[Pkg-openmpi-maintainers] Bug#584699: programs freeze on first MPI op. when run on multihomed IPv6 hosts

[Ivan Shmakov]

Source: openmpi
Version: 1.4.1-1

	Programs run under mpirun(1) freeze on first MPI operation when
	multiple addresses per interface are involved.

	The configuration was roughly as follows:

$ ip addr 
…
2: eth0: …
    …
    inet6 2001:db8::2XX:XXXX:XXXX:XXXX/64 scope global dynamic 
       …
    inet6 2001:db8::17a:170:1:4/64 scope global 
       valid_lft forever preferred_lft forever
…
$ 

	(I. e., one address was configured in interfaces(5), while the
	other was thanks to the stateless IPv6 autoconfiguration.)

	The mpirun(1) was invoked like:

$ mpirun -nperboard 4 -H node1…,node2…,node3… hpcc… < /dev/null &

	which resulted in orted(1) being spawned on the nodes, with both
	of the IPv6 addresses in the tcp6:// URI's.  The payload
	processes were consuming 100% CPU each, but no progress was
	made.  (While we've tried to diagnose the problem, it was
	observed that the nodes have actually formed two disjoint sets,
	with the nodes of a single set being able to participate in a
	parallel computation spawned at any node, but all the attempts
	to spawn a task using the nodes from different sets have
	resulted in the behavior described above; apparently, the sets
	were formed with some dependence on the MAC address.)

	The behavior was 100%-reproducible.

	Switching the stateless configuration off on the nodes with
	sysctl(8) and removing the extra IP have fixed the problem.

# sysctl -w net.ipv6.conf.eth0.accept_ra=0 
# ip addr del 2001:db8::2XX:XXXX:XXXX:XXXX/64 dev eth0 
# 

-- 
FSF associate member #7257
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 196 bytes
Desc: not available
URL: <http://lists.alioth.debian.org/pipermail/pkg-openmpi-maintainers/attachments/20100606/0ab5e2a8/attachment-0001.pgp>