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/*
* Copyright (c) 2004, Oracle and/or its affiliates. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* - Neither the name of Oracle nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* This source code is provided to illustrate the usage of a given feature
* or technique and has been deliberately simplified. Additional steps
* required for a production-quality application, such as security checks,
* input validation and proper error handling, might not be present in
* this sample code.
*/
/* Example of using JVMTI_EVENT_GARBAGE_COLLECTION_START and
* JVMTI_EVENT_GARBAGE_COLLECTION_FINISH events.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "jni.h"
#include "jvmti.h"
/* For stdout_message(), fatal_error(), and check_jvmti_error() */
#include "agent_util.h"
/* Global static data */
static jvmtiEnv *jvmti;
static int gc_count;
static jrawMonitorID lock;
/* Worker thread that waits for garbage collections */
static void JNICALL
worker(jvmtiEnv* jvmti, JNIEnv* jni, void *p)
{
jvmtiError err;
stdout_message("GC worker started...\n");
for (;;) {
err = (*jvmti)->RawMonitorEnter(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor enter");
while (gc_count == 0) {
err = (*jvmti)->RawMonitorWait(jvmti, lock, 0);
if (err != JVMTI_ERROR_NONE) {
err = (*jvmti)->RawMonitorExit(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor wait");
return;
}
}
gc_count = 0;
err = (*jvmti)->RawMonitorExit(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor exit");
/* Perform arbitrary JVMTI/JNI work here to do post-GC cleanup */
stdout_message("post-GarbageCollectionFinish actions...\n");
}
}
/* Creates a new jthread */
static jthread
alloc_thread(JNIEnv *env)
{
jclass thrClass;
jmethodID cid;
jthread res;
thrClass = (*env)->FindClass(env, "java/lang/Thread");
if ( thrClass == NULL ) {
fatal_error("Cannot find Thread class\n");
}
cid = (*env)->GetMethodID(env, thrClass, "<init>", "()V");
if ( cid == NULL ) {
fatal_error("Cannot find Thread constructor method\n");
}
res = (*env)->NewObject(env, thrClass, cid);
if ( res == NULL ) {
fatal_error("Cannot create new Thread object\n");
}
return res;
}
/* Callback for JVMTI_EVENT_VM_INIT */
static void JNICALL
vm_init(jvmtiEnv *jvmti, JNIEnv *env, jthread thread)
{
jvmtiError err;
stdout_message("VMInit...\n");
err = (*jvmti)->RunAgentThread(jvmti, alloc_thread(env), &worker, NULL,
JVMTI_THREAD_MAX_PRIORITY);
check_jvmti_error(jvmti, err, "running agent thread");
}
/* Callback for JVMTI_EVENT_GARBAGE_COLLECTION_START */
static void JNICALL
gc_start(jvmtiEnv* jvmti_env)
{
stdout_message("GarbageCollectionStart...\n");
}
/* Callback for JVMTI_EVENT_GARBAGE_COLLECTION_FINISH */
static void JNICALL
gc_finish(jvmtiEnv* jvmti_env)
{
jvmtiError err;
stdout_message("GarbageCollectionFinish...\n");
err = (*jvmti)->RawMonitorEnter(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor enter");
gc_count++;
err = (*jvmti)->RawMonitorNotify(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor notify");
err = (*jvmti)->RawMonitorExit(jvmti, lock);
check_jvmti_error(jvmti, err, "raw monitor exit");
}
/* Agent_OnLoad() is called first, we prepare for a VM_INIT event here. */
JNIEXPORT jint JNICALL
Agent_OnLoad(JavaVM *vm, char *options, void *reserved)
{
jint rc;
jvmtiError err;
jvmtiCapabilities capabilities;
jvmtiEventCallbacks callbacks;
/* Get JVMTI environment */
rc = (*vm)->GetEnv(vm, (void **)&jvmti, JVMTI_VERSION);
if (rc != JNI_OK) {
fatal_error("ERROR: Unable to create jvmtiEnv, rc=%d\n", rc);
return -1;
}
/* Get/Add JVMTI capabilities */
(void)memset(&capabilities, 0, sizeof(capabilities));
capabilities.can_generate_garbage_collection_events = 1;
err = (*jvmti)->AddCapabilities(jvmti, &capabilities);
check_jvmti_error(jvmti, err, "add capabilities");
/* Set callbacks and enable event notifications */
memset(&callbacks, 0, sizeof(callbacks));
callbacks.VMInit = &vm_init;
callbacks.GarbageCollectionStart = &gc_start;
callbacks.GarbageCollectionFinish = &gc_finish;
err = (*jvmti)->SetEventCallbacks(jvmti, &callbacks, sizeof(callbacks));
check_jvmti_error(jvmti, err, "set event callbacks");
err = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
JVMTI_EVENT_VM_INIT, NULL);
check_jvmti_error(jvmti, err, "set event notification");
err = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
JVMTI_EVENT_GARBAGE_COLLECTION_START, NULL);
check_jvmti_error(jvmti, err, "set event notification");
err = (*jvmti)->SetEventNotificationMode(jvmti, JVMTI_ENABLE,
JVMTI_EVENT_GARBAGE_COLLECTION_FINISH, NULL);
check_jvmti_error(jvmti, err, "set event notification");
/* Create the necessary raw monitor */
err = (*jvmti)->CreateRawMonitor(jvmti, "lock", &lock);
check_jvmti_error(jvmti, err, "create raw monitor");
return 0;
}
/* Agent_OnUnload() is called last */
JNIEXPORT void JNICALL
Agent_OnUnload(JavaVM *vm)
{
}
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