Handling out of order execution

Question

I recently stumbled upon this Wikipedia article. From my experience with multi-threading I am aware of the multitude of issues caused by the program being able to switch threads

Answer 1

So essentially you're asking about the memory consistency model. Some languages/environments, such as Java and .NET, define a memory model, and it's the responsibility of the programmer to not do things which are not allowed, or results in undefined behavior. If you're unsure about the atomicity behavior of "normal" operations, it's better to be safe than sorry and just use the mutex primitives.

For C and C++ the situation is not as nice, as those language standards don't define a memory model. And no, contrary to the unfortunately popular opinion, volatile doesn't guarantee anything wrt atomicity. In this case, you have to rely on the platform threads library (which among other things executes required memory barriers) or compiler/hw-specific atomic intrinsics, and hope that the compiler doesn't do any optimizations that break program semantics. As long as you avoid conditional locking within a function (or translation unit if using IPA) you ought to be relatively safe.

Luckily, C++0x and the next C standard are rectifying this issue by defining a memory model. I asked a question related to this and, as it turned out, conditional locking here; the question contains links to some documents that go into the issue in some detail. I recommend you to read those documents.