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?

On 15/11/2017 11:57 AM, Vladimirs Nordholm wrote:
> 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?

You're fine, a __gshared variable will do this nicely.

On Wednesday, November 15, 2017 11:57:25 Vladimirs Nordholm via Digitalmars- d-learn wrote:
> 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?

If you don't know about mutexes, then I would strongly advise that you go read up on them before you do much of anything with multi-threaded code.

In this case, I would suggest that you use std.concurrency with send and receive (or probably receiveTimeout) to send a message to the thread that you want to shut down.

I would suggest that you read http://ddili.org/ders/d.en/concurrency.html for info on using std.concurrency. And in general, reading the entire book would likely benefit you:

http://ddili.org/ders/d.en/index.html

- Jonathan M Davis

On Wednesday, 15 November 2017 at 11:57:25 UTC, Vladimirs Nordholm wrote:
> 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?


An easy way out is to have a shared(bool) and to use atomicLoad in T2, and atomicStore in the other thread T1.

For memory model reasons in x86, your code will work though because it's equivalent to atomicLoad(MemoryOrder.raw, x) but this isn't valid otherwise.

On Wednesday, 15 November 2017 at 11:57:25 UTC, Vladimirs Nordholm wrote:
> 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(...)`.
>
> [...]

Thanks for the replies given! Will look into the options given :)