While backporting the necessary kernel patches to get CRIU running on s390x (https://bugzilla.redhat.com/show_bug.cgi?id=1466682) I detected a problem in RHEL's python which is already fixed upstream:

https://bugs.python.org/issue22821

It can be reproduced with:

#!/usr/bin/env python2
import fcntl
import tempfile
import struct
import errno

F_OFD_SETLK = 37

try:
	with tempfile.TemporaryFile() as fd:
		flock = struct.pack('hhllhh', fcntl.F_RDLCK, 0, 0, 0, 0, 0)
		fcntl.fcntl(fd.fileno(), F_OFD_SETLK, flock)
except IOError as e:
	if e.errno == errno.EINVAL:
		print "I/O error({0}): {1}".format(e.errno, e.strerror)
		print "OFD locks are not supported."
		exit(1)

exit(0)

On x86_64 I get an error (as expected) and on s390x I do not get the error, which leads to wrong results of the CRIU test suite. I am about to also test it on powerpc big-endian to see if it is reproducible on another big-endian platform.