Question

My thread runs forever and calls ConcurrentLinkedQueue#poll() after a ConcurrentLinkedQueue#peek().

But under some conditions, the thread seems to hang. I know this is a bit vague but can people confirm for me that the methods poll() or peek() will NEVER block. Thanks.

Answer 1

For what I can tell, the ConcurrentLinkedQueue is a ‘wait-free’ implementation.

So I must assume that each independent call to poll() or peek() will NEVER block.

Atomic operations on this collection are synchronized and each individual call to the queue is guaranteed thread-safe.

There must be a problem with your code. For instance, if you do:

Object obj;  if (queue.peek() != null)    obj = queue.poll() 

Does not garentee that obj will not be null.