fix: make PyObject cleanup thread-safe in free-threaded Python and reduce contention

setup.py

@@ -222,7 +222,10 @@ def test_python_java_classes():
 
 def test_maven():
     jpy_config = os.path.join(_build_dir(), 'jpyconfig.properties')
-    mvn_args = '-DargLine=-Xmx512m -Djpy.config=' + jpy_config + ' -Djpy.debug=true'
+    mvn_args = ('-DargLine=-Xmx512m -Djpy.config=' + jpy_config + ' -Djpy.debug=true' +
+                # disable the PyObject cleanup thread because the asynchronous nature of it makes
+                # stopPython/startPython flakey.
+                ' -DPyObject.cleanup_on_thread=false')
     log.info("Executing Maven goal 'test' with arg line " + repr(mvn_args))
     code = subprocess.call(['mvn', 'test', mvn_args], shell=platform.system() == 'Windows')
     return code == 0
@@ -282,8 +285,7 @@ def test_java(self):
 
     suite.addTest(test_python_with_java_runtime)
     suite.addTest(test_python_with_java_classes)
-    # comment out because the asynchronous nature of the PyObject GC in Java makes stopPython/startPython flakey.
-    # suite.addTest(test_java)
+    suite.addTest(test_java)
 
     return suite
 

src/main/java/org/jpy/PyObject.java

@@ -42,8 +42,6 @@ public class PyObject implements AutoCloseable {
 
     private static final AtomicReference<Thread> CLEANUP_THREAD = new AtomicReference<>();
 
-    private static final boolean CLEANUP_ON_INIT = Boolean.parseBoolean(System.getProperty("PyObject.cleanup_on_init", "true"));
-
     private static final boolean CLEANUP_ON_THREAD = Boolean.parseBoolean(System.getProperty("PyObject.cleanup_on_thread", "true"));
 
     private static void startCleanupThread() {
@@ -71,9 +69,6 @@ public static int cleanup() {
     PyObject(long pointer, boolean fromJNI) {
         state = new PyObjectState(pointer);
         if (fromJNI) {
-            if (CLEANUP_ON_INIT) {
-                REFERENCES.threadSafeCleanup(); // only performs *one* cleanup
-            }
             if (CLEANUP_ON_THREAD) {
                 // ensures that we've only started after python has been started, and we know there is something to cleanup
                 startCleanupThread();

src/main/java/org/jpy/PyObjectReferences.java

@@ -76,11 +76,7 @@ private Reference<PyObject> asRef(PyObject pyObject) {
     /**
      * This should *only* be invoked through the proxy, or when we *know* we have the GIL.
      */
-    public int threadSafeCleanup() {
-        return threadSafeCleanup(buffer);
-    }
-
-    private int threadSafeCleanup(long[] buffer) {
+    public synchronized int threadSafeCleanup() {
         return PyLib.ensureGil(() -> {
             int index = 0;
             while (index < buffer.length) {

src/test/java/org/jpy/PyObjectTest.java

@@ -204,16 +204,17 @@ public void testCall() throws Exception {
     public void testGetSetAttributes() throws Exception {
         // Python equivalent:
         //
-        // >>> import imp
-        // >>> myobj = imp.new_module('myobj')
+        // >>> import impportlib.util
+        // >>> mod_spec = importlib.util.spec_from_loader('myobj', loader=None)
+        // >>> myobj = importlib.util.module_from_spec(mod_spec)
         // >>> myobj.a = 'Tut tut!'
         // >>> myobj.a
         // 'Tut tut!'
         //
         try (
-            final PyModule imp = PyModule.importModule("imp");
-            final PyObject myobj = imp.call("new_module", "myobj")) {
-            // Call imp.new_module('') module
+            final PyModule imp = PyModule.importModule("importlib.util");
+            final PyObject moduleSpec = imp.call("spec_from_loader", "myobj", null);
+            final PyObject myobj = imp.call("module_from_spec", moduleSpec)) {
             myobj.setAttribute("a", "Tut tut!");
             Assert.assertEquals("Tut tut!", myobj.getAttribute("a", String.class));
             try (final PyObject a = myobj.getAttribute("a")) {