Infinite loop in Physics2DServerSW::_update_shapes with Multi-Threaded physics

[DrMoriarty]

---

Bugsquad note: This issue has been confirmed several times already. No need to confirm it further.

---

Godot version:
Godot 3.2.beta 6 (commit 02cd144)

OS/device including version:
MacOSX 10.14.6 (18G95)

Issue description:

I have a lot of KinematicBody2D in one scene. In _physics_process I call move_and_collide and some times the game hungs up with logs:

ERROR: remove: Condition ' p_elem->_root != this ' is true.
   At: ./core/self_list.h:84.

This lines repeates many times. Actually infinite amount of times, because it prints from the infinite loop.

I catched the bug with xcode debugger and it shows me that the problem is in void Physics2DServerSW::_update_shapes():

godot/servers/physics_2d/physics_2d_server_sw.cpp

Line 1421 in 02cd144

pending_shape_update_list.remove(pending_shape_update_list.first());

I have no ideas why pending_shape_update_list became broken. Does anybody have?

Steps to reproduce:

Minimal reproduction project:

[DrMoriarty]

Also I double checked that all my object manipulations was in physics frame. Also set all timer and tweens to physics process mode.

[DrMoriarty]

The bug only reproduced in multi-threaded physics. When I set physics/2d/thread_model to Single-Safe all works as expected.

[Xrayez]

I recently tested similar multi-threaded physics issue in #29369 (comment).

[creikey]

Perhaps a read-write lock could be used to mitigate this issue on the pending shape update list? As I cannot reliably reproduce I can't test.

[KoBeWi]

Can anyone still reproduce this bug in Godot 3.2.3 or any later release?

If yes, please ensure that an up-to-date Minimal Reproduction Project (MRP) is included in this report (a MRP is a zipped Godot project with the minimal elements necessary to reliably trigger the bug). You can upload ZIP files in an issue comment with a drag and drop.

[yuraj11]

I am still getting similar issue (v3.2.4.rc.mono.custom_build.4b9b9ed2f), multi-thread rendering is on:
ERROR: SelfList<class CollisionObject2DSW>::List::remove: Condition "p_elem->_root != this" is true. (core/self_list.h:84)
happens randomly when trying to call .instance() on scene which contains physics body (in my case KinematicBody2D) in thread (C#).

EDIT: Well it doesn't happen with physics Multi-Threaded option for me.

[Reapetitive]

I still get this problem in 3.3.3, even with single-safe. With multi-threaded it happens way more often. I use many kinematic bodies.

[hodgerti]

I am having this issue on 3.3.4-stable, but resolved it by switching from Multi-Threaded Physics thread model to Single-Safe.

Here is a visual studio minidump:
_update_shapes-bug-godot.windows.tools.64.dmp.zip

[rburing]

Somebody please attach a reproduction project. From the information so far it seems to be a 3.x issue, so I'm changing the milestone. If it is reproducible in 4.0 then please let us know (with a reproduction project).