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Re: [libvirt] [PATCH 04/13] Add a generic reference counted virObject type



On 07/17/2012 02:25 PM, Eric Blake wrote:
> On 07/11/2012 07:35 AM, Daniel P. Berrange wrote:
>> From: "Daniel P. Berrange" <berrange redhat com>
>>
>> This introduces a fairly basic reference counted virObject type
>> and an associated virClass type, that use atomic operations for
>> ref counting.
>>
>> +void *virObjectNew(virClassPtr klass)
>> +{
>> +    virObjectPtr obj = NULL;
>> +    char *somebytes;
>> +
>> +    if (VIR_ALLOC_N(somebytes, klass->objectSize) < 0) {
>> +        virReportOOMError();
>> +        return NULL;
>> +    }
>> +    obj = (void*)somebytes;
>> +
>> +    obj->magic = klass->magic;
>> +    obj->klass = klass;
>> +    virAtomicIntSet(&obj->refs, 1);
> 
> In this instance (and no where else), can't we just do 'obj-refs = 1'

obj->refs, obviously

> instead of going through virAtomic, since the object hasn't yet been
> publicized?  It might make life slightly faster.
> 

Perhaps answering myself - the only reason that might exist to avoid
direct assignment would be if we need the memory fence semantics
guaranteed by virAtomicIntSet that we would not have with direct assignment.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org



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