You should only use reader-writer locks when:

1. You have both readers and writers
1. People can read concurrently but only one person can write at a time
1. You have people reading all the time and very few writes (i.e. 80%+ of acquires are read acquires)

Otherwise Reader-Writer locks are twice as slow as normal locks, and in the case of logging, it can actually add up to a pretty big hit, since threads are going to end up rescheduled