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TelluIoT / ThingML

The ThingML modelling language
https://github.com/TelluIoT/ThingML
Apache License 2.0
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Usage of threads in single-threaded POSIX compiler? #150

Closed jakhog closed 7 years ago

jakhog commented 7 years ago

The single-threaded POSIX compiler generates code for thread-safe access to the fifo. This is a little bit confusing to me. Is the idea that threads should still be used in the POSIX compiler (e.g. in network plugins), but that all the state machines live in a single thread?

Somewhat related; the way that processMessageQueue() is implemented now breaks polling code. The function will block until a message is put on the fifo.

jakhog commented 7 years ago

So I guess the answer to my question is yes.

And for the second part, no polling code should be added to the POSIX compiler, and the current behavior is OK. Since any events has to come through the fifo.

nharrand commented 7 years ago

Short answer: yes network listener can be in separated thread in the posix compiler, and they do post messages in the fifo.

Long answer: I think it is just a matter of legacy architecture. The arduino compiler produced full single threaded code (no other choices), and the posix one had network listeners that could post messages from separated thread. But as most code was shared by both compilers, all instances remained in the same thread. Then we added the multi thread posix compiler that create one thread per instance. I think the good question concerning the posix (pseudo) single thread compiler, is what target does it aim, and should it be fully single threaded (even for network listener).