Description of problem:
loss data while transfer data from guest to host by chardev


Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.369.el6.x86_64

How reproducible:
100%

Steps to Reproduce:
1.boot up guest with follow command line:
/usr/libexec/qemu-kvm \
-cpu SandyBridge \
-M rhel6.5.0 \
-enable-kvm \
-m 4096 \
-smp 2,sockets=2,cores=1,threads=1 \
-name rhel6.5-64 \
-uuid 9a0e67ec-f286-d8e7-0548-0c1c9ec93001 \
-nodefconfig \
-nodefaults \
-monitor stdio \
-rtc base=utc,clock=host,driftfix=slew \
-no-kvm-pit-reinjection \
-drive file=/home/images/rhel6u5.qcow2,if=none,id=drive-virtio-disk0,format=qcow2,cache=none \
-device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=2 \
-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 \
-vga qxl \
-netdev tap,id=hostnet0,downscript=no \
-device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:1a:4a:2e:28:1c,bus=pci.0,addr=0x4,bootindex=1 \
-qmp tcp:0:5555,server,nowait \
-global PIIX4_PM.disable_s3=0 \
-global PIIX4_PM.disable_s4=0 \
-spice port=5900,disable-ticketing \
-device virtio-serial-pci,id=virtio-serial0,max_ports=16,bus=pci.0 \
-chardev socket,id=channel1,path=/tmp/serial-socket-0,server,nowait \
-device virtserialport,chardev=channel1,name=org.linux-kvm.port.1,bus=virtio-serial0.0,id=port1 \

2.Transfer data from guest to host use follow two scenario.
a. open-write-close test:

for seq in $(seq 1 100); do echo "test $seq" > /dev/virtio-ports/org.kraxel.test; sleep 1; done

b. keep-device-open test:

(for seq in $(seq 1 100); do echo "test $seq"; sleep 1; done) > /dev/virtio-ports/org.kraxel.test

  
Actual results:
host receive data
test 3
test 4
test 5
test 6
test 7
test 8
test 9
test 10
...

loss "test 1" and "test 2"

Expected results:
ensure data integrity

Additional info:
it didn't happen in qemu-kvm-0.12.1.2-2.367.el6.x86_64,this bug is a regression by bz909059 fix.