Deadlock on thread if "wait_to_finish" has been called by the parent thread and child executes Texture2D.get_image()

[JohnPandich]

Godot version

v4.0.rc6

System information

Linux Mint, Forward+, ntel© Xeon© CPU E5-2650 v4 @ 2.20GHz × 12, 64gb ram

Issue description

A thread will be deadlocked when executing Texture2D.get_image() if and only if the parent thread has called Thread.wait_to_finish() on the child thread.

I would expect the thread to execute as normal.

Steps to reproduce

1. spawn child thread
2. start execution of child
3. execute wait_to_finish() on the child thread
4. execute "get_image()" on a Texture2D in the child thread

Minimal reproduction project

repro.zip

[Jimmio92]

Threads aren't implemented correctly #71408 and my changes that needed work so I closed #71097

Basically, they're detaching always in the destructor, so when the thread function returns, it detaches and cleans up automatically. This means you cannot call wait_to_finish on it (which is a join, btw). Joining a thread pauses the current thread's execution until the other thread is done.

Yes, it warns you must always call it, but good luck calling join on a detached and dead thread, which is an error, because it erroneously treats an invalid handle as the main thread, and you can't join the main thread from the main thread.

[JohnPandich]

thanks Jimmio! Closing as a duplicate of #71097