How are mutexes implemented?

Question

Are some implementations better than others for specific applications? Is there anything to earn by rolling out your own?

Answer 1

I used Reflector.NET to decompile the source for System.Threading.ReaderWriterLockSlim, which was added to a recent version of the .NET framework.

It mostly uses Interlocked.CompareExchange, Thread.SpinWait and Thread.Sleep to achieve synchronisation. There are a few EventWaitHandle (kernel object) instances that are used under some circumstances.

There's also some complexity added to support reentrancy on a single thread.

If you're interested in this area and working in .NET (or at least, can read it) then you might find it quite interesting to check this class out.