in kernel-2.6.18-194.28.1.el5

linux-2.6-net-tun-orphan-an-skb-on-tx.patch

Retest on  ,this issue still exists.
# uname -r 
2.6.18-194.30.1.el5
# rpm -q kvm
kvm-83-164.el5_5.29

steps:
1.start guest A:
/usr/libexec/qemu-kvm -m 4G -smp 4 -name RHEL5.5.z-32 -uuid 3a362be4-61c3-9780-7169-be9599b7e93b -no-kvm-pit-reinjection -boot dc -drive file=/home/mike,if=virtio,boot=on,format=qcow2,cache=none,werror=stop -net nic,macaddr=14:52:30:1a:8b:c1,vlan=0,model=virtio -net tap,script=/etc/qemu-ifup,vlan=0 -usb -vnc :10 -k en-us -vga cirrus -balloon none -monitor stdio -cpu qemu64,+sse2 -notify all
2.start guest B:
/usr/libexec/qemu-kvm -m 4G -smp 4 -name np1 -uuid 3a362be4-61c3-9780-7169-be9599b7e93b -no-kvm-pit-reinjection -boot dc -drive file=/home/mike1,if=virtio,boot=on,format=qcow2,cache=none,werror=stop -net nic,macaddr=14:52:30:1a:8b:c2,vlan=0,model=virtio -net tap,script=/etc/qemu-ifup,vlan=0 -usb -vnc :11 -k en-us -vga cirrus -balloon none -monitor stdio -cpu qemu64,+sse2 -notify all

3.in guest B ,#arp -i eth0 -s <ip of guest A> <macaddr of guest A>
4,in guest B ,ping guest A # ping <ip of guest A> -c 1
5,in guest A ,#ifdown eth0
6,in guest B ,ping guest A # ping <ip of guest A> -i 0.01
7,after more or less 1 min ,kill guest B #kill -9 <pid of guest B>

Actual Results:
root      5601  4838  5 02:14 pts/1    00:00:42 [qemu-kvm] <defunct>

dmesg on the host:
kernel: unregister_netdevice: waiting for tap1 to become free. Usage count = 1

addtional info:
cat /sys/class/net/tap0/statistics/tx_fifo_errors (guest A)
1



Base on above ,this issue haven't been fixed .