Java program stopped running when using JVMPI

Question

Hi!
I'm writting a very simple profiler using JVMPI. I intended to pause/continue it by sending signal, like kill -SIGUSR2 PID, to it, but whenever I did this, the java program that ran with the profiler stopped running, however the profiler kept running properly.
Here's the code of the simple profiler and the testing java program.
//myprofiler.cc
#include <jvmpi.h>
#include <pthread.h>
#include <stdio.h>
#include <signal.h>
void sig_handler_pause(int);
static JVMPI_Interface *jvmpi_interface;
void notifyEvent(JVMPI_Event *event) {
switch(event->event_type) {
case JVMPI_EVENT_CLASS_LOAD:
fprintf(stderr, "myprofiler> Class Load : %s\n", event->u.class_load.class_name);
break;
case JVMPI_EVENT_OBJECT_ALLOC:
fprintf(stderr, "myprofiler>object alloc \n");
break;
extern "C" {
JNIEXPORT jint JNICALL JVM_OnLoad(JavaVM jvm, char options, void *reserved) {
fprintf(stderr, "myprofiler> initializing ..... \n");
// get jvmpi interface pointer
if ((jvm->GetEnv((void **)&jvmpi_interface, JVMPI_VERSION_1)) < 0) {
fprintf(stderr, "myprofiler> error in obtaining jvmpi interface pointer\n");
return JNI_ERR;
// initialize jvmpi interface
jvmpi_interface->NotifyEvent = notifyEvent;
// enabling class load event notification
jvmpi_interface->EnableEvent(JVMPI_EVENT_CLASS_LOAD, NULL);
fprintf(stderr, "myprofiler> .... ok \n\n");
signal(SIGUSR2,sig_handler_pause);
return JNI_OK;
void start(){
          fprintf(stderr,"start...\n");
     jvmpi_interface->EnableEvent(JVMPI_EVENT_OBJECT_ALLOC, NULL);
jvmpi_interface->EnableEvent(JVMPI_EVENT_CLASS_LOAD,NULL);
void pause(){
          fprintf(stderr,"pause...\n");
          jvmpi_interface->DisableEvent(JVMPI_EVENT_OBJECT_ALLOC, NULL);
jvmpi_interface->DisableEvent(JVMPI_EVENT_CLASS_LOAD,NULL);
int status=0;
void sig_handler_pause(int sig){
     if(status == 0){
          start();
          status = 1;
     else if(status == 1){
          pause();
          status = 0;
//Test.java
public class Test {
public static void main(String[] args) {
     try {
                    int i = 0;
while(true)
                         Thread.sleep(1000);
                    System.out.println(i++);
          catch (Exception e) {
                    e.printStackTrace();
Here're some notes:
1)If I didn't call
jvmpi_interface->EnableEvent(JVMPI_EVENT_OBJECT_ALLOC, NULL);
in "start()" function, the java program Test ran properly after I sent signal to the process by using kill command in an command line;
or
2) If I delete "Thread.sleep(1000)" in Test.java, then whether I call
jvmpi_interface->EnableEvent(JVMPI_EVENT_OBJECT_ALLOC, NULL);
in "start()" or not, the Test program ran properly after I sent signal to the process.
It seems to be a thread dead lock, but I'm not sure. Can any body help?Thanks very much.

Answer 1

I should strongly recommend moving from JVMPI to JVM TI if you can. The reason is that JVMPI has been deprecated since 5.0 and can not be used with Java SE 6 and newer.
Anyway, the issue you have may be due to the signal you are using. I'm not sure which operating system this is but on Linux the USR2 signal is used for the suspend/resume implementation. Have you looked at the Troubleshooting Guide or the Signal Chaining page for details on how signals are used and how to chain handlers? Another idea is to remove the signal handling code implementation and to use the data dump event. This is supported by both JVMPI and JVM TI so that you get an event (via the QUIT signal).