Java example source code file (waiters.cpp)

This example Java source code file (waiters.cpp) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

agent, error, getenvironmentlocalstorage, jni_false, jni_ok, jni_true, jnicall, jnienv, jniexport, jvmti_event_monitor_contended_enter, jvmti_event_monitor_contended_entered, jvmti_event_thread_end, jvmti_event_vm_death, null

The waiters.cpp Java example source code

/*
 * Copyright (c) 2004, 2011, 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 events:
 *      JVMTI_EVENT_VM_INIT
 *      JVMTI_EVENT_VM_DEATH
 *      JVMTI_EVENT_THREAD_START
 *      JVMTI_EVENT_THREAD_END
 *      JVMTI_EVENT_MONITOR_CONTENDED_ENTER
 *      JVMTI_EVENT_MONITOR_WAIT
 *      JVMTI_EVENT_MONITOR_WAITED
 *      JVMTI_EVENT_OBJECT_FREE
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "jni.h"
#include "jvmti.h"

#include "agent_util.h"

#include "Monitor.hpp"
#include "Thread.hpp"
#include "Agent.hpp"

static jrawMonitorID vm_death_lock;
static jboolean      vm_death_active;

/* Given a jvmtiEnv*, return the C++ Agent class instance */
static Agent *
get_agent(jvmtiEnv *jvmti)
{
    jvmtiError err;
    Agent     *agent;

    agent = NULL;
    err = jvmti->GetEnvironmentLocalStorage((void**)&agent);
    check_jvmti_error(jvmti, err, "get env local storage");
    if ( agent == NULL ) {
        /* This should never happen, but we should check */
        fatal_error("ERROR: GetEnvironmentLocalStorage() returned NULL");
    }
    return agent;
}

/* Enter raw monitor */
static void
menter(jvmtiEnv *jvmti, jrawMonitorID rmon)
{
    jvmtiError err;

    err = jvmti->RawMonitorEnter(rmon);
    check_jvmti_error(jvmti, err, "raw monitor enter");
}

/* Exit raw monitor */
static void
mexit(jvmtiEnv *jvmti, jrawMonitorID rmon)
{
    jvmtiError err;

    err = jvmti->RawMonitorExit(rmon);
    check_jvmti_error(jvmti, err, "raw monitor exit");
}


/* All callbacks need to be extern "C" */
extern "C" {
    static void JNICALL
    vm_init(jvmtiEnv *jvmti, JNIEnv *env, jthread thread)
    {
        jvmtiError err;
        Agent     *agent;

        /* Create raw monitor to protect against threads running after death */
        err = jvmti->CreateRawMonitor("Waiters vm_death lock", &vm_death_lock);
        check_jvmti_error(jvmti, err, "create raw monitor");
        vm_death_active = JNI_FALSE;

        /* Create an Agent instance, set JVMTI Local Storage */
        agent = new Agent(jvmti, env, thread);
        err = jvmti->SetEnvironmentLocalStorage((const void*)agent);
        check_jvmti_error(jvmti, err, "set env local storage");

        /* Enable all other events we want */
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_VM_DEATH, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_THREAD_START, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_THREAD_END, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_MONITOR_CONTENDED_ENTER, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_MONITOR_CONTENDED_ENTERED, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_MONITOR_WAIT, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_MONITOR_WAITED, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_OBJECT_FREE, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
    }
    static void JNICALL
    vm_death(jvmtiEnv *jvmti, JNIEnv *env)
    {
        jvmtiError err;
        Agent     *agent;

        /* Block all callbacks */
        menter(jvmti, vm_death_lock); {
            /* Set flag for other callbacks */
            vm_death_active = JNI_TRUE;

            /* Inform Agent instance of VM_DEATH */
            agent = get_agent(jvmti);
            agent->vm_death(jvmti, env);

            /* Reclaim space of Agent */
            err = jvmti->SetEnvironmentLocalStorage((const void*)NULL);
            check_jvmti_error(jvmti, err, "set env local storage");
            delete agent;
        } mexit(jvmti, vm_death_lock);

    }
    static void JNICALL
    thread_start(jvmtiEnv *jvmti, JNIEnv *env, jthread thread)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->thread_start(jvmti, env, thread);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    thread_end(jvmtiEnv *jvmti, JNIEnv *env, jthread thread)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->thread_end(jvmti, env, thread);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    monitor_contended_enter(jvmtiEnv* jvmti, JNIEnv *env,
                 jthread thread, jobject object)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->monitor_contended_enter(jvmti, env,
                                                          thread, object);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    monitor_contended_entered(jvmtiEnv* jvmti, JNIEnv *env,
                   jthread thread, jobject object)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->monitor_contended_entered(jvmti, env,
                                                            thread, object);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    monitor_wait(jvmtiEnv* jvmti, JNIEnv *env,
                 jthread thread, jobject object, jlong timeout)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->monitor_wait(jvmti, env, thread,
                                               object, timeout);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    monitor_waited(jvmtiEnv* jvmti, JNIEnv *env,
                   jthread thread, jobject object, jboolean timed_out)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->monitor_waited(jvmti, env, thread,
                                                 object, timed_out);
            }
        } mexit(jvmti, vm_death_lock);
    }
    static void JNICALL
    object_free(jvmtiEnv* jvmti, jlong tag)
    {
        menter(jvmti, vm_death_lock); {
            if ( !vm_death_active ) {
                get_agent(jvmti)->object_free(jvmti, tag);
            }
        } mexit(jvmti, vm_death_lock);
    }

    /* Agent_OnLoad() is called first, we prepare for a VM_INIT event here. */
    JNIEXPORT jint JNICALL
    Agent_OnLoad(JavaVM *vm, char *options, void *reserved)
    {
        jvmtiEnv           *jvmti;
        jint                rc;
        jvmtiError          err;
        jvmtiCapabilities   capabilities;
        jvmtiEventCallbacks callbacks;

        /* Get JVMTI environment */
        rc = vm->GetEnv((void **)&jvmti, JVMTI_VERSION);
        if (rc != JNI_OK) {
            fatal_error("ERROR: Unable to create jvmtiEnv, GetEnv failed, error=%d\n", rc);
            return -1;
        }

        /* Get/Add JVMTI capabilities */
        (void)memset(&capabilities, 0, sizeof(capabilities));
        capabilities.can_generate_monitor_events        = 1;
        capabilities.can_get_monitor_info               = 1;
        capabilities.can_tag_objects                    = 1;
        capabilities.can_generate_object_free_events    = 1;
        err = jvmti->AddCapabilities(&capabilities);
        check_jvmti_error(jvmti, err, "add capabilities");

        /* Set all callbacks and enable VM_INIT event notification */
        memset(&callbacks, 0, sizeof(callbacks));
        callbacks.VMInit                  = &vm_init;
        callbacks.VMDeath                 = &vm_death;
        callbacks.ThreadStart             = &thread_start;
        callbacks.ThreadEnd               = &thread_end;
        callbacks.MonitorContendedEnter   = &monitor_contended_enter;
        callbacks.MonitorContendedEntered = &monitor_contended_entered;
        callbacks.MonitorWait             = &monitor_wait;
        callbacks.MonitorWaited           = &monitor_waited;
        callbacks.ObjectFree              = &object_free;
        err = jvmti->SetEventCallbacks(&callbacks, (jint)sizeof(callbacks));
        check_jvmti_error(jvmti, err, "set event callbacks");
        err = jvmti->SetEventNotificationMode(JVMTI_ENABLE,
                        JVMTI_EVENT_VM_INIT, NULL);
        check_jvmti_error(jvmti, err, "set event notify");
        return 0;
    }

    /* Agent_OnUnload() is called last */
    JNIEXPORT void JNICALL
    Agent_OnUnload(JavaVM *vm)
    {
    }

} /* of extern "C" */