Expose the x86 WaitPkg intrinsics

[tannergooding]

This resolves #66873

[jkotas]

Does this instruction require special handling in thread suspension to avoid GC starvation? For example, if the program executes this instruction in a non-interruptible loop, can it lead to thread suspension hang?

[tannergooding]

Does this instruction require special handling in thread suspension to avoid GC starvation? For example, if the program executes this instruction in a non-interruptible loop, can it lead to thread suspension hang?

Yes, most likely.

The upper limit is dictated by the OS and can be 0 (no limit) or any 32-bit value where the lower two bits are cleared, defining the number of TSC units (e.g. 4, 8, .., 4294967292 TSC).

There's something in Mono blocking this which I've not finished looking at as well.

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I don't plan on getting to this for .NET 10 at this point, we'll wait for .NET 11 and ideally take advantage of it in the runtime where applicable.

[dotnet-policy-service]

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