Segfault seen in netmap_compat app on Power8

[Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>]

Hi,

For netmap_compat bridge application on Power8, in netmap_regif
function, the assignment to nmif->ring_ofs[i] is not getting reflected
immediately.

As a result, the subsequent call to netmap_ring_setup ends up writing
data at wrong offset. This causes segfault in the app.

If we print the nmif->ring_ofs[i] after assignment, then, we see the
correct offset and application starts fine.

So, probably, some kind of barrier or mechanism to flush write is
required on Power8?

BTW, this was tried with ToT dpdk git tree on RHEL 7.3 having below
gcc version:

gcc version 4.8.5 20150623 (Red Hat 4.8.5-11) (GCC)

Thanks,
Rahul