Resolution:
RV uses "advisory locking" - this is a cooperative file locking used to guarantee sequential access to files among processes.
It is normally a process' responsibility to check for locks on a file it wishes to update, before applying its own lock, updating the file and unlocking it again. In this case then if all processes attempting to write to a file use the same advisory lock mechanism, then write access can be guaranteed unique (exclusive), but if another process attempts a write that does not use advisory lock method, it may be able to write to the file (in the case of accessing a store file, the daemon could be left in an inconsistent state where the information on the store are different from the one in memory).