btree2q.c Single Threaded/MultiProcess with latching supplied by advisory file locking. Works with network file systems.
threads2h.c Multi-Threaded/Multi-Process with latching implemented with test & set locks in the btree pages.
+threads2i.c Multi-Threaded/Multi-Process with latching implemented with test & set locks in the btree pages with Linux futex system calls for contention.
The Foster set includes three types of latching: