Use `_PyThreadState_UncheckedGet()` to check that the current thread is
tracked by Python before checking whether it has the GIL. The latter
will abort when the former is false.
Evaluating the dependency graph potentially executes Python code when
evaluating drivers. In specific situations (see T91046) this could
deadlock Blender entirely. Temporarily releasing the GIL when evaluating
the depsgraph resolves this.
This is an improved version of
rBfc460351170478e712740ae1917a2e24803eba3b, thanks @brecht for the diff!
Manifest task: T91046
Calling PyEval_ReleaseLock() was crashing with Python 3.9
because it accessed the NULL pointer set by PyThreadState_Swap().
This happened when calling ViewLayer.update() for example.
While the existing logic could be fixed by swapping the thread-state
back before calling PyEval_ReleaseLock(), this depends on functions
which are tagged to be removed by v4.0.
Replace use of deprecated functions by calling PyEval_SaveThread(),
instead of inlining the logic, using _PyThreadState_UncheckedGet()
to prevent Python aborting.
The call to PyEval_ThreadsInitialized has been removed
as threads are now initialized with Python.
This could be replaced with Py_IsInitialized() however it doesn't look
like this is necessary.
This is compatible with Python 3.7 & 3.9.
BF-admins agree to remove header information that isn't useful,
to reduce noise.
- BEGIN/END license blocks
Developers should add non license comments as separate comment blocks.
No need for separator text.
- Contributors
This is often invalid, outdated or misleading
especially when splitting files.
It's more useful to git-blame to find out who has developed the code.
See P901 for script to perform these edits.
This way blender player can easily use BPY_thread_save/restore.
Not so much important for master branch, but crucial to solve
linking issues in threaded depsgraph branch.
