Blender Git Commit Log

Fix T39180: Particle with fluid physics unstable.

Fluid sims have a very nasty feature for interaction, in which a psys
can directly update the bvhtree for //another object's psys//. This
breaks with threaded depsgraph evaluation and is generally a no-go.

To avoid crashes for now, use a global mutex to avoid concurrent writes
to an object psys' bvhtree.