CODEWITHSUNDEEP
c#.netmutex
richard
richard

Reputation: 12498

How does .NET implement a mutex?

I understand the concept of a mutex. It was very well explained here.

But now I want to know what a mutex really is. My guess is that .NET is taking some primitive system resource (maybe even just a memory address?) and wrapping it in an object that it calls a mutex.

Anyone know exactly how a mutex is achieved in .NET?

Upvotes: 2

Views: 2246

Answers (2)

Ana Betts
Ana Betts

Reputation: 74654

http://msdn.microsoft.com/en-us/magazine/cc164040.aspx will give you the details. .NET Mutexes are based at the end of the day, on Win32 thread primitives, though some things are a bit different (remember that the 'lock' statement works on any object, so there are some things in the CLR called SyncBlocks that deal with that).

Upvotes: 0

Nicholas Carey
Nicholas Carey

Reputation: 74197

How a mutex gets implemented is quite likely hardware-dependent. Most CPUs have some sort of atomic compare-and-swap instruction that provides the guts of the thing.

But yes, under the hood, it's just a semaphore — a thing (word, probably) whose value indicates whether its signaled or not. The OS provides a means for a thread or process to do an idle wait, waiting for the semaphore to enter the desired state. Most implementation, I believe don't guarantee the order in which a thread might gain ownership of a mutex — just because you were first in line, doesn't mean that you'll be the first to get it.

Upvotes: 5

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