On Tue, Nov 25, 2008 at 04:32:00PM -0800, Bryan McLellan wrote: > I recently started configuring guests to use both a serial console and > a graphics element. One of the nodes with this configuration kept > locking up after running for some time. Trying to access the guest > through virt-manager would leave virt-viewer hung at the connecting to > screen. The guest would not respond to any network traffic including > icmp. The user would destroy the domain and restart it to recover. > Eventually the problem came to me and I found that immediately upon > running 'virsh console domain' the guest would recover. The console > contained: > > BUG: soft lockup - CPU#0 stuck for 94393s! [postgresql-8.3:4975] > > I discovered a bug in a puppet recipe caused postgres to reload > regularly, printing a message to the console each time. Running puppet > in a loop to continue producing these messages to the console caused > another lockup that was recoverable by accessing the serial console in > the same manner. I have since fixed that recipe, but I'm uncomfortable > about the possibility of this happening again. > > Is there a way to configure libvirt to cache the serial console on the > host so the buffer on the guest does not fill up when you aren't > connected to the console, or should I disable the serial console? This is actually a bug in QEMU. It should never block the VM when the serial port buffer fills up. Unfortunately when the serial port was connected to a TTY, QEMU would block on the write :-( The recent KVM releases fix this, but QEMU goes years without a release so it still suffers from this. I'd recommend filing a bug against QEMU in your distro. There's nothing libvirt can do to fix this. Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://ovirt.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :| -- Libvir-list mailing list Libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list