[libvirt] problems starting several qemu VMS simultaneously

[Serge Hallyn]

Hi,

I grabbed today's git head of libvirt.  Created a VM (clean install of
ubuntu oneiric, installed through virt-manager), and cloned it 3 times.
Then I did

serge at ubuntu:~$ for i in `seq 1 4`; do virsh start o$i  > /tmp/o$i 2>&1 & done
[1] 12184
[2] 12185
[3] 12186
[4] 12187
serge at ubuntu:~$ virsh list
error: Failed to list active domains
error: End of file while reading data: Input/output error

serge at ubuntu:~$ virsh list
 Id    Name                           State
----------------------------------------------------
 5     o2                             shut off
 7     o3                             shut off
 8     o4                             shut off

[1]   Exit 1                  virsh start o$i > /tmp/o$i 2>&1
[2]   Done                    virsh start o$i > /tmp/o$i 2>&1
serge at ubuntu:~$ virsh list
 Id    Name                           State
----------------------------------------------------
 5     o2                             running
 7     o3                             running
 8     o4                             running

[3]-  Done                    virsh start o$i > /tmp/o$i 2>&1
[4]+  Done                    virsh start o$i > /tmp/o$i 2>&1
serge at ubuntu:~$ cat /tmp/o1
error: Failed to start domain o1
error: Unable to wait for child process: Bad file descriptor

It's quite reproducible.  An ubuntu bug report was filed at
https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/961217

It's also very reminiscent of some lxc startup handshake issues
which have been fixed.

You can find the last chunk of the log file at
http://people.canonical.com/~serge/libvirtd-parallel-startup.log

-serge