[Issue]: Random crash when loading chunks

[team1257Simon]

What happened?

When I load ungenerated chunks, the game sometimes randomly freezes and displays an error message when I close it. The error is a concurrent modification exception that's tied to a lambda in the server tick loop, which means it's a pain to figure out which mod is causing it -- the mixins are there, of course, but I don't actually have that good a picture of what happens in that method, so I can't say for sure what's happening (the lambda is almost certainly part of a for-each loop on, from what I can tell, chunk entity sections).

Pack Version

Version: LL8 0.20

To Reproduce

1. Generate a new chunk.
2. ...? The crash seems to occur randomly, i.e. only some of the time when I generate chunks.

Are you using Iris? (For shaders).

• Yes. I am using Iris.
• No. My instance is unmodified, stock install.

Are you on a Server?

• Yes.
• No.

whole latest.log output & crash report.

latest.log:
https://gist.github.com/team1257Simon/7c658a48a240cbb9f96215be8d6c40d0
crash report:
https://gist.github.com/team1257Simon/a8af547d94a00d4d4cabaf57f5331051

Anything else to add?

This has gotten really irritating as it's making exploration a lot harder. I know it's tough to debug a crash like this, and I've already tried repairing my install so it isn't the install itself.

[Gbergz]

Tough one, log doesn't say much but does contain an error.

What it means though, not sure as of this moment.

[Gbergz]

There is a performance issue in 0.20.0 which will be resolved next update. But if you wanna try remove the mod that is causing it, be my guest.

Do a fresh install of v0.20.0, then remove logbegone-neoforge-1.21.1-1.0.3.jar from the mods folder. Try again.

[team1257Simon]

Okay, I'll disable that mod and see what happens. If the crash happens again I'll let you know

[team1257Simon]

It happened again. Twice, latest version, same crash log, same everything.

[team1257Simon]

crash-2024-10-11_19.12.52-server.txt
crash-2024-10-10_21.20.20-server.txt
It's still happening -- I'm using a fresh install of the pack now.
It seems to happen most often when I teleport (either via a command or via a waystone, either one can cause it).
Previous attempts at solving it were most successful when they involved disabling the mods listed in the mixin lists -- the smoothchunk mod and a couple of others made by the same author.

[Gbergz]

Can't reproduce this issue, sadly. And if I can't, I can't make an attempt to locate a fix.

[team1257Simon]

Maybe it's an environment thing? I'm running on curseforge, so it's possible the OpenJDK environment that CF uses involves a different core Java thing that could be behind it, but I dunno
The irritating thing is that I completely reinstalled the pack and it's still crashing -- changing the configs for a few mods shouldn't be the problem, and I can't imagine it's a data thing either.
The reinstall DID fix the hanging thread on server exit problem, though.

[team1257Simon]

I've determined with a very high degree of confidence that the mod causing this crash is "Fast Async World Saving" -- the lack of reproducibility is virtually certain to be platform-specific, but if that mod isn't doing anything essential it might be best to remove it until the dev finds a fix