Re: [libvirt] [PATCH 2/2] qemu: completely rework reference counting
On Wed, Dec 03, 2014 at 06:49:04AM +0100, Martin Kletzander wrote:
@@ -109,7 +117,6 @@ To lock the virDomainObjPtr
To acquire the normal job condition
qemuDomainObjBeginJob()
- - Increments ref count on virDomainObjPtr
- Waits until the job is compatible with current async job or no
async job is running
- Waits for job.cond condition 'job.active != 0' using virDomainObjPtr
@@ -122,14 +129,12 @@ To acquire the normal job condition
qemuDomainObjEndJob()
- Sets job.active to 0
- Signals on job.cond condition
- - Decrements ref count on virDomainObjPtr
I think this is really the key improvement here. Currently we have
this error prone code where we have to check for NULLs after leaving
the job
if (qemuDomainObjEndJob() < 0)
vm = NULL;
if (vm)
virObjectUnlock(vm)
With the methods now fully owning a reference, the 'vm' object can
never be disposed off by another thread. So it will let us make the
code simpler and less error prone.
+void
+qemuDomObjEndAPI(virDomainObjPtr vm)
+{
+ if (virObjectUnref(vm))
+ virObjectUnlock(vm);
+}
I've not thought about it too deeply, so could be missing something,
but I wonder if it is not sufficient todo
virObjectUnlock(vm);
virObjectUnref(vm);
As there is no requirement for the object to be locked now we're
using atomic ints for reference counting. This would avoid the
need go hide the unlock/unref behind this qemuDomObjEndAPI method.
Just have this inline so it is obvious to the casual reader that
we're unrefing + unlocking the object
Regards,
Daniel
--
|: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org -o- http://virt-manager.org :|
|: http://autobuild.org -o- http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|