CODEWITHSUNDEEP
python-3.xmultithreadingraspberry-pi3
glenneroo
glenneroo

Reputation: 2054

Why is my thread the MainThread?

I'm creating 5 threads for handling various tasks such as reading from sensors (Raspberry Pi), TCP connections and recently recording audio (pyAudio).

I am instantiating all threads in main() identically e.g.:

if __name__ == '__main__':
    main()

def main():
    global network_thread
    network_thread = threading.Thread(name="NET-CONN", target=network_thread_run, args=())
    network_thread.start()

I keep a global reference so I can kill the threads at shutdown with join().

Now, I have added thread #5:

global audio_thread
audio_thread = threading.Thread(name="AUDIO", target=audio_thread_run(), args=())
audio_thread.start()

...but my logging indicates it's running on the MainThread. I also double-checked inside the audio_thread_run() function and it is indeed running on MainThread:

if threading.current_thread() is threading.main_thread():
    logger.warning("Audio thread is the same as MainThread!")

Why is this thread running on the MainThread? Have I hit a limit on the Pi?

Upvotes: 1

Views: 160

Answers (1)

paxdiablo
paxdiablo

Reputation: 881373

Let's have a look at the two places where you create threads, modified slightly so they'll fit on one line, and with white-space inserted so they line up:

net_thread = threading.Thread(name="NET", target=net_run  , args=())
aud_thread = threading.Thread(name="AUD", target=aud_run(), args=())
# Hmmm, what's this suspicious-looking thing here? ---->^^

Enough fun :-) The problem is that you are actually calling the audio_thread_run() function directly from your main thread and presumably, if it ever returned, you would then try to use the result as a callable to start a thread.

If you actually got rid of the thread start stuff altogether, it would boil down to the much simpler:

audio_thread_run()

which will very much run that function from the context of the main thread.

What you need to do is to remove the parentheses so it matches what you've down with the network threads:

audio_thread = threading.Thread(name="AUDIO", target=audio_thread_run, args=())

Upvotes: 1

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