Crash in BVH when using move_and_slide or move_and_collide with multi-threaded physics server

[pouleyKetchoupp]

Godot version

3.4-beta6

System information

Windows 10

Issue description

Based on #24050 (comment).

Random crash happens in the BVH with multi-threaded physics server due to possible calls to _update_shapes on both the main thread (test_body_motion in _physics_process) and the physics server thread syncing commands.

The repro case is 2D only on 3.x, but it probably also happens on master and in 3D.
Edit: it looks like the issue is on 3.x only and was fixed on master with #45852.

Callstack on the main thread:

 	godot.windows.tools.64.exe!LocalVector<BVH_Tree<CollisionObject2DSW,2,128,1,Rect2,Vector2>::TNode,unsigned int,1>::operator[](unsigned int p_index) Line 162	C++
 	godot.windows.tools.64.exe!PooledList<BVH_Tree<CollisionObject2DSW,2,128,1,Rect2,Vector2>::TNode,1>::operator[](unsigned int p_index) Line 70	C++
 	godot.windows.tools.64.exe!BVH_Tree<CollisionObject2DSW,2,128,1,Rect2,Vector2>::item_move(BVHHandle p_handle, const Rect2 & p_aabb) Line 119	C++
 	godot.windows.tools.64.exe!BVH_Manager<CollisionObject2DSW,1,128,Rect2,Vector2,1>::move(BVHHandle p_handle, const Rect2 & p_aabb) Line 196	C++
 	godot.windows.tools.64.exe!BVH_Manager<CollisionObject2DSW,1,128,Rect2,Vector2,1>::move(unsigned int p_handle, const Rect2 & p_aabb) Line 143	C++
 	godot.windows.tools.64.exe!BroadPhase2DBVH::move(unsigned int p_id, const Rect2 & p_aabb) Line 42	C++
 	godot.windows.tools.64.exe!CollisionObject2DSW::_update_shapes() Line 187	C++
 	godot.windows.tools.64.exe!CollisionObject2DSW::_shape_changed() Line 240	C++
 	godot.windows.tools.64.exe!Physics2DServerSW::_update_shapes() Line 1295	C++
 	godot.windows.tools.64.exe!Physics2DServerSW::body_test_motion(RID p_body, const Transform2D & p_from, const Vector2 & p_motion, bool p_infinite_inertia, float p_margin, Physics2DServer::MotionResult * r_result, bool p_exclude_raycast_shapes, const Set<RID,Comparator<RID>,DefaultAllocator> & p_exclude) Line 944	C++
 	godot.windows.tools.64.exe!Physics2DServerWrapMT::body_test_motion(RID p_body, const Transform2D & p_from, const Vector2 & p_motion, bool p_infinite_inertia, float p_margin, Physics2DServer::MotionResult * r_result, bool p_exclude_raycast_shapes, const Set<RID,Comparator<RID>,DefaultAllocator> & p_exclude) Line 257	C++
 	godot.windows.tools.64.exe!KinematicBody2D::move_and_collide(const Vector2 & p_motion, bool p_infinite_inertia, KinematicBody2D::Collision & r_collision, bool p_exclude_raycast_shapes, bool p_test_only, bool p_cancel_sliding, const Set<RID,Comparator<RID>,DefaultAllocator> & p_exclude) Line 1042	C++

Callstack on the physics thread:

 	godot.windows.tools.64.exe!VectorWriteProxy<CollisionObject2DSW::Shape>::operator[](int p_index) Line 51	C++
 	godot.windows.tools.64.exe!CollisionObject2DSW::_update_shapes() Line 169	C++
 	godot.windows.tools.64.exe!CollisionObject2DSW::_set_transform(const Transform2D & p_transform, bool p_update_shapes) Line 93	C++
 	godot.windows.tools.64.exe!Body2DSW::set_state(Physics2DServer::BodyState p_state, const Variant & p_variant) Line 271	C++
 	godot.windows.tools.64.exe!Physics2DServerSW::body_set_state(RID p_body, Physics2DServer::BodyState p_state, const Variant & p_variant) Line 751	C++
 	godot.windows.tools.64.exe!CommandQueueMT::Command3<Physics2DServer,void (__cdecl Physics2DServer::*)(RID,enum Physics2DServer::BodyState,Variant const &),RID,enum Physics2DServer::BodyState,Variant>::call() Line 300	C++
 	godot.windows.tools.64.exe!CommandQueueMT::flush_one(bool p_lock) Line 442	C++
 	godot.windows.tools.64.exe!CommandQueueMT::wait_and_flush_one() Line 479	C++
 	godot.windows.tools.64.exe!Physics2DServerWrapMT::thread_loop() Line 60	C++

Steps to reproduce

Using the MRP, just try starting the game until it crashes immediately (happens about once every 4 times for me).

Minimal reproduction project

Sonic Outbreak project from #24050:
Sonic_Outbreak.zip

[akien-mga]

Fixed by #53498.