bool Dictionary::do_unloading() {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
bool class_was_unloaded = false;
int index = 0; // Defined here for portability! Do not move
// Remove unloadable entries and classes from system dictionary
// The placeholder array has been handled in always_strong_oops_do.
DictionaryEntry* probe = NULL;
for (index = 0; index < table_size(); index++) {
for (DictionaryEntry** p = bucket_addr(index); *p != NULL; ) {
probe = *p;
Klass* e = probe->klass();
ClassLoaderData* loader_data = probe->loader_data();
InstanceKlass* ik = InstanceKlass::cast(e);
// Non-unloadable classes were handled in always_strong_oops_do
if (!is_strongly_reachable(loader_data, e)) {
// Entry was not visited in phase1 (negated test from phase1)
assert(!loader_data->is_the_null_class_loader_data(), "unloading entry with null class loader");
ClassLoaderData* k_def_class_loader_data = ik->class_loader_data();
// Do we need to delete this system dictionary entry?
bool purge_entry = false;
// Do we need to delete this system dictionary entry?
if (loader_data->is_unloading()) {
// If the loader is not live this entry should always be
// removed (will never be looked up again). Note that this is
// not the same as unloading the referred class.
if (k_def_class_loader_data == loader_data) {
// This is the defining entry, so the referred class is about
// to be unloaded.
class_was_unloaded = true;
}
// Also remove this system dictionary entry.
purge_entry = true;
} else {
// The loader in this entry is alive. If the klass is dead,
// (determined by checking the defining class loader)
// the loader must be an initiating loader (rather than the
// defining loader). Remove this entry.
if (k_def_class_loader_data->is_unloading()) {
// If we get here, the class_loader_data must not be the defining
// loader, it must be an initiating one.
assert(k_def_class_loader_data != loader_data,
"cannot have live defining loader and unreachable klass");
// Loader is live, but class and its defining loader are dead.
// Remove the entry. The class is going away.
purge_entry = true;
}
}
if (purge_entry) {
*p = probe->next();
if (probe == _current_class_entry) {
_current_class_entry = NULL;
}
free_entry(probe);
continue;
}
}
p = probe->next_addr();
}
}
return class_was_unloaded;
}
