A Bug about the JVM Attach mechanism

[nijiaben]

Hi, All,






There is a bug that has been discovered for a long time, but it has not been 
fixed. 


We usually use some shell scripts to clean up the /tmp directory. 
When we have executed a similar jstack command based on the attach mechanism, 
it will generate a .java_pidXXX socket file in the /tmp directory. 
Once this file is clean up, and then will not be attached anymore.


The main reason is that once the Attach Listener thread is created, 
the file of  “/tmp/.java_pidXXX” will be created and the markup initialization 
is complete. 
If .java_pidXXX is cleaned up, it will not be created anymore and cannot be 
attached.



bool AttachListener::is_init_trigger() {
  if (init_at_startup() || is_initialized()) { // initialized at startup or 
already initialized
    return false;               
  }
  char fn[PATH_MAX+1];
  sprintf(fn, ".attach_pid%d", os::current_process_id());
  int ret;
  struct stat64 st;
  RESTARTABLE(::stat64(fn, &st), ret);
  if (ret == -1) {
    snprintf(fn, sizeof(fn), "%s/.attach_pid%d",
             os::get_temp_directory(), os::current_process_id());
    RESTARTABLE(::stat64(fn, &st), ret);
  }
  if (ret == 0) {
    if (st.st_uid == geteuid()) {
      init(); // will create Attach Listener Thread
      return true;
    }
  }
  return false;
}




This bug has a big impact on troubleshooting some problems. 
Can it be fixed as soon as possible?


Thanks,

nijiaben @ PerfMa