Description of problem:
vdsmd is unstable on a hypervisor and crashes frequently.
So it causes rhevm lost connection with hypervisor and all the VMs went to non-response status. vdsmd seems was killed by SEVG signal:
~~~
Apr 22 10:24:26 h-p-27 kernel: vdsm[39698]: segfault at 20 ip 00000036dac09220 sp 00007f7ae61f9da8 error 4 in libpthread-2.12.so[36dac00000+17000]
~~~
There are also other useful information:
~~~
Apr 22 15:02:12 h-p-27 abrt: detected unhandled Python exception in '/usr/share/vdsm/nwfilter.pyc'
Apr 22 15:02:12 h-p-27 abrt: can't communicate with ABRT daemon, is it running? [Errno 2] No such file or directory
Apr 22 15:02:12 h-p-27 init: libvirtd main process (34563) killed by SEGV signal
Apr 22 15:02:12 h-p-27 init: libvirtd main process ended, respawning
~~~
~~~
Thread-266::ERROR::2013-04-22 14:06:36,837::utils::416::vm.Vm::(collect) vmId=`5e614c36-37e0-42ea-a7bc-9c65bb2c977b`::Stats function failed: <AdvancedStatsFunction _sampleNet at 0x15cd298>
Traceback (most recent call last):
  File "/usr/lib64/python2.6/site-packages/vdsm/utils.py", line 412, in collect
    statsFunction()
  File "/usr/lib64/python2.6/site-packages/vdsm/utils.py", line 287, in __call__
    retValue = self._function(*args, **kwargs)
  File "/usr/share/vdsm/libvirtvm.py", line 168, in _sampleNet
    netSamples[nic.name] = self._vm._dom.interfaceStats(nic.name)
  File "/usr/share/vdsm/libvirtvm.py", line 515, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/vdsm/libvirtconnection.py", line 83, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 1867, in interfaceStats
    if ret is None: raise libvirtError ('virDomainInterfaceStats() failed', dom=self)
libvirtError: internal error received hangup / error event on socket
Thread-194::ERROR::2013-04-22 14:06:36,838::utils::416::vm.Vm::(collect) vmId=`c19ea273-40b3-4df1-92e8-d343bc0c03d9`::Stats function failed: <AdvancedStatsFunction _sampleCpu at 0x15cd1b8>
Traceback (most recent call last):
  File "/usr/lib64/python2.6/site-packages/vdsm/utils.py", line 412, in collect
    statsFunction()
  File "/usr/lib64/python2.6/site-packages/vdsm/utils.py", line 287, in __call__
    retValue = self._function(*args, **kwargs)
  File "/usr/share/vdsm/libvirtvm.py", line 137, in _sampleCpu
    cpuStats = self._vm._dom.getCPUStats(True, 0)
  File "/usr/share/vdsm/libvirtvm.py", line 515, in f
    ret = attr(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/vdsm/libvirtconnection.py", line 83, in wrapper
    ret = f(*args, **kwargs)
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 1849, in getCPUStats
    if ret is None: raise libvirtError ('virDomainGetCPUStats() failed', dom=self)
libvirtError: internal error client socket is closed
~~~~

Version-Release number of selected component (if applicable):
* libvirt-0.10.2-18.el6_4.2.x86_64
* vdsm-4.10.2-1.8.el6ev.x86_64
* rhevm-3.1.0-43.el6ev.noarch

How reproducible:
Since the issue happened occasionally, so we don't know how to reproduce it at this time.

Steps to Reproduce:
N/A
  
Actual results:
vdsmd and libvirtd crashed, and lost connection with hypervisor

Expected results:
vdsmd and libvirtd running well.

Additional info:
Customer has uploaded the Log-collector to our ftp server:
ftp://dropbox.redhat.com/sosreport-LogCollector-m3-20130422141119-993b.tar.xz