OSX/M1 window resizing crashes the engine when rendering thread model is set to multi-threaded

[lekoder]

Godot version

3.5.2

System information

MacBook Air M1 2020 8GB Sonoma 14.0

Issue description

On some M1 Mac systems, setting the rendering thread model to multi-threaded causes the engine to crash when the window size is changed.

This seems to be a race condition and gets progressively worse when the game is actually doing stuff - to the point where a game like ΔV: Rings of Saturn will crash on any attempt to resize the window or switch between full-screen and windowed modes. I have verified that adding a command line of --render-thread safe fixes the problem, so I'm confident that it's caused by the multi-threaded rendering model.

You can replicate this with an empty project without code - it just requires more vigorous mouse movements to trigger.

• Crash recording: https://imgur.com/a/ERIE01f
• OS crash report: crash-report.txt

Steps to reproduce

This replicates only on M1 Macs.

1. Create a new project
2. Set the rendering thread model to multi-threaded
3. Create an empty Node2D
4. Run it
5. Resize the window rapidly

MRP attached.

Minimal reproduction project

mrp.zip

[lekoder]

Also happening in 3.6 beta 3.

[akien-mga]

Fixed by #81442.

[lekoder]

TL;DR: Huge stability improvement, but I still get reports of crashes in production.

Unfortunately, it seems that this was not the root cause. While the #81442 does greatly reduce the rate of crashes (from "in a second" from before the patch to "in few minutes if you play with setting" after the patch), there seems to be another underlying problem that causes the instability, and disabling the live resize just makes it not immediately apparent. It seems that window resizing still has a small chance of crashing the engine, but after the patch we are just not resizing 60 times per second.

I am unable to replicate this anymore with a minimal project, but it does still happen in production. If you grab the free demo build from itch.io, enter the settings and either keep changing the fullscreen mode, or set the mode to windowed and keep resizing the window (and releasing the mouse button), it will cause a crash in a dozen of tries or so on an M1 system.

The .pck file in there should be compatible with any 3.5.3 build.