Register a single classmethod to stop threads for all HistoryManager instances

takluyver · takluyver · commit e6026949304c · 2026-01-22T13:40:33.000Z
diff --git a/IPython/core/history.py b/IPython/core/history.py
@@ -703,8 +703,6 @@ def __init__(
                 self.hist_file = ":memory:"
             else:
                 self.using_thread = True
-                if hasattr(os, "register_at_fork"):
-                    os.register_at_fork(before=self._stop_thread)
         self._instances.add(self)
         assert len(HistoryManager._instances) <= HistoryManager._max_inst, (
             len(HistoryManager._instances),
@@ -715,11 +713,13 @@ def __del__(self) -> None:
         if self.save_thread is not None:
             self.save_thread.stop()
 
-    def _stop_thread(self) -> None:
+    @classmethod
+    def _stop_thread(cls) -> None:
         # Used before forking so the thread isn't running at fork
-        if self.save_thread is not None:
-            self.save_thread.stop()
-            self.save_thread = None
+        for inst in cls._instances:
+            if inst.save_thread is not None:
+                inst.save_thread.stop()
+                inst.save_thread = None
 
     def _restart_thread_if_stopped(self) -> None:
         # Start the thread again after it was stopped for forking
@@ -1081,6 +1081,10 @@ def writeout_cache(self, conn: Optional[sqlite3.Connection] = None) -> None:
                 self.db_output_cache = []
 
 
+if hasattr(os, "register_at_fork"):
+    os.register_at_fork(before=HistoryManager._stop_thread)
+
+
 from collections.abc import Callable, Iterator
 from weakref import ReferenceType
 
