spinwait

MSDN "Thread-Safe Collections .NET Framework 4" states: "Some of the concurrent collection types use lightweight synchronization mechanisms such as SpinLock , SpinWait , SemaphoreSlim , and CountdownEvent , which are new in the .NET Framework 4" while MSDN website tells that SpinWaitwas was available as far as .NET 1.1 while another MSDN article starts SpinWaitwas from .NET 4.0 Well, the curiosity is from the comment by Lee Grissom to answer What is the difference between SynchronizedCollection and the other concurrent collections? : "@Matt, the .NET4 concurrent classes use SpinWait objects to

While reading Albahari's Threading in C# , I've noticed that the "lock free update" pattern uses a SpinWait at the end of the cycle: static void LockFreeUpdate<T> (ref T field, Func <T, T> updateFunction) where T : class { var spinWait = new SpinWait(); while (true) { // read T snapshot1 = field; // apply transformation T calc = updateFunction (snapshot1); // compare if not preempted T snapshot2 = Interlocked.CompareExchange (ref field, calc, snapshot1); // if succeeded, we're done if (snapshot1 == snapshot2) return; // otherwise spin spinWait.SpinOnce(); } } Note the spinWait.SpinOnce() call