8339725: Concurrent GC crashed due to GetMethodDeclaringClass

make/test/JtregNativeHotspot.gmk

@@ -873,7 +873,7 @@ BUILD_HOTSPOT_JTREG_EXECUTABLES_LIBS_exesigtest := -ljvm
 
 ifeq ($(call isTargetOs, windows), true)
     BUILD_HOTSPOT_JTREG_EXECUTABLES_CFLAGS_exeFPRegs := -MT
-    BUILD_HOTSPOT_JTREG_EXCLUDE += exesigtest.c libterminatedThread.c libTestJNI.c libnativeStack.c exeGetCreatedJavaVMs.c
+    BUILD_HOTSPOT_JTREG_EXCLUDE += exesigtest.c libterminatedThread.c libTestJNI.c libnativeStack.c exeGetCreatedJavaVMs.c libTestUnloadedClass.cpp
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libatExit := jvm.lib
 else
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libbootclssearch_agent += -lpthread
@@ -1511,6 +1511,7 @@ else
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libterminatedThread += -lpthread
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libatExit += -ljvm
     BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libnativeStack += -lpthread
+    BUILD_HOTSPOT_JTREG_LIBRARIES_LIBS_libTestUnloadedClass += -lpthread
     BUILD_HOTSPOT_JTREG_EXECUTABLES_LIBS_exeGetCreatedJavaVMs := -ljvm -lpthread
 endif
 

src/hotspot/share/prims/jvmtiEnv.cpp

@@ -2747,7 +2747,9 @@ JvmtiEnv::GetFieldName(fieldDescriptor* fdesc_ptr, char** name_ptr, char** signa
 // declaring_class_ptr - pre-checked for NULL
 jvmtiError
 JvmtiEnv::GetFieldDeclaringClass(fieldDescriptor* fdesc_ptr, jclass* declaring_class_ptr) {
-
+  // As for the GetFieldDeclaringClass method, the XSL generated C++ code that calls it has
+  // a jclass of the relevant class or a subclass of it, which is fine in terms of ensuring
+  // the holder is kept alive.
   *declaring_class_ptr = get_jni_class_non_null(fdesc_ptr->field_holder());
   return JVMTI_ERROR_NONE;
 } /* end GetFieldDeclaringClass */
@@ -2825,7 +2827,9 @@ JvmtiEnv::GetMethodName(Method* method, char** name_ptr, char** signature_ptr, c
 jvmtiError
 JvmtiEnv::GetMethodDeclaringClass(Method* method, jclass* declaring_class_ptr) {
   NULL_CHECK(method, JVMTI_ERROR_INVALID_METHODID);
-  (*declaring_class_ptr) = get_jni_class_non_null(method->method_holder());
+  Klass* k = method->method_holder();
+  Handle holder(Thread::current(), k->klass_holder()); // keep the klass alive
+  (*declaring_class_ptr) = get_jni_class_non_null(k);
   return JVMTI_ERROR_NONE;
 } /* end GetMethodDeclaringClass */
 

src/hotspot/share/prims/jvmtiEnvBase.cpp

@@ -584,6 +584,7 @@ JvmtiEnvBase::vframeForNoProcess(JavaThread* java_thread, jint depth) {
 jclass
 JvmtiEnvBase::get_jni_class_non_null(Klass* k) {
   assert(k != NULL, "k != NULL");
+  assert(k->is_loader_alive(), "Must be alive");
   Thread *thread = Thread::current();
   return (jclass)jni_reference(Handle(thread, k->java_mirror()));
 }

test/hotspot/jtreg/serviceability/jvmti/GetMethodDeclaringClass/TestUnloadedClass.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
+ * Copyright (c) 2024, Alibaba Group Holding Limited. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/**
+ * @test
+ * @bug 8339725
+ * @summary Stress test GetMethodDeclaringClass
+ * @requires vm.jvmti
+ * @requires (os.family == "linux")
+ * @library /test/lib
+ * @run driver/timeout=300 TestUnloadedClass
+ */
+
+import jdk.test.lib.process.OutputAnalyzer;
+import jdk.test.lib.Utils;
+import jdk.test.lib.process.ProcessTools;
+import jdk.test.lib.Platform;
+
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.InputStream;
+import java.lang.reflect.Constructor;
+
+public class TestUnloadedClass {
+    public static void main(String[] args) throws Exception {
+        ProcessBuilder pb = ProcessTools.createTestJavaProcessBuilder(
+                "-agentpath:" + Utils.TEST_NATIVE_PATH + File.separator + System.mapLibraryName("TestUnloadedClass"),
+                "-Xmx50m",
+                "Test");
+        OutputAnalyzer output = new OutputAnalyzer(pb.start());
+        if (!Platform.isDebugBuild()) {
+            output.shouldContain("OutOfMemoryError");
+        }
+    }
+}
+
+class Test {
+    public static void main(String[] args) throws Exception {
+        long last = System.nanoTime();
+        for (int i = 0;;i++) {
+            if (Platform.isDebugBuild() && i >= 1000) {
+                // Debug build costs too much time to OOM so limit the loop iteration
+                break;
+            }
+            CustomClassLoader loader = new CustomClassLoader();
+            Class<?> k = loader.findClass("MyClass");
+            Constructor<?> c = k.getDeclaredConstructor();
+            c.setAccessible(true);
+            c.newInstance();
+
+            // call gc every ~1 second.
+            if ((System.nanoTime() - last) >= 1e9) {
+                System.gc();
+                last = System.nanoTime();
+            }
+        }
+    }
+}
+
+class CustomClassLoader extends ClassLoader {
+    static byte[] BYTES;
+
+    static {
+        try (InputStream in = CustomClassLoader.class.getResourceAsStream("MyClass.class")) {
+            try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+                byte[] buf = new byte[4096];
+                int len;
+                while ((len = in.read(buf)) != -1) {
+                    baos.write(buf, 0, len);
+                }
+                BYTES = baos.toByteArray();
+            }
+        } catch (Throwable t) {
+            throw new RuntimeException(t);
+        }
+    }
+
+    @Override
+    public Class findClass(String name) throws ClassNotFoundException {
+        return defineClass(name, BYTES, 0, BYTES.length);
+    }
+}
+
+class MyClass {
+}

test/hotspot/jtreg/serviceability/jvmti/GetMethodDeclaringClass/libTestUnloadedClass.cpp

@@ -0,0 +1,129 @@
+/*
+ * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
+ * Copyright (c) 2024, Alibaba Group Holding Limited. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include <atomic>
+
+#include <jvmti.h>
+#include <jni.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+static jvmtiEnv *_jvmti;
+static JavaVM *_jvm;
+
+#define BUFFER_SIZE 100000
+static std::atomic<jmethodID> ring_buffer[BUFFER_SIZE];
+
+void get_method_details(jmethodID method) {
+  jclass method_class;
+  char *class_name = NULL;
+  if (_jvmti->GetMethodDeclaringClass(method, &method_class) == JVMTI_ERROR_NONE) {
+    if (_jvmti->GetClassSignature(method_class, &class_name, NULL) == JVMTI_ERROR_NONE) {
+      _jvmti->Deallocate((unsigned char *)class_name);
+    }
+  }
+}
+
+void* read_ringbuffer(void* arg) {
+  JNIEnv *env;
+  _jvm->AttachCurrentThreadAsDaemon((void **)&env, NULL);
+  for (;;) {
+    jmethodID id = ring_buffer[rand() % BUFFER_SIZE].load(std::memory_order_relaxed);
+    if (id != (jmethodID)0) {
+      get_method_details(id);
+    }
+  }
+  return NULL;
+}
+
+static void JNICALL ClassPrepareCallback(jvmtiEnv *jvmti_env,
+                                         JNIEnv *jni_env,
+                                         jthread thread,
+                                         jclass klass) {
+  static bool reader_created = false;
+  static int ring_buffer_idx = 0;
+
+  char *class_name = NULL;
+  if (jvmti_env->GetClassSignature(klass, &class_name, NULL) != JVMTI_ERROR_NONE) {
+    return;
+  }
+  // We only care MyClass and only one thread loads it
+  bool is_my_class = strcmp(class_name, "LMyClass;") == 0;
+  jvmti_env->Deallocate((unsigned char *)class_name);
+  if (!is_my_class) {
+    return;
+  }
+
+  if (!reader_created) {
+    pthread_t tid;
+    pthread_create(&tid, NULL, read_ringbuffer, NULL);
+    reader_created = true;
+  }
+
+  jint method_count;
+  jmethodID *methods;
+  if (jvmti_env->GetClassMethods(klass, &method_count, &methods) == JVMTI_ERROR_NONE) {
+    ring_buffer[ring_buffer_idx++].store(methods[0], std::memory_order_relaxed);
+    ring_buffer_idx = ring_buffer_idx % BUFFER_SIZE;
+    jvmti_env->Deallocate((unsigned char *)methods);
+  }
+}
+
+JNIEXPORT jint JNICALL Agent_OnLoad(JavaVM *jvm, char *options, void *reserved) {
+  for (int i = 0; i < BUFFER_SIZE; i++) {
+    ring_buffer[i].store(0, std::memory_order_relaxed);
+  }
+
+  jvmtiEventCallbacks callbacks;
+  jvmtiError error;
+
+  _jvm = jvm;
+
+  if (jvm->GetEnv((void **)&_jvmti, JVMTI_VERSION_1_0) != JNI_OK) {
+    fprintf(stderr, "Unable to access JVMTI!\n");
+    return JNI_ERR;
+  }
+
+  // Set up the event callbacks
+  memset(&callbacks, 0, sizeof(callbacks));
+  callbacks.ClassPrepare = &ClassPrepareCallback;
+
+  // Register the callbacks
+  error = _jvmti->SetEventCallbacks(&callbacks, sizeof(callbacks));
+  if (error != JVMTI_ERROR_NONE) {
+    fprintf(stderr, "Error setting event callbacks: %d\n", error);
+    return JNI_ERR;
+  }
+
+  // Enable the ClassPrepare event
+  error = _jvmti->SetEventNotificationMode(JVMTI_ENABLE, JVMTI_EVENT_CLASS_PREPARE, NULL);
+  if (error != JVMTI_ERROR_NONE) {
+    fprintf(stderr, "Error enabling ClassPrepare event: %d\n", error);
+    return JNI_ERR;
+  }
+
+  return JNI_OK;
+}