libvirt users - May 2012 - serial console locking for a domain (concurrent access = garbled output)

Hi,

I am seeing an issue in libvirt-0.9.4-23.el6_2.7.x86_64.rpm where my
virsh console output for a domain gets garbled because I have
virt-manager running and it is also trying to access the serial device
for the guest domain. Basically there is concurrent serial access and
half the text ends up on one end while the rest ends up on the other
end.

Closing virt-manager does not help. Disconnecting and reconnecting
using virsh console does not help. The only way to recover is to
destroy the domain and then start the guest again and never start
virt-manager. Note that the domain does not have VNC graphics so
virt-manager defaults to try to access the serial port when started
for a particular domain.

Should there be locking within libvirt to only allow for a single
client to access a specific serial port of a domain?

Thanks,

Dusty Mabe

On 05/01/2012 12:51 PM, Dusty Mabe wrote:
> Hi,
> 
> I am seeing an issue in libvirt-0.9.4-23.el6_2.7.x86_64.rpm where my
> virsh console output for a domain gets garbled because I have
> virt-manager running and it is also trying to access the serial device
> for the guest domain. Basically there is concurrent serial access and
> half the text ends up on one end while the rest ends up on the other
> end.
Sounds like you are running into the issue that was fixed for 0.9.11
with this patch:

commit 4716138229ae47c5492c13a8622b779889560fd7
Author: Peter Krempa <pkrempa at redhat.com>
Date:   Thu Oct 6 12:24:47 2011 +0200

    qemu: Add ability to abort existing console while creating new one

    This patch fixes console corruption, that happens if two concurrent
    sessions are opened for a single console on a domain. Result of this
    corruption was that each of the console streams recieved just a part
    of the data written to the pipe so every console rendered unusable.

and which is already present in the RHEL 6.3 beta build of libvirt,
thanks to https://bugzilla.redhat.com/show_bug.cgi?id=729940.

-- 
Eric Blake   eblake at redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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