[Docs] Document that Worker are never destroyed (even if pthreads end)

[aharondavid]

Worker Thread that created by pthread_create, pthread_detach, seem in the debugger (Chrome Dev Tool) although it ended and returned.
it removed only when calling to pthread_kill

Version of emscripten/emsdk:
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.4 (14cd48e)
clang version 15.0.0 (https://github.com/llvm/llvm-project ce5588fdf478b6af724977c11a405685cebc3d26)
Target: wasm32-unknown-emscripten
Thread model: posix

[aharondavid]

probably the same as : #16763

[sbc100]

emscripten doesn't currently ever destroy workers.. it keeps them around for future pthreads to run on.

[aharondavid]

Hi,
Good to know! I think that there is no any treatment to that important fact in emscripten pthread documentation:
https://emscripten.org/docs/porting/pthreads.html

[kripken]

I agree it would be good to document this. Let's reopen this issue for that.

[zekiparlak]

So there is no meaning using pthread_kill ?
I dont specify PTHREAD_POOL_SIZE and using PTHREAD_POOL_SIZE_STRICT=0 still not should use pthread_kill because this flags mean there is no limit for spawning threads(workers) so my module always generate new worker and not use unused ones.

[sbc100]

Emscripten uses a worker pool regardless of whether you specify PTHREAD_POOL_SIZE. The purpose of PTHREAD_POOL_SIZE is simply to pre-populate the pool.

If you create 10 threads and then destroy them you will end up with a pool of 10 workers. Those workers are kept around a long as your app is running.