Re: [libvirt] [PATCH 4/5] qemu: implement virConnectListAllDomains() for qemu driver

> I just realized: Since we are executing this under the driver lock, and > no VM can change state until we let go of the driver lock, it is not > necessary to lock vms in this loop. That will help things go faster in > computing the list. Hmm, this feels slightly dangerous to me. Saying that is in effect saying you can do reads on a virDomainObjPtr without locking. This would be ok if it were impossible for the fields we're reading to be changed without driver lock held. 1. Thread A lock(driver) 2. Thread A lock(vm1) 3. Thread A unlock(driver) 4. Thread B lock(driver) 5. Thread B ...starts getting the list of domains... Now consider Thread A changes the 'id' feld in a virDomainPtr eg due to the guest shutting down. Won't thread B be doing unsafe reads of 'id' now ? The only way I can see that this is safe, is if we are sure that every change of the 'name', 'uuid' and 'id' fields is protected by the driver lock.