jvmtiError
JvmtiEnvBase::get_current_contended_monitor(JavaThread *calling_thread, JavaThread *java_thread, jobject *monitor_ptr) {
#ifdef ASSERT
uint32_t debug_bits = 0;
#endif
assert((SafepointSynchronize::is_at_safepoint() ||
is_thread_fully_suspended(java_thread, false, &debug_bits)),
"at safepoint or target thread is suspended");
oop obj = NULL;
ObjectMonitor *mon = java_thread->current_waiting_monitor();
if (mon == NULL) {
// thread is not doing an Object.wait() call
mon = java_thread->current_pending_monitor();
if (mon != NULL) {
// The thread is trying to enter() or raw_enter() an ObjectMonitor.
obj = (oop)mon->object();
// If obj == NULL, then ObjectMonitor is raw which doesn't count
// as contended for this API
}
// implied else: no contended ObjectMonitor
} else {
// thread is doing an Object.wait() call
obj = (oop)mon->object();
assert(obj != NULL, "Object.wait() should have an object");
}
if (obj == NULL) {
*monitor_ptr = NULL;
} else {
HandleMark hm;
Handle hobj(obj);
*monitor_ptr = jni_reference(calling_thread, hobj);
}
return JVMTI_ERROR_NONE;
}
jobject *
JvmtiEnvBase::new_jobjectArray(int length, Handle *handles) {
if (length == 0) {
return NULL;
}
jobject *objArray = (jobject *) jvmtiMalloc(sizeof(jobject) * length);
NULL_CHECK(objArray, NULL);
for (int i=0; i<length; i++) {
objArray[i] = jni_reference(handles[i]);
}
return objArray;
}
jvmtiError
JvmtiEnvBase::get_object_monitor_usage(JavaThread* calling_thread, jobject object, jvmtiMonitorUsage* info_ptr) {
HandleMark hm;
Handle hobj;
bool at_safepoint = SafepointSynchronize::is_at_safepoint();
// Check arguments
{
oop mirror = JNIHandles::resolve_external_guard(object);
NULL_CHECK(mirror, JVMTI_ERROR_INVALID_OBJECT);
NULL_CHECK(info_ptr, JVMTI_ERROR_NULL_POINTER);
hobj = Handle(mirror);
}
JavaThread *owning_thread = NULL;
ObjectMonitor *mon = NULL;
jvmtiMonitorUsage ret = {
NULL, 0, 0, NULL, 0, NULL
};
uint32_t debug_bits = 0;
// first derive the object's owner and entry_count (if any)
{
// Revoke any biases before querying the mark word
if (SafepointSynchronize::is_at_safepoint()) {
BiasedLocking::revoke_at_safepoint(hobj);
} else {
BiasedLocking::revoke_and_rebias(hobj, false, calling_thread);
}
address owner = NULL;
{
markOop mark = hobj()->mark();
if (!mark->has_monitor()) {
// this object has a lightweight monitor
if (mark->has_locker()) {
owner = (address)mark->locker(); // save the address of the Lock word
}
// implied else: no owner
} else {
// this object has a heavyweight monitor
mon = mark->monitor();
// The owner field of a heavyweight monitor may be NULL for no
// owner, a JavaThread * or it may still be the address of the
// Lock word in a JavaThread's stack. A monitor can be inflated
// by a non-owning JavaThread, but only the owning JavaThread
// can change the owner field from the Lock word to the
// JavaThread * and it may not have done that yet.
owner = (address)mon->owner();
}
}
if (owner != NULL) {
// This monitor is owned so we have to find the owning JavaThread.
// Since owning_thread_from_monitor_owner() grabs a lock, GC can
// move our object at this point. However, our owner value is safe
// since it is either the Lock word on a stack or a JavaThread *.
owning_thread = Threads::owning_thread_from_monitor_owner(owner, !at_safepoint);
// Cannot assume (owning_thread != NULL) here because this function
// may not have been called at a safepoint and the owning_thread
// might not be suspended.
if (owning_thread != NULL) {
// The monitor's owner either has to be the current thread, at safepoint
// or it has to be suspended. Any of these conditions will prevent both
// contending and waiting threads from modifying the state of
// the monitor.
if (!at_safepoint && !JvmtiEnv::is_thread_fully_suspended(owning_thread, true, &debug_bits)) {
// Don't worry! This return of JVMTI_ERROR_THREAD_NOT_SUSPENDED
// will not make it back to the JVM/TI agent. The error code will
// get intercepted in JvmtiEnv::GetObjectMonitorUsage() which
// will retry the call via a VM_GetObjectMonitorUsage VM op.
return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
}
HandleMark hm;
Handle th(owning_thread->threadObj());
ret.owner = (jthread)jni_reference(calling_thread, th);
}
// implied else: no owner
}
if (owning_thread != NULL) { // monitor is owned
// The recursions field of a monitor does not reflect recursions
// as lightweight locks before inflating the monitor are not included.
// We have to count the number of recursive monitor entries the hard way.
// We pass a handle to survive any GCs along the way.
ResourceMark rm;
ret.entry_count = count_locked_objects(owning_thread, hobj);
}
// implied else: entry_count == 0
}
jint nWant, nWait;
if (mon != NULL) {
// this object has a heavyweight monitor
nWant = mon->contentions(); // # of threads contending for monitor
nWait = mon->waiters(); // # of threads in Object.wait()
ret.waiter_count = nWant + nWait;
ret.notify_waiter_count = nWait;
} else {
// this object has a lightweight monitor
ret.waiter_count = 0;
ret.notify_waiter_count = 0;
}
// Allocate memory for heavyweight and lightweight monitor.
jvmtiError err;
err = allocate(ret.waiter_count * sizeof(jthread *), (unsigned char**)&ret.waiters);
if (err != JVMTI_ERROR_NONE) {
return err;
}
err = allocate(ret.notify_waiter_count * sizeof(jthread *),
(unsigned char**)&ret.notify_waiters);
if (err != JVMTI_ERROR_NONE) {
deallocate((unsigned char*)ret.waiters);
return err;
}
// now derive the rest of the fields
if (mon != NULL) {
// this object has a heavyweight monitor
// Number of waiters may actually be less than the waiter count.
// So NULL out memory so that unused memory will be NULL.
memset(ret.waiters, 0, ret.waiter_count * sizeof(jthread *));
memset(ret.notify_waiters, 0, ret.notify_waiter_count * sizeof(jthread *));
if (ret.waiter_count > 0) {
// we have contending and/or waiting threads
HandleMark hm;
if (nWant > 0) {
// we have contending threads
ResourceMark rm;
// get_pending_threads returns only java thread so we do not need to
// check for non java threads.
GrowableArray<JavaThread*>* wantList = Threads::get_pending_threads(
nWant, (address)mon, !at_safepoint);
if (wantList->length() < nWant) {
// robustness: the pending list has gotten smaller
nWant = wantList->length();
}
for (int i = 0; i < nWant; i++) {
JavaThread *pending_thread = wantList->at(i);
// If the monitor has no owner, then a non-suspended contending
// thread could potentially change the state of the monitor by
// entering it. The JVM/TI spec doesn't allow this.
if (owning_thread == NULL && !at_safepoint &
!JvmtiEnv::is_thread_fully_suspended(pending_thread, true, &debug_bits)) {
if (ret.owner != NULL) {
destroy_jni_reference(calling_thread, ret.owner);
}
for (int j = 0; j < i; j++) {
destroy_jni_reference(calling_thread, ret.waiters[j]);
}
deallocate((unsigned char*)ret.waiters);
deallocate((unsigned char*)ret.notify_waiters);
return JVMTI_ERROR_THREAD_NOT_SUSPENDED;
}
Handle th(pending_thread->threadObj());
ret.waiters[i] = (jthread)jni_reference(calling_thread, th);
}
}
if (nWait > 0) {
// we have threads in Object.wait()
int offset = nWant; // add after any contending threads
ObjectWaiter *waiter = mon->first_waiter();
for (int i = 0, j = 0; i < nWait; i++) {
if (waiter == NULL) {
// robustness: the waiting list has gotten smaller
nWait = j;
break;
}
Thread *t = mon->thread_of_waiter(waiter);
if (t != NULL && t->is_Java_thread()) {
JavaThread *wjava_thread = (JavaThread *)t;
// If the thread was found on the ObjectWaiter list, then
// it has not been notified. This thread can't change the
// state of the monitor so it doesn't need to be suspended.
Handle th(wjava_thread->threadObj());
ret.waiters[offset + j] = (jthread)jni_reference(calling_thread, th);
ret.notify_waiters[j++] = (jthread)jni_reference(calling_thread, th);
}
waiter = mon->next_waiter(waiter);
}
}
}
// Adjust count. nWant and nWait count values may be less than original.
ret.waiter_count = nWant + nWait;
ret.notify_waiter_count = nWait;
} else {
// this object has a lightweight monitor and we have nothing more
// to do here because the defaults are just fine.
}
// we don't update return parameter unless everything worked
*info_ptr = ret;
return JVMTI_ERROR_NONE;
}
// Save JNI local handles for any objects that this frame owns.
jvmtiError
JvmtiEnvBase::get_locked_objects_in_frame(JavaThread* calling_thread, JavaThread* java_thread,
javaVFrame *jvf, GrowableArray<jvmtiMonitorStackDepthInfo*>* owned_monitors_list, int stack_depth) {
jvmtiError err = JVMTI_ERROR_NONE;
ResourceMark rm;
GrowableArray<MonitorInfo*>* mons = jvf->monitors();
if (mons->is_empty()) {
return err; // this javaVFrame holds no monitors
}
HandleMark hm;
oop wait_obj = NULL;
{
// save object of current wait() call (if any) for later comparison
ObjectMonitor *mon = java_thread->current_waiting_monitor();
if (mon != NULL) {
wait_obj = (oop)mon->object();
}
}
oop pending_obj = NULL;
{
// save object of current enter() call (if any) for later comparison
ObjectMonitor *mon = java_thread->current_pending_monitor();
if (mon != NULL) {
pending_obj = (oop)mon->object();
}
}
for (int i = 0; i < mons->length(); i++) {
MonitorInfo *mi = mons->at(i);
if (mi->owner_is_scalar_replaced()) continue;
oop obj = mi->owner();
if (obj == NULL) {
// this monitor doesn't have an owning object so skip it
continue;
}
if (wait_obj == obj) {
// the thread is waiting on this monitor so it isn't really owned
continue;
}
if (pending_obj == obj) {
// the thread is pending on this monitor so it isn't really owned
continue;
}
if (owned_monitors_list->length() > 0) {
// Our list has at least one object on it so we have to check
// for recursive object locking
bool found = false;
for (int j = 0; j < owned_monitors_list->length(); j++) {
jobject jobj = ((jvmtiMonitorStackDepthInfo*)owned_monitors_list->at(j))->monitor;
oop check = JNIHandles::resolve(jobj);
if (check == obj) {
found = true; // we found the object
break;
}
}
if (found) {
// already have this object so don't include it
continue;
}
}
// add the owning object to our list
jvmtiMonitorStackDepthInfo *jmsdi;
err = allocate(sizeof(jvmtiMonitorStackDepthInfo), (unsigned char **)&jmsdi);
if (err != JVMTI_ERROR_NONE) {
return err;
}
Handle hobj(obj);
jmsdi->monitor = jni_reference(calling_thread, hobj);
jmsdi->stack_depth = stack_depth;
owned_monitors_list->append(jmsdi);
}
return err;
}
jclass
JvmtiEnvBase::get_jni_class_non_null(Klass* k) {
assert(k != NULL, "k != NULL");
return (jclass)jni_reference(k->java_mirror());
}
jclass
JvmtiEnvBase::get_jni_class_non_null(klassOop k) {
assert(k != NULL, "k != NULL");
return (jclass)jni_reference(Klass::cast(k)->java_mirror());
}
