b..165afc6 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -1042,18 +1042,7 @@ EXPORT_SYMBOL_GPL(thermal_zone_unbind_cooling_device);
>
> static void thermal_release(struct device *dev)
> {
> - struct thermal_zone_device *tz;
> - struct thermal_cooling_device *cdev;
> -
> - if (!strncmp(dev_name(dev), "thermal_zone",
> - sizeof("thermal_zone") - 1)) {
> - tz = to_thermal_zone(dev);
> - kfree(tz);
> - } else if(!strncmp(dev_name(dev), "cooling_device",
> - sizeof("cooling_device") - 1)){
> - cdev = to_cooling_device(dev);
> - kfree(cdev);
> - }
> + /* No-op since kfree(dev) is done in _unregister functions */
> }
>
> static struct class thermal_class = {
> @@ -1146,6 +1135,7 @@ __thermal_cooling_device_register(struct device_node *np,
> unregister:
> release_idr(&thermal_cdev_idr, &thermal_idr_lock, cdev->id);
> device_unregister(&cdev->device);
> + kfree(cdev);

This is broken, you can not assume that you are holding the last
reference. Please observe help text of DEBUG_KOBJECT_RELEASE config
option, activate said option and try unregistering thermal device.

Thanks.

--
Dmitry


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