Re: [PATCH 8/19]: SCST SYSFS interface implementation

[Boaz Harrosh <bharrosh@panasas.com>]

On 11/11/2010 02:04 PM, Greg KH wrote:
> On Thu, Nov 11, 2010 at 11:59:28AM +0200, Boaz Harrosh wrote:
>> 4. Exactly Like 3 but without the extra kref member
>>    Only x_put() changes and x_kref_release() now receives
>>    an x_object
>>
>> int x_put(struct object_x *x)
>> {
>> 	if (kobject_put(&x->kobj) == 1)
>> 		// Like above [3] x_kref_release()
>> 		x_kref_release(x);
>> }
> 
> This is racy, please never do this.
> 

The last ref belongs to the core code. 1 means there are no
more external clients on the object. So it can not race with
decrements. But I guess there is a possibility that it can
race with new increments. If it is the case that new increments
can only come from, say, sysfs access, then if we call the
x_put() == 1 after we are unregistered from sysfs and no new
users are allowed then the counter can only go down and we
have the last reference. No?

Like I said option 4 is delicate it must be done carefully.

> thanks,
> 
> greg k-h

Thanks
Boaz