An ubuntu pastebin for a CentOS issue seems a bit... odd. Unfortunately, pastebins tend to expire, so linking to them in mail isn't always the most reliable, compared to just pasting relevant sections inline.
2013-05-16 04:08:11.063+0000: 21636: debug : qemuDomainObjBeginJobInternal:813 : Starting async job: snapshot 2013-05-16 04:08:11.103+0000: 21636: debug : virFileClose:72 : Closed fd 23 2013-05-16 04:08:11.103+0000: 21636: debug : virCgroupNew:617 : New group /libvirt/qemu/testvm 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 0:cpu at /cgroup/cpu in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 1:cpuacct at /cgroup/cpuacct in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 2:cpuset at /cgroup/cpuset in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 3:memory at /cgroup/memory in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 4:devices at /cgroup/devices in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 5:freezer at /cgroup/freezer in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupDetect:273 : Detected mount/mapping 6:blkio at /cgroup/blkio in 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupMakeGroup:535 : Make group /libvirt/qemu/testvm 2013-05-16 04:08:11.105+0000: 21636: debug : virCgroupMakeGroup:560 : Make controller /cgroup/cpu/libvirt/qemu/testvm/ 2013-05-16 04:08:11.106+0000: 21636: error : qemuDomainSnapshotCreateDiskActive:11299 : internal error Unable to find cgroup for testvm 2013-05-16 04:08:11.106+0000: 21636: debug : qemuProcessStartCPUs:2825 : Using lock state '(null)'
At this point, all I can say is that our logging for cgroups is LOUSY. Can you retry with the just-released 1.0.5.1 or even libvirt.git, as it makes no sense trying to debug stale versions unless we can prove the problem also affects the latest? There have been some recent cgroups patches.
Thanks. :-) I'll try 1.0.5.1 later.