Re: [libvirt] race condtion in getting VNC port for libvirt
On Sun, Nov 07, 2010 at 08:53:32PM +0800, Guangya Liu wrote:
Hi,
We are encountering a problem of race conditions for getting VNC port
when VM start up.
In a very powerful hypervisor, if we try to start up more than 1 VM
concurrently, then there might be some VMs failed to start up due to VNC
port confilict.
We searched libvirt bugs and found that some one report the problem and
we have give a fix, but the fix can not resolve the problem.
http://osdir.com/ml/libvir-list/2010-05/msg00530.html
https://build.opensuse.org/package/view_file?file=vnc-race-3.patch&packa
ge=libvirt&project=Virtualization:openSUSE11.3
This patch is already merged in current GIT repos.
The bitmap test-and-set operation is not atomic, so that there still
is
a time-window in which a VNC port could be reserved for two caller.
The virBitmap APIs for getting & setting don't need to be atomic, because
they are only called when the QEMU driver mutex is held, which ensures
serialization of VM startup.
Regards,
Daniel
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