linux-kernel - Re: [PATCH 2/3] thermal: core: Reorder 'thermal_zone_device

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Date:   Tue, 8 Aug 2017 14:31:56 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     linux-kernel@...r.kernel.org
Cc:     linux-pm@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/3] thermal: core: Reorder
 'thermal_zone_device_register()' error handling code

Le 08/08/2017 à 10:49, Zhang Rui a écrit :
> On Sun, 2017-07-16 at 08:59 +0200, Christophe JAILLET wrote:
>> Reorder code in the error handling path in order to match the way
>> resources
>> have been allocated.
>>
>> With this new order, we can avoid a call to 'device_unregister()' if
>> 'thermal_zone_create_device_groups'()' fails. At this point,
>> 'device_register()' has not been called yet.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
>> ---
>>   drivers/thermal/thermal_core.c | 5 +++--
>>   1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/thermal/thermal_core.c
>> b/drivers/thermal/thermal_core.c
>> index 9743f3e65eb0..c58714800660 100644
>> --- a/drivers/thermal/thermal_core.c
>> +++ b/drivers/thermal/thermal_core.c
>> @@ -1232,7 +1232,7 @@ thermal_zone_device_register(const char *type,
>> int trips, int mask,
>>   	/* Add nodes that are always present via .groups */
>>   	result = thermal_zone_create_device_groups(tz, mask);
>>   	if (result)
>> -		goto unregister;
>> +		goto remove_id;
>>
> I agree we should release ida and free tz, like you did in this patch.
>
> But the problem is in the code below, where device_register() fails,
> we should free the resources allocated in
> thermal_zone_create_device_groups() explicitly.
>
> thanks,
> rui
Hi,

Thanks for the review.


I will propose a v2 patch serie with some new helper functions:
    void destroy_trip_attrs(struct thermal_zone_device *tz)
    void thermal_zone_destroy_device_groups(struct thermal_zone_device *tz)

'thermal_zone_destroy_device_groups()' will then be called in the error 
handling path of 'thermal_zone_device_register()', when 
'device_register()' fails.


Would you like me to keep the same patch granularity:
    - (new patch in the serie) - Add some new helper functions to free 
resources
    - add kfree(tz) in the actual error handling path    (despite your 
comment on patch 1/3, I still think it is needed in thie error handling 
path)
    - reorder error handling code
    - avoid code duplication

Or the 3 last ones can be merged together under a generic "Fix resources 
release in error paths in thermal_zone_device_register()" ?

CJ

>>   	/* A new thermal zone needs to be updated anyway. */
>>   	atomic_set(&tz->need_update, 1);
>> @@ -1294,8 +1294,9 @@ thermal_zone_device_register(const char *type,
>> int trips, int mask,
>>   	return tz;
>>   
>>   unregister:
>> -	ida_simple_remove(&thermal_tz_ida, tz->id);
>>   	device_unregister(&tz->device);
>> +remove_id:
>> +	ida_simple_remove(&thermal_tz_ida, tz->id);
>>   	kfree(tz);
>>   	return ERR_PTR(result);
>>   }