RdMentalMap getters are not thread-safe

Currently, the getters of the RdMentalMap are not thread-safe, so they may have problems when running in different threads.

Start by locating RdMentalMap and its getter implementations, then inspect how callers use them across threads. Reproduce the reported problem with the relevant test suite or a focused concurrent test. The issue is done when the getters behave safely under concurrent access without changing their intended results.

Written by the indexing model from the issue text.