Hi Keith,
Keith McGuigan said the following on 01/11/11 03:36:
This closes a race condition hole between
JvmtiThreadState::state_for_while_locked() and ~JavaThread(). Without
this, the state_for_while_locked() could see a value of false for
thread->is_exiting(), then the entirety of ~JavaThread() could run, the
state_for_while_locked() could then finish leaving the JvmtiThreadState
referring to a zombie thread.
webrev: http://cr.openjdk.java.net/~kamg/6814943/webrev.00/
I think it would be slightly cleaner, as per my private email, to keep
the locking internal to the JVMTI methods ie:
void
JvmtiEventControllerPrivate::thread_ended(JavaThread *thread) {
// Removes the JvmtiThreadState associated with the specified thread.
// May be called after all environments have been disposed.
EC_TRACE(("JVMTI [%s] # thread ended",
JvmtiTrace::safe_get_thread_name(thread)));
MutexLocker mu(JvmtiThreadState_lock);
JvmtiThreadState *state = thread->jvmti_thread_state();
if (state != NULL) {
delete state;
}
}
and then in JavaThread::exit just do:
if (JvmtiEnv::environments_might_exist()) {
JvmtiExport::cleanup_thread(this);
}
as cleanup_thread already does a null check. Note that if an environment
comes into existence we are still relying on another thread seeing that
this thread has terminated prior to the above check.
David
