Description of problem:
guest will Call Trace ,when second time do S4 with qemu-ga command( {"execute":"guest-suspend-disk"})

Version-Release number of selected component (if applicable):

host:
# uname -r
2.6.32-315.el6.x86_64
rpm -q qemu-kvm
qemu-kvm-0.12.1.2-2.320.el6.x86_64
guest:
# uname -r
2.6.32-325.el6.x86_64
qemu-guest-agent-0.12.1.2-2.321.el6.x86_64


How reproducible:
10%
Steps to Reproduce:

1.boot guest with 
/usr/libexec/qemu-kvm -M rhel6.3.0 -cpu Penryn -enable-kvm -uuid `uuidgen` -rtc base=localtime,driftfix=slew -m 8G -smp 2,sockets=1,cores=2,threads=1 -name rhel6.3-64 -drive file=/home/RHEL-Server-6.3-64-virtio.qcow2,if=none,id=drive-virtio-disk0,format=qcow2,serial=zhang,cache=none,werror=stop,rerror=stop,aio=native -device virtio-blk-pci,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,scsi=off -drive if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -netdev tap,id=hostnet0,vhost=on,script=/etc/qemu-ifup -device virtio-net-pci,netdev=hostnet0,id=net0,mac=04:1a:4a:42:0b:00,bus=pci.0,addr=0x3 -monitor stdio -boot c -qmp tcp:0:5555,server,nowait -vnc :10 -device sga -device virtio-balloon-pci,id=balloon0,bus=pci.0,id=0x6  -chardev socket,path=/tmp/qga.sock,server,nowait,id=qga0 -device  virtio-serial -device virtserialport,chardev=qga0,name=org.qemu.guest_agent.0  -global PIIX4_PM.disable_s3=0 -global PIIX4_PM.disable_s4=0
2.Inside guest: #service qemu-ga start

3. On host:
# nc -U /tmp/qga.sock
{"execute":"guest-suspend-hybrid"}
{"error": {"class": "Unsupported", "data": {}}}
{"execute":"guest-sync"}
{"error": {"class": "InvalidParameterType", "data": {"name": "id", "expected": "integer"}}}
{"execute":"guest-suspend-ram"}--->do S3
{"execute":"guest-suspend-disk"}---->do S4
4.boot guest with same CLI
inside guest:
#service qemu-ga status
qemu-ga (pid  2227) is running ...

on host:
# nc -U /tmp/qga.sock
{"execute":"guest-sync","arguments":{"id":1234}}
{"return": 1234}
{"execute":"guest-suspend-hybrid"}
{"error": {"class": "Unsupported", "data": {}}}
{"execute":"guest-suspend-ram"}-->second time do S3
{"execute":"guest-suspend-disk"}--->second time do S4,guest hang,see the attachment about show on guest

  
Actual results:
guest hang

Expected results:

guest can be do S4 successfully

Additional info:when guest hang.

#top
Tasks: 161 total,   1 running, 160 sleeping,   0 stopped,   0 zombie
Cpu(s): 25.1%us,  0.0%sy,  0.0%ni, 74.9%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   7509328k total,  5932360k used,  1576968k free,    48968k buffers
Swap: 58720240k total,      628k used, 58719612k free,  3930996k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                          
 1968 root      20   0 8764m 1.5g 4408 S 101.4 21.6   2:29.89 qemu-kvm  


addinfo:
1)tried step2 to use 
#qemu-ga -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0
(instead of "service qemu-ga start")
also have the problem
2)tried use command "echo disk >/sys/power/state" in guest ,second time do S4  not hit the problem.


attention:when guest hang ,please wait about 2 min,guest will show Call Trace.
for this issue ,tried above 10 times ,only hit 2 times.