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1 /*
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2 * Copyright 2005-2006 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 # include "incls/_precompiled.incl"
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25 # include "incls/_vmCMSOperations.cpp.incl"
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26
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27 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
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28 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
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29
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30 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
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31 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
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32
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33 //////////////////////////////////////////////////////////
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34 // Methods in abstract class VM_CMS_Operation
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35 //////////////////////////////////////////////////////////
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36 void VM_CMS_Operation::acquire_pending_list_lock() {
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37 // The caller may block while communicating
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38 // with the SLT thread in order to acquire/release the PLL.
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39 ConcurrentMarkSweepThread::slt()->
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40 manipulatePLL(SurrogateLockerThread::acquirePLL);
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41 }
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42
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43 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
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44 // The caller may block while communicating
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45 // with the SLT thread in order to acquire/release the PLL.
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46 ConcurrentMarkSweepThread::slt()->
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47 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
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48 }
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49
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50 void VM_CMS_Operation::verify_before_gc() {
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51 if (VerifyBeforeGC &&
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52 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
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53 HandleMark hm;
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54 FreelistLocker x(_collector);
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55 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
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56 Universe::heap()->prepare_for_verify();
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57 Universe::verify(true);
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58 }
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59 }
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60
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61 void VM_CMS_Operation::verify_after_gc() {
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62 if (VerifyAfterGC &&
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63 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
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64 HandleMark hm;
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65 FreelistLocker x(_collector);
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66 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
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67 Universe::verify(true);
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68 }
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69 }
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70
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71 bool VM_CMS_Operation::lost_race() const {
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72 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
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73 // We lost a race to a foreground collection
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74 // -- there's nothing to do
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75 return true;
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76 }
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77 assert(CMSCollector::abstract_state() == legal_state(),
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78 "Inconsistent collector state?");
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79 return false;
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80 }
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81
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82 bool VM_CMS_Operation::doit_prologue() {
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83 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
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84 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
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85 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
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86 "Possible deadlock");
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87
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88 if (needs_pll()) {
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89 acquire_pending_list_lock();
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90 }
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91 // Get the Heap_lock after the pending_list_lock.
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92 Heap_lock->lock();
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93 if (lost_race()) {
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94 assert(_prologue_succeeded == false, "Initialized in c'tor");
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95 Heap_lock->unlock();
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96 if (needs_pll()) {
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97 release_and_notify_pending_list_lock();
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98 }
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99 } else {
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100 _prologue_succeeded = true;
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101 }
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102 return _prologue_succeeded;
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103 }
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104
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105 void VM_CMS_Operation::doit_epilogue() {
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106 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
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107 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
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108 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
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109 "Possible deadlock");
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110
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111 // Release the Heap_lock first.
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112 Heap_lock->unlock();
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113 if (needs_pll()) {
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114 release_and_notify_pending_list_lock();
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115 }
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116 }
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117
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118 //////////////////////////////////////////////////////////
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119 // Methods in class VM_CMS_Initial_Mark
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120 //////////////////////////////////////////////////////////
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121 void VM_CMS_Initial_Mark::doit() {
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122 if (lost_race()) {
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123 // Nothing to do.
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124 return;
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125 }
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126 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
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127
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128 GenCollectedHeap* gch = GenCollectedHeap::heap();
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129 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
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130
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131 VM_CMS_Operation::verify_before_gc();
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132
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133 IsGCActiveMark x; // stop-world GC active
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134 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial);
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135
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136 VM_CMS_Operation::verify_after_gc();
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137 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
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138 }
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139
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140 //////////////////////////////////////////////////////////
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141 // Methods in class VM_CMS_Final_Remark_Operation
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142 //////////////////////////////////////////////////////////
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143 void VM_CMS_Final_Remark::doit() {
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144 if (lost_race()) {
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145 // Nothing to do.
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146 return;
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147 }
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148 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
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149
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150 GenCollectedHeap* gch = GenCollectedHeap::heap();
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151 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
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152
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153 VM_CMS_Operation::verify_before_gc();
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154
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155 IsGCActiveMark x; // stop-world GC active
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156 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal);
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157
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158 VM_CMS_Operation::verify_after_gc();
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159 HS_DTRACE_PROBE(hs_private, cms__remark__end);
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160 }
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161
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162 // VM operation to invoke a concurrent collection of a
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163 // GenCollectedHeap heap.
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164 void VM_GenCollectFullConcurrent::doit() {
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165 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
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166
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167 GenCollectedHeap* gch = GenCollectedHeap::heap();
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168 if (_gc_count_before == gch->total_collections()) {
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169 // The "full" of do_full_collection call below "forces"
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170 // a collection; the second arg, 0, below ensures that
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171 // only the young gen is collected. XXX In the future,
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172 // we'll probably need to have something in this interface
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173 // to say do this only if we are sure we will not bail
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174 // out to a full collection in this attempt, but that's
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175 // for the future.
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176 assert(SafepointSynchronize::is_at_safepoint(),
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177 "We can only be executing this arm of if at a safepoint");
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178 GCCauseSetter gccs(gch, _gc_cause);
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179 gch->do_full_collection(gch->must_clear_all_soft_refs(),
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180 0 /* collect only youngest gen */);
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181 } // Else no need for a foreground young gc
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182 assert((_gc_count_before < gch->total_collections()) ||
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183 (GC_locker::is_active() /* gc may have been skipped */
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184 && (_gc_count_before == gch->total_collections())),
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185 "total_collections() should be monotonically increasing");
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186
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187 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
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188 if (gch->total_full_collections() == _full_gc_count_before) {
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189 // Disable iCMS until the full collection is done.
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190 CMSCollector::disable_icms();
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191 // In case CMS thread was in icms_wait(), wake it up.
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192 CMSCollector::start_icms();
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193 // Nudge the CMS thread to start a concurrent collection
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194 CMSCollector::request_full_gc(_full_gc_count_before);
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195 } else {
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196 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
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197 }
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198 }
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199
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200 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
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201 Thread* thr = Thread::current();
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202 assert(thr != NULL, "Unexpected tid");
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203 if (!thr->is_Java_thread()) {
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204 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
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205 GenCollectedHeap* gch = GenCollectedHeap::heap();
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206 if (_gc_count_before != gch->total_collections()) {
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207 // No need to do a young gc, we'll just nudge the CMS thread
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208 // in the doit() method above, to be executed soon.
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209 assert(_gc_count_before < gch->total_collections(),
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210 "total_collections() should be monotnically increasing");
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211 return false; // no need for foreground young gc
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212 }
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213 }
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214 return true; // may still need foreground young gc
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215 }
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216
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217
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218 void VM_GenCollectFullConcurrent::doit_epilogue() {
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219 Thread* thr = Thread::current();
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220 assert(thr->is_Java_thread(), "just checking");
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221 JavaThread* jt = (JavaThread*)thr;
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222 // Release the Heap_lock first.
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223 Heap_lock->unlock();
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224 release_and_notify_pending_list_lock();
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225
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226 // It is fine to test whether completed collections has
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227 // exceeded our request count without locking because
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228 // the completion count is monotonically increasing;
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229 // this will break for very long-running apps when the
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230 // count overflows and wraps around. XXX fix me !!!
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231 // e.g. at the rate of 1 full gc per ms, this could
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232 // overflow in about 1000 years.
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233 GenCollectedHeap* gch = GenCollectedHeap::heap();
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234 if (gch->total_full_collections_completed() <= _full_gc_count_before) {
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235 // Now, wait for witnessing concurrent gc cycle to complete,
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236 // but do so in native mode, because we want to lock the
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237 // FullGCEvent_lock, which may be needed by the VM thread
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238 // or by the CMS thread, so we do not want to be suspended
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239 // while holding that lock.
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240 ThreadToNativeFromVM native(jt);
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241 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
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242 // Either a concurrent or a stop-world full gc is sufficient
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243 // witness to our request.
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244 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
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245 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
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246 }
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247 }
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248 // Enable iCMS back.
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249 CMSCollector::enable_icms();
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250 }
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