Remove lock from CancelContext

src/prefect/_internal/concurrency/timeouts.py

@@ -25,21 +25,17 @@ class CancelContext:
     def __init__(self, timeout: Optional[float]) -> None:
         self._timeout = timeout
         self._cancelled: bool = False
-        self._lock = threading.Lock()
 
     @property
     def timeout(self) -> Optional[float]:
         return self._timeout
 
     @property
     def cancelled(self):
-        with self._lock:
-            return self._cancelled
+        return self._cancelled
 
-    @cancelled.setter
-    def cancelled(self, value: bool):
-        with self._lock:
-            self._cancelled = value
+    def mark_cancelled(self):
+        self._mark_cancelled()
 
 
 @contextlib.contextmanager
@@ -194,7 +190,7 @@ def _alarm_based_timeout(timeout: float):
     ctx = CancelContext(timeout=timeout)
 
     def raise_alarm_as_timeout(signum, frame):
-        ctx.cancelled = True
+        ctx.mark_cancelled()
         logger.debug(
             "Cancel fired for alarm based timeout of thread %r", current_thread.name
         )
@@ -229,7 +225,7 @@ def timeout_enforcer():
                 "Cancel fired for watcher based timeout of thread %r",
                 supervised_thread.name,
             )
-            ctx.cancelled = True
+            ctx.mark_cancelled()
             _send_exception_to_thread(supervised_thread, TimeoutError)
 
     enforcer = threading.Thread(target=timeout_enforcer, daemon=True)