Locking Guidelines

Here are some simple guidelines for locking.

• Try not to hold locks across long operations like I/O where performance can be adversely affected.

• Don't hold locks when calling a function that is outside the module and that might reenter the module.

• In general, start with a coarse-grained approach, identify bottlenecks, and add finer-grained locking where necessary to alleviate the bottlenecks. Most locks are held for short amounts of time and contention is rare, so fix only those locks that have measured contention.

• When using multiple locks, avoid deadlocks by making sure that all threads acquire the locks in the same order.