Provide an inter-process variant of SpinLock

[The-Futurist]

Currently to spin-synchronize threads in different processes that are sharing mapped memory, we must roll our own spinlock-like primitive based on interlocked operations. It would be most helpful to have an alternative SpinLock implementation that took an additional ref lockDatum arg to the Enter method (or perhaps a new constructor overload) so that the memory used for the internal interlocked operation can be situated in shared memory.

Users of this would be expected to ensure appropriate initialization of the lock datum before making use of it (much as we do now when using Interlocked.CompareExchange directly).

[huoyaoyuan]

You can just put the SpinLock instance into shared memory.

[tannergooding]

It would likely be better, safer, and more efficient to use the dedicated OS primitives to do such cross-process locking.

That is what things like "named" mutexes are for, after all, and which are setup to ensure that this all happens in a way that doesn't waste processor cycles or unnecessarily yield.

https://learn.microsoft.com/en-us/dotnet/api/system.threading.mutex.-ctor?view=net-9.0#system-threading-mutex-ctor(system-boolean-system-string-system-boolean@)