What's an example of it not being true in Windows? I think it's mostly true in Linux and the situations where it isn't true are subtle and require expert knowl

What's an example of it not being true in Windows? I think it's mostly true in Linux and the situations where it isn't true are subtle and require expert knowledge in some specific areas. It's not like there's a big sticker on Linux that says threads are generally not symmetric. I get the bit of half the process being in one space and half in another. I just find it odd. Can half the process run as root and half the process run as another user? Maybe yes? Can a file be open in half the process and not open in the other? At any rate, I think it's not black and white. Green threads do make sense in general and introducing different thread types and more granular control makes things more complicated. I think you're missing my point about APIs and handles: handle = open_namespace("test") syscall(handle, "yes") if handle can be used across threads then this sequence will run correctly regardless of what thread is executing it, it doesn't rely on anything bestowed on a thread. (EDIT: thread local storage I guess is an example of asymmetry between threads but it's intentional/clear asymmetry designed for specific purposes and something you don't need to access in Go e.g. because you don't use threads directly).