`ClassDB::can_instantiate()` and other reflection methods deadlock if the type is an script global class, when such script indirectly uses a not-yet-registered class. The reason is the `ClassDB` read lock is still held when invoking the `ResourceLoader` to load the class script, which may in turn need to lock for writing (for the class registration).
In particular, this happens with some types related to animation tree, that aren't registered at engine startup, but can happen with others, especially ones from the user. Registration statements are also added for the animation-related types that were lacking them.
This fixes a rare but possible deadlock, maybe due to undefined behavior. The new implementation is safer, at the cost of some added boilerplate.
(cherry picked from commit f4d76853b9)
Benefits:
- Simpler code. The main load function is renamed so it's apparent that it's not just a thread entry point anymore.
- Cache and thread modes of the original task are honored. A beautiful consequence of this is that, unlike formerly, re-issued loads can use the resource cache, which makes this mechanism much more performant.
- The newly added getter for caller task id in WorkerThreadPool allows to remove the custom tracking of that in ResourceLoader.
- The check to replace a cached resource and the replacement itself happen atomically. That fixes deadlock prevention leading to multiple resource instances of the same one on disk. As a side effect, it also makes the regular check for replace load mode more robust.
(cherry picked from commit 28619e26cf)
ResourceLoader:
- Fix invalid tokens being returned.
- Remove no longer written `ThreadLoadTask::dependent_path` and the code reading from it.
- Clear deadlock hazard by keeping the mutex unlocked during userland polling.
WorkerThreadPool:
- Include thread call queue override in the thread state reset set, which allows to simplify the code that handled that (imperfectly) in the ResourceLoader.
- Handle the mutex type correctly on entering an allowance zone.
CommandQueueMT:
- Handle the additional possibility of command buffer reallocation that mutex unlock allowance introduces.
Editor code is not instantiable outside of the editor
(1d14c054a1/core/object/class_db.cpp (L369)).
This is fine for editor plugins and the like, but the GDScript analyzer
balks at it, causing F5 runs to fail: #73525.
Instead, we really just want to know if the type is abstract - so add
a new ClassDB method to check that and nothing else.
Update core/object/class_db.cpp
Apply code review comments
Co-Authored-By: Bryce <1522777+baptr@users.noreply.github.com>
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* Added conversion from `Iterator` to `ConstIterator`
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