Merge pull request #5047 from tuffnatty/fix/scriptingpython-gil

ScriptingPython: fix locking on the first call with Python 3.12+

Plugins/ScriptingPython/scriptingpython.cpp

@@ -43,7 +43,10 @@ bool ScriptingPython::init()
  QMutexLocker locker(mainInterpMutex);
 
  PyImport_AppendInittab("db", &pyDbModuleInit);
+
  Py_Initialize();
+ // GIL is held, thread state is set.
+
  PyRun_SimpleString("import db");
 
  mainContext = new ContextPython();
@@ -55,7 +58,12 @@ void ScriptingPython::deinit()
 {
  QMutexLocker locker(mainInterpMutex);
  contexts.clear();
+
+ // Acquire GIL and set thread state
+ PyEval_RestoreThread(mainContext->interp);
  Py_Finalize();
+ // GIL and thread state no longer exist
+
  SQLS_CLEANUP_RESOURCE(scriptingpython);
 }
 
@@ -66,7 +74,16 @@ QString ScriptingPython::getLanguage() const
 
 ScriptingPlugin::Context* ScriptingPython::createContext()
 {
+#ifdef PYTHON_DYNAMIC_BINDING
+ if (!library.isLoaded())
+ return nullptr;
+#endif
+
+ // ContextPython() expects that GIL is held and thread state is set
+ PyEval_RestoreThread(mainContext->interp);
  ContextPython* ctx = new ContextPython();
+ // No GIL is held
+
  contexts[ctx->interp] = ctx;
  return ctx;
 }
@@ -79,7 +96,8 @@ void ScriptingPython::releaseContext(ScriptingPlugin::Context* context)
 
  contexts.remove(ctx->interp);
  delete ctx;
- PyThreadState_Swap(mainContext->interp);
+ // Thread state has been destroyed. Don't switch to main thread state,
+ // as we'll do it as needed anyway, and it needs GIL.
 }
 
 void ScriptingPython::resetContext(ScriptingPlugin::Context* context)
@@ -109,8 +127,15 @@ QVariant ScriptingPython::getVariable(ScriptingPlugin::Context* context, const Q
  if (!ctx)
  return QVariant();
 
- PyThreadState_Swap(ctx->interp);
- return getVariable(name);
+ // Acquire GIL and set thread state
+ PyEval_RestoreThread(ctx->interp);
+
+ QVariant value = getVariable(name);
+
+ // Release GIL
+ PyEval_ReleaseThread(ctx->interp);
+
+ return value;
 }
 
 bool ScriptingPython::hasError(ScriptingPlugin::Context* context) const
@@ -168,13 +193,17 @@ ScriptingPython::ContextPython* ScriptingPython::getContext(ScriptingPlugin::Con
 QVariant ScriptingPython::compileAndEval(ScriptingPython::ContextPython* ctx, const QString& code, const FunctionInfo& funcInfo,
  const QList<QVariant>& args, Db* db, bool locking)
 {
- PyThreadState_Swap(ctx->interp);
+ // Acquire GIL and set thread state
+ PyEval_RestoreThread(ctx->interp);
+
  clearError(ctx);
 
  ScriptObject* scriptObj = getScriptObject(code, funcInfo, ctx);
  if (PyErr_Occurred() || !scriptObj->getCompiled())
  {
  ctx->error = extractError();
+ // Release GIL
+ PyEval_ReleaseThread(ctx->interp);
  return QVariant();
  }
 
@@ -192,11 +221,15 @@ QVariant ScriptingPython::compileAndEval(ScriptingPython::ContextPython* ctx, co
  {
  Py_XDECREF(result);
  ctx->error = extractError();
+ // Release GIL
+ PyEval_ReleaseThread(ctx->interp);
  return QVariant();
  }
 
  QVariant resultVariant = pythonObjToVariant(result);
  Py_XDECREF(result);
+ // Release GIL
+ PyEval_ReleaseThread(ctx->interp);
  return resultVariant;
 }
 
@@ -658,19 +691,30 @@ void ScriptingPython::ContextPython::reset()
 
 void ScriptingPython::ContextPython::init()
 {
+ // Py_NewInterpreter() expects that GIL is held and thread state is set
  interp = Py_NewInterpreter();
- PyThreadState_Swap(interp);
+ // GIL is still held, thread state has changed
+
  mainModule = PyImport_AddModule("__main__");
  envDict = PyModule_GetDict(mainModule);
  PyRun_SimpleString("import db");
+
+ // Release GIL
+ PyEval_ReleaseThread(interp);
 }
 
 void ScriptingPython::ContextPython::clear()
 {
- PyThreadState_Swap(interp);
+ // Acquire GIL and set thread state
+ PyEval_RestoreThread(interp);
+
  PyDict_Clear(envDict);
  scriptCache.clear();
  PyErr_Clear();
+
+ // Py_EndInterpreter expects thread state to be already set
  Py_EndInterpreter(interp);
+ // Thread state is destroyed, no GIL is held
+
  error = QString();
 }