Re: [PATCH v9 4/8] PM / devfreq: Move more initialization before registration

[Chanwoo Choi <cw00.choi@samsung.com>]

On 19. 10. 31. 오후 10:31, Leonard Crestez wrote:
> On 31.10.2019 05:10, Chanwoo Choi wrote:
>> Hi Leonard,
>>
>> This patch didn't get the acked-by from devfreq maintainer.
>> I think that we need to discuss this patch with more time.
>> Also, it is possible to make it as the separate patch
>> from this series.
>>
>> IMHO, if you make the separate patch for this and
>> resend the separate patch on later, I think that
>> we can merge the remained patch related to PM_QOS.
> 
> The devfreq initialization cleanups are required for dev_pm_qos support, 
> otherwise lockdep warnings are triggered. I can post the cleanups as a 
> separate series but the PM QoS one would depend on the cleanups.
> 
> Do you prefer multiple smaller series?

After read the v10, I think v9 is better than v10
for this issue. 

> 
> I try to order my patches with uncontroversial fixes and cleanups first 
> so in theory the earlier parts could be applied separately. It's very 
> rare to see series partially applied though.
> 
> Earlier objection was that devm should be kept, I think this can be 
> accomplished by splitting device_register into device_initialize and 
> device_add.
> 
>> On 19. 10. 3. 오전 4:25, Leonard Crestez wrote:
>>> In general it is a better to initialize an object before making it
>>> accessible externally (through device_register).
>>>
>>> This makes it possible to avoid remove locking the partially initialized
>>> object and simplifies the code. However devm is not available before
>>> device_register (only after the device_initialize step) so the two
>>> allocations need to be managed manually.
>>>
>>> Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
>>> Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
>>> ---
>>>   drivers/devfreq/devfreq.c | 43 +++++++++++++++++++++++----------------
>>>   1 file changed, 25 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>> index 3e0e936185a3..0b40f40ee7aa 100644
>>> --- a/drivers/devfreq/devfreq.c
>>> +++ b/drivers/devfreq/devfreq.c
>>> @@ -591,10 +591,12 @@ static void devfreq_dev_release(struct device *dev)
>>>   	mutex_unlock(&devfreq_list_lock);
>>>   
>>>   	if (devfreq->profile->exit)
>>>   		devfreq->profile->exit(devfreq->dev.parent);
>>>   
>>> +	kfree(devfreq->time_in_state);
>>> +	kfree(devfreq->trans_table);
>>>   	mutex_destroy(&devfreq->lock);
>>>   	kfree(devfreq);
>>>   }
>>>   
>>>   /**
>>> @@ -674,44 +676,43 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>>   	devfreq->max_freq = devfreq->scaling_max_freq;
>>>   
>>>   	devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
>>>   	atomic_set(&devfreq->suspend_count, 0);
>>>   
>>> -	dev_set_name(&devfreq->dev, "devfreq%d",
>>> -				atomic_inc_return(&devfreq_no));
>>> -	err = device_register(&devfreq->dev);
>>> -	if (err) {
>>> -		mutex_unlock(&devfreq->lock);
>>> -		put_device(&devfreq->dev);
>>> -		goto err_out;
>>> -	}
>>> -
>>> -	devfreq->trans_table = devm_kzalloc(&devfreq->dev,
>>> +	devfreq->trans_table = kzalloc(
>>>   			array3_size(sizeof(unsigned int),
>>>   				    devfreq->profile->max_state,
>>>   				    devfreq->profile->max_state),
>>>   			GFP_KERNEL);
>>>   	if (!devfreq->trans_table) {
>>>   		mutex_unlock(&devfreq->lock);
>>>   		err = -ENOMEM;
>>> -		goto err_devfreq;
>>> +		goto err_dev;
>>>   	}
>>>   
>>> -	devfreq->time_in_state = devm_kcalloc(&devfreq->dev,
>>> -			devfreq->profile->max_state,
>>> -			sizeof(unsigned long),
>>> -			GFP_KERNEL);
>>> +	devfreq->time_in_state = kcalloc(devfreq->profile->max_state,
>>> +					 sizeof(unsigned long),
>>> +					 GFP_KERNEL);
>>>   	if (!devfreq->time_in_state) {
>>>   		mutex_unlock(&devfreq->lock);
>>>   		err = -ENOMEM;
>>> -		goto err_devfreq;
>>> +		goto err_dev;
>>>   	}
>>>   
>>>   	devfreq->last_stat_updated = jiffies;
>>>   
>>>   	srcu_init_notifier_head(&devfreq->transition_notifier_list);
>>>   
>>> +	dev_set_name(&devfreq->dev, "devfreq%d",
>>> +				atomic_inc_return(&devfreq_no));
>>> +	err = device_register(&devfreq->dev);
>>> +	if (err) {
>>> +		mutex_unlock(&devfreq->lock);
>>> +		put_device(&devfreq->dev);
>>> +		goto err_out;

err_out -> err_dev
When failed to register, have to free resource.

>>> +	}
>>> +
>>>   	mutex_unlock(&devfreq->lock);
>>>   
>>>   	mutex_lock(&devfreq_list_lock);
>>>   
>>>   	governor = try_then_request_governor(devfreq->governor_name);
>>> @@ -737,14 +738,20 @@ struct devfreq *devfreq_add_device(struct device *dev,
>>>   
>>>   	return devfreq;
>>>   
>>>   err_init:
>>>   	mutex_unlock(&devfreq_list_lock);
>>> -err_devfreq:
>>>   	devfreq_remove_device(devfreq);
>>> -	devfreq = NULL;
>>> +	return ERR_PTR(err);


It is not proper to return on the middle 
of the exception handling. Need to consider more clean method.

>>> +
>>>   err_dev:
>>> +	/*
>>> +	 * Cleanup path for errors that happen before registration.
>>> +	 * Otherwise we rely on devfreq_dev_release.
>>> +	 */
>>> +	kfree(devfreq->time_in_state);
>>> +	kfree(devfreq->trans_table);
>>>   	kfree(devfreq);
>>>   err_out:
>>>   	return ERR_PTR(err);
>>>   }
>>>   EXPORT_SYMBOL(devfreq_add_device);


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics

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