Operating system: Linux-4.18.0-25-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1060 6GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 390.116
Broken: version: 2.81 (sub 16), branch: master, commit date: 2019-12-04 11:32, hash: rBf1aa4d18d49d
Short description of error
Blender crashes while scrubbing when AV Sync is enabled and system is using JACK audio
Exact steps for others to reproduce the error
- open blender 2.81a with fresh config dir
- enter prefs -> System and choose JACK as audio device
- go to VSE, add audio clip of whatever length to at least fill the default frames (I used a standard stereo 16bit PCM .wav in this case)
- in Timeline, enable AV Sync option
- play the animation, and scrub around with the mouse on the timeline
It takes a while of constant scrubbing for me -- sometimes 30 seconds or even 1-2 minutes, but I can reliably make Blender crash this way. (Sometimes I stop and jump around in the timeline, left/right-arrow a little, etc... not sure if any of that is necessary.) Two crash.txt's are attached.
The issue is caused by race condition between JACK callback and dependency graph update.
One of the ideas to get it solved is to make JACK callback to act more like a tag (rahtehr than an actual action) which will allow handling it as soon as possible but not from the place where it can't be happening in a thread-safe manner.