[libvirt] heisenbug in command.c

[Serge Hallyn]

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