Pkg xen devel - Oct 2014 - Bug#767261: xen-hypervisor-4.4-amd64: host lockup when DomU network iface is down

Package: xen-hypervisor-4.4-amd64
Version: 4.4.1-3
Severity: important

Hi,

I have some domUs with two network interfaces, eth0 and eth1. eth0 is 
not configured in /etc/network/interfaces and so is not brought up at 
boot time.
eth0 is on the host's external network bridge and eth1 is on the host's 
local network bridge.
On dom0 I get messages like 'vif vif-10-0 vif10.0: draining TX queue', 
starting as soon as the domU's boot up. I'm pretty sure this is a 
regression from Xen 4.1 in wheezy.
The real problem is that after a couple of hours with just the above 
message, the entire host locks up completely, with the following message:
INFO: task jbd2/dm-32-8:1206 blocked for more than 120 seconds.
At this point the machine is not responding to ping and nothing much can 
be done at the console either, I can't even do a proper reboot, so I use 
the reset button.
dm-32 corresponds to dom0's /var.
I've looked at this repeatedly and I'm 100% that this lockup is related 
to the network interface being down on the domU.
To avoid this I'm simply doing 'ip link set eth0 up' within the
relevant
domU's as soon as they boot up. This keeps my Xen box safe and stable.

dom0 and domU kernel is linux 3.16-3-amd64 3.16.5-1

-- System Information:
Debian Release: jessie/sid
   APT prefers testing-updates
   APT policy: (500, 'testing-updates'), (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16-3-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

xen-hypervisor-4.4-amd64 depends on no packages.

Versions of packages xen-hypervisor-4.4-amd64 recommends:
ii  xen-utils-4.4  4.4.1-3

xen-hypervisor-4.4-amd64 suggests no packages.

-- no debconf information

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Control: reassign -1 src:linux
Control: found -1 3.16.5-1

On Wed, 2014-10-29 at 12:57 -0400, Gedalya wrote:
> On dom0 I get messages like 'vif vif-10-0 vif10.0: draining TX
queue',
> starting as soon as the domU's boot up. I'm pretty sure this is a 
> regression from Xen 4.1 in wheezy.
[...]
> dom0 and domU kernel is linux 3.16-3-amd64 3.16.5-1
This is most likely to be a dom0 kernel side issue, so reassigning.

Are there any interesting messages preceeding the "draining TX queue"
ones?

I suspect we will need to backport some xen-netback patch or other. I've
put some feelers out to see if any of the upstream devs have any
hints...

Ian.

Processing control commands:
> reassign -1 src:linux
Bug #767261 [xen-hypervisor-4.4-amd64] xen-hypervisor-4.4-amd64: host lockup
when DomU network iface is down
Bug reassigned from package 'xen-hypervisor-4.4-amd64' to
'src:linux'.
No longer marked as found in versions xen/4.4.1-3.
Ignoring request to alter fixed versions of bug #767261 to the same values
previously set
> found -1 3.16.5-1
Bug #767261 [src:linux] xen-hypervisor-4.4-amd64: host lockup when DomU network
iface is down
Marked as found in versions linux/3.16.5-1.

-- 
767261: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=767261
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