> Linux historically has not, the new thread keeps the parent stack pointer and has to implement careful entry code to switch it without messing up the parent t

> Linux historically has not, the new thread keeps the parent stack pointer and has to implement careful entry code to switch it without messing up the parent thread. Well, for calls to fork(2) and clone(2), sure, but the kernel will setup a stack for you on exec(2). It has to have somewhere to stick the command line args, env, and some other extra bits of information like a random seed.