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8337548: Parallel class loading can pass is_superclass true for interfaces

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Reviewed-by: iklam
This commit is contained in:
Coleen Phillimore 2025-02-03 13:55:00 +00:00
parent 3f1d9b5735
commit d330421d28
2 changed files with 28 additions and 26 deletions
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52
src/hotspot/share/classfile/systemDictionary.cpp
View File

@ -424,36 +424,39 @@ InstanceKlass* SystemDictionary::resolve_with_circularity_detection(Symbol* clas
assert(next_name != nullptr, "null superclass for resolving");
assert(!Signature::is_array(next_name), "invalid superclass name");
// If class_name is already loaded, just return the superclass or superinterface.
// Make sure there's a placeholder for the class_name before resolving.
// This is used as a claim that this thread is currently loading superclass/classloader
// and for ClassCircularity checks.
ClassLoaderData* loader_data = class_loader_data(class_loader);
Dictionary* dictionary = loader_data->dictionary();
if (is_superclass) {
InstanceKlass* klassk = loader_data->dictionary()->find_class(THREAD, class_name);
if (klassk != nullptr) {
// We can come here for two reasons:
// (a) RedefineClasses -- the class is already loaded
// (b) Rarely, the class might have been loaded by a parallel thread
// We can do a quick check against the already assigned superclass's name and loader.
InstanceKlass* superk = klassk->java_super();
if (superk != nullptr &&
superk->name() == next_name &&
superk->class_loader() == class_loader()) {
return superk;
}
}
}
// can't throw error holding a lock
bool throw_circularity_error = false;
{
MutexLocker mu(THREAD, SystemDictionary_lock);
InstanceKlass* klassk = dictionary->find_class(THREAD, class_name);
InstanceKlass* quicksuperk;
// To support parallel loading: if class is done loading, just return the superclass
// if the next_name matches class->super()->name() and if the class loaders match.
if (klassk != nullptr && is_superclass &&
((quicksuperk = klassk->java_super()) != nullptr) &&
((quicksuperk->name() == next_name) &&
(quicksuperk->class_loader() == class_loader()))) {
return quicksuperk;
} else {
// Must check ClassCircularity before checking if superclass is already loaded.
PlaceholderEntry* probe = PlaceholderTable::get_entry(class_name, loader_data);
if (probe && probe->check_seen_thread(THREAD, PlaceholderTable::DETECT_CIRCULARITY)) {
log_circularity_error(class_name, probe);
throw_circularity_error = true;
}
// Must check ClassCircularity before resolving next_name (superclass or interface).
PlaceholderEntry* probe = PlaceholderTable::get_entry(class_name, loader_data);
if (probe != nullptr && probe->check_seen_thread(THREAD, PlaceholderTable::DETECT_CIRCULARITY)) {
log_circularity_error(class_name, probe);
throw_circularity_error = true;
}
// Make sure there's a placeholder for the class_name before resolving.
// This is used as a claim that this thread is currently loading superclass/classloader
// and for ClassCircularity checks.
if (!throw_circularity_error) {
// Be careful not to exit resolve_with_circularity_detection without removing this placeholder.
PlaceholderEntry* newprobe = PlaceholderTable::find_and_add(class_name,
@ -501,12 +504,11 @@ static void handle_parallel_super_load(Symbol* name,
TRAPS) {
// The result superk is not used; resolve_with_circularity_detection is called for circularity check only.
// This passes true to is_superclass even though it might not be the super class in order to perform the
// optimization anyway.
// This passes false to is_superclass to skip doing the unlikely optimization.
Klass* superk = SystemDictionary::resolve_with_circularity_detection(name,
superclassname,
class_loader,
true,
false,
CHECK);
}

2
src/hotspot/share/classfile/systemDictionary.hpp
View File

@ -1,5 +1,5 @@
/*
* Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 1997, 2025, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it