Best practices for multithread global flags

[Vladimirs Nordholm]

Hello people from D-land.

To summarise my problem: I have a program in the terminal (Posix) 
with two threads: one which my main program is run on, and a 
second one which polls input via `poll(...)` and `read(...)`.

Let's call main thread T1, and a semi-blocking input-thread T2.

Every second T2 checks if T1 is terminated by checking if the a 
global flag is set to true. This is done with a 
`while(global_flag)`.

This feels to me like iffy code. So my question becomes: what is 
the best way to do this check with?

Also: I do not know that much about multithreading. __gshared is 
super global in my mind, but unsafe. Also bumped into the word 
mutex, but I also do not know what it means.


// i have tried Thread.isDaemon(true), but never managed to get 
the thread to terminate. now i use `spawn(...)` and don't see a 
clear way to use that. is it worth looking into even more?