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1 /*
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2 * Copyright 1997-2007 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/_gcLocker.cpp.incl"
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27
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28 volatile jint GC_locker::_jni_lock_count = 0;
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29 volatile jint GC_locker::_lock_count = 0;
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30 volatile bool GC_locker::_needs_gc = false;
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31 volatile bool GC_locker::_doing_gc = false;
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32
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33 void GC_locker::stall_until_clear() {
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34 assert(!JavaThread::current()->in_critical(), "Would deadlock");
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35 MutexLocker ml(JNICritical_lock);
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36 // Wait for _needs_gc to be cleared
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37 while (GC_locker::needs_gc()) {
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38 JNICritical_lock->wait();
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39 }
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40 }
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41
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42 void GC_locker::jni_lock_slow() {
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43 MutexLocker mu(JNICritical_lock);
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44 // Block entering threads if we know at least one thread is in a
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45 // JNI critical region and we need a GC.
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46 // We check that at least one thread is in a critical region before
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47 // blocking because blocked threads are woken up by a thread exiting
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48 // a JNI critical region.
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49 while ((is_jni_active() && needs_gc()) || _doing_gc) {
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50 JNICritical_lock->wait();
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51 }
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52 jni_lock();
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53 }
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54
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55 void GC_locker::jni_unlock_slow() {
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56 MutexLocker mu(JNICritical_lock);
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57 jni_unlock();
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58 if (needs_gc() && !is_jni_active()) {
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59 // We're the last thread out. Cause a GC to occur.
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60 // GC will also check is_active, so this check is not
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61 // strictly needed. It's added here to make it clear that
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62 // the GC will NOT be performed if any other caller
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63 // of GC_locker::lock() still needs GC locked.
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64 if (!is_active()) {
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65 _doing_gc = true;
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66 {
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67 // Must give up the lock while at a safepoint
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68 MutexUnlocker munlock(JNICritical_lock);
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69 Universe::heap()->collect(GCCause::_gc_locker);
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70 }
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71 _doing_gc = false;
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72 }
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73 clear_needs_gc();
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74 JNICritical_lock->notify_all();
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75 }
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76 }
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77
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78 // Implementation of No_GC_Verifier
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79
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80 #ifdef ASSERT
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81
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82 No_GC_Verifier::No_GC_Verifier(bool verifygc) {
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83 _verifygc = verifygc;
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84 if (_verifygc) {
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85 CollectedHeap* h = Universe::heap();
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86 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
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87 _old_invocations = h->total_collections();
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88 }
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89 }
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90
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91
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92 No_GC_Verifier::~No_GC_Verifier() {
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93 if (_verifygc) {
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94 CollectedHeap* h = Universe::heap();
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95 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
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96 if (_old_invocations != h->total_collections()) {
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97 fatal("collection in a No_GC_Verifier secured function");
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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 Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
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103 _ngcv = ngcv;
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104 if (_ngcv->_verifygc) {
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105 // if we were verifying, then make sure that nothing is
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106 // wrong before we "pause" verification
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107 CollectedHeap* h = Universe::heap();
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108 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
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109 if (_ngcv->_old_invocations != h->total_collections()) {
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110 fatal("collection in a No_GC_Verifier secured function");
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111 }
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112 }
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113 }
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114
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115
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116 Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
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117 if (_ngcv->_verifygc) {
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118 // if we were verifying before, then reenable verification
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119 CollectedHeap* h = Universe::heap();
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120 assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
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121 _ngcv->_old_invocations = h->total_collections();
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122 }
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123 }
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124
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125
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126 // JRT_LEAF rules:
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127 // A JRT_LEAF method may not interfere with safepointing by
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128 // 1) acquiring or blocking on a Mutex or JavaLock - checked
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129 // 2) allocating heap memory - checked
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130 // 3) executing a VM operation - checked
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131 // 4) executing a system call (including malloc) that could block or grab a lock
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132 // 5) invoking GC
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133 // 6) reaching a safepoint
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134 // 7) running too long
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135 // Nor may any method it calls.
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136 JRT_Leaf_Verifier::JRT_Leaf_Verifier()
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137 : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
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138 {
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139 }
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140
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141 JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
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142 {
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143 }
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144
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145 bool JRT_Leaf_Verifier::should_verify_GC() {
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146 switch (JavaThread::current()->thread_state()) {
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147 case _thread_in_Java:
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148 // is in a leaf routine, there must be no safepoint.
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149 return true;
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150 case _thread_in_native:
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151 // A native thread is not subject to safepoints.
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152 // Even while it is in a leaf routine, GC is ok
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153 return false;
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154 default:
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155 // Leaf routines cannot be called from other contexts.
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156 ShouldNotReachHere();
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157 return false;
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158 }
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159 }
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160 #endif
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