1 /*
2 * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 #include "precompiled.hpp"
25 #include "classfile/classLoaderData.hpp"
26 #include "classfile/placeholders.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "oops/symbol.hpp"
29 #include "runtime/interfaceSupport.inline.hpp"
30 #include "runtime/mutexLocker.hpp"
31 #include "threadHelper.inline.hpp"
32 #include "unittest.hpp"
33
34 // Test that multiple threads calling handle_parallel_super_load don't underflow supername refcount.
35 TEST_VM(PlaceholderTable, supername) {
36 JavaThread* THREAD = JavaThread::current();
37 JavaThread* T2 = THREAD;
38 // the thread should be in vm to use locks
39 ThreadInVMfromNative tivfn(THREAD);
40
41 // Assert messages assume these symbols are unique, and the refcounts start at one.
42 Symbol* A = SymbolTable::new_symbol("abc2_8_2023_class");
43 Symbol* D = SymbolTable::new_symbol("def2_8_2023_class");
44 Symbol* super = SymbolTable::new_symbol("super2_8_2023_supername");
45 Symbol* interf = SymbolTable::new_symbol("interface2_8_2023_supername");
46
47 ClassLoaderData* loader_data = ClassLoaderData::the_null_class_loader_data();
48
49 {
50 MutexLocker ml(THREAD, SystemDictionary_lock);
51
52 PlaceholderTable::classloadAction super_action = PlaceholderTable::LOAD_SUPER;
53 PlaceholderTable::classloadAction define_action = PlaceholderTable::DEFINE_CLASS;
54
55 // DefineClass A and D
56 PlaceholderTable::find_and_add(A, loader_data, define_action, nullptr, THREAD);
57 PlaceholderTable::find_and_add(D, loader_data, define_action, nullptr, T2);
58
59 // Load interfaces first to get supername replaced
60 PlaceholderTable::find_and_add(A, loader_data, super_action, interf, THREAD);
61 PlaceholderTable::find_and_remove(A, loader_data, super_action, THREAD);
62
63 PlaceholderTable::find_and_add(D, loader_data, super_action, interf, T2);
64 PlaceholderTable::find_and_remove(D, loader_data, super_action, T2);
65
66 ASSERT_EQ(interf->refcount(), 1) << "supername is replaced with null";
67
68 // Add placeholder to the table for loading A and super, and D also loading super
69 PlaceholderTable::find_and_add(A, loader_data, super_action, super, THREAD);
70 PlaceholderTable::find_and_add(D, loader_data, super_action, super, T2);
71
72 // Another thread comes in and finds A loading Super
73 PlaceholderEntry* placeholder = PlaceholderTable::get_entry(A, loader_data);
74 SymbolHandle supername = placeholder->supername();
75
76 // Other thread is done before handle_parallel_super_load
77 PlaceholderTable::find_and_remove(A, loader_data, super_action, THREAD);
78
79 // if THREAD drops reference to supername (loading failed or class unloaded), we're left with
80 // a supername without refcount
81 super->decrement_refcount();
82
83 // handle_parallel_super_load (same thread doesn't assert)
84 PlaceholderTable::find_and_add(A, loader_data, super_action, supername, T2);
85
86 // Refcount should be 3: one in table for class A, one in table for class D
87 // and one locally with SymbolHandle keeping it alive
88 placeholder = PlaceholderTable::get_entry(A, loader_data);
89 supername = placeholder->supername();
90 EXPECT_EQ(super->refcount(), 3) << "super class name refcount should be 3";
91
92 // Second thread's done too
93 PlaceholderTable::find_and_remove(D, loader_data, super_action, T2);
94
95 // Other threads are done.
96 PlaceholderTable::find_and_remove(A, loader_data, super_action, THREAD);
97
98 // Remove A and D define_class placeholder
99 PlaceholderTable::find_and_remove(A, loader_data, define_action, THREAD);
100 PlaceholderTable::find_and_remove(D, loader_data, define_action, T2);
101
102 placeholder = PlaceholderTable::get_entry(A, loader_data);
103 ASSERT_TRUE(placeholder == nullptr) << "placeholder should be removed";
104 placeholder = PlaceholderTable::get_entry(D, loader_data);
105 ASSERT_TRUE(placeholder == nullptr) << "placeholder should be removed";
106
107 EXPECT_EQ(super->refcount(), 1) << "super class name refcount should be 1 - kept alive in this scope";
108 }
109
110 EXPECT_EQ(A->refcount(), 1) << "first lass name refcount should be 1";
111 EXPECT_EQ(D->refcount(), 1) << "second class name refcount should be 1";
112 EXPECT_EQ(super->refcount(), 0) << "super class name refcount should be 0 - was unloaded.";
113
114 // clean up temporary symbols
115 A->decrement_refcount();
116 D->decrement_refcount();
117 interf->decrement_refcount();
118 }