diff --git a/CHANGELOG b/CHANGELOG
index e382233..589adbf 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,6 +1,7 @@
 0.20.4
  - enh: reserve one CPU for writer thread and control logic
  - enh: disentangle logging and debugging keyword arguments
+ - enh: do not initialize slot_chunks and slot_states with lock
 0.20.3
  - enh: improve strategy for stalling for slow writer
 0.20.2
diff --git a/src/dcnum/logic/ctrl.py b/src/dcnum/logic/ctrl.py
index 90511b1..8ea8ec1 100644
--- a/src/dcnum/logic/ctrl.py
+++ b/src/dcnum/logic/ctrl.py
@@ -670,8 +670,8 @@ def task_segment_extract(self):
         num_segmenters = max(1, num_segmenters)
         self.job.kwargs["segmenter_kwargs"]["num_workers"] = num_segmenters
         self.job.kwargs["segmenter_kwargs"]["debug"] = self.job["debug"]
-        slot_chunks = mp_spawn.Array("i", num_slots)
-        slot_states = mp_spawn.Array("u", num_slots)
+        slot_chunks = mp_spawn.Array("i", num_slots, lock=False)
+        slot_states = mp_spawn.Array("u", num_slots, lock=False)
 
         self.logger.debug(f"Number of slots: {num_slots}")
         self.logger.debug(f"Number of segmenters: {num_segmenters}")