Is this lock-free .NET queue thread safe?

Question

My question is, is the class included below for a single-reader single-writer queue class thread-safe? This kind of queue is called lock-free, even if it will block if the queue

Answer 1

Beware of the double checked - single lock pattern (as in a link quoted above: http://www.yoda.arachsys.com/csharp/singleton.html)

Quoting verbatim from the "Modern C++ Design" by Andrei Alexandrescu

Very experienced multithreaded programmers know that even the Double-Checked Locking pattern, although correct on paper, is not always correct in practice. In certain symmetric multiprocessor environments (the ones featuring the so-called relaxed memory model), the writes are committed to the main memory in bursts, rather than one by one. The bursts occur in increasing order of addresses, not in chronological order. Due to this rearranging of writes, the memory as seen by one processor at a time might look as if the operations are not performed in the correct order by another processor. Concretely, the assignment to pInstance_ performed by a processor might occur before the Singleton object has been fully initialized! Thus, sadly, the Double-Checked Locking pattern is known to be defective for such systems