Blender freezes when saving with active VR session #93649

New Issue

Peter Kim · 2021-12-04T12:52:25+01:00

Peter Kim commented

2021-12-04 12:52:25 +01:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 497.09

Blender Version
Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: f1cca30557
Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-12-04 01:26, hash: 5ef5a9fc24
Worked: 2.93.6

Short description of error
Blender freezes completely when saving while a VR session is active. This does not recover and the user must force quit Blender.

Exact steps for others to reproduce the error

Open Blender and start a new VR session (enable the VR Scene Inspection add-on)
Save the current file

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 497.09 **Blender Version** Broken: version: 3.0.0, branch: master, commit date: 2021-12-02 18:35, hash: `f1cca30557` Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-12-04 01:26, hash: `5ef5a9fc24` Worked: 2.93.6 **Short description of error** Blender freezes completely when saving while a VR session is active. This does not recover and the user must force quit Blender. **Exact steps for others to reproduce the error** 1. Open Blender and start a new VR session (enable the VR Scene Inspection add-on) 2. Save the current file

Peter Kim commented

2021-12-04 12:52:25 +01:00

Added subscriber: @muxed-reality

Peter Kim commented

2021-12-04 13:05:13 +01:00

Added subscriber: @JulianEisel

Peter Kim commented

2021-12-04 13:05:13 +01:00

This seems to be caused by calling BKE_scene_graph_evaluated_ensure() when drawing to the XR surface (wm_xr_session_surface_draw()).
The main thread hangs at pthread_cond_wait(&ticket->cond, &ticket->mutex); in BLI_ticket_mutex_lock().

@JulianEisel Would you happen to know how to fix this? I think this is a quite serious issue and should be included in the next 3.0 corrective release if possible.

This seems to be caused by calling `BKE_scene_graph_evaluated_ensure()` when drawing to the XR surface (`wm_xr_session_surface_draw()`). The main thread hangs at `pthread_cond_wait(&ticket->cond, &ticket->mutex);` in `BLI_ticket_mutex_lock()`. ![vr-save-freeze-callstack.png](https://archive.blender.org/developer/F12688999/vr-save-freeze-callstack.png) @JulianEisel Would you happen to know how to fix this? I think this is a quite serious issue and should be included in the next 3.0 corrective release if possible.

Peter Kim commented

2021-12-04 13:06:05 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Jacob Merrill commented

2021-12-08 17:05:39 +01:00

Added subscriber: @JacobMerrill-1

Peter Kim commented

2021-12-09 09:30:39 +01:00

@JulianEisel The hang occurs because DST.gl_context_mutex is already locked in DRW_xr_drawing_begin(), which is set as the "activate" callback for the XR surface.
Then if the depsgraph is not evaluated at the time of surface drawing (which only seems to occur when saving files), BKE_scene_graph_evaluated_ensure() will call DRW_notify_view_update() which will also try to lock DST.gl_context_mutex.

Not sure what the best solution is, maybe we can skip ensuring an evaluated depsgraph before drawing? Or do this instead in wm_xr_events_handle()?

@JulianEisel The hang occurs because `DST.gl_context_mutex` is already locked in `DRW_xr_drawing_begin()`, which is set as the "activate" callback for the XR surface. Then if the depsgraph is not evaluated at the time of surface drawing (which only seems to occur when saving files), `BKE_scene_graph_evaluated_ensure()` will call `DRW_notify_view_update()` which will also try to lock `DST.gl_context_mutex`. Not sure what the best solution is, maybe we can skip ensuring an evaluated depsgraph before drawing? Or do this instead in `wm_xr_events_handle()`?

blender-admin commented

2021-12-14 15:12:23 +01:00

This issue was referenced by 58ee4852b6

This issue was referenced by 58ee4852b6e2d745965f34ef347d5bd6d6e03fbb

blender-admin commented

2021-12-14 15:12:23 +01:00

This issue was referenced by b5c18288f5

This issue was referenced by b5c18288f5bdcc95ac012a1ee32d1e2859a97779

Julian Eisel commented

2021-12-14 15:24:14 +01:00

Changed status from 'Confirmed' to: 'Resolved'

Julian Eisel closed this issue