Mercurial > hg > truffle
annotate src/share/vm/memory/referenceProcessor.cpp @ 2369:92da084fefc9
6668573: CMS: reference processing crash if ParallelCMSThreads > ParallelGCThreads
Summary: Use _max_num_q = max(discovery_degree, processing_degree), and let balance_queues() redistribute from discovery_degree to processing_degree of queues. This should also allow a more dynamic and flexible parallelism policy in the future.
Reviewed-by: jmasa, johnc
| author | ysr |
|---|---|
| date | Thu, 17 Mar 2011 10:32:46 -0700 |
| parents | 8df09fb45352 |
| children | c2bf0120ee5d |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved. |
| 0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| 4 * | |
| 5 * This code is free software; you can redistribute it and/or modify it | |
| 6 * under the terms of the GNU General Public License version 2 only, as | |
| 7 * published by the Free Software Foundation. | |
| 8 * | |
| 9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 12 * version 2 for more details (a copy is included in the LICENSE file that | |
| 13 * accompanied this code). | |
| 14 * | |
| 15 * You should have received a copy of the GNU General Public License version | |
| 16 * 2 along with this work; if not, write to the Free Software Foundation, | |
| 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 18 * | |
|
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
| 0 | 22 * |
| 23 */ | |
| 24 | |
| 1972 | 25 #include "precompiled.hpp" |
| 26 #include "classfile/javaClasses.hpp" | |
| 27 #include "classfile/systemDictionary.hpp" | |
| 28 #include "gc_interface/collectedHeap.hpp" | |
| 29 #include "gc_interface/collectedHeap.inline.hpp" | |
| 30 #include "memory/referencePolicy.hpp" | |
| 31 #include "memory/referenceProcessor.hpp" | |
| 32 #include "oops/oop.inline.hpp" | |
| 33 #include "runtime/java.hpp" | |
| 34 #include "runtime/jniHandles.hpp" | |
| 0 | 35 |
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36 ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = NULL; |
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37 ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = NULL; |
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38 oop ReferenceProcessor::_sentinelRef = NULL; |
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39 const int subclasses_of_ref = REF_PHANTOM - REF_OTHER; |
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40 |
| 0 | 41 // List of discovered references. |
| 42 class DiscoveredList { | |
| 43 public: | |
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44 DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { } |
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45 oop head() const { |
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46 return UseCompressedOops ? oopDesc::decode_heap_oop_not_null(_compressed_head) : |
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47 _oop_head; |
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48 } |
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49 HeapWord* adr_head() { |
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50 return UseCompressedOops ? (HeapWord*)&_compressed_head : |
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51 (HeapWord*)&_oop_head; |
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52 } |
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53 void set_head(oop o) { |
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54 if (UseCompressedOops) { |
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55 // Must compress the head ptr. |
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56 _compressed_head = oopDesc::encode_heap_oop_not_null(o); |
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57 } else { |
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58 _oop_head = o; |
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59 } |
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60 } |
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61 bool empty() const { return head() == ReferenceProcessor::sentinel_ref(); } |
| 0 | 62 size_t length() { return _len; } |
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63 void set_length(size_t len) { _len = len; } |
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64 void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); } |
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65 void dec_length(size_t dec) { _len -= dec; } |
| 0 | 66 private: |
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67 // Set value depending on UseCompressedOops. This could be a template class |
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68 // but then we have to fix all the instantiations and declarations that use this class. |
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69 oop _oop_head; |
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70 narrowOop _compressed_head; |
| 0 | 71 size_t _len; |
| 72 }; | |
| 73 | |
| 74 void referenceProcessor_init() { | |
| 75 ReferenceProcessor::init_statics(); | |
| 76 } | |
| 77 | |
| 78 void ReferenceProcessor::init_statics() { | |
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79 assert(_sentinelRef == NULL, "should be initialized precisely once"); |
| 0 | 80 EXCEPTION_MARK; |
| 81 _sentinelRef = instanceKlass::cast( | |
| 1142 | 82 SystemDictionary::Reference_klass())-> |
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83 allocate_permanent_instance(THREAD); |
| 0 | 84 |
| 85 // Initialize the master soft ref clock. | |
| 86 java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); | |
| 87 | |
| 88 if (HAS_PENDING_EXCEPTION) { | |
| 89 Handle ex(THREAD, PENDING_EXCEPTION); | |
| 90 vm_exit_during_initialization(ex); | |
| 91 } | |
| 92 assert(_sentinelRef != NULL && _sentinelRef->is_oop(), | |
| 93 "Just constructed it!"); | |
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94 _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
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95 _default_soft_ref_policy = new COMPILER2_PRESENT(LRUMaxHeapPolicy()) |
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96 NOT_COMPILER2(LRUCurrentHeapPolicy()); |
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97 if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { |
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98 vm_exit_during_initialization("Could not allocate reference policy object"); |
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99 } |
| 0 | 100 guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
| 101 RefDiscoveryPolicy == ReferentBasedDiscovery, | |
| 102 "Unrecongnized RefDiscoveryPolicy"); | |
| 103 } | |
| 104 | |
| 105 ReferenceProcessor::ReferenceProcessor(MemRegion span, | |
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106 bool mt_processing, |
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107 int mt_processing_degree, |
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108 bool mt_discovery, |
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109 int mt_discovery_degree, |
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110 bool atomic_discovery, |
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111 BoolObjectClosure* is_alive_non_header, |
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112 bool discovered_list_needs_barrier) : |
| 0 | 113 _discovering_refs(false), |
| 114 _enqueuing_is_done(false), | |
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115 _is_alive_non_header(is_alive_non_header), |
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116 _discovered_list_needs_barrier(discovered_list_needs_barrier), |
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117 _bs(NULL), |
| 0 | 118 _processing_is_mt(mt_processing), |
| 119 _next_id(0) | |
| 120 { | |
| 121 _span = span; | |
| 122 _discovery_is_atomic = atomic_discovery; | |
| 123 _discovery_is_mt = mt_discovery; | |
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124 _num_q = MAX2(1, mt_processing_degree); |
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125 _max_num_q = MAX2(_num_q, mt_discovery_degree); |
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126 _discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, _max_num_q * subclasses_of_ref); |
| 0 | 127 if (_discoveredSoftRefs == NULL) { |
| 128 vm_exit_during_initialization("Could not allocated RefProc Array"); | |
| 129 } | |
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130 _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_q]; |
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131 _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_q]; |
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132 _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q]; |
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133 assert(sentinel_ref() != NULL, "_sentinelRef is NULL"); |
| 0 | 134 // Initialized all entries to _sentinelRef |
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135 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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136 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 137 _discoveredSoftRefs[i].set_length(0); |
| 138 } | |
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139 // If we do barreirs, cache a copy of the barrier set. |
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140 if (discovered_list_needs_barrier) { |
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141 _bs = Universe::heap()->barrier_set(); |
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142 } |
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143 setup_policy(false /* default soft ref policy */); |
| 0 | 144 } |
| 145 | |
| 146 #ifndef PRODUCT | |
| 147 void ReferenceProcessor::verify_no_references_recorded() { | |
| 148 guarantee(!_discovering_refs, "Discovering refs?"); | |
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149 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 150 guarantee(_discoveredSoftRefs[i].empty(), |
| 151 "Found non-empty discovered list"); | |
| 152 } | |
| 153 } | |
| 154 #endif | |
| 155 | |
| 156 void ReferenceProcessor::weak_oops_do(OopClosure* f) { | |
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157 // Should this instead be |
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158 // for (int i = 0; i < subclasses_of_ref; i++_ { |
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159 // for (int j = 0; j < _num_q; j++) { |
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160 // int index = i * _max_num_q + j; |
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161 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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162 if (UseCompressedOops) { |
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163 f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head()); |
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164 } else { |
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165 f->do_oop((oop*)_discoveredSoftRefs[i].adr_head()); |
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166 } |
| 0 | 167 } |
| 168 } | |
| 169 | |
| 170 void ReferenceProcessor::oops_do(OopClosure* f) { | |
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171 f->do_oop(adr_sentinel_ref()); |
| 0 | 172 } |
| 173 | |
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174 void ReferenceProcessor::update_soft_ref_master_clock() { |
| 0 | 175 // Update (advance) the soft ref master clock field. This must be done |
| 176 // after processing the soft ref list. | |
| 177 jlong now = os::javaTimeMillis(); | |
| 178 jlong clock = java_lang_ref_SoftReference::clock(); | |
| 179 NOT_PRODUCT( | |
| 180 if (now < clock) { | |
| 181 warning("time warp: %d to %d", clock, now); | |
| 182 } | |
| 183 ) | |
| 184 // In product mode, protect ourselves from system time being adjusted | |
| 185 // externally and going backward; see note in the implementation of | |
| 186 // GenCollectedHeap::time_since_last_gc() for the right way to fix | |
| 187 // this uniformly throughout the VM; see bug-id 4741166. XXX | |
| 188 if (now > clock) { | |
| 189 java_lang_ref_SoftReference::set_clock(now); | |
| 190 } | |
| 191 // Else leave clock stalled at its old value until time progresses | |
| 192 // past clock value. | |
| 193 } | |
| 194 | |
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195 void ReferenceProcessor::process_discovered_references( |
| 0 | 196 BoolObjectClosure* is_alive, |
| 197 OopClosure* keep_alive, | |
| 198 VoidClosure* complete_gc, | |
| 199 AbstractRefProcTaskExecutor* task_executor) { | |
| 200 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
| 201 | |
| 202 assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); | |
| 203 // Stop treating discovered references specially. | |
| 204 disable_discovery(); | |
| 205 | |
| 206 bool trace_time = PrintGCDetails && PrintReferenceGC; | |
| 207 // Soft references | |
| 208 { | |
| 209 TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); | |
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210 process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, |
| 0 | 211 is_alive, keep_alive, complete_gc, task_executor); |
| 212 } | |
| 213 | |
| 214 update_soft_ref_master_clock(); | |
| 215 | |
| 216 // Weak references | |
| 217 { | |
| 218 TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); | |
| 219 process_discovered_reflist(_discoveredWeakRefs, NULL, true, | |
| 220 is_alive, keep_alive, complete_gc, task_executor); | |
| 221 } | |
| 222 | |
| 223 // Final references | |
| 224 { | |
| 225 TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); | |
| 226 process_discovered_reflist(_discoveredFinalRefs, NULL, false, | |
| 227 is_alive, keep_alive, complete_gc, task_executor); | |
| 228 } | |
| 229 | |
| 230 // Phantom references | |
| 231 { | |
| 232 TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); | |
| 233 process_discovered_reflist(_discoveredPhantomRefs, NULL, false, | |
| 234 is_alive, keep_alive, complete_gc, task_executor); | |
| 235 } | |
| 236 | |
| 237 // Weak global JNI references. It would make more sense (semantically) to | |
| 238 // traverse these simultaneously with the regular weak references above, but | |
| 239 // that is not how the JDK1.2 specification is. See #4126360. Native code can | |
| 240 // thus use JNI weak references to circumvent the phantom references and | |
| 241 // resurrect a "post-mortem" object. | |
| 242 { | |
| 243 TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); | |
| 244 if (task_executor != NULL) { | |
| 245 task_executor->set_single_threaded_mode(); | |
| 246 } | |
| 247 process_phaseJNI(is_alive, keep_alive, complete_gc); | |
| 248 } | |
| 249 } | |
| 250 | |
| 251 #ifndef PRODUCT | |
| 252 // Calculate the number of jni handles. | |
|
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253 uint ReferenceProcessor::count_jni_refs() { |
| 0 | 254 class AlwaysAliveClosure: public BoolObjectClosure { |
| 255 public: | |
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256 virtual bool do_object_b(oop obj) { return true; } |
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257 virtual void do_object(oop obj) { assert(false, "Don't call"); } |
| 0 | 258 }; |
| 259 | |
| 260 class CountHandleClosure: public OopClosure { | |
| 261 private: | |
| 262 int _count; | |
| 263 public: | |
| 264 CountHandleClosure(): _count(0) {} | |
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265 void do_oop(oop* unused) { _count++; } |
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266 void do_oop(narrowOop* unused) { ShouldNotReachHere(); } |
| 0 | 267 int count() { return _count; } |
| 268 }; | |
| 269 CountHandleClosure global_handle_count; | |
| 270 AlwaysAliveClosure always_alive; | |
| 271 JNIHandles::weak_oops_do(&always_alive, &global_handle_count); | |
| 272 return global_handle_count.count(); | |
| 273 } | |
| 274 #endif | |
| 275 | |
| 276 void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, | |
| 277 OopClosure* keep_alive, | |
| 278 VoidClosure* complete_gc) { | |
| 279 #ifndef PRODUCT | |
| 280 if (PrintGCDetails && PrintReferenceGC) { | |
| 281 unsigned int count = count_jni_refs(); | |
| 282 gclog_or_tty->print(", %u refs", count); | |
| 283 } | |
| 284 #endif | |
| 285 JNIHandles::weak_oops_do(is_alive, keep_alive); | |
| 286 // Finally remember to keep sentinel around | |
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287 keep_alive->do_oop(adr_sentinel_ref()); |
| 0 | 288 complete_gc->do_void(); |
| 289 } | |
| 290 | |
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291 |
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292 template <class T> |
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293 bool enqueue_discovered_ref_helper(ReferenceProcessor* ref, |
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294 AbstractRefProcTaskExecutor* task_executor) { |
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295 |
| 0 | 296 // Remember old value of pending references list |
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297 T* pending_list_addr = (T*)java_lang_ref_Reference::pending_list_addr(); |
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298 T old_pending_list_value = *pending_list_addr; |
| 0 | 299 |
| 300 // Enqueue references that are not made active again, and | |
| 301 // clear the decks for the next collection (cycle). | |
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302 ref->enqueue_discovered_reflists((HeapWord*)pending_list_addr, task_executor); |
| 0 | 303 // Do the oop-check on pending_list_addr missed in |
| 304 // enqueue_discovered_reflist. We should probably | |
| 305 // do a raw oop_check so that future such idempotent | |
| 306 // oop_stores relying on the oop-check side-effect | |
| 307 // may be elided automatically and safely without | |
| 308 // affecting correctness. | |
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309 oop_store(pending_list_addr, oopDesc::load_decode_heap_oop(pending_list_addr)); |
| 0 | 310 |
| 311 // Stop treating discovered references specially. | |
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312 ref->disable_discovery(); |
| 0 | 313 |
| 314 // Return true if new pending references were added | |
| 315 return old_pending_list_value != *pending_list_addr; | |
| 316 } | |
| 317 | |
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318 bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
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319 NOT_PRODUCT(verify_ok_to_handle_reflists()); |
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320 if (UseCompressedOops) { |
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321 return enqueue_discovered_ref_helper<narrowOop>(this, task_executor); |
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322 } else { |
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323 return enqueue_discovered_ref_helper<oop>(this, task_executor); |
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324 } |
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325 } |
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326 |
| 0 | 327 void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
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328 HeapWord* pending_list_addr) { |
| 0 | 329 // Given a list of refs linked through the "discovered" field |
| 330 // (java.lang.ref.Reference.discovered) chain them through the | |
| 331 // "next" field (java.lang.ref.Reference.next) and prepend | |
| 332 // to the pending list. | |
| 333 if (TraceReferenceGC && PrintGCDetails) { | |
| 334 gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " | |
| 335 INTPTR_FORMAT, (address)refs_list.head()); | |
| 336 } | |
| 337 oop obj = refs_list.head(); | |
| 338 // Walk down the list, copying the discovered field into | |
| 339 // the next field and clearing it (except for the last | |
| 340 // non-sentinel object which is treated specially to avoid | |
| 341 // confusion with an active reference). | |
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342 while (obj != sentinel_ref()) { |
| 0 | 343 assert(obj->is_instanceRef(), "should be reference object"); |
| 344 oop next = java_lang_ref_Reference::discovered(obj); | |
| 345 if (TraceReferenceGC && PrintGCDetails) { | |
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346 gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next " INTPTR_FORMAT, |
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347 obj, next); |
| 0 | 348 } |
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349 assert(java_lang_ref_Reference::next(obj) == NULL, |
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350 "The reference should not be enqueued"); |
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351 if (next == sentinel_ref()) { // obj is last |
| 0 | 352 // Swap refs_list into pendling_list_addr and |
| 353 // set obj's next to what we read from pending_list_addr. | |
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354 oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
| 0 | 355 // Need oop_check on pending_list_addr above; |
| 356 // see special oop-check code at the end of | |
| 357 // enqueue_discovered_reflists() further below. | |
| 358 if (old == NULL) { | |
| 359 // obj should be made to point to itself, since | |
| 360 // pending list was empty. | |
| 361 java_lang_ref_Reference::set_next(obj, obj); | |
| 362 } else { | |
| 363 java_lang_ref_Reference::set_next(obj, old); | |
| 364 } | |
| 365 } else { | |
| 366 java_lang_ref_Reference::set_next(obj, next); | |
| 367 } | |
| 368 java_lang_ref_Reference::set_discovered(obj, (oop) NULL); | |
| 369 obj = next; | |
| 370 } | |
| 371 } | |
| 372 | |
| 373 // Parallel enqueue task | |
| 374 class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { | |
| 375 public: | |
| 376 RefProcEnqueueTask(ReferenceProcessor& ref_processor, | |
| 377 DiscoveredList discovered_refs[], | |
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378 HeapWord* pending_list_addr, |
| 0 | 379 oop sentinel_ref, |
| 380 int n_queues) | |
| 381 : EnqueueTask(ref_processor, discovered_refs, | |
| 382 pending_list_addr, sentinel_ref, n_queues) | |
| 383 { } | |
| 384 | |
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385 virtual void work(unsigned int work_id) { |
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386 assert(work_id < (unsigned int)_ref_processor.max_num_q(), "Index out-of-bounds"); |
| 0 | 387 // Simplest first cut: static partitioning. |
| 388 int index = work_id; | |
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389 // The increment on "index" must correspond to the maximum number of queues |
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390 // (n_queues) with which that ReferenceProcessor was created. That |
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391 // is because of the "clever" way the discovered references lists were |
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392 // allocated and are indexed into. |
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393 assert(_n_queues == (int) _ref_processor.max_num_q(), "Different number not expected"); |
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394 for (int j = 0; |
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395 j < subclasses_of_ref; |
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396 j++, index += _n_queues) { |
| 0 | 397 _ref_processor.enqueue_discovered_reflist( |
| 398 _refs_lists[index], _pending_list_addr); | |
| 399 _refs_lists[index].set_head(_sentinel_ref); | |
| 400 _refs_lists[index].set_length(0); | |
| 401 } | |
| 402 } | |
| 403 }; | |
| 404 | |
| 405 // Enqueue references that are not made active again | |
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406 void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr, |
| 0 | 407 AbstractRefProcTaskExecutor* task_executor) { |
| 408 if (_processing_is_mt && task_executor != NULL) { | |
| 409 // Parallel code | |
| 410 RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, | |
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411 pending_list_addr, sentinel_ref(), _max_num_q); |
| 0 | 412 task_executor->execute(tsk); |
| 413 } else { | |
| 414 // Serial code: call the parent class's implementation | |
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415 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 416 enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
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417 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 418 _discoveredSoftRefs[i].set_length(0); |
| 419 } | |
| 420 } | |
| 421 } | |
| 422 | |
| 423 // Iterator for the list of discovered references. | |
| 424 class DiscoveredListIterator { | |
| 425 public: | |
| 426 inline DiscoveredListIterator(DiscoveredList& refs_list, | |
| 427 OopClosure* keep_alive, | |
| 428 BoolObjectClosure* is_alive); | |
| 429 | |
| 430 // End Of List. | |
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431 inline bool has_next() const { return _next != ReferenceProcessor::sentinel_ref(); } |
| 0 | 432 |
| 433 // Get oop to the Reference object. | |
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434 inline oop obj() const { return _ref; } |
| 0 | 435 |
| 436 // Get oop to the referent object. | |
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437 inline oop referent() const { return _referent; } |
| 0 | 438 |
| 439 // Returns true if referent is alive. | |
| 440 inline bool is_referent_alive() const; | |
| 441 | |
| 442 // Loads data for the current reference. | |
| 443 // The "allow_null_referent" argument tells us to allow for the possibility | |
| 444 // of a NULL referent in the discovered Reference object. This typically | |
| 445 // happens in the case of concurrent collectors that may have done the | |
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446 // discovery concurrently, or interleaved, with mutator execution. |
| 0 | 447 inline void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); |
| 448 | |
| 449 // Move to the next discovered reference. | |
| 450 inline void next(); | |
| 451 | |
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452 // Remove the current reference from the list |
| 0 | 453 inline void remove(); |
| 454 | |
| 455 // Make the Reference object active again. | |
| 456 inline void make_active() { java_lang_ref_Reference::set_next(_ref, NULL); } | |
| 457 | |
| 458 // Make the referent alive. | |
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459 inline void make_referent_alive() { |
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460 if (UseCompressedOops) { |
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461 _keep_alive->do_oop((narrowOop*)_referent_addr); |
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462 } else { |
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463 _keep_alive->do_oop((oop*)_referent_addr); |
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464 } |
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465 } |
| 0 | 466 |
| 467 // Update the discovered field. | |
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468 inline void update_discovered() { |
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469 // First _prev_next ref actually points into DiscoveredList (gross). |
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470 if (UseCompressedOops) { |
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471 _keep_alive->do_oop((narrowOop*)_prev_next); |
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472 } else { |
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473 _keep_alive->do_oop((oop*)_prev_next); |
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474 } |
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475 } |
| 0 | 476 |
| 477 // NULL out referent pointer. | |
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478 inline void clear_referent() { oop_store_raw(_referent_addr, NULL); } |
| 0 | 479 |
| 480 // Statistics | |
| 481 NOT_PRODUCT( | |
| 482 inline size_t processed() const { return _processed; } | |
| 483 inline size_t removed() const { return _removed; } | |
| 484 ) | |
| 485 | |
| 486 inline void move_to_next(); | |
| 487 | |
| 488 private: | |
| 489 DiscoveredList& _refs_list; | |
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490 HeapWord* _prev_next; |
| 0 | 491 oop _ref; |
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492 HeapWord* _discovered_addr; |
| 0 | 493 oop _next; |
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494 HeapWord* _referent_addr; |
| 0 | 495 oop _referent; |
| 496 OopClosure* _keep_alive; | |
| 497 BoolObjectClosure* _is_alive; | |
| 498 DEBUG_ONLY( | |
| 499 oop _first_seen; // cyclic linked list check | |
| 500 ) | |
| 501 NOT_PRODUCT( | |
| 502 size_t _processed; | |
| 503 size_t _removed; | |
| 504 ) | |
| 505 }; | |
| 506 | |
| 507 inline DiscoveredListIterator::DiscoveredListIterator(DiscoveredList& refs_list, | |
| 508 OopClosure* keep_alive, | |
| 509 BoolObjectClosure* is_alive) | |
| 510 : _refs_list(refs_list), | |
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511 _prev_next(refs_list.adr_head()), |
| 0 | 512 _ref(refs_list.head()), |
| 513 #ifdef ASSERT | |
| 514 _first_seen(refs_list.head()), | |
| 515 #endif | |
| 516 #ifndef PRODUCT | |
| 517 _processed(0), | |
| 518 _removed(0), | |
| 519 #endif | |
| 520 _next(refs_list.head()), | |
| 521 _keep_alive(keep_alive), | |
| 522 _is_alive(is_alive) | |
| 523 { } | |
| 524 | |
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525 inline bool DiscoveredListIterator::is_referent_alive() const { |
| 0 | 526 return _is_alive->do_object_b(_referent); |
| 527 } | |
| 528 | |
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529 inline void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
| 0 | 530 _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
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531 oop discovered = java_lang_ref_Reference::discovered(_ref); |
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532 assert(_discovered_addr && discovered->is_oop_or_null(), |
| 0 | 533 "discovered field is bad"); |
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534 _next = discovered; |
| 0 | 535 _referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
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536 _referent = java_lang_ref_Reference::referent(_ref); |
| 0 | 537 assert(Universe::heap()->is_in_reserved_or_null(_referent), |
| 538 "Wrong oop found in java.lang.Reference object"); | |
| 539 assert(allow_null_referent ? | |
| 540 _referent->is_oop_or_null() | |
| 541 : _referent->is_oop(), | |
| 542 "bad referent"); | |
| 543 } | |
| 544 | |
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545 inline void DiscoveredListIterator::next() { |
| 0 | 546 _prev_next = _discovered_addr; |
| 547 move_to_next(); | |
| 548 } | |
| 549 | |
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550 inline void DiscoveredListIterator::remove() { |
| 0 | 551 assert(_ref->is_oop(), "Dropping a bad reference"); |
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552 oop_store_raw(_discovered_addr, NULL); |
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553 // First _prev_next ref actually points into DiscoveredList (gross). |
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554 if (UseCompressedOops) { |
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555 // Remove Reference object from list. |
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556 oopDesc::encode_store_heap_oop_not_null((narrowOop*)_prev_next, _next); |
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557 } else { |
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558 // Remove Reference object from list. |
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559 oopDesc::store_heap_oop((oop*)_prev_next, _next); |
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560 } |
| 0 | 561 NOT_PRODUCT(_removed++); |
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562 _refs_list.dec_length(1); |
| 0 | 563 } |
| 564 | |
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565 inline void DiscoveredListIterator::move_to_next() { |
| 0 | 566 _ref = _next; |
| 567 assert(_ref != _first_seen, "cyclic ref_list found"); | |
| 568 NOT_PRODUCT(_processed++); | |
| 569 } | |
| 570 | |
| 571 // NOTE: process_phase*() are largely similar, and at a high level | |
| 572 // merely iterate over the extant list applying a predicate to | |
| 573 // each of its elements and possibly removing that element from the | |
| 574 // list and applying some further closures to that element. | |
| 575 // We should consider the possibility of replacing these | |
| 576 // process_phase*() methods by abstracting them into | |
| 577 // a single general iterator invocation that receives appropriate | |
| 578 // closures that accomplish this work. | |
| 579 | |
| 580 // (SoftReferences only) Traverse the list and remove any SoftReferences whose | |
| 581 // referents are not alive, but that should be kept alive for policy reasons. | |
| 582 // Keep alive the transitive closure of all such referents. | |
| 583 void | |
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584 ReferenceProcessor::process_phase1(DiscoveredList& refs_list, |
| 0 | 585 ReferencePolicy* policy, |
| 586 BoolObjectClosure* is_alive, | |
| 587 OopClosure* keep_alive, | |
| 588 VoidClosure* complete_gc) { | |
| 589 assert(policy != NULL, "Must have a non-NULL policy"); | |
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590 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 591 // Decide which softly reachable refs should be kept alive. |
| 592 while (iter.has_next()) { | |
| 593 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); | |
| 594 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); | |
| 595 if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { | |
| 596 if (TraceReferenceGC) { | |
| 597 gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", | |
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598 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 599 } |
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600 // Remove Reference object from list |
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601 iter.remove(); |
| 0 | 602 // Make the Reference object active again |
| 603 iter.make_active(); | |
| 604 // keep the referent around | |
| 605 iter.make_referent_alive(); | |
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606 iter.move_to_next(); |
| 0 | 607 } else { |
| 608 iter.next(); | |
| 609 } | |
| 610 } | |
| 611 // Close the reachable set | |
| 612 complete_gc->do_void(); | |
| 613 NOT_PRODUCT( | |
| 614 if (PrintGCDetails && TraceReferenceGC) { | |
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615 gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d " |
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616 "discovered Refs by policy list " INTPTR_FORMAT, |
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617 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 618 } |
| 619 ) | |
| 620 } | |
| 621 | |
| 622 // Traverse the list and remove any Refs that are not active, or | |
| 623 // whose referents are either alive or NULL. | |
| 624 void | |
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625 ReferenceProcessor::pp2_work(DiscoveredList& refs_list, |
| 0 | 626 BoolObjectClosure* is_alive, |
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627 OopClosure* keep_alive) { |
| 0 | 628 assert(discovery_is_atomic(), "Error"); |
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629 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 630 while (iter.has_next()) { |
| 631 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
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632 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) |
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633 assert(next == NULL, "Should not discover inactive Reference"); |
| 0 | 634 if (iter.is_referent_alive()) { |
| 635 if (TraceReferenceGC) { | |
| 636 gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", | |
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637 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 638 } |
| 639 // The referent is reachable after all. | |
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640 // Remove Reference object from list. |
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641 iter.remove(); |
| 0 | 642 // Update the referent pointer as necessary: Note that this |
| 643 // should not entail any recursive marking because the | |
| 644 // referent must already have been traversed. | |
| 645 iter.make_referent_alive(); | |
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646 iter.move_to_next(); |
| 0 | 647 } else { |
| 648 iter.next(); | |
| 649 } | |
| 650 } | |
| 651 NOT_PRODUCT( | |
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652 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) { |
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653 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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654 "Refs in discovered list " INTPTR_FORMAT, |
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655 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 656 } |
| 657 ) | |
| 658 } | |
| 659 | |
| 660 void | |
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661 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, |
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662 BoolObjectClosure* is_alive, |
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663 OopClosure* keep_alive, |
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664 VoidClosure* complete_gc) { |
| 0 | 665 assert(!discovery_is_atomic(), "Error"); |
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666 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 667 while (iter.has_next()) { |
| 668 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
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669 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
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670 oop next = java_lang_ref_Reference::next(iter.obj()); |
| 0 | 671 if ((iter.referent() == NULL || iter.is_referent_alive() || |
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672 next != NULL)) { |
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673 assert(next->is_oop_or_null(), "bad next field"); |
| 0 | 674 // Remove Reference object from list |
| 675 iter.remove(); | |
| 676 // Trace the cohorts | |
| 677 iter.make_referent_alive(); | |
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678 if (UseCompressedOops) { |
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679 keep_alive->do_oop((narrowOop*)next_addr); |
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680 } else { |
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681 keep_alive->do_oop((oop*)next_addr); |
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682 } |
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683 iter.move_to_next(); |
| 0 | 684 } else { |
| 685 iter.next(); | |
| 686 } | |
| 687 } | |
| 688 // Now close the newly reachable set | |
| 689 complete_gc->do_void(); | |
| 690 NOT_PRODUCT( | |
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691 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) { |
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692 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
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693 "Refs in discovered list " INTPTR_FORMAT, |
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694 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 695 } |
| 696 ) | |
| 697 } | |
| 698 | |
| 699 // Traverse the list and process the referents, by either | |
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700 // clearing them or keeping them (and their reachable |
| 0 | 701 // closure) alive. |
| 702 void | |
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703 ReferenceProcessor::process_phase3(DiscoveredList& refs_list, |
| 0 | 704 bool clear_referent, |
| 705 BoolObjectClosure* is_alive, | |
| 706 OopClosure* keep_alive, | |
| 707 VoidClosure* complete_gc) { | |
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708 ResourceMark rm; |
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709 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 0 | 710 while (iter.has_next()) { |
| 711 iter.update_discovered(); | |
| 712 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); | |
| 713 if (clear_referent) { | |
| 714 // NULL out referent pointer | |
| 715 iter.clear_referent(); | |
| 716 } else { | |
| 717 // keep the referent around | |
| 718 iter.make_referent_alive(); | |
| 719 } | |
| 720 if (TraceReferenceGC) { | |
| 721 gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", | |
| 722 clear_referent ? "cleared " : "", | |
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723 iter.obj(), iter.obj()->blueprint()->internal_name()); |
| 0 | 724 } |
| 725 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); | |
| 726 iter.next(); | |
| 727 } | |
| 728 // Remember to keep sentinel pointer around | |
| 729 iter.update_discovered(); | |
| 730 // Close the reachable set | |
| 731 complete_gc->do_void(); | |
| 732 } | |
| 733 | |
| 734 void | |
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735 ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& refs_list) { |
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736 oop obj = refs_list.head(); |
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737 while (obj != sentinel_ref()) { |
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738 oop discovered = java_lang_ref_Reference::discovered(obj); |
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739 java_lang_ref_Reference::set_discovered_raw(obj, NULL); |
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740 obj = discovered; |
| 0 | 741 } |
|
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742 refs_list.set_head(sentinel_ref()); |
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743 refs_list.set_length(0); |
| 0 | 744 } |
| 745 | |
|
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746 void ReferenceProcessor::abandon_partial_discovery() { |
|
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747 // loop over the lists |
|
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748 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
|
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749 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
|
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750 gclog_or_tty->print_cr("\nAbandoning %s discovered list", |
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751 list_name(i)); |
|
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752 } |
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753 abandon_partial_discovered_list(_discoveredSoftRefs[i]); |
| 0 | 754 } |
| 755 } | |
| 756 | |
| 757 class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 758 public: | |
| 759 RefProcPhase1Task(ReferenceProcessor& ref_processor, | |
| 760 DiscoveredList refs_lists[], | |
| 761 ReferencePolicy* policy, | |
| 762 bool marks_oops_alive) | |
| 763 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
| 764 _policy(policy) | |
| 765 { } | |
| 766 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 767 OopClosure& keep_alive, | |
| 768 VoidClosure& complete_gc) | |
| 769 { | |
|
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770 Thread* thr = Thread::current(); |
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771 int refs_list_index = ((WorkerThread*)thr)->id(); |
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772 _ref_processor.process_phase1(_refs_lists[refs_list_index], _policy, |
| 0 | 773 &is_alive, &keep_alive, &complete_gc); |
| 774 } | |
| 775 private: | |
| 776 ReferencePolicy* _policy; | |
| 777 }; | |
| 778 | |
| 779 class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 780 public: | |
| 781 RefProcPhase2Task(ReferenceProcessor& ref_processor, | |
| 782 DiscoveredList refs_lists[], | |
| 783 bool marks_oops_alive) | |
| 784 : ProcessTask(ref_processor, refs_lists, marks_oops_alive) | |
| 785 { } | |
| 786 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 787 OopClosure& keep_alive, | |
| 788 VoidClosure& complete_gc) | |
| 789 { | |
| 790 _ref_processor.process_phase2(_refs_lists[i], | |
| 791 &is_alive, &keep_alive, &complete_gc); | |
| 792 } | |
| 793 }; | |
| 794 | |
| 795 class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { | |
| 796 public: | |
| 797 RefProcPhase3Task(ReferenceProcessor& ref_processor, | |
| 798 DiscoveredList refs_lists[], | |
| 799 bool clear_referent, | |
| 800 bool marks_oops_alive) | |
| 801 : ProcessTask(ref_processor, refs_lists, marks_oops_alive), | |
| 802 _clear_referent(clear_referent) | |
| 803 { } | |
| 804 virtual void work(unsigned int i, BoolObjectClosure& is_alive, | |
| 805 OopClosure& keep_alive, | |
| 806 VoidClosure& complete_gc) | |
| 807 { | |
|
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808 // Don't use "refs_list_index" calculated in this way because |
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809 // balance_queues() has moved the Ref's into the first n queues. |
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810 // Thread* thr = Thread::current(); |
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811 // int refs_list_index = ((WorkerThread*)thr)->id(); |
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812 // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent, |
| 0 | 813 _ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
| 814 &is_alive, &keep_alive, &complete_gc); | |
| 815 } | |
| 816 private: | |
| 817 bool _clear_referent; | |
| 818 }; | |
| 819 | |
| 820 // Balances reference queues. | |
|
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821 // Move entries from all queues[0, 1, ..., _max_num_q-1] to |
|
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822 // queues[0, 1, ..., _num_q-1] because only the first _num_q |
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823 // corresponding to the active workers will be processed. |
| 0 | 824 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
| 825 { | |
| 826 // calculate total length | |
| 827 size_t total_refs = 0; | |
|
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828 if (TraceReferenceGC && PrintGCDetails) { |
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829 gclog_or_tty->print_cr("\nBalance ref_lists "); |
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830 } |
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831 |
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832 for (int i = 0; i < _max_num_q; ++i) { |
| 0 | 833 total_refs += ref_lists[i].length(); |
|
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834 if (TraceReferenceGC && PrintGCDetails) { |
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835 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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836 } |
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837 } |
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838 if (TraceReferenceGC && PrintGCDetails) { |
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839 gclog_or_tty->print_cr(" = %d", total_refs); |
| 0 | 840 } |
| 841 size_t avg_refs = total_refs / _num_q + 1; | |
| 842 int to_idx = 0; | |
|
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843 for (int from_idx = 0; from_idx < _max_num_q; from_idx++) { |
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844 bool move_all = false; |
|
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845 if (from_idx >= _num_q) { |
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846 move_all = ref_lists[from_idx].length() > 0; |
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847 } |
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848 while ((ref_lists[from_idx].length() > avg_refs) || |
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849 move_all) { |
| 0 | 850 assert(to_idx < _num_q, "Sanity Check!"); |
| 851 if (ref_lists[to_idx].length() < avg_refs) { | |
| 852 // move superfluous refs | |
|
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853 size_t refs_to_move; |
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854 // Move all the Ref's if the from queue will not be processed. |
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855 if (move_all) { |
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856 refs_to_move = MIN2(ref_lists[from_idx].length(), |
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857 avg_refs - ref_lists[to_idx].length()); |
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858 } else { |
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859 refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, |
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860 avg_refs - ref_lists[to_idx].length()); |
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861 } |
| 0 | 862 oop move_head = ref_lists[from_idx].head(); |
| 863 oop move_tail = move_head; | |
| 864 oop new_head = move_head; | |
| 865 // find an element to split the list on | |
| 866 for (size_t j = 0; j < refs_to_move; ++j) { | |
| 867 move_tail = new_head; | |
|
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868 new_head = java_lang_ref_Reference::discovered(new_head); |
| 0 | 869 } |
| 870 java_lang_ref_Reference::set_discovered(move_tail, ref_lists[to_idx].head()); | |
| 871 ref_lists[to_idx].set_head(move_head); | |
|
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872 ref_lists[to_idx].inc_length(refs_to_move); |
| 0 | 873 ref_lists[from_idx].set_head(new_head); |
|
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874 ref_lists[from_idx].dec_length(refs_to_move); |
|
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875 if (ref_lists[from_idx].length() == 0) { |
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876 break; |
|
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877 } |
| 0 | 878 } else { |
|
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879 to_idx = (to_idx + 1) % _num_q; |
| 0 | 880 } |
| 881 } | |
| 882 } | |
|
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883 #ifdef ASSERT |
|
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884 size_t balanced_total_refs = 0; |
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885 for (int i = 0; i < _max_num_q; ++i) { |
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886 balanced_total_refs += ref_lists[i].length(); |
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887 if (TraceReferenceGC && PrintGCDetails) { |
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888 gclog_or_tty->print("%d ", ref_lists[i].length()); |
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889 } |
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890 } |
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891 if (TraceReferenceGC && PrintGCDetails) { |
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892 gclog_or_tty->print_cr(" = %d", balanced_total_refs); |
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893 gclog_or_tty->flush(); |
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894 } |
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895 assert(total_refs == balanced_total_refs, "Balancing was incomplete"); |
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896 #endif |
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897 } |
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898 |
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899 void ReferenceProcessor::balance_all_queues() { |
|
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900 balance_queues(_discoveredSoftRefs); |
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901 balance_queues(_discoveredWeakRefs); |
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902 balance_queues(_discoveredFinalRefs); |
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903 balance_queues(_discoveredPhantomRefs); |
| 0 | 904 } |
| 905 | |
| 906 void | |
| 907 ReferenceProcessor::process_discovered_reflist( | |
| 908 DiscoveredList refs_lists[], | |
| 909 ReferencePolicy* policy, | |
| 910 bool clear_referent, | |
| 911 BoolObjectClosure* is_alive, | |
| 912 OopClosure* keep_alive, | |
| 913 VoidClosure* complete_gc, | |
| 914 AbstractRefProcTaskExecutor* task_executor) | |
| 915 { | |
|
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916 bool mt_processing = task_executor != NULL && _processing_is_mt; |
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917 // If discovery used MT and a dynamic number of GC threads, then |
|
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918 // the queues must be balanced for correctness if fewer than the |
|
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919 // maximum number of queues were used. The number of queue used |
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920 // during discovery may be different than the number to be used |
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921 // for processing so don't depend of _num_q < _max_num_q as part |
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922 // of the test. |
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923 bool must_balance = _discovery_is_mt; |
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924 |
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925 if ((mt_processing && ParallelRefProcBalancingEnabled) || |
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926 must_balance) { |
| 0 | 927 balance_queues(refs_lists); |
| 928 } | |
| 929 if (PrintReferenceGC && PrintGCDetails) { | |
| 930 size_t total = 0; | |
|
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931 for (int i = 0; i < _max_num_q; ++i) { |
| 0 | 932 total += refs_lists[i].length(); |
| 933 } | |
| 934 gclog_or_tty->print(", %u refs", total); | |
| 935 } | |
| 936 | |
| 937 // Phase 1 (soft refs only): | |
| 938 // . Traverse the list and remove any SoftReferences whose | |
| 939 // referents are not alive, but that should be kept alive for | |
| 940 // policy reasons. Keep alive the transitive closure of all | |
| 941 // such referents. | |
| 942 if (policy != NULL) { | |
|
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943 if (mt_processing) { |
| 0 | 944 RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
| 945 task_executor->execute(phase1); | |
| 946 } else { | |
|
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947 for (int i = 0; i < _max_num_q; i++) { |
| 0 | 948 process_phase1(refs_lists[i], policy, |
| 949 is_alive, keep_alive, complete_gc); | |
| 950 } | |
| 951 } | |
| 952 } else { // policy == NULL | |
| 953 assert(refs_lists != _discoveredSoftRefs, | |
| 954 "Policy must be specified for soft references."); | |
| 955 } | |
| 956 | |
| 957 // Phase 2: | |
| 958 // . Traverse the list and remove any refs whose referents are alive. | |
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959 if (mt_processing) { |
| 0 | 960 RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
| 961 task_executor->execute(phase2); | |
| 962 } else { | |
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963 for (int i = 0; i < _max_num_q; i++) { |
| 0 | 964 process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); |
| 965 } | |
| 966 } | |
| 967 | |
| 968 // Phase 3: | |
| 969 // . Traverse the list and process referents as appropriate. | |
|
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970 if (mt_processing) { |
| 0 | 971 RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
| 972 task_executor->execute(phase3); | |
| 973 } else { | |
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974 for (int i = 0; i < _max_num_q; i++) { |
| 0 | 975 process_phase3(refs_lists[i], clear_referent, |
| 976 is_alive, keep_alive, complete_gc); | |
| 977 } | |
| 978 } | |
| 979 } | |
| 980 | |
| 981 void ReferenceProcessor::clean_up_discovered_references() { | |
| 982 // loop over the lists | |
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983 // Should this instead be |
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984 // for (int i = 0; i < subclasses_of_ref; i++_ { |
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985 // for (int j = 0; j < _num_q; j++) { |
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986 // int index = i * _max_num_q + j; |
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987 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
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988 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
| 0 | 989 gclog_or_tty->print_cr( |
| 990 "\nScrubbing %s discovered list of Null referents", | |
| 991 list_name(i)); | |
| 992 } | |
| 993 clean_up_discovered_reflist(_discoveredSoftRefs[i]); | |
| 994 } | |
| 995 } | |
| 996 | |
| 997 void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { | |
| 998 assert(!discovery_is_atomic(), "Else why call this method?"); | |
| 999 DiscoveredListIterator iter(refs_list, NULL, NULL); | |
| 1000 while (iter.has_next()) { | |
| 1001 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
|
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1002 oop next = java_lang_ref_Reference::next(iter.obj()); |
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1003 assert(next->is_oop_or_null(), "bad next field"); |
| 0 | 1004 // If referent has been cleared or Reference is not active, |
| 1005 // drop it. | |
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1006 if (iter.referent() == NULL || next != NULL) { |
| 0 | 1007 debug_only( |
| 1008 if (PrintGCDetails && TraceReferenceGC) { | |
| 1009 gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " | |
| 1010 INTPTR_FORMAT " with next field: " INTPTR_FORMAT | |
| 1011 " and referent: " INTPTR_FORMAT, | |
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1012 iter.obj(), next, iter.referent()); |
| 0 | 1013 } |
| 1014 ) | |
| 1015 // Remove Reference object from list | |
| 1016 iter.remove(); | |
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1017 iter.move_to_next(); |
| 0 | 1018 } else { |
| 1019 iter.next(); | |
| 1020 } | |
| 1021 } | |
| 1022 NOT_PRODUCT( | |
| 1023 if (PrintGCDetails && TraceReferenceGC) { | |
| 1024 gclog_or_tty->print( | |
| 1025 " Removed %d Refs with NULL referents out of %d discovered Refs", | |
| 1026 iter.removed(), iter.processed()); | |
| 1027 } | |
| 1028 ) | |
| 1029 } | |
| 1030 | |
| 1031 inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { | |
| 1032 int id = 0; | |
| 1033 // Determine the queue index to use for this object. | |
| 1034 if (_discovery_is_mt) { | |
| 1035 // During a multi-threaded discovery phase, | |
| 1036 // each thread saves to its "own" list. | |
| 1037 Thread* thr = Thread::current(); | |
|
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1038 id = thr->as_Worker_thread()->id(); |
| 0 | 1039 } else { |
| 1040 // single-threaded discovery, we save in round-robin | |
| 1041 // fashion to each of the lists. | |
| 1042 if (_processing_is_mt) { | |
| 1043 id = next_id(); | |
| 1044 } | |
| 1045 } | |
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1046 assert(0 <= id && id < _max_num_q, "Id is out-of-bounds (call Freud?)"); |
| 0 | 1047 |
| 1048 // Get the discovered queue to which we will add | |
| 1049 DiscoveredList* list = NULL; | |
| 1050 switch (rt) { | |
| 1051 case REF_OTHER: | |
| 1052 // Unknown reference type, no special treatment | |
| 1053 break; | |
| 1054 case REF_SOFT: | |
| 1055 list = &_discoveredSoftRefs[id]; | |
| 1056 break; | |
| 1057 case REF_WEAK: | |
| 1058 list = &_discoveredWeakRefs[id]; | |
| 1059 break; | |
| 1060 case REF_FINAL: | |
| 1061 list = &_discoveredFinalRefs[id]; | |
| 1062 break; | |
| 1063 case REF_PHANTOM: | |
| 1064 list = &_discoveredPhantomRefs[id]; | |
| 1065 break; | |
| 1066 case REF_NONE: | |
| 1067 // we should not reach here if we are an instanceRefKlass | |
| 1068 default: | |
| 1069 ShouldNotReachHere(); | |
| 1070 } | |
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1071 if (TraceReferenceGC && PrintGCDetails) { |
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1072 gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT, id, list); |
|
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1073 } |
| 0 | 1074 return list; |
| 1075 } | |
| 1076 | |
|
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1077 inline void |
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1078 ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, |
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1079 oop obj, |
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1080 HeapWord* discovered_addr) { |
| 0 | 1081 assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
| 1082 // First we must make sure this object is only enqueued once. CAS in a non null | |
| 1083 // discovered_addr. | |
|
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1084 oop current_head = refs_list.head(); |
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1085 |
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1086 // Note: In the case of G1, this specific pre-barrier is strictly |
|
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1087 // not necessary because the only case we are interested in |
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1088 // here is when *discovered_addr is NULL (see the CAS further below), |
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1089 // so this will expand to nothing. As a result, we have manually |
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1090 // elided this out for G1, but left in the test for some future |
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1091 // collector that might have need for a pre-barrier here. |
|
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1092 if (_discovered_list_needs_barrier && !UseG1GC) { |
|
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1093 if (UseCompressedOops) { |
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1094 _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
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1095 } else { |
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1096 _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
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1097 } |
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1098 guarantee(false, "Need to check non-G1 collector"); |
|
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1099 } |
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1100 oop retest = oopDesc::atomic_compare_exchange_oop(current_head, discovered_addr, |
|
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1101 NULL); |
| 0 | 1102 if (retest == NULL) { |
| 1103 // This thread just won the right to enqueue the object. | |
| 1104 // We have separate lists for enqueueing so no synchronization | |
| 1105 // is necessary. | |
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1106 refs_list.set_head(obj); |
|
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1107 refs_list.inc_length(1); |
|
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1108 if (_discovered_list_needs_barrier) { |
|
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1109 _bs->write_ref_field((void*)discovered_addr, current_head); |
|
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1110 } |
|
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1111 |
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1112 if (TraceReferenceGC) { |
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1113 gclog_or_tty->print_cr("Enqueued reference (mt) (" INTPTR_FORMAT ": %s)", |
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1114 obj, obj->blueprint()->internal_name()); |
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1115 } |
| 0 | 1116 } else { |
| 1117 // If retest was non NULL, another thread beat us to it: | |
| 1118 // The reference has already been discovered... | |
| 1119 if (TraceReferenceGC) { | |
| 1120 gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", | |
| 1121 obj, obj->blueprint()->internal_name()); | |
| 1122 } | |
| 1123 } | |
| 1124 } | |
| 1125 | |
|
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1126 #ifndef PRODUCT |
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1127 // Non-atomic (i.e. concurrent) discovery might allow us |
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1128 // to observe j.l.References with NULL referents, being those |
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1129 // cleared concurrently by mutators during (or after) discovery. |
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1130 void ReferenceProcessor::verify_referent(oop obj) { |
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1131 bool da = discovery_is_atomic(); |
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1132 oop referent = java_lang_ref_Reference::referent(obj); |
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1133 assert(da ? referent->is_oop() : referent->is_oop_or_null(), |
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1134 err_msg("Bad referent " INTPTR_FORMAT " found in Reference " |
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1135 INTPTR_FORMAT " during %satomic discovery ", |
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1136 (intptr_t)referent, (intptr_t)obj, da ? "" : "non-")); |
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1137 } |
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1138 #endif |
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1139 |
| 0 | 1140 // We mention two of several possible choices here: |
| 1141 // #0: if the reference object is not in the "originating generation" | |
| 1142 // (or part of the heap being collected, indicated by our "span" | |
| 1143 // we don't treat it specially (i.e. we scan it as we would | |
| 1144 // a normal oop, treating its references as strong references). | |
| 1145 // This means that references can't be enqueued unless their | |
| 1146 // referent is also in the same span. This is the simplest, | |
| 1147 // most "local" and most conservative approach, albeit one | |
| 1148 // that may cause weak references to be enqueued least promptly. | |
| 1149 // We call this choice the "ReferenceBasedDiscovery" policy. | |
| 1150 // #1: the reference object may be in any generation (span), but if | |
| 1151 // the referent is in the generation (span) being currently collected | |
| 1152 // then we can discover the reference object, provided | |
| 1153 // the object has not already been discovered by | |
| 1154 // a different concurrently running collector (as may be the | |
| 1155 // case, for instance, if the reference object is in CMS and | |
| 1156 // the referent in DefNewGeneration), and provided the processing | |
| 1157 // of this reference object by the current collector will | |
| 1158 // appear atomic to every other collector in the system. | |
| 1159 // (Thus, for instance, a concurrent collector may not | |
| 1160 // discover references in other generations even if the | |
| 1161 // referent is in its own generation). This policy may, | |
| 1162 // in certain cases, enqueue references somewhat sooner than | |
| 1163 // might Policy #0 above, but at marginally increased cost | |
| 1164 // and complexity in processing these references. | |
| 1165 // We call this choice the "RefeferentBasedDiscovery" policy. | |
| 1166 bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { | |
| 1167 // We enqueue references only if we are discovering refs | |
| 1168 // (rather than processing discovered refs). | |
| 1169 if (!_discovering_refs || !RegisterReferences) { | |
| 1170 return false; | |
| 1171 } | |
| 1172 // We only enqueue active references. | |
|
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1173 oop next = java_lang_ref_Reference::next(obj); |
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1174 if (next != NULL) { |
| 0 | 1175 return false; |
| 1176 } | |
| 1177 | |
| 1178 HeapWord* obj_addr = (HeapWord*)obj; | |
| 1179 if (RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
| 1180 !_span.contains(obj_addr)) { | |
| 1181 // Reference is not in the originating generation; | |
| 1182 // don't treat it specially (i.e. we want to scan it as a normal | |
| 1183 // object with strong references). | |
| 1184 return false; | |
| 1185 } | |
| 1186 | |
| 1187 // We only enqueue references whose referents are not (yet) strongly | |
| 1188 // reachable. | |
| 1189 if (is_alive_non_header() != NULL) { | |
|
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1190 verify_referent(obj); |
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1191 if (is_alive_non_header()->do_object_b(java_lang_ref_Reference::referent(obj))) { |
| 0 | 1192 return false; // referent is reachable |
| 1193 } | |
| 1194 } | |
|
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1195 if (rt == REF_SOFT) { |
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1196 // For soft refs we can decide now if these are not |
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|
1197 // current candidates for clearing, in which case we |
|
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1198 // can mark through them now, rather than delaying that |
|
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1199 // to the reference-processing phase. Since all current |
|
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|
1200 // time-stamp policies advance the soft-ref clock only |
|
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|
1201 // at a major collection cycle, this is always currently |
|
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|
1202 // accurate. |
|
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|
1203 if (!_current_soft_ref_policy->should_clear_reference(obj)) { |
|
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|
1204 return false; |
|
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|
1205 } |
|
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|
1206 } |
| 0 | 1207 |
|
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1208 HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
|
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1209 const oop discovered = java_lang_ref_Reference::discovered(obj); |
|
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1210 assert(discovered->is_oop_or_null(), "bad discovered field"); |
|
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1211 if (discovered != NULL) { |
| 0 | 1212 // The reference has already been discovered... |
| 1213 if (TraceReferenceGC) { | |
| 1214 gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", | |
|
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1215 obj, obj->blueprint()->internal_name()); |
| 0 | 1216 } |
| 1217 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
| 1218 // assumes that an object is not processed twice; | |
| 1219 // if it's been already discovered it must be on another | |
| 1220 // generation's discovered list; so we won't discover it. | |
| 1221 return false; | |
| 1222 } else { | |
| 1223 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, | |
| 1224 "Unrecognized policy"); | |
| 1225 // Check assumption that an object is not potentially | |
| 1226 // discovered twice except by concurrent collectors that potentially | |
| 1227 // trace the same Reference object twice. | |
|
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1228 assert(UseConcMarkSweepGC || UseG1GC, |
|
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1229 "Only possible with a concurrent marking collector"); |
| 0 | 1230 return true; |
| 1231 } | |
| 1232 } | |
| 1233 | |
| 1234 if (RefDiscoveryPolicy == ReferentBasedDiscovery) { | |
|
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|
1235 verify_referent(obj); |
| 0 | 1236 // enqueue if and only if either: |
| 1237 // reference is in our span or | |
| 1238 // we are an atomic collector and referent is in our span | |
| 1239 if (_span.contains(obj_addr) || | |
|
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1240 (discovery_is_atomic() && |
|
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|
1241 _span.contains(java_lang_ref_Reference::referent(obj)))) { |
| 0 | 1242 // should_enqueue = true; |
| 1243 } else { | |
| 1244 return false; | |
| 1245 } | |
| 1246 } else { | |
| 1247 assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && | |
| 1248 _span.contains(obj_addr), "code inconsistency"); | |
| 1249 } | |
| 1250 | |
| 1251 // Get the right type of discovered queue head. | |
| 1252 DiscoveredList* list = get_discovered_list(rt); | |
| 1253 if (list == NULL) { | |
| 1254 return false; // nothing special needs to be done | |
| 1255 } | |
| 1256 | |
| 1257 if (_discovery_is_mt) { | |
| 1258 add_to_discovered_list_mt(*list, obj, discovered_addr); | |
| 1259 } else { | |
|
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1260 // If "_discovered_list_needs_barrier", we do write barriers when |
|
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1261 // updating the discovered reference list. Otherwise, we do a raw store |
|
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1262 // here: the field will be visited later when processing the discovered |
|
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|
1263 // references. |
|
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|
1264 oop current_head = list->head(); |
|
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|
1265 // As in the case further above, since we are over-writing a NULL |
|
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1266 // pre-value, we can safely elide the pre-barrier here for the case of G1. |
|
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|
1267 assert(discovered == NULL, "control point invariant"); |
|
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|
1268 if (_discovered_list_needs_barrier && !UseG1GC) { // safe to elide for G1 |
|
845
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|
1269 if (UseCompressedOops) { |
|
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|
1270 _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
|
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|
1271 } else { |
|
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|
1272 _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
|
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|
1273 } |
|
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|
1274 guarantee(false, "Need to check non-G1 collector"); |
|
342
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|
1275 } |
|
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|
1276 oop_store_raw(discovered_addr, current_head); |
|
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|
1277 if (_discovered_list_needs_barrier) { |
|
845
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1278 _bs->write_ref_field((void*)discovered_addr, current_head); |
|
342
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|
1279 } |
| 0 | 1280 list->set_head(obj); |
|
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|
1281 list->inc_length(1); |
| 0 | 1282 |
|
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|
1283 if (TraceReferenceGC) { |
| 0 | 1284 gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)", |
|
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|
1285 obj, obj->blueprint()->internal_name()); |
| 0 | 1286 } |
| 1287 } | |
| 1288 assert(obj->is_oop(), "Enqueued a bad reference"); | |
|
1995
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|
1289 verify_referent(obj); |
| 0 | 1290 return true; |
| 1291 } | |
| 1292 | |
| 1293 // Preclean the discovered references by removing those | |
| 1294 // whose referents are alive, and by marking from those that | |
| 1295 // are not active. These lists can be handled here | |
| 1296 // in any order and, indeed, concurrently. | |
| 1297 void ReferenceProcessor::preclean_discovered_references( | |
| 1298 BoolObjectClosure* is_alive, | |
| 1299 OopClosure* keep_alive, | |
| 1300 VoidClosure* complete_gc, | |
|
1190
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6895236: CMS: cmsOopClosures.inline.hpp:43 assert(..., "Should remember klasses in this context")
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|
1301 YieldClosure* yield, |
|
4788266644c1
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diff
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|
1302 bool should_unload_classes) { |
| 0 | 1303 |
| 1304 NOT_PRODUCT(verify_ok_to_handle_reflists()); | |
| 1305 | |
| 935 | 1306 #ifdef ASSERT |
| 1307 bool must_remember_klasses = ClassUnloading && !UseConcMarkSweepGC || | |
|
1190
4788266644c1
6895236: CMS: cmsOopClosures.inline.hpp:43 assert(..., "Should remember klasses in this context")
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1144
diff
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|
1308 CMSClassUnloadingEnabled && UseConcMarkSweepGC || |
|
4788266644c1
6895236: CMS: cmsOopClosures.inline.hpp:43 assert(..., "Should remember klasses in this context")
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diff
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|
1309 ExplicitGCInvokesConcurrentAndUnloadsClasses && |
|
4788266644c1
6895236: CMS: cmsOopClosures.inline.hpp:43 assert(..., "Should remember klasses in this context")
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|
1310 UseConcMarkSweepGC && should_unload_classes; |
| 935 | 1311 RememberKlassesChecker mx(must_remember_klasses); |
| 1312 #endif | |
| 0 | 1313 // Soft references |
| 1314 { | |
| 1315 TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, | |
| 1316 false, gclog_or_tty); | |
|
1833
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6984287: Regularize how GC parallel workers are specified.
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|
1317 for (int i = 0; i < _max_num_q; i++) { |
|
452
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|
1318 if (yield->should_return()) { |
|
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|
1319 return; |
|
00b023ae2d78
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|
1320 } |
| 0 | 1321 preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
| 1322 keep_alive, complete_gc, yield); | |
| 1323 } | |
| 1324 } | |
| 1325 | |
| 1326 // Weak references | |
| 1327 { | |
| 1328 TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, | |
| 1329 false, gclog_or_tty); | |
|
2369
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6668573: CMS: reference processing crash if ParallelCMSThreads > ParallelGCThreads
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diff
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|
1330 for (int i = 0; i < _max_num_q; i++) { |
|
452
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|
1331 if (yield->should_return()) { |
|
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|
1332 return; |
|
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|
1333 } |
| 0 | 1334 preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
| 1335 keep_alive, complete_gc, yield); | |
| 1336 } | |
| 1337 } | |
| 1338 | |
| 1339 // Final references | |
| 1340 { | |
| 1341 TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, | |
| 1342 false, gclog_or_tty); | |
|
2369
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diff
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|
1343 for (int i = 0; i < _max_num_q; i++) { |
|
452
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|
1344 if (yield->should_return()) { |
|
00b023ae2d78
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|
1345 return; |
|
00b023ae2d78
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|
1346 } |
| 0 | 1347 preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
| 1348 keep_alive, complete_gc, yield); | |
| 1349 } | |
| 1350 } | |
| 1351 | |
| 1352 // Phantom references | |
| 1353 { | |
| 1354 TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, | |
| 1355 false, gclog_or_tty); | |
|
2369
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diff
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|
1356 for (int i = 0; i < _max_num_q; i++) { |
|
452
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|
1357 if (yield->should_return()) { |
|
00b023ae2d78
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|
1358 return; |
|
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|
1359 } |
| 0 | 1360 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
| 1361 keep_alive, complete_gc, yield); | |
| 1362 } | |
| 1363 } | |
| 1364 } | |
| 1365 | |
| 1366 // Walk the given discovered ref list, and remove all reference objects | |
| 1367 // whose referents are still alive, whose referents are NULL or which | |
|
452
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|
1368 // are not active (have a non-NULL next field). NOTE: When we are |
|
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|
1369 // thus precleaning the ref lists (which happens single-threaded today), |
|
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|
1370 // we do not disable refs discovery to honour the correct semantics of |
|
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|
1371 // java.lang.Reference. As a result, we need to be careful below |
|
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|
1372 // that ref removal steps interleave safely with ref discovery steps |
|
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|
1373 // (in this thread). |
|
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|
1374 void |
|
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|
1375 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
|
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|
1376 BoolObjectClosure* is_alive, |
|
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|
1377 OopClosure* keep_alive, |
|
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|
1378 VoidClosure* complete_gc, |
|
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|
1379 YieldClosure* yield) { |
| 0 | 1380 DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
| 1381 while (iter.has_next()) { | |
| 1382 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); | |
|
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|
1383 oop obj = iter.obj(); |
|
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|
1384 oop next = java_lang_ref_Reference::next(obj); |
| 0 | 1385 if (iter.referent() == NULL || iter.is_referent_alive() || |
|
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|
1386 next != NULL) { |
| 0 | 1387 // The referent has been cleared, or is alive, or the Reference is not |
| 1388 // active; we need to trace and mark its cohort. | |
| 1389 if (TraceReferenceGC) { | |
| 1390 gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", | |
| 1391 iter.obj(), iter.obj()->blueprint()->internal_name()); | |
| 1392 } | |
| 1393 // Remove Reference object from list | |
| 1394 iter.remove(); | |
| 1395 // Keep alive its cohort. | |
| 1396 iter.make_referent_alive(); | |
|
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1397 if (UseCompressedOops) { |
|
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|
1398 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); |
|
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|
1399 keep_alive->do_oop(next_addr); |
|
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1400 } else { |
|
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|
1401 oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); |
|
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|
1402 keep_alive->do_oop(next_addr); |
|
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1403 } |
|
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|
1404 iter.move_to_next(); |
| 0 | 1405 } else { |
| 1406 iter.next(); | |
| 1407 } | |
| 1408 } | |
| 1409 // Close the reachable set | |
| 1410 complete_gc->do_void(); | |
| 1411 | |
| 1412 NOT_PRODUCT( | |
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1413 if (PrintGCDetails && PrintReferenceGC && (iter.processed() > 0)) { |
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1414 gclog_or_tty->print_cr(" Dropped %d Refs out of %d " |
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1415 "Refs in discovered list " INTPTR_FORMAT, |
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1416 iter.removed(), iter.processed(), (address)refs_list.head()); |
| 0 | 1417 } |
| 1418 ) | |
| 1419 } | |
| 1420 | |
| 1421 const char* ReferenceProcessor::list_name(int i) { | |
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1422 assert(i >= 0 && i <= _max_num_q * subclasses_of_ref, "Out of bounds index"); |
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1423 int j = i / _max_num_q; |
| 0 | 1424 switch (j) { |
| 1425 case 0: return "SoftRef"; | |
| 1426 case 1: return "WeakRef"; | |
| 1427 case 2: return "FinalRef"; | |
| 1428 case 3: return "PhantomRef"; | |
| 1429 } | |
| 1430 ShouldNotReachHere(); | |
| 1431 return NULL; | |
| 1432 } | |
| 1433 | |
| 1434 #ifndef PRODUCT | |
| 1435 void ReferenceProcessor::verify_ok_to_handle_reflists() { | |
| 1436 // empty for now | |
| 1437 } | |
| 1438 #endif | |
| 1439 | |
| 1440 void ReferenceProcessor::verify() { | |
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1441 guarantee(sentinel_ref() != NULL && sentinel_ref()->is_oop(), "Lost _sentinelRef"); |
| 0 | 1442 } |
| 1443 | |
| 1444 #ifndef PRODUCT | |
| 1445 void ReferenceProcessor::clear_discovered_references() { | |
| 1446 guarantee(!_discovering_refs, "Discovering refs?"); | |
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1447 for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
| 0 | 1448 oop obj = _discoveredSoftRefs[i].head(); |
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1449 while (obj != sentinel_ref()) { |
| 0 | 1450 oop next = java_lang_ref_Reference::discovered(obj); |
| 1451 java_lang_ref_Reference::set_discovered(obj, (oop) NULL); | |
| 1452 obj = next; | |
| 1453 } | |
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1454 _discoveredSoftRefs[i].set_head(sentinel_ref()); |
| 0 | 1455 _discoveredSoftRefs[i].set_length(0); |
| 1456 } | |
| 1457 } | |
| 1458 #endif // PRODUCT |