[libvirt-users] "virsh list" hangs

[Daniel P. Berrange]

On Tue, Feb 21, 2017 at 12:07:41PM +0800, Yunchih Chen wrote:
> On 02/20/2017 09:10 PM, Michal Privoznik wrote:
> > On 17.02.2017 17:18, Yunchih Chen wrote:
> > > `virsh list` hangs on my server that hosts a bunch of VMs.
> > > This might be due to the Debian upgrade I did on Feb 15, which upgrades
> > > `libvirt` from 2.4.0-1 to 3.0.0-2.
> > > I have tried restarting libvirtd for a few times, without luck.
> > > 
> > > Attached below are some relevant logs; let me know if you need some more
> > > for debugging.
> > > Thanks for your help!!
> > > 
> > > root at vm-host:~# uname -a
> > > Linux vm-host 4.6.0-1-amd64 #1 SMP Debian 4.6.4-1 (2016-07-18) x86_64
> > > GNU/Linux
> > > 
> > > root at vm-host:~# apt-cache policy libvirt-daemon
> > > libvirt-daemon:
> > >    Installed: 3.0.0-2
> > >    Candidate: 3.0.0-2
> > >    Version table:
> > >   *** 3.0.0-2 500
> > >          500 http://debian.csie.ntu.edu.tw/debian testing/main amd64
> > > Packages
> > >          100 /var/lib/dpkg/status
> > > 
> > > root at vm-host:~# strace -o /tmp/trace -e trace=network,file,poll virsh
> > > list  # hangs forever .....
> > > ^C
> > > root at vm-host:~# tail -10 /tmp/trace
> > > access("/etc/libvirt/libvirt.conf", F_OK) = 0
> > > open("/etc/libvirt/libvirt.conf", O_RDONLY) = 5
> > > access("/proc/vz", F_OK)                = -1 ENOENT (No such file or
> > > directory)
> > > socket(AF_UNIX, SOCK_STREAM, 0)         = 5
> > > connect(5, {sa_family=AF_UNIX,
> > > sun_path="/var/run/libvirt/libvirt-sock"}, 110) = 0
> > > getsockname(5, {sa_family=AF_UNIX}, [128->2]) = 0
> > > poll([{fd=5, events=POLLOUT}, {fd=6, events=POLLIN}], 2, -1) = 1
> > > ([{fd=5, revents=POLLOUT}])
> > > poll([{fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 2, -1) = ?
> > > ERESTART_RESTARTBLOCK (Interrupted by signal)
> > > --- SIGINT {si_signo=SIGINT, si_code=SI_KERNEL} ---
> > > +++ killed by SIGINT +++
> > > 
> > > root at vm-host:~# lsof /var/run/libvirt/libvirt-sock # hangs too ...
> > This is very suspicious. Looks like the daemon is in some weird state
> > and hence virsh is unable to get list of domains.
> > 
> > # ps axf | grep libvirtd
> > # gdb -p $(pgrep libvirtd)
> > (gdb) t a a bt
> > 
> > if you could run those commands and share the output that might shed
> > more light.
> > 
> > Michal
> 
> Unfortunately, gdb also hangs when attaching to libvirt ....
> 
> root at vm-host:~# gdb -q -p $(pgrep libvirtd)
> Attaching to process 9556
> [New LWP 9557]
> [New LWP 9558]
> [New LWP 9559]
> [New LWP 9560]
> [New LWP 9561]
> [New LWP 9562]
> [New LWP 9563]
> [New LWP 9564]
> [New LWP 9565]
> [New LWP 9566]
> [New LWP 9567]
> [New LWP 9568]
> [New LWP 9569]
> [New LWP 9570]
> [New LWP 9571]
> [New LWP 9572]
> ^C^C^C^C^C^C^C^C^C^C^C
> 
> It must be killed with SIGKILL, and libvirtd will die with gdb.
> 
> Here[1] is the output of the following command:
>
> strace -o /tmp/gdb-full-trace.txt -s 1024 -f gdb -q -p $(pgrep libvirtd)

Err, that is useless - you've just straced GDB, not libvirtd

You need to strace libvirtd as it starts

   strace -o libvirt.log -f -s 1000 /usr/sbin/libvirtd

Regards,
Daniel
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