Close threads on exec()

[rennergade]

I'm realizing this is a bug that we never addressed in NaCl-Lind which is incorrect, we should do this correctly here. The spec for exec says that all threads should be terminated on exec: https://stackoverflow.com/questions/36588387/what-happens-to-threads-when-exec-is-called

This issue is closely related to the issues with exit() we've been talking about here: Lind-Project/RawPOSIX#50

[qianxichen233]

Yeah, this is also an existing bug on exit syscall in lind-wasm that threads aren not terminated when when the main process exit. I wonder what are reliable ways to forcely terminate a running thread? Like pthread_cancel?

[rennergade]

We were handling this using pthread_cancel in lind-nacl, but it was always sort of a workaround since cancelling threads is pretty scary.

I talk a bit about a potential solution here: Lind-Project/RawPOSIX#50 (comment)