Bug (Case 1277297) Calling Resources.Load() while asynchronously loading assetbundle makes app freezed

Hi. I found app freezing issue related to Resources.Load() and AssetBundles.

If you calling Resources.Load() while asynchronously loading other assets from AssetBundle by using UnityWebRequest, main thread is freezed.

This only occurred on Android/iOS device, not Editor. And reproduced by both Unity 2020.2.0b2 and 2020.1.5f1.

Minimal reproducible project was sent as Case 1277297.

 

https://issuetracker.unity3d.com/is...le-by-unitywebrequest-makes-main-thread-stuck

 

I received the response from Unity that "async/await" makes this freezing issue, but I highly doubt it because async/await does not made any special things itself.

I re-created same reproducible project without async/await and sent modified scripts.

Also found that calling Resourceds.Load in UnityWebRequestAsyncOperation.completed makes 100% freezing.

 

I reported non async/await version of 100% reproducible project as Case 1310359. I hope that this help Unity developers to find and fix freezing issue.

 

Hi!
We also encountered this problem. Could you please attach a link to Case 1310359 here?

 

Unity said 1310359 is merged to 1277297 internally. So you can track ticket status in above link.

 

Thank you for your reply
We use the latest lts Unity for production builds. Is there plans to backport the fix to the 2019.4? We have checked versions 2019.4.9-2019.4.20 and we have the problem there. 2019.4.8 works ok, but we need update for Unity IAP and it needs update of the Unity to the latest version.

 

Hi, LeonhardP,

Thank you for your response. We will try to reproduce the bug and will send report

 

I'm also on 2019.4.21f1 and experiencing something similar. It's definitely asset bundle related, I thought it might be addressable related so I posted a forum post here:

https://forum.unity.com/threads/201...ng-to-load-asset-from-cached-bundles.1069187/

 

Hi @LeonhardP
Thank you for your reply! Are there any approximate predictions when the fix will be accepted in 2019.4?

 

Hi, we are expecting for the update too. There is an issue with our game (Unity 2019.4.21), it's using AssetBundles with async loading resulting in a very long loading times for some devices (Nexus 5X). Maybe could it be related with this case.

I tried to do a quick switch to Unity 2021 for checking the fix, but some libraries are not compatible so we will wait for the 2019 release.

I hope it go out soon.

 

Just confirmed Android working for me now on multiple play throughs with 2019.4.23f1! Thanks for the fix!

 

Is there a download link to the bug-reproducing project? I'm using 2019.4.22f1 and I'm using Resources.Load and Addressables.LoadAssetAsync at the same time somewhere in my project. But I have never encountered this issue up until now. I guess it needs some other preconditions to trigger this bug.

 

I found that if I only allowed one Addressables.LoadAssetAsync command at a time, I could avoid the freeze. So I think if we load multiple AssetBundles asynchronously, we are at risk of app freezing.

Edit: The freeze still occurred after all, but it was related to using Resources.Load while asynchronously loading an asset bundle.

 

I encountered this issue sparsely in my project. I am using Unity 2019.4.22f1, which is the version that this fix hasn't been backported. I saw there were indeed "Resources.Load" and "AssetBundleLoadFromAsyncOperation" presented in the same thread. However, I am struggling to reproduce this issue in an empty project. Upgrading Unity engine version is considered a much greater risk in my workplace, workaround is preferred. Can anyone send me a project that can reproduce this issue?