UE 5.2 Deadlock in UAnimSequencerController::RemoveBoneTracksMissingFromSkeleton & FAnimationSequenceAsyncCacheTask::BuildData

Development Character & Animation
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1

I have an Anim Sequence, and whenever I try to open it in 5.2, it deadlocks the editor. The reason seems to be because FAnimationSequenceAsyncCacheTask job gets kicked when the asset is loaded, but then later while that task is running it RemoveBoneTracksMissingFromSkeleton, which causes it to fire a callback which calls into UAnimSequence::OnModelModified and this tries canceling the FAnimationSequenceAsyncCacheTask job but since the FAnimationSequenceAsyncCacheTask is waiting on the lock that is locked in RemoveBoneTracksMissingFromSkeleton, it deadlocks.

2

deleting the anim sequence and reimporting it is a workaround.

3

Hello :slight_smile: How did you know which animation is broken?

4

since it deadlocked, I just hit pause in the debugger and inspected the thread stacks until I found the data.