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0
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1 /*
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2 * Copyright 1998-2007 Sun Microsystems, Inc. All Rights Reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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20 * CA 95054 USA or visit www.sun.com if you need additional information or
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21 * have any questions.
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22 *
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23 */
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24
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_jniHandles.cpp.incl"
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27
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28
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29 JNIHandleBlock* JNIHandles::_global_handles = NULL;
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30 JNIHandleBlock* JNIHandles::_weak_global_handles = NULL;
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31 oop JNIHandles::_deleted_handle = NULL;
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32
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33
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34 jobject JNIHandles::make_local(oop obj) {
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35 if (obj == NULL) {
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36 return NULL; // ignore null handles
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37 } else {
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38 Thread* thread = Thread::current();
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39 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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40 return thread->active_handles()->allocate_handle(obj);
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41 }
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42 }
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43
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44
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45 // optimized versions
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46
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47 jobject JNIHandles::make_local(Thread* thread, oop obj) {
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48 if (obj == NULL) {
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49 return NULL; // ignore null handles
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50 } else {
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51 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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52 return thread->active_handles()->allocate_handle(obj);
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53 }
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54 }
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55
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56
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57 jobject JNIHandles::make_local(JNIEnv* env, oop obj) {
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58 if (obj == NULL) {
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59 return NULL; // ignore null handles
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60 } else {
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61 JavaThread* thread = JavaThread::thread_from_jni_environment(env);
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62 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
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63 return thread->active_handles()->allocate_handle(obj);
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64 }
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65 }
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66
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67
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68 jobject JNIHandles::make_global(Handle obj) {
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69 jobject res = NULL;
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70 if (!obj.is_null()) {
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71 // ignore null handles
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72 MutexLocker ml(JNIGlobalHandle_lock);
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73 assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
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74 res = _global_handles->allocate_handle(obj());
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75 } else {
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76 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
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77 }
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78
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79 return res;
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80 }
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81
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82
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83 jobject JNIHandles::make_weak_global(Handle obj) {
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84 jobject res = NULL;
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85 if (!obj.is_null()) {
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86 // ignore null handles
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87 MutexLocker ml(JNIGlobalHandle_lock);
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88 assert(Universe::heap()->is_in_reserved(obj()), "sanity check");
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89 res = _weak_global_handles->allocate_handle(obj());
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90 } else {
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91 CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
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92 }
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93 return res;
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94 }
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95
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96 jmethodID JNIHandles::make_jmethod_id(methodHandle mh) {
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97 return (jmethodID) make_weak_global(mh);
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98 }
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99
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100
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101
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102 void JNIHandles::change_method_associated_with_jmethod_id(jmethodID jmid, methodHandle mh) {
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103 MutexLocker ml(JNIGlobalHandle_lock); // Is this necessary?
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104 Handle obj = (Handle)mh;
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105 oop* jobj = (oop*)jmid;
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106 *jobj = obj();
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107 }
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108
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109
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110 void JNIHandles::destroy_global(jobject handle) {
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111 if (handle != NULL) {
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112 assert(is_global_handle(handle), "Invalid delete of global JNI handle");
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113 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
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114 }
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115 }
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116
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117
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118 void JNIHandles::destroy_weak_global(jobject handle) {
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119 if (handle != NULL) {
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120 assert(!CheckJNICalls || is_weak_global_handle(handle), "Invalid delete of weak global JNI handle");
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121 *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
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122 }
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123 }
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124
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125 void JNIHandles::destroy_jmethod_id(jmethodID mid) {
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126 destroy_weak_global((jobject)mid);
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127 }
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128
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129
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130 void JNIHandles::oops_do(OopClosure* f) {
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131 f->do_oop(&_deleted_handle);
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132 _global_handles->oops_do(f);
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133 }
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134
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135
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136 void JNIHandles::weak_oops_do(BoolObjectClosure* is_alive, OopClosure* f) {
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137 _weak_global_handles->weak_oops_do(is_alive, f);
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138 }
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139
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140
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141 void JNIHandles::initialize() {
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142 _global_handles = JNIHandleBlock::allocate_block();
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143 _weak_global_handles = JNIHandleBlock::allocate_block();
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144 EXCEPTION_MARK;
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145 // We will never reach the CATCH below since Exceptions::_throw will cause
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146 // the VM to exit if an exception is thrown during initialization
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147 klassOop k = SystemDictionary::object_klass();
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148 _deleted_handle = instanceKlass::cast(k)->allocate_permanent_instance(CATCH);
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149 }
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150
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151
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152 bool JNIHandles::is_local_handle(Thread* thread, jobject handle) {
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153 JNIHandleBlock* block = thread->active_handles();
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154
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155 // Look back past possible native calls to jni_PushLocalFrame.
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156 while (block != NULL) {
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157 if (block->chain_contains(handle)) {
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158 return true;
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159 }
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160 block = block->pop_frame_link();
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161 }
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162 return false;
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163 }
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164
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165
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166 // Determine if the handle is somewhere in the current thread's stack.
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167 // We easily can't isolate any particular stack frame the handle might
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168 // come from, so we'll check the whole stack.
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169
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170 bool JNIHandles::is_frame_handle(JavaThread* thr, jobject obj) {
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171 // If there is no java frame, then this must be top level code, such
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172 // as the java command executable, in which case, this type of handle
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173 // is not permitted.
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174 return (thr->has_last_Java_frame() &&
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175 (void*)obj < (void*)thr->stack_base() &&
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176 (void*)obj >= (void*)thr->last_Java_sp());
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177 }
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178
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179
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180 bool JNIHandles::is_global_handle(jobject handle) {
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181 return _global_handles->chain_contains(handle);
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182 }
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183
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184
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185 bool JNIHandles::is_weak_global_handle(jobject handle) {
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186 return _weak_global_handles->chain_contains(handle);
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187 }
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188
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189 long JNIHandles::global_handle_memory_usage() {
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190 return _global_handles->memory_usage();
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191 }
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192
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193 long JNIHandles::weak_global_handle_memory_usage() {
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194 return _weak_global_handles->memory_usage();
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195 }
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196
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197
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198 class AlwaysAliveClosure: public BoolObjectClosure {
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199 public:
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200 bool do_object_b(oop obj) { return true; }
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201 void do_object(oop obj) { assert(false, "Don't call"); }
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202 };
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203
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204 class CountHandleClosure: public OopClosure {
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205 private:
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206 int _count;
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207 public:
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208 CountHandleClosure(): _count(0) {}
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209 void do_oop(oop* unused) {
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210 _count++;
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211 }
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212 int count() { return _count; }
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213 };
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214
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215 // We assume this is called at a safepoint: no lock is needed.
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216 void JNIHandles::print_on(outputStream* st) {
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217 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
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218 assert(_global_handles != NULL && _weak_global_handles != NULL,
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219 "JNIHandles not initialized");
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220
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221 CountHandleClosure global_handle_count;
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222 AlwaysAliveClosure always_alive;
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223 oops_do(&global_handle_count);
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224 weak_oops_do(&always_alive, &global_handle_count);
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225
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226 st->print_cr("JNI global references: %d", global_handle_count.count());
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227 st->cr();
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228 st->flush();
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229 }
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230
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231 class VerifyHandleClosure: public OopClosure {
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232 public:
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233 void do_oop(oop* root) {
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234 (*root)->verify();
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235 }
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236 };
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237
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238 void JNIHandles::verify() {
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239 VerifyHandleClosure verify_handle;
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240 AlwaysAliveClosure always_alive;
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241
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242 oops_do(&verify_handle);
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243 weak_oops_do(&always_alive, &verify_handle);
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244 }
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245
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246
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247
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248 void jni_handles_init() {
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249 JNIHandles::initialize();
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250 }
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251
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252
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253 int JNIHandleBlock::_blocks_allocated = 0;
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254 JNIHandleBlock* JNIHandleBlock::_block_free_list = NULL;
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255 #ifndef PRODUCT
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256 JNIHandleBlock* JNIHandleBlock::_block_list = NULL;
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257 #endif
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258
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259
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260 void JNIHandleBlock::zap() {
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261 // Zap block values
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262 _top = 0;
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263 for (int index = 0; index < block_size_in_oops; index++) {
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264 _handles[index] = badJNIHandle;
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265 }
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266 }
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267
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268 JNIHandleBlock* JNIHandleBlock::allocate_block(Thread* thread) {
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269 assert(thread == NULL || thread == Thread::current(), "sanity check");
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270 JNIHandleBlock* block;
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271 // Check the thread-local free list for a block so we don't
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272 // have to acquire a mutex.
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273 if (thread != NULL && thread->free_handle_block() != NULL) {
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274 block = thread->free_handle_block();
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275 thread->set_free_handle_block(block->_next);
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276 }
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277 else {
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278 // locking with safepoint checking introduces a potential deadlock:
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279 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
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280 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
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281 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
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282 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
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283 Mutex::_no_safepoint_check_flag);
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284 if (_block_free_list == NULL) {
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285 // Allocate new block
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286 block = new JNIHandleBlock();
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287 _blocks_allocated++;
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288 if (TraceJNIHandleAllocation) {
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289 tty->print_cr("JNIHandleBlock " INTPTR_FORMAT " allocated (%d total blocks)",
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290 block, _blocks_allocated);
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291 }
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292 if (ZapJNIHandleArea) block->zap();
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293 #ifndef PRODUCT
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294 // Link new block to list of all allocated blocks
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295 block->_block_list_link = _block_list;
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296 _block_list = block;
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297 #endif
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298 } else {
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299 // Get block from free list
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300 block = _block_free_list;
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301 _block_free_list = _block_free_list->_next;
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302 }
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303 }
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304 block->_top = 0;
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305 block->_next = NULL;
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306 block->_pop_frame_link = NULL;
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307 // _last, _free_list & _allocate_before_rebuild initialized in allocate_handle
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308 debug_only(block->_last = NULL);
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309 debug_only(block->_free_list = NULL);
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310 debug_only(block->_allocate_before_rebuild = -1);
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311 return block;
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312 }
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313
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314
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315 void JNIHandleBlock::release_block(JNIHandleBlock* block, Thread* thread) {
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316 assert(thread == NULL || thread == Thread::current(), "sanity check");
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317 JNIHandleBlock* pop_frame_link = block->pop_frame_link();
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318 // Put returned block at the beginning of the thread-local free list.
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319 // Note that if thread == NULL, we use it as an implicit argument that
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320 // we _don't_ want the block to be kept on the free_handle_block.
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321 // See for instance JavaThread::exit().
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322 if (thread != NULL ) {
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323 if (ZapJNIHandleArea) block->zap();
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324 JNIHandleBlock* freelist = thread->free_handle_block();
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325 block->_pop_frame_link = NULL;
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326 thread->set_free_handle_block(block);
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327
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328 // Add original freelist to end of chain
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329 if ( freelist != NULL ) {
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330 while ( block->_next != NULL ) block = block->_next;
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331 block->_next = freelist;
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332 }
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333 block = NULL;
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334 }
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335 if (block != NULL) {
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336 // Return blocks to free list
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337 // locking with safepoint checking introduces a potential deadlock:
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338 // - we would hold JNIHandleBlockFreeList_lock and then Threads_lock
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339 // - another would hold Threads_lock (jni_AttachCurrentThread) and then
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340 // JNIHandleBlockFreeList_lock (JNIHandleBlock::allocate_block)
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341 MutexLockerEx ml(JNIHandleBlockFreeList_lock,
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342 Mutex::_no_safepoint_check_flag);
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343 while (block != NULL) {
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344 if (ZapJNIHandleArea) block->zap();
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345 JNIHandleBlock* next = block->_next;
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346 block->_next = _block_free_list;
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347 _block_free_list = block;
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348 block = next;
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349 }
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350 }
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351 if (pop_frame_link != NULL) {
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352 // As a sanity check we release blocks pointed to by the pop_frame_link.
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353 // This should never happen (only if PopLocalFrame is not called the
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354 // correct number of times).
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355 release_block(pop_frame_link, thread);
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356 }
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357 }
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358
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359
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360 void JNIHandleBlock::oops_do(OopClosure* f) {
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361 JNIHandleBlock* current_chain = this;
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362 // Iterate over chain of blocks, followed by chains linked through the
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363 // pop frame links.
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364 while (current_chain != NULL) {
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365 for (JNIHandleBlock* current = current_chain; current != NULL;
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366 current = current->_next) {
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367 assert(current == current_chain || current->pop_frame_link() == NULL,
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368 "only blocks first in chain should have pop frame link set");
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369 for (int index = 0; index < current->_top; index++) {
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370 oop* root = &(current->_handles)[index];
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371 oop value = *root;
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372 // traverse heap pointers only, not deleted handles or free list
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373 // pointers
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374 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
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375 f->do_oop(root);
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376 }
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377 }
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378 // the next handle block is valid only if current block is full
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379 if (current->_top < block_size_in_oops) {
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380 break;
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381 }
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382 }
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383 current_chain = current_chain->pop_frame_link();
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384 }
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385 }
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386
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387
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388 void JNIHandleBlock::weak_oops_do(BoolObjectClosure* is_alive,
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389 OopClosure* f) {
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390 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
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391 assert(current->pop_frame_link() == NULL,
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392 "blocks holding weak global JNI handles should not have pop frame link set");
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393 for (int index = 0; index < current->_top; index++) {
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394 oop* root = &(current->_handles)[index];
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395 oop value = *root;
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396 // traverse heap pointers only, not deleted handles or free list pointers
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397 if (value != NULL && Universe::heap()->is_in_reserved(value)) {
|
|
|
398 if (is_alive->do_object_b(value)) {
|
|
|
399 // The weakly referenced object is alive, update pointer
|
|
|
400 f->do_oop(root);
|
|
|
401 } else {
|
|
|
402 // The weakly referenced object is not alive, clear the reference by storing NULL
|
|
|
403 if (TraceReferenceGC) {
|
|
|
404 tty->print_cr("Clearing JNI weak reference (" INTPTR_FORMAT ")", root);
|
|
|
405 }
|
|
|
406 *root = NULL;
|
|
|
407 }
|
|
|
408 }
|
|
|
409 }
|
|
|
410 // the next handle block is valid only if current block is full
|
|
|
411 if (current->_top < block_size_in_oops) {
|
|
|
412 break;
|
|
|
413 }
|
|
|
414 }
|
|
|
415 }
|
|
|
416
|
|
|
417
|
|
|
418 jobject JNIHandleBlock::allocate_handle(oop obj) {
|
|
|
419 assert(Universe::heap()->is_in_reserved(obj), "sanity check");
|
|
|
420 if (_top == 0) {
|
|
|
421 // This is the first allocation or the initial block got zapped when
|
|
|
422 // entering a native function. If we have any following blocks they are
|
|
|
423 // not valid anymore.
|
|
|
424 for (JNIHandleBlock* current = _next; current != NULL;
|
|
|
425 current = current->_next) {
|
|
|
426 assert(current->_last == NULL, "only first block should have _last set");
|
|
|
427 assert(current->_free_list == NULL,
|
|
|
428 "only first block should have _free_list set");
|
|
|
429 current->_top = 0;
|
|
|
430 if (ZapJNIHandleArea) current->zap();
|
|
|
431 }
|
|
|
432 // Clear initial block
|
|
|
433 _free_list = NULL;
|
|
|
434 _allocate_before_rebuild = 0;
|
|
|
435 _last = this;
|
|
|
436 if (ZapJNIHandleArea) zap();
|
|
|
437 }
|
|
|
438
|
|
|
439 // Try last block
|
|
|
440 if (_last->_top < block_size_in_oops) {
|
|
|
441 oop* handle = &(_last->_handles)[_last->_top++];
|
|
|
442 *handle = obj;
|
|
|
443 return (jobject) handle;
|
|
|
444 }
|
|
|
445
|
|
|
446 // Try free list
|
|
|
447 if (_free_list != NULL) {
|
|
|
448 oop* handle = _free_list;
|
|
|
449 _free_list = (oop*) *_free_list;
|
|
|
450 *handle = obj;
|
|
|
451 return (jobject) handle;
|
|
|
452 }
|
|
|
453 // Check if unused block follow last
|
|
|
454 if (_last->_next != NULL) {
|
|
|
455 // update last and retry
|
|
|
456 _last = _last->_next;
|
|
|
457 return allocate_handle(obj);
|
|
|
458 }
|
|
|
459
|
|
|
460 // No space available, we have to rebuild free list or expand
|
|
|
461 if (_allocate_before_rebuild == 0) {
|
|
|
462 rebuild_free_list(); // updates _allocate_before_rebuild counter
|
|
|
463 } else {
|
|
|
464 // Append new block
|
|
|
465 Thread* thread = Thread::current();
|
|
|
466 Handle obj_handle(thread, obj);
|
|
|
467 // This can block, so we need to preserve obj accross call.
|
|
|
468 _last->_next = JNIHandleBlock::allocate_block(thread);
|
|
|
469 _last = _last->_next;
|
|
|
470 _allocate_before_rebuild--;
|
|
|
471 obj = obj_handle();
|
|
|
472 }
|
|
|
473 return allocate_handle(obj); // retry
|
|
|
474 }
|
|
|
475
|
|
|
476
|
|
|
477 void JNIHandleBlock::rebuild_free_list() {
|
|
|
478 assert(_allocate_before_rebuild == 0 && _free_list == NULL, "just checking");
|
|
|
479 int free = 0;
|
|
|
480 int blocks = 0;
|
|
|
481 for (JNIHandleBlock* current = this; current != NULL; current = current->_next) {
|
|
|
482 for (int index = 0; index < current->_top; index++) {
|
|
|
483 oop* handle = &(current->_handles)[index];
|
|
|
484 if (*handle == JNIHandles::deleted_handle()) {
|
|
|
485 // this handle was cleared out by a delete call, reuse it
|
|
|
486 *handle = (oop) _free_list;
|
|
|
487 _free_list = handle;
|
|
|
488 free++;
|
|
|
489 }
|
|
|
490 }
|
|
|
491 // we should not rebuild free list if there are unused handles at the end
|
|
|
492 assert(current->_top == block_size_in_oops, "just checking");
|
|
|
493 blocks++;
|
|
|
494 }
|
|
|
495 // Heuristic: if more than half of the handles are free we rebuild next time
|
|
|
496 // as well, otherwise we append a corresponding number of new blocks before
|
|
|
497 // attempting a free list rebuild again.
|
|
|
498 int total = blocks * block_size_in_oops;
|
|
|
499 int extra = total - 2*free;
|
|
|
500 if (extra > 0) {
|
|
|
501 // Not as many free handles as we would like - compute number of new blocks to append
|
|
|
502 _allocate_before_rebuild = (extra + block_size_in_oops - 1) / block_size_in_oops;
|
|
|
503 }
|
|
|
504 if (TraceJNIHandleAllocation) {
|
|
|
505 tty->print_cr("Rebuild free list JNIHandleBlock " INTPTR_FORMAT " blocks=%d used=%d free=%d add=%d",
|
|
|
506 this, blocks, total-free, free, _allocate_before_rebuild);
|
|
|
507 }
|
|
|
508 }
|
|
|
509
|
|
|
510
|
|
|
511 bool JNIHandleBlock::contains(jobject handle) const {
|
|
|
512 return ((jobject)&_handles[0] <= handle && handle<(jobject)&_handles[_top]);
|
|
|
513 }
|
|
|
514
|
|
|
515
|
|
|
516 bool JNIHandleBlock::chain_contains(jobject handle) const {
|
|
|
517 for (JNIHandleBlock* current = (JNIHandleBlock*) this; current != NULL; current = current->_next) {
|
|
|
518 if (current->contains(handle)) {
|
|
|
519 return true;
|
|
|
520 }
|
|
|
521 }
|
|
|
522 return false;
|
|
|
523 }
|
|
|
524
|
|
|
525
|
|
|
526 int JNIHandleBlock::length() const {
|
|
|
527 int result = 1;
|
|
|
528 for (JNIHandleBlock* current = _next; current != NULL; current = current->_next) {
|
|
|
529 result++;
|
|
|
530 }
|
|
|
531 return result;
|
|
|
532 }
|
|
|
533
|
|
|
534 // This method is not thread-safe, i.e., must be called whule holding a lock on the
|
|
|
535 // structure.
|
|
|
536 long JNIHandleBlock::memory_usage() const {
|
|
|
537 return length() * sizeof(JNIHandleBlock);
|
|
|
538 }
|
|
|
539
|
|
|
540
|
|
|
541 #ifndef PRODUCT
|
|
|
542
|
|
|
543 bool JNIHandleBlock::any_contains(jobject handle) {
|
|
|
544 for (JNIHandleBlock* current = _block_list; current != NULL; current = current->_block_list_link) {
|
|
|
545 if (current->contains(handle)) {
|
|
|
546 return true;
|
|
|
547 }
|
|
|
548 }
|
|
|
549 return false;
|
|
|
550 }
|
|
|
551
|
|
|
552 void JNIHandleBlock::print_statistics() {
|
|
|
553 int used_blocks = 0;
|
|
|
554 int free_blocks = 0;
|
|
|
555 int used_handles = 0;
|
|
|
556 int free_handles = 0;
|
|
|
557 JNIHandleBlock* block = _block_list;
|
|
|
558 while (block != NULL) {
|
|
|
559 if (block->_top > 0) {
|
|
|
560 used_blocks++;
|
|
|
561 } else {
|
|
|
562 free_blocks++;
|
|
|
563 }
|
|
|
564 used_handles += block->_top;
|
|
|
565 free_handles += (block_size_in_oops - block->_top);
|
|
|
566 block = block->_block_list_link;
|
|
|
567 }
|
|
|
568 tty->print_cr("JNIHandleBlocks statistics");
|
|
|
569 tty->print_cr("- blocks allocated: %d", used_blocks + free_blocks);
|
|
|
570 tty->print_cr("- blocks in use: %d", used_blocks);
|
|
|
571 tty->print_cr("- blocks free: %d", free_blocks);
|
|
|
572 tty->print_cr("- handles in use: %d", used_handles);
|
|
|
573 tty->print_cr("- handles free: %d", free_handles);
|
|
|
574 }
|
|
|
575
|
|
|
576 #endif
|
