An additional info:
if you use # virsh console guest and do the step 4 and 5. the virsh console will not hang.

Hmm, not being able to ctrl-c significantly reduces the usefulness of the text console.

Does restarting virt-manager fix the console hang? How about connecting to virsh console when virt-manager text connection is hung? Any error messages in the virt-manager --debug output?

zhpeng, any info on the questions in comment #2?

Created attachment 558127 [details]
virt-manager debug message

(In reply to comment #2)
> Hmm, not being able to ctrl-c significantly reduces the usefulness of the text
> console.
> 
> Does restarting virt-manager fix the console hang? How about connecting to
> virsh console when virt-manager text connection is hung? Any error messages in
> the virt-manager --debug output?


Does restarting virt-manager fix the console hang?
Yes.

How about connecting to virsh console when virt-manager text connection is hung?
2 ways 2 results:

Case 1:
virt-manager text connection is hung. DO NOT CLOSE virt-manager.
I can connect virsh console, but input/output messages are not good like:
...
Escape character is ^]

-bash: asdf: com ~]# ot found
7 ~]# ]# -bash: asdf: command[root@dhcp-93-237 ~]# -bash: asdf: command not[root@dhcp-93-23ound7 ~]# -bash: sdf: command not f[root@dhcp-93-237 ~]# -b[ro-bash: f: command not found[root@dhcp-93-237 ~]# d not found
# 
...

Case 2:
virt-manager text connection is hung. CLOSE virt-manager.
I can connect virsh console, input/output messages are good.

Any error messages in the virt-manager --debug output?
PLS check the attachment.

Thanks, fixed upstream now:

http://git.fedorahosted.org/git?p=virt-manager.git;a=commit;h=e830f91d27963fae9b929c86f1f4e72c36335b29

Fixed in virt-manager-0.9.0-8.el6

This bug can be reproduced with:
virt-manager-0.9.0-7.el6.x86_64
kernel-2.6.32-220.el6.x86_64
libvirt-0.9.4-23.el6.x86_64
python-virtinst-0.600.0-5.el6.noarch

Verified with:
kernel-2.6.32-220.el6.x86_64
libvirt-0.9.10-0rc2.el6.x86_64
python-virtinst-0.600.0-7.el6.noarch
virt-manager-0.9.0-9.el6.x86_64

Steps:
1. Prepared a rhel6.2 guest:
# virsh dumpxml rhel6.2
<domain type='kvm' id='3'>
  <name>rhel6.2</name>
  <uuid>68cadd65-7868-df7c-e685-2745334c7bf4</uuid>
  <memory>1048576</memory>
  <currentMemory>1048576</currentMemory>
  <vcpu>1</vcpu>
  <os>
    <type arch='x86_64' machine='rhel6.2.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='raw' cache='none'/>
      <source file='/var/lib/libvirt/images/rhel6.2.img'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </disk>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </controller>
    <controller type='ide' index='0'>
      <alias name='ide0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:21:47:9f'/>
      <source network='default'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/1'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/1'>
      <source path='/dev/pts/1'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'>
      <alias name='input0'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5900' autoport='yes' listen='127.0.0.1'>
      <listen type='address' address='127.0.0.1'/>
    </graphics>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </memballoon>
  </devices>
  <seclabel type='dynamic' model='selinux' relabel='yes'>
    <label>system_u:system_r:svirt_t:s0:c301,c803</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c301,c803</imagelabel>
  </seclabel>
</domain>

2. Add console=tty0 console=ttyS0,115200 to the guest kernel line.

3. Open virt-manager and open the guest window. start the guest.
   click "View" --> "Text Consoles" shift the vnc and serial console make sure
they are both work fine.

4. Login in the guest run
   # cat /var/log/messages

5. Ctrl+C before "cat /var/log/messages" finished.

6. Do 10+ times of step4 and step5

7. Guest works well and console not hang.

Changed the status to VERIFIED.

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Prior to this update, the glib integration did not work correctly. As a consequence, serial consoles of virtual machines could stall when transferring large amounts of data. This update modifies the underlying code to allow the transfer of larger amounts of data without stalling.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2012-0785.html