Messages in this thread Patch in this message | | | Date | Fri, 13 Apr 2018 11:29:34 +0900 | From | Chanwoo Choi <> | Subject | Re: [PATCH] PM / devfreq: use put_device() instead of kfree() |
| |
On 2018년 04월 13일 11:15, arvindY wrote: > Hi Chanwoo, > > On Friday 13 April 2018 06:43 AM, Chanwoo Choi wrote: >> On 2018년 04월 13일 10:03, Chanwoo Choi wrote: >>> Hi, >>> >>> I'm sorry for the late reply. >>> >>> On 2018년 03월 30일 20:44, Arvind Yadav wrote: >>>> Never directly free @dev after calling device_register() or >>>> device_unregister(), even if device_register() returned an error. >>>> Always use put_device() to give up the reference initialized. >>>> >>>> Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com> >>>> --- >>>> drivers/devfreq/devfreq.c | 4 +++- >>>> 1 file changed, 3 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c >>>> index fe2af6a..a225b94 100644 >>>> --- a/drivers/devfreq/devfreq.c >>>> +++ b/drivers/devfreq/devfreq.c >>>> @@ -625,7 +625,8 @@ struct devfreq *devfreq_add_device(struct device *dev, >>>> err = device_register(&devfreq->dev); >>>> if (err) { >>>> mutex_unlock(&devfreq->lock); >>>> - goto err_dev; >>>> + put_device(&devfreq->dev); >>>> + goto err_out; >>> why do you change the goto postion? >>> err_out is correct to free the memory of devfreq instance. >> Sorry. err_dev is correct instead of err_out. > > If you will see the comment for device_register(drivers/base/core.c) > there is mentioned that 'NOTE: _Never_ directly free @dev > after calling this function, even if it returned an error! > Always use put_device() to give up the reference initialized > in this function instead. Here put_device() will decrement > the last reference and then free the memory by calling dev->release. > Internally put_device() -> kobject_put() -> kobject_cleanup() which > is responsible to call 'dev -> release' and also free other kobject resources. > > We are releasing devfreq in devfreq_dev_release(). So no need > to call kfree() again. It'll be redundant. 'err_out' is correct.
You're right. err_out is correct. put_device() -> dev->release() -> devfreq_dev_release() -> kfree(devfreq)
>> >>>> } >>>> devfreq->trans_table = devm_kzalloc(&devfreq->dev, >>>> @@ -671,6 +672,7 @@ struct devfreq *devfreq_add_device(struct device *dev, >>>> mutex_unlock(&devfreq_list_lock); >>>> device_unregister(&devfreq->dev); >>>> + devfreq = NULL; >>> It is wrong. If you initialize the devfreq as NULL, >>> never free the 'devfreq' instance. > > No need to release memory after device_unregister(). > driver core will take care of this. It will release memory > So no need to call free again.
If you have to initialize the devfreq instance as NULL, I think that you better to init in the devfreq_dev_release() as following:
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index fe2af6aa88fc..8c52a13d3887 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -543,6 +543,7 @@ static void devfreq_dev_release(struct device *dev) mutex_destroy(&devfreq->lock); kfree(devfreq); + devfreq = NULL; }
>>>> err_dev: >>>> if (devfreq) >>>> kfree(devfreq); >>>> >>> >> > > ~arvind > > >
-- Best Regards, Chanwoo Choi Samsung Electronics
| |