1 /*
  2  * Copyright (c) 2020, 2024, 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 
 25 #include "precompiled.hpp"
 26 #include "memory/allocation.hpp"
 27 #include "memory/universe.hpp"
 28 #include "oops/oop.inline.hpp"
 29 #include "oops/weakHandle.inline.hpp"
 30 #include "prims/jvmtiExport.hpp"
 31 #include "prims/jvmtiTagMapTable.hpp"
 32 
 33 
 34 JvmtiTagMapKey::JvmtiTagMapKey(oop obj) : _obj(obj) {}
 35 
 36 JvmtiTagMapKey::JvmtiTagMapKey(const JvmtiTagMapKey& src) {
 37   // move object into WeakHandle when copying into the table
 38   if (src._obj != nullptr) {
 39 
 40     // obj was read with AS_NO_KEEPALIVE, or equivalent, like during
 41     // a heap walk.  The object needs to be kept alive when it is published.
 42     Universe::heap()->keep_alive(src._obj);
 43 
 44     _wh = WeakHandle(JvmtiExport::weak_tag_storage(), src._obj);
 45   } else {
 46     // resizing needs to create a copy.
 47     _wh = src._wh;
 48   }
 49   // obj is always null after a copy.
 50   _obj = nullptr;
 51 }
 52 
 53 void JvmtiTagMapKey::release_weak_handle() {
 54   _wh.release(JvmtiExport::weak_tag_storage());
 55 }
 56 
 57 oop JvmtiTagMapKey::object() const {
 58   assert(_obj == nullptr, "Must have a handle and not object");
 59   return _wh.resolve();
 60 }
 61 
 62 oop JvmtiTagMapKey::object_no_keepalive() const {
 63   assert(_obj == nullptr, "Must have a handle and not object");
 64   return _wh.peek();
 65 }
 66 
 67 unsigned JvmtiTagMapKey::get_hash(const JvmtiTagMapKey& entry) {
 68   oop obj = entry._obj;
 69   assert(obj != nullptr, "must lookup obj to hash");
 70   if (obj->is_inline_type()) {
 71     // For inline types, use the klass as a hash code and let the equals match the obj.
 72     // It might have a long bucket but TBD to improve this if a customer situation arises.
 73     return (unsigned)((int64_t)obj->klass() >> 3);
 74   } else {
 75     return (unsigned)obj->identity_hash();
 76   }
 77 }
 78 
 79 // Inline types don't use hash for this table.
 80 static inline bool fast_no_hash_check(oop obj) {
 81   return (obj->fast_no_hash_check() && !obj->is_inline_type());
 82 }
 83 
 84 static const int INITIAL_TABLE_SIZE = 1007;
 85 static const int MAX_TABLE_SIZE     = 0x3fffffff;
 86 
 87 JvmtiTagMapTable::JvmtiTagMapTable() : _table(INITIAL_TABLE_SIZE, MAX_TABLE_SIZE) {}
 88 
 89 void JvmtiTagMapTable::clear() {
 90   struct RemoveAll {
 91     bool do_entry(JvmtiTagMapKey& entry, const jlong& tag) {
 92       entry.release_weak_handle();
 93       return true;
 94     }
 95   } remove_all;
 96   // The unlink method of ResourceHashTable gets a pointer to a type whose 'do_entry(K,V)' method is callled
 97   // while iterating over all the elements of the table. If the do_entry() method returns true the element
 98   // will be removed.
 99   // In this case, we always return true from do_entry to clear all the elements.
100   _table.unlink(&remove_all);
101 
102   assert(_table.number_of_entries() == 0, "should have removed all entries");
103 }
104 
105 JvmtiTagMapTable::~JvmtiTagMapTable() {
106   clear();
107 }
108 
109 jlong JvmtiTagMapTable::find(oop obj) {
110   if (is_empty()) {
111     return 0;
112   }
113 
114   if (fast_no_hash_check(obj)) {
115     // Objects in the table all have a hashcode, unless inlined types.
116     return 0;
117   }
118 
119   JvmtiTagMapKey jtme(obj);
120   jlong* found = _table.get(jtme);
121   return found == nullptr ? 0 : *found;
122 }
123 
124 void JvmtiTagMapTable::add(oop obj, jlong tag) {
125   JvmtiTagMapKey new_entry(obj);
126   bool is_added;
127   if (fast_no_hash_check(obj)) {
128     // Can't be in the table so add it fast.
129     is_added = _table.put_when_absent(new_entry, tag);
130   } else {
131     jlong* value = _table.put_if_absent(new_entry, tag, &is_added);
132     *value = tag; // assign the new tag
133   }
134   if (is_added) {
135     if (_table.maybe_grow(5, true /* use_large_table_sizes */)) {
136       int max_bucket_size = DEBUG_ONLY(_table.verify()) NOT_DEBUG(0);
137       log_info(jvmti, table) ("JvmtiTagMap table resized to %d for %d entries max bucket %d",
138                               _table.table_size(), _table.number_of_entries(), max_bucket_size);
139     }
140   }
141 }
142 
143 void JvmtiTagMapTable::remove(oop obj) {
144   JvmtiTagMapKey jtme(obj);
145   auto clean = [] (JvmtiTagMapKey& entry, jlong tag) {
146     entry.release_weak_handle();
147   };
148   _table.remove(jtme, clean);
149 }
150 
151 void JvmtiTagMapTable::entry_iterate(JvmtiTagMapKeyClosure* closure) {
152   _table.iterate(closure);
153 }
154 
155 void JvmtiTagMapTable::remove_dead_entries(GrowableArray<jlong>* objects) {
156   struct IsDead {
157     GrowableArray<jlong>* _objects;
158     IsDead(GrowableArray<jlong>* objects) : _objects(objects) {}
159     bool do_entry(JvmtiTagMapKey& entry, jlong tag) {
160       if (entry.object_no_keepalive() == nullptr) {
161         if (_objects != nullptr) {
162           _objects->append(tag);
163         }
164         entry.release_weak_handle();
165         return true;
166       }
167       return false;;
168     }
169   } is_dead(objects);
170   _table.unlink(&is_dead);
171 }