[libvirt] heisenbug in command.c

Hi, It seems I've run into quite the heisenbug, reported at https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/922628 It manifests itself as virPidWait returning status=4 for iptables (which should never exit with status=4). But it's only been seen on two (very different) machines, and the slightest shifting of the winds makes it go away. Given how sneaky this bug appears to be, there's a slight temptation to have iptablesAddRemoveRule pass in a int* for status and better deal with the -EINTR. But I fear that might be papering over a worse race. Does anyone have any ideas on this? Has anyone else ever seen this? -serge