Fix T102292: deadlock in geometry nodes evaluation with task isolation

As described in the comment on `BLI_task_isolate`, deadlocks can happen
when isolation is used with threading primitives that separate spawning tasks
from executing them. All threads are waiting the tasks to complete but no
thread is able to continue working due to task isolation.

The fix is to not pass lazy-threading hints through task isolations. This way
isolated regions can't create new tasks in a scheduler further up the call stack.
This may lead to minor slowdowns because less threading may be used.
It's generally possible to get rid of the slowdown again by sending the
lazy-threading hint before entering the isolated region.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_task.hh b/source/blender/blenlib/BLI_task.hh
index 9f9a57be634..e7d9a21439a 100644
--- a/source/blender/blenlib/BLI_task.hh
+++ b/source/blender/blenlib/BLI_task.hh
@@ -129,6 +129,7 @@ void parallel_invoke(const bool use_threading, Functions &&...functions)
 template<typename Function> void isolate_task(const Function &function)
 {
 #ifdef WITH_TBB
+  lazy_threading::ReceiverIsolation isolation;
   tbb::this_task_arena::isolate(function);
 #else
   function();