ReadWriteLock与StampedLock

Question

I've been using ReadWriteLock `s to implement/maintain a locking idioms.

Since JDK8 StampedLock has been introduced. And as RWLocks are known with their slowness and bad performance, StampedLock's look like an alternative (they are not reentrant, so much faster).

However except the performance, it looks to me that StampedLock's are much harder and complex to maintain and use - eg threads can now deadlock against themselves - so corresponding actions should be taken.

What are the benefits of StampedLock over RWLock ?

Answer 1

This article explains the differences in detail.

The ReentrantReadWriteLock had a lot of shortcomings: It suffered from starvation. You could not upgrade a read lock into a write lock. There was no support for optimistic reads. Programmers "in the know" mostly avoided using them.

Doug Lea's new Java 8 StampedLock addresses all these shortcomings. With some clever code idioms we can also get better performance.

Answer 2

Well, yes ReentrantReadWriteLock had problems (when compared to the traditional synchronized block) in 5.0 but they fixed it in java 6.0.

So, if you guys use Java 6 in production, you can use the lock API with confidence.

Performance wise lock & traditional synchronization gives you same.

The good thing about lock API is that it uses CAS/non-blocking so it will never end up with deadlock unless you forget to unlock it in the finally block.