Does Interlocked.CompareExchange use a memory barrier?

Question

I\'m reading Joe Duffy\'s post about Volatile reads and writes, and timeliness, and i\'m trying to understand something about the last code sample in the post:

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Answer 1

The interlocked functions are guaranteed to stall the bus and the cpu while it resolves the operands. The immediate consequence is that no thread switch, on your cpu or another one, will interrupt the interlocked function in the middle of its execution.

Since you're passing a reference to the c# function, the underlying assembler code will work with the address of the actual integer, so the variable access won't be optimized away. It will work exactly as expected.

edit: Here's a link that explains the behaviour of the asm instruction better: http://faydoc.tripod.com/cpu/cmpxchg.htm
As you can see, the bus is stalled by forcing a write cycle, so any other "threads" (read: other cpu cores) that would try to use the bus at the same time would be put in a waiting queue.