Looking at the changes to StartupMultiXact, you're changing the locking
so that both MultiXactOffsetControlLock and MultiXactMemberControlLock
are acquired first before changing anything. Why? Looking at the other
functions in that file, all others that access both files are happy to
acquire one lock at a time, like StartupMultiXact does without the patch.
-- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com