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| 1 | +/* |
| 2 | + * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved. |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 | + * |
| 5 | + * This code is free software; you can redistribute it and/or modify it |
| 6 | + * under the terms of the GNU General Public License version 2 only, as |
| 7 | + * published by the Free Software Foundation. |
| 8 | + * |
| 9 | + * This code is distributed in the hope that it will be useful, but WITHOUT |
| 10 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 11 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| 12 | + * version 2 for more details (a copy is included in the LICENSE file that |
| 13 | + * accompanied this code). |
| 14 | + * |
| 15 | + * You should have received a copy of the GNU General Public License version |
| 16 | + * 2 along with this work; if not, write to the Free Software Foundation, |
| 17 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| 18 | + * |
| 19 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| 20 | + * or visit www.oracle.com if you need additional information or have any |
| 21 | + * questions. |
| 22 | + */ |
| 23 | + |
| 24 | +#include <jni.h> |
| 25 | +#include <pthread.h> |
| 26 | +#include <stdio.h> |
| 27 | +#include <stdlib.h> |
| 28 | +#include <unistd.h> |
| 29 | + |
| 30 | +#ifdef __cplusplus |
| 31 | +extern "C" { |
| 32 | +#endif |
| 33 | + |
| 34 | +static JavaVM* jvm; |
| 35 | +static pthread_t attacher; |
| 36 | + |
| 37 | +#define die(x) do { printf("%s:%s\n",x , __func__); perror(x); exit(EXIT_FAILURE); } while (0) |
| 38 | + |
| 39 | +static void check_exception(JNIEnv* env, const char* msg) { |
| 40 | + if ((*env)->ExceptionCheck(env)) { |
| 41 | + fprintf(stderr, "Error: %s", msg); |
| 42 | + exit(-1); |
| 43 | + } |
| 44 | +} |
| 45 | + |
| 46 | +#define check(env, what, msg) \ |
| 47 | + check_exception((env), (msg)); \ |
| 48 | + do { \ |
| 49 | + if ((what) == 0) { \ |
| 50 | + fprintf(stderr, #what "is null: %s", (msg)); \ |
| 51 | + exit(-2); \ |
| 52 | + } \ |
| 53 | + } while (0) |
| 54 | + |
| 55 | +static jobject create_object(JNIEnv* env) { |
| 56 | + jclass clazz = (*env)->FindClass(env, "java/lang/Object"); |
| 57 | + check(env, clazz, "No class"); |
| 58 | + |
| 59 | + jmethodID constructor = (*env)->GetMethodID(env, clazz, "<init>", "()V"); |
| 60 | + check(env, constructor, "No constructor"); |
| 61 | + |
| 62 | + jobject obj = (*env)->NewObject(env, clazz, constructor); |
| 63 | + check(env, constructor, "No object"); |
| 64 | + |
| 65 | + return obj; |
| 66 | +} |
| 67 | + |
| 68 | +static void system_gc(JNIEnv* env) { |
| 69 | + jclass clazz = (*env)->FindClass(env, "java/lang/System"); |
| 70 | + check(env, clazz, "No class"); |
| 71 | + |
| 72 | + jmethodID method = (*env)->GetStaticMethodID(env, clazz, "gc", "()V"); |
| 73 | + check(env, method, "No method"); |
| 74 | + |
| 75 | + (*env)->CallStaticVoidMethod(env, clazz, method); |
| 76 | + check_exception(env, "Calling System.gc()"); |
| 77 | +} |
| 78 | + |
| 79 | +static void thread_dump_with_locked_monitors(JNIEnv* env) { |
| 80 | + jclass ManagementFactoryClass = (*env)->FindClass(env, "java/lang/management/ManagementFactory"); |
| 81 | + check(env, ManagementFactoryClass, "No ManagementFactory class"); |
| 82 | + |
| 83 | + jmethodID getThreadMXBeanMethod = (*env)->GetStaticMethodID(env, ManagementFactoryClass, "getThreadMXBean", "()Ljava/lang/management/ThreadMXBean;"); |
| 84 | + check(env, getThreadMXBeanMethod, "No getThreadMXBean method"); |
| 85 | + |
| 86 | + jobject threadBean = (*env)->CallStaticObjectMethod(env, ManagementFactoryClass, getThreadMXBeanMethod); |
| 87 | + check(env, threadBean, "Calling getThreadMXBean()"); |
| 88 | + |
| 89 | + jclass ThreadMXBeanClass = (*env)->FindClass(env, "java/lang/management/ThreadMXBean"); |
| 90 | + check(env, ThreadMXBeanClass, "No ThreadMXBean class"); |
| 91 | + |
| 92 | + jmethodID dumpAllThreadsMethod = (*env)->GetMethodID(env, ThreadMXBeanClass, "dumpAllThreads", "(ZZ)[Ljava/lang/management/ThreadInfo;"); |
| 93 | + check(env, dumpAllThreadsMethod, "No dumpAllThreads method"); |
| 94 | + |
| 95 | + // The 'lockedMonitors == true' is what causes the monitor with a dead object to be examined. |
| 96 | + jobject array = (*env)->CallObjectMethod(env, threadBean, dumpAllThreadsMethod, JNI_TRUE /* lockedMonitors */, JNI_FALSE /* lockedSynchronizers*/); |
| 97 | + check(env, array, "Calling dumpAllThreads(true, false)"); |
| 98 | +} |
| 99 | + |
| 100 | +static void create_monitor_with_dead_object(JNIEnv* env) { |
| 101 | + jobject obj = create_object(env); |
| 102 | + |
| 103 | + if ((*env)->MonitorEnter(env, obj) != 0) die("MonitorEnter"); |
| 104 | + |
| 105 | + // Drop the last strong reference to the object associated with the monitor. |
| 106 | + // The monitor only keeps a weak reference to the object. |
| 107 | + (*env)->DeleteLocalRef(env, obj); |
| 108 | + |
| 109 | + // Let the GC clear the weak reference to the object. |
| 110 | + system_gc(env); |
| 111 | +} |
| 112 | + |
| 113 | +static void* create_monitor_with_dead_object_in_thread(void* arg) { |
| 114 | + JNIEnv* env; |
| 115 | + int res = (*jvm)->AttachCurrentThread(jvm, (void**)&env, NULL); |
| 116 | + if (res != JNI_OK) die("AttachCurrentThread"); |
| 117 | + |
| 118 | + // Make the correct incantation to create a monitor with a dead object. |
| 119 | + create_monitor_with_dead_object(env); |
| 120 | + |
| 121 | + // DetachCurrentThread will try to unlock held monitors. This has been a |
| 122 | + // source of at least two bugs: |
| 123 | + // - When the object reference in the monitor was cleared, the monitor |
| 124 | + // iterator code would skip it, preventing it from being unlocked when |
| 125 | + // the owner thread detached, leaving it lingering in the system. |
| 126 | + // - When the monitor iterator API was rewritten the code was changed to |
| 127 | + // assert that we didn't have "owned" monitors with dead objects. This |
| 128 | + // test provokes that situation and that asserts. |
| 129 | + if ((*jvm)->DetachCurrentThread(jvm) != JNI_OK) die("DetachCurrentThread"); |
| 130 | + |
| 131 | + return NULL; |
| 132 | +} |
| 133 | + |
| 134 | +static void* create_monitor_with_dead_object_and_dump_threads_in_thread(void* arg) { |
| 135 | + JNIEnv* env; |
| 136 | + int res = (*jvm)->AttachCurrentThread(jvm, (void**)&env, NULL); |
| 137 | + if (res != JNI_OK) die("AttachCurrentThread"); |
| 138 | + |
| 139 | + // Make the correct incantation to create a monitor with a dead object. |
| 140 | + create_monitor_with_dead_object(env); |
| 141 | + |
| 142 | + // Perform a thread dump that checks for all thread's monitors. |
| 143 | + // That code didn't expect the monitor iterators to return monitors |
| 144 | + // with dead objects and therefore asserted/crashed. |
| 145 | + thread_dump_with_locked_monitors(env); |
| 146 | + |
| 147 | + if ((*jvm)->DetachCurrentThread(jvm) != JNI_OK) die("DetachCurrentThread"); |
| 148 | + |
| 149 | + return NULL; |
| 150 | +} |
| 151 | + |
| 152 | +JNIEXPORT void JNICALL Java_MonitorWithDeadObjectTest_createMonitorWithDeadObject(JNIEnv* env, jclass jc) { |
| 153 | + void* ret; |
| 154 | + |
| 155 | + (*env)->GetJavaVM(env, &jvm); |
| 156 | + |
| 157 | + if (pthread_create(&attacher, NULL, create_monitor_with_dead_object_in_thread, NULL) != 0) die("pthread_create"); |
| 158 | + if (pthread_join(attacher, &ret) != 0) die("pthread_join"); |
| 159 | +} |
| 160 | + |
| 161 | +JNIEXPORT void JNICALL Java_MonitorWithDeadObjectTest_createMonitorWithDeadObjectDumpThreadsBeforeDetach(JNIEnv* env, jclass jc) { |
| 162 | + void* ret; |
| 163 | + |
| 164 | + (*env)->GetJavaVM(env, &jvm); |
| 165 | + |
| 166 | + if (pthread_create(&attacher, NULL, create_monitor_with_dead_object_and_dump_threads_in_thread, NULL) != 0) die("pthread_create"); |
| 167 | + if (pthread_join(attacher, &ret) != 0) die("pthread_join"); |
| 168 | +} |
| 169 | + |
| 170 | +#ifdef __cplusplus |
| 171 | +} |
| 172 | +#endif |
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