linux-kernel - Re: [PATCH] kernel/workqueue.c: need call device_remove_file() when failure occurs after called device_create

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Date:	Thu, 16 May 2013 12:16:16 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Tejun Heo <tj@...nel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/workqueue.c: need call device_remove_file() when
 failure occurs after called device_create_file()

On 05/16/2013 11:33 AM, Chen Gang wrote:
> On 05/16/2013 05:22 AM, Tejun Heo wrote:
>> On Wed, May 15, 2013 at 02:13:14PM +0800, Chen Gang wrote:
>>>
>>> In workqueue_sysfs_register(), when failure occurs after called
>>> device_create_file(), need call device_remove_file() to release the
>>> related resources, then call device_unregister().
>>>
>>> Or it will cause issue.
>>>
>>> For individual 'device_attributs' (just like our case), need call
>>> device_remove_file() explictly and then call device_unregister(),
>>> please reference drivers/base/*.c (e.g node.c or cpu.c).
>>
>> Hmm... isn't this already taken care of by __sysfs_remove_dir() which
>> device_unregister() calls?  That function removes all non-directory
>> files under the directory being removed.
>>
> 
> It just like what you said:
>   device_unregister() ->
>     kobject_del() ->
>       sysfs_remove_dir() ->
>         __sysfs_remove_dir() ->
>           sysfs_remove_one()
> But:
>   device_remove_file() ->
>     sysfs_remove_file() ->
>       ...
>       sysfs_attr_ns() ->
>         ops->namespace()  (such as device_namespace() in workqueue.c)
>       ...
>       sysfs_hash_and_remove() ->
>         sysfs_remove_one().
> 
> So if not call device_remove_file() explicitly, the device_namespace()
> may be not called.
> 

It seems, if not call ops->namespace(), it still is OK. To get a result,
it still has much details to continue to read.

But all together, reference the related code of another subsystems, we
really need device_remove_file() before call device_unregister().


> 
> Even in device_unregister(), it still call device_remove_file() to
> release the related attributes firstly, then call kobject_del().
> 
> 
> 
> Thanks.
> 


-- 
Chen Gang

Asianux Corporation
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