Index: lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
===================================================================
--- lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -421,7 +421,7 @@
   bool m_session_is_active;
   bool m_pty_secondary_is_open;
   bool m_valid_session;
-  uint32_t m_lock_count;
+  std::atomic<uint32_t> m_lock_count;
   PyThreadState *m_command_thread_state;
 };
 
Index: lldb/source/Target/Process.cpp
===================================================================
--- lldb/source/Target/Process.cpp
+++ lldb/source/Target/Process.cpp
@@ -2467,6 +2467,7 @@
 }
 
 void Process::LoadOperatingSystemPlugin(bool flush) {
+  std::lock_guard<std::recursive_mutex> guard(m_thread_mutex);
   if (flush)
     m_thread_list.Clear();
   m_os_up.reset(OperatingSystem::FindPlugin(this, nullptr));