[BoardTracker]

Marco van Herwaarden's review is correct in principal.
There are some things to take into account when describing MySQL's locking mechanism, including DELAYED INSERT, LOW/HIGH PRIORITY and row level locking which effect how locks and tables interact

However..
In case of FTS search, this doesn't really help. When using MyISAM table which are the foundation of MySQL's FTS built in index, locks are always Table-level locks.
Further more, when causing many reads to be queued, the load on the DB server, memory usage and overall caused slowness, can greatly drag the server performance down causing it great difficulties in getting rid of the heavy load (creating a vicious circle). This is ESPECIALLY true if you define the memory parameters incorrectly, causing Swap to be heavily used, which may create a situation where the only solution is restarting the web server, DB server or even both in some cases.