Locking, by its very nature, is a complex beast; it tends to give rise to complex interlocking scenarios. Not understanding it well enough can lead to both performance headaches and bugs – deadlocks, circular dependencies, interrupt-unsafe locking, and more. The following locking guidelines are key to ensuring correctly written code when using locking:
- Locking granularity: The 'distance' between the lock and the unlock (in effect, the length of the critical section) should not be coarse (too long a critical section) it should be 'fine enough'; what does this mean? The points below explain this:
- You need to be careful here. When you're working on large projects, keeping too few locks is a problem, as is keeping too many! Too few locks can lead to performance issues (as the same locks are repeatedly used and thus tend to be highly contended).
- Having a lot of locks is actually good for performance, but...
