setting time in guest with ntpdate results in VM hang

[Dale Swanston <swanston@sedsystems.ca>]

Hello.

We are running a guest OS of CentOS 4.4 (kernel 2.6.12) for legacy 
reasons, upgrading is not an option.   NTP is running on the host and 
synching with a local GPS NTP server.  But due to frequency drift in the 
guest it restarts itself periodically and upon start up performs an 
ntpdate to force a time jump on the guest.

I have seen 2 occasions now (over 2 months) where the VM hangs right as 
the ntpdate command alters the guest clock (based on output in 
/var/log/messages).

 From the host's perspective the VM is still running but it appears to 
be using very high CPU percentage (more than typical).  The only 
recovery option is to force shutdown of the VM and restart it.

1.  Are there any known issues with ntpdate and VMs hanging?  Any 
workarounds?
2.  Are there any debugging tools further characterise the problem?

Thanks in advance,
Dale


Further specifics, let me know if more details are needed:

Host:
# uname -a
Linux s1pscu01host 2.6.32-220.el6.x86_64 #1 SMP Sat Dec 10 17:04:11 CST 
2011 x86_64 x86_64 x86_64 GNU/Linux

on  Intel(R) Xeon(R) CPU           E5620  @ 2.40GHz

with qemu-kvm-0.12.1.2-2.209.el6.x86_64

Guest:
I don't use any kernel time modifiers in the guest ...
kernel /vmlinuz-2.6.12 ro root=/dev/VolGroup00/LogVol00 rhgb quiet

CentOS 4.4