Thanks for your note, but I'm confused by your statement. Take Linux go/src/runtime/os_linux.c:/^runtime·newosproc. It passes the already-allocated stack to clo

Thanks for your note, but I'm confused by your statement. Take Linux go/src/runtime/os_linux.c:/^runtime·newosproc. It passes the already-allocated stack to clone(2). runtime·newosproc is called from go/src/runtime/proc.c:/^newm, which uses runtime·allocm to allocate a M. go/src/runtime/proc.c:/^runtime·allocm allocates this memory using runtime·malg on everything except Solaris, Windows, Plan 9, or when using cgo. The comment even reads: // In case of cgo or Solaris, pthread_create will make us a stack. // Windows and Plan 9 will layout sched stack on OS stack. For that class of systems, runtime·newosproc (or _cgo_sys_thread_start) indeed does use the system stacks, but that's what I said too. Let's take a look at runtime·malg again. runtime·malg calls go/src/runtime/stack.c:^/runtime·stackalloc which uses runtime·sysAlloc to allocate memory. Moving back to Linux, go/src/runtime/mem_linux.c:/^runtime·sysAlloc just calls mmap(2). So, the answer to "who allocates system stacks" seems to be "it depends", but I already qualified this in my original answer (omitting cgo; sorry about that). Now, is there anything wrong in my description?