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1 /*
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2 * Copyright 2001-2006 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
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25 # include "incls/_precompiled.incl"
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26 # include "incls/_concurrentMarkSweepThread.cpp.incl"
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27
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28 // ======= Concurrent Mark Sweep Thread ========
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29
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30 // The CMS thread is created when Concurrent Mark Sweep is used in the
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31 // older of two generations in a generational memory system.
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32
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33 ConcurrentMarkSweepThread*
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34 ConcurrentMarkSweepThread::_cmst = NULL;
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35 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
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36 bool ConcurrentMarkSweepThread::_should_terminate = false;
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37 int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
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38
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39 volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
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40 volatile jint ConcurrentMarkSweepThread::_pending_decrements = 0;
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41
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42 volatile bool ConcurrentMarkSweepThread::_icms_enabled = false;
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43 volatile bool ConcurrentMarkSweepThread::_should_run = false;
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44 // When icms is enabled, the icms thread is stopped until explicitly
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45 // started.
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46 volatile bool ConcurrentMarkSweepThread::_should_stop = true;
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47
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48 SurrogateLockerThread*
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49 ConcurrentMarkSweepThread::_slt = NULL;
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50 SurrogateLockerThread::SLT_msg_type
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51 ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
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52 Monitor*
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53 ConcurrentMarkSweepThread::_sltMonitor = NULL;
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54
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55 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
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56 : ConcurrentGCThread() {
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57 assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
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58 assert(_cmst == NULL, "CMS thread already created");
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59 _cmst = this;
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60 assert(_collector == NULL, "Collector already set");
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61 _collector = collector;
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62
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63 set_name("Concurrent Mark-Sweep GC Thread");
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64
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65 if (os::create_thread(this, os::cgc_thread)) {
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66 // XXX: need to set this to low priority
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67 // unless "agressive mode" set; priority
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68 // should be just less than that of VMThread.
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69 os::set_priority(this, NearMaxPriority);
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70 if (!DisableStartThread) {
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71 os::start_thread(this);
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72 }
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73 }
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74 _sltMonitor = SLT_lock;
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75 set_icms_enabled(CMSIncrementalMode);
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76 }
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77
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78 void ConcurrentMarkSweepThread::run() {
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79 assert(this == cmst(), "just checking");
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80
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81 this->record_stack_base_and_size();
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82 this->initialize_thread_local_storage();
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83 this->set_active_handles(JNIHandleBlock::allocate_block());
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84 // From this time Thread::current() should be working.
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85 assert(this == Thread::current(), "just checking");
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86 if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
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87 warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
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88 }
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89 // Wait until Universe::is_fully_initialized()
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90 {
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91 CMSLoopCountWarn loopX("CMS::run", "waiting for "
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92 "Universe::is_fully_initialized()", 2);
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93 MutexLockerEx x(CGC_lock, true);
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94 set_CMS_flag(CMS_cms_wants_token);
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95 // Wait until Universe is initialized and all initialization is completed.
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96 while (!is_init_completed() && !Universe::is_fully_initialized() &&
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97 !_should_terminate) {
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98 CGC_lock->wait(true, 200);
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99 loopX.tick();
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100 }
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101 // Wait until the surrogate locker thread that will do
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102 // pending list locking on our behalf has been created.
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103 // We cannot start the SLT thread ourselves since we need
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104 // to be a JavaThread to do so.
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105 CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
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106 while (_slt == NULL && !_should_terminate) {
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107 CGC_lock->wait(true, 200);
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108 loopY.tick();
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109 }
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110 clear_CMS_flag(CMS_cms_wants_token);
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111 }
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112
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113 while (!_should_terminate) {
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114 sleepBeforeNextCycle();
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115 if (_should_terminate) break;
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116 _collector->collect_in_background(false); // !clear_all_soft_refs
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117 }
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118 assert(_should_terminate, "just checking");
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119 // Check that the state of any protocol for synchronization
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120 // between background (CMS) and foreground collector is "clean"
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121 // (i.e. will not potentially block the foreground collector,
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122 // requiring action by us).
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123 verify_ok_to_terminate();
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124 // Signal that it is terminated
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125 {
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126 MutexLockerEx mu(Terminator_lock,
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127 Mutex::_no_safepoint_check_flag);
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128 assert(_cmst == this, "Weird!");
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129 _cmst = NULL;
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130 Terminator_lock->notify();
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131 }
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132
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133 // Thread destructor usually does this..
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134 ThreadLocalStorage::set_thread(NULL);
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135 }
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136
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137 #ifndef PRODUCT
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138 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
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139 assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
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140 cms_thread_wants_cms_token()),
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141 "Must renounce all worldly possessions and desires for nirvana");
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142 _collector->verify_ok_to_terminate();
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143 }
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144 #endif
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145
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146 // create and start a new ConcurrentMarkSweep Thread for given CMS generation
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147 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
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148 if (!_should_terminate) {
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149 assert(cmst() == NULL, "start() called twice?");
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150 ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
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151 assert(cmst() == th, "Where did the just-created CMS thread go?");
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152 return th;
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153 }
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154 return NULL;
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155 }
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156
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157 void ConcurrentMarkSweepThread::stop() {
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158 if (CMSIncrementalMode) {
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159 // Disable incremental mode and wake up the thread so it notices the change.
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160 disable_icms();
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161 start_icms();
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162 }
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163 // it is ok to take late safepoints here, if needed
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164 {
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165 MutexLockerEx x(Terminator_lock);
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166 _should_terminate = true;
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167 }
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168 { // Now post a notify on CGC_lock so as to nudge
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169 // CMS thread(s) that might be slumbering in
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170 // sleepBeforeNextCycle.
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171 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
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172 CGC_lock->notify_all();
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173 }
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174 { // Now wait until (all) CMS thread(s) have exited
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175 MutexLockerEx x(Terminator_lock);
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176 while(cmst() != NULL) {
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177 Terminator_lock->wait();
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178 }
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179 }
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180 }
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181
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182 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
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183 assert(tc != NULL, "Null ThreadClosure");
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184 if (_cmst != NULL) {
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185 tc->do_thread(_cmst);
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186 }
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187 assert(Universe::is_fully_initialized(),
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188 "Called too early, make sure heap is fully initialized");
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189 if (_collector != NULL) {
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190 AbstractWorkGang* gang = _collector->conc_workers();
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191 if (gang != NULL) {
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192 gang->threads_do(tc);
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193 }
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194 }
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195 }
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196
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197 void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
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198 st->print("\"%s\" ", name());
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199 Thread::print_on(st);
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200 st->cr();
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201 }
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202
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203 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
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204 if (_cmst != NULL) {
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205 _cmst->print_on(st);
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206 }
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207 if (_collector != NULL) {
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208 AbstractWorkGang* gang = _collector->conc_workers();
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209 if (gang != NULL) {
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210 gang->print_worker_threads_on(st);
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211 }
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212 }
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213 }
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214
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215 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
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216 assert(UseConcMarkSweepGC, "just checking");
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217
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218 MutexLockerEx x(CGC_lock,
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219 Mutex::_no_safepoint_check_flag);
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220 if (!is_cms_thread) {
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221 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
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222 CMSSynchronousYieldRequest yr;
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223 while (CMS_flag_is_set(CMS_cms_has_token)) {
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224 // indicate that we want to get the token
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225 set_CMS_flag(CMS_vm_wants_token);
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226 CGC_lock->wait(true);
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227 }
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228 // claim the token and proceed
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229 clear_CMS_flag(CMS_vm_wants_token);
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230 set_CMS_flag(CMS_vm_has_token);
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231 } else {
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232 assert(Thread::current()->is_ConcurrentGC_thread(),
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233 "Not a CMS thread");
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234 // The following barrier assumes there's only one CMS thread.
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235 // This will need to be modified is there are more CMS threads than one.
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236 while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
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237 set_CMS_flag(CMS_cms_wants_token);
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238 CGC_lock->wait(true);
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239 }
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240 // claim the token
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241 clear_CMS_flag(CMS_cms_wants_token);
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242 set_CMS_flag(CMS_cms_has_token);
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243 }
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244 }
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245
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246 void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
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247 assert(UseConcMarkSweepGC, "just checking");
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248
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249 MutexLockerEx x(CGC_lock,
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250 Mutex::_no_safepoint_check_flag);
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251 if (!is_cms_thread) {
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252 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
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253 assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
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254 clear_CMS_flag(CMS_vm_has_token);
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255 if (CMS_flag_is_set(CMS_cms_wants_token)) {
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256 // wake-up a waiting CMS thread
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257 CGC_lock->notify();
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258 }
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259 assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
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260 "Should have been cleared");
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261 } else {
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262 assert(Thread::current()->is_ConcurrentGC_thread(),
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263 "Not a CMS thread");
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264 assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
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265 clear_CMS_flag(CMS_cms_has_token);
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266 if (CMS_flag_is_set(CMS_vm_wants_token)) {
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267 // wake-up a waiting VM thread
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268 CGC_lock->notify();
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269 }
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270 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
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271 "Should have been cleared");
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272 }
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273 }
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274
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275 // Wait until the next synchronous GC or a timeout, whichever is earlier.
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276 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t) {
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277 MutexLockerEx x(CGC_lock,
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278 Mutex::_no_safepoint_check_flag);
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279 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
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280 CGC_lock->wait(Mutex::_no_safepoint_check_flag, t);
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281 clear_CMS_flag(CMS_cms_wants_token);
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282 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
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283 "Should not be set");
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284 }
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285
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286 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
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287 while (!_should_terminate) {
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288 if (CMSIncrementalMode) {
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289 icms_wait();
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290 return;
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291 } else {
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292 // Wait until the next synchronous GC or a timeout, whichever is earlier
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293 wait_on_cms_lock(CMSWaitDuration);
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294 }
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295 // Check if we should start a CMS collection cycle
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296 if (_collector->shouldConcurrentCollect()) {
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297 return;
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298 }
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299 // .. collection criterion not yet met, let's go back
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300 // and wait some more
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301 }
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302 }
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303
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304 // Incremental CMS
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305 void ConcurrentMarkSweepThread::start_icms() {
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306 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
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307 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
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308 trace_state("start_icms");
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309 _should_run = true;
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310 iCMS_lock->notify_all();
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311 }
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312
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313 void ConcurrentMarkSweepThread::stop_icms() {
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314 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
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315 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
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316 if (!_should_stop) {
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317 trace_state("stop_icms");
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318 _should_stop = true;
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319 _should_run = false;
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320 asynchronous_yield_request();
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321 iCMS_lock->notify_all();
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322 }
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323 }
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324
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325 void ConcurrentMarkSweepThread::icms_wait() {
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326 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
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327 if (_should_stop && icms_enabled()) {
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328 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
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329 trace_state("pause_icms");
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330 _collector->stats().stop_cms_timer();
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331 while(!_should_run && icms_enabled()) {
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332 iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
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333 }
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334 _collector->stats().start_cms_timer();
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335 _should_stop = false;
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336 trace_state("pause_icms end");
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337 }
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338 }
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339
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340 // Note: this method, although exported by the ConcurrentMarkSweepThread,
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341 // which is a non-JavaThread, can only be called by a JavaThread.
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342 // Currently this is done at vm creation time (post-vm-init) by the
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343 // main/Primordial (Java)Thread.
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344 // XXX Consider changing this in the future to allow the CMS thread
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345 // itself to create this thread?
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346 void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
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347 assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
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348 assert(_slt == NULL, "SLT already created");
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349 _slt = SurrogateLockerThread::make(THREAD);
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350 }
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