On 06.03.2015 14:31, Peter Krempa wrote:
> On Thu, Mar 05, 2015 at 12:05:24 +0100, Michal Privoznik wrote:
>> This patch alone does not make much sense, I know. But it
>> prepares ground for next patch which when looking up a network in
>> the object list will not lock each network separately when
>> accessing its definition. Therefore we must have all the places
>> changing network definition lock the list.
>>
>> Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
>> ---
>> src/conf/network_conf.c | 9 ++++++++-
>> src/conf/network_conf.h | 3 ++-
>> src/network/bridge_driver.c | 4 ++--
>> 3 files changed, 12 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
>> index 3d318ce..007cebb 100644
>> --- a/src/conf/network_conf.c
>> +++ b/src/conf/network_conf.c
>> @@ -537,12 +537,19 @@ virNetworkObjSetDefTransient(virNetworkObjPtr network, bool live)
>> * This *undoes* what virNetworkObjSetDefTransient did.
>> */
>> void
>
> I've looked through the next patch and you are basically trying to make
> the name and UUID pointers for domain immutable or at leas write locked
> ...
>
>> -virNetworkObjUnsetDefTransient(virNetworkObjPtr network)
>> +virNetworkObjUnsetDefTransient(virNetworkObjListPtr nets,
>> + virNetworkObjPtr network)
>> {
>> if (network->newDef) {
>> + virObjectRef(network);
>> + virObjectUnlock(network);
>> + virObjectLock(nets);
>> + virObjectLock(network);
>> + virObjectUnref(network);
>
> But I don't really like pulling in the complexity into this helper.
>
>
>> virNetworkDefFree(network->def);
>> network->def = network->newDef;
>> network->newDef = NULL;
>> + virObjectUnlock(nets);
>> }
>> }
>
> While I like the idea, I'd rather see a conversion to R/W locks or
> making of the name and UUID pointers immutable than this hack.
Well:
1) We don't have an virObjectRWLockable or something similar. I can add
it, but that would postpone merging this patchset for yet another version.
2) Nor UUID nor name can be made immutable, as we are storing just a
pointers to network objects in the array. Not UUID or name. It's not a
hash table like in virDomainObjList* [1]. And when looking up an object,
we access each object's definition directly. Therefore all other places
changing definition must lock the object list.
I agree, that one day we can change this to RW locks, but then again -
that'd require more rework which can be saved for a follow up series.
Moreover, if I introduce new RWLockable object, other drivers might
benefit from it too.
Michal
1: Yes, one day we can turn the array into hash table too. There's
plenty of work to be done. I agree. But I prefer it to be divided into
smaller pieces instead of this one big patchset of hundreds of patches :-P
--
libvir-list mailing list
libvir-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/libvir-list