Update thread.py

Author: GoodManWEN

ThreadPoolExecutorPlus/thread.py

@@ -228,7 +228,11 @@ def weakref_cb(_, q=self._work_queue):
         # TODO(bquinlan): Should avoid creating new threads if there are more
         # idle threads than items in the work queue.
         num_threads = len(self._threads)
-        if self._free_thread_count < self._min_workers and num_threads < self._max_workers:
+        
+        with self._free_thread_count_lock:
+            _tflag = True if self._free_thread_count < self._min_workers else False
+                
+        if _tflag and num_threads < self._max_workers:
             thread_name = '%s_%d' % (self._thread_name_prefix or self,
                                      num_threads)
             t = _CustomThread(name=thread_name, 
@@ -272,4 +276,4 @@ def shutdown(self, wait=True):
         if wait:
             for t in self._threads:
                 t.join()
-    shutdown.__doc__ = _base.Executor.shutdown.__doc__
+    shutdown.__doc__ = _base.Executor.shutdown.__doc__