[TazeTSchnitzel]

> That seems woefully underspecified compared to multithreading in C.

It's not even multithreading yet, it's just a means that support for it might be added.

Also, I don't see why you're complaining about it "compared to multithreading in C". To write for asm.js, you write in C. All this is implementation details for how the C compiler (emscripten, probably) will generate its code.

> Where's my test_and_set? How do I implement locking/mutexes? What's the equivalent of volatile in asmjs? Does it have a memory model like the Java Memory Model/OpenMP Memory Model?

Presumably, locks would be added somehow.

[cromwellian]

pthreads exist in NaCL/PNaCL today, that's the point. There's not many big games on the market today that don't use multiple cores.

[TazeTSchnitzel]

Yes, NaCl has them today. What's your point? Yes, that means NaCl is somewhat faster for the time being. It doesn't mean it always will be.