glusterd: compare friend data within mutex

During friend handshake if the glusterd receives more than one friend
updates, it might very well become possible that two threads would end
up working on two different volinfo references and glusterd might end up
updating the store with a old volinfo reference. While debugging
glusterd crash from validating-server-quorum.t test file from the
line-coverage regression the same was observed.

Solution is to run glusterd_compare_friend_data under a mutex.

Test:

As the crash was more visible in the line-coverage run (given lcov does
some instrumentation and exposes the races), 6 manual lcov runs were
triggered starting from https://build.gluster.org/job/line-coverage/443
to https://build.gluster.org/job/line-coverage/449/ and no crash was
observed from validating-server-quorum.t

Change-Id: I86fce473a76fd24742d51bf17a685d28b90a8941
Fixes: bz#1603063
Signed-off-by: Atin Mukherjee <amukherj@redhat.com>

0 files changed, 0 insertions, 0 deletions