multi-threading: attempting to load very large XCF files results in "GEGL-WARNING **: blocking when trying to lock tile"
Submitted by Sam Trahan
Link to original bug (#790699)
Description
I am trying to open some huge images I made with gimp 2.8.x and GIMP deadlocks if I enable threads. The largest image is 10k x 15k pixels with ~40 layers. The machine has enough memory to store the image, the tile cache is set quite large (80 GB of the machine's 96 GB RAM) and there is 2 TB available for on-disk tiles. I get the following message N-1 times where N is the number of threads:
(gimp:74538): GEGL-WARNING **: blocking when trying to lock tile
GIMP keeps running, taking up CPU time, and never responds gain.
This bug is exclusive to multi-threading; I can open the files if I disable threading (max threads 1). However, even 2 threads will trigger the bug.
I tried smaller tile cache sizes: 48 GB and 60 GB. That didn't make a difference. Also, I tried some slightly smaller files, about 5k x 4k, ~60 layers, and that triggers the bug too. Smaller files are fine. I'm not sure what the cut-off size is to trigger the deadlock.
gimp --version GNU Image Manipulation Program version 2.9.7
This is from Otto Meier's Ubuntu package 2.9.723-ubu16.04.1ppa~1b804e57
Version: git master