Thu, 09 Dec 2010 09:22:57 -0800
7005259: CMS: BubbleUpRef asserts referent(obj)->is_oop() failed: Enqueued a bad referent
Summary: Relaxed the assert by allowing NULL referents when discovery may be concurrent.
Reviewed-by: johnc, jcoomes
duke@435 | 1 | /* |
jmasa@2188 | 2 | * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved. |
duke@435 | 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
duke@435 | 4 | * |
duke@435 | 5 | * This code is free software; you can redistribute it and/or modify it |
duke@435 | 6 | * under the terms of the GNU General Public License version 2 only, as |
duke@435 | 7 | * published by the Free Software Foundation. |
duke@435 | 8 | * |
duke@435 | 9 | * This code is distributed in the hope that it will be useful, but WITHOUT |
duke@435 | 10 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
duke@435 | 11 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
duke@435 | 12 | * version 2 for more details (a copy is included in the LICENSE file that |
duke@435 | 13 | * accompanied this code). |
duke@435 | 14 | * |
duke@435 | 15 | * You should have received a copy of the GNU General Public License version |
duke@435 | 16 | * 2 along with this work; if not, write to the Free Software Foundation, |
duke@435 | 17 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
duke@435 | 18 | * |
trims@1907 | 19 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
trims@1907 | 20 | * or visit www.oracle.com if you need additional information or have any |
trims@1907 | 21 | * questions. |
duke@435 | 22 | * |
duke@435 | 23 | */ |
duke@435 | 24 | |
stefank@2314 | 25 | #include "precompiled.hpp" |
stefank@2314 | 26 | #include "classfile/javaClasses.hpp" |
stefank@2314 | 27 | #include "classfile/systemDictionary.hpp" |
stefank@2314 | 28 | #include "gc_interface/collectedHeap.hpp" |
stefank@2314 | 29 | #include "gc_interface/collectedHeap.inline.hpp" |
stefank@2314 | 30 | #include "memory/referencePolicy.hpp" |
stefank@2314 | 31 | #include "memory/referenceProcessor.hpp" |
stefank@2314 | 32 | #include "oops/oop.inline.hpp" |
stefank@2314 | 33 | #include "runtime/java.hpp" |
stefank@2314 | 34 | #include "runtime/jniHandles.hpp" |
duke@435 | 35 | |
ysr@888 | 36 | ReferencePolicy* ReferenceProcessor::_always_clear_soft_ref_policy = NULL; |
ysr@888 | 37 | ReferencePolicy* ReferenceProcessor::_default_soft_ref_policy = NULL; |
ysr@888 | 38 | oop ReferenceProcessor::_sentinelRef = NULL; |
ysr@888 | 39 | const int subclasses_of_ref = REF_PHANTOM - REF_OTHER; |
ysr@888 | 40 | |
duke@435 | 41 | // List of discovered references. |
duke@435 | 42 | class DiscoveredList { |
duke@435 | 43 | public: |
coleenp@548 | 44 | DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { } |
coleenp@548 | 45 | oop head() const { |
coleenp@548 | 46 | return UseCompressedOops ? oopDesc::decode_heap_oop_not_null(_compressed_head) : |
coleenp@548 | 47 | _oop_head; |
coleenp@548 | 48 | } |
coleenp@548 | 49 | HeapWord* adr_head() { |
coleenp@548 | 50 | return UseCompressedOops ? (HeapWord*)&_compressed_head : |
coleenp@548 | 51 | (HeapWord*)&_oop_head; |
coleenp@548 | 52 | } |
coleenp@548 | 53 | void set_head(oop o) { |
coleenp@548 | 54 | if (UseCompressedOops) { |
coleenp@548 | 55 | // Must compress the head ptr. |
coleenp@548 | 56 | _compressed_head = oopDesc::encode_heap_oop_not_null(o); |
coleenp@548 | 57 | } else { |
coleenp@548 | 58 | _oop_head = o; |
coleenp@548 | 59 | } |
coleenp@548 | 60 | } |
coleenp@548 | 61 | bool empty() const { return head() == ReferenceProcessor::sentinel_ref(); } |
duke@435 | 62 | size_t length() { return _len; } |
ysr@887 | 63 | void set_length(size_t len) { _len = len; } |
ysr@887 | 64 | void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); } |
ysr@887 | 65 | void dec_length(size_t dec) { _len -= dec; } |
duke@435 | 66 | private: |
coleenp@548 | 67 | // Set value depending on UseCompressedOops. This could be a template class |
coleenp@548 | 68 | // but then we have to fix all the instantiations and declarations that use this class. |
coleenp@548 | 69 | oop _oop_head; |
coleenp@548 | 70 | narrowOop _compressed_head; |
duke@435 | 71 | size_t _len; |
duke@435 | 72 | }; |
duke@435 | 73 | |
duke@435 | 74 | void referenceProcessor_init() { |
duke@435 | 75 | ReferenceProcessor::init_statics(); |
duke@435 | 76 | } |
duke@435 | 77 | |
duke@435 | 78 | void ReferenceProcessor::init_statics() { |
coleenp@548 | 79 | assert(_sentinelRef == NULL, "should be initialized precisely once"); |
duke@435 | 80 | EXCEPTION_MARK; |
duke@435 | 81 | _sentinelRef = instanceKlass::cast( |
never@1577 | 82 | SystemDictionary::Reference_klass())-> |
coleenp@548 | 83 | allocate_permanent_instance(THREAD); |
duke@435 | 84 | |
duke@435 | 85 | // Initialize the master soft ref clock. |
duke@435 | 86 | java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); |
duke@435 | 87 | |
duke@435 | 88 | if (HAS_PENDING_EXCEPTION) { |
duke@435 | 89 | Handle ex(THREAD, PENDING_EXCEPTION); |
duke@435 | 90 | vm_exit_during_initialization(ex); |
duke@435 | 91 | } |
duke@435 | 92 | assert(_sentinelRef != NULL && _sentinelRef->is_oop(), |
duke@435 | 93 | "Just constructed it!"); |
ysr@888 | 94 | _always_clear_soft_ref_policy = new AlwaysClearPolicy(); |
ysr@888 | 95 | _default_soft_ref_policy = new COMPILER2_PRESENT(LRUMaxHeapPolicy()) |
ysr@888 | 96 | NOT_COMPILER2(LRUCurrentHeapPolicy()); |
ysr@888 | 97 | if (_always_clear_soft_ref_policy == NULL || _default_soft_ref_policy == NULL) { |
ysr@888 | 98 | vm_exit_during_initialization("Could not allocate reference policy object"); |
ysr@888 | 99 | } |
duke@435 | 100 | guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
duke@435 | 101 | RefDiscoveryPolicy == ReferentBasedDiscovery, |
duke@435 | 102 | "Unrecongnized RefDiscoveryPolicy"); |
duke@435 | 103 | } |
duke@435 | 104 | |
coleenp@548 | 105 | ReferenceProcessor* |
coleenp@548 | 106 | ReferenceProcessor::create_ref_processor(MemRegion span, |
coleenp@548 | 107 | bool atomic_discovery, |
coleenp@548 | 108 | bool mt_discovery, |
coleenp@548 | 109 | BoolObjectClosure* is_alive_non_header, |
coleenp@548 | 110 | int parallel_gc_threads, |
ysr@777 | 111 | bool mt_processing, |
ysr@777 | 112 | bool dl_needs_barrier) { |
duke@435 | 113 | int mt_degree = 1; |
duke@435 | 114 | if (parallel_gc_threads > 1) { |
duke@435 | 115 | mt_degree = parallel_gc_threads; |
duke@435 | 116 | } |
duke@435 | 117 | ReferenceProcessor* rp = |
duke@435 | 118 | new ReferenceProcessor(span, atomic_discovery, |
duke@435 | 119 | mt_discovery, mt_degree, |
ysr@777 | 120 | mt_processing && (parallel_gc_threads > 0), |
ysr@777 | 121 | dl_needs_barrier); |
duke@435 | 122 | if (rp == NULL) { |
duke@435 | 123 | vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); |
duke@435 | 124 | } |
duke@435 | 125 | rp->set_is_alive_non_header(is_alive_non_header); |
ysr@892 | 126 | rp->setup_policy(false /* default soft ref policy */); |
duke@435 | 127 | return rp; |
duke@435 | 128 | } |
duke@435 | 129 | |
duke@435 | 130 | ReferenceProcessor::ReferenceProcessor(MemRegion span, |
coleenp@548 | 131 | bool atomic_discovery, |
coleenp@548 | 132 | bool mt_discovery, |
coleenp@548 | 133 | int mt_degree, |
ysr@777 | 134 | bool mt_processing, |
ysr@777 | 135 | bool discovered_list_needs_barrier) : |
duke@435 | 136 | _discovering_refs(false), |
duke@435 | 137 | _enqueuing_is_done(false), |
duke@435 | 138 | _is_alive_non_header(NULL), |
ysr@777 | 139 | _discovered_list_needs_barrier(discovered_list_needs_barrier), |
ysr@777 | 140 | _bs(NULL), |
duke@435 | 141 | _processing_is_mt(mt_processing), |
duke@435 | 142 | _next_id(0) |
duke@435 | 143 | { |
duke@435 | 144 | _span = span; |
duke@435 | 145 | _discovery_is_atomic = atomic_discovery; |
duke@435 | 146 | _discovery_is_mt = mt_discovery; |
duke@435 | 147 | _num_q = mt_degree; |
jmasa@2188 | 148 | _max_num_q = mt_degree; |
jmasa@2188 | 149 | _discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, _max_num_q * subclasses_of_ref); |
duke@435 | 150 | if (_discoveredSoftRefs == NULL) { |
duke@435 | 151 | vm_exit_during_initialization("Could not allocated RefProc Array"); |
duke@435 | 152 | } |
jmasa@2188 | 153 | _discoveredWeakRefs = &_discoveredSoftRefs[_max_num_q]; |
jmasa@2188 | 154 | _discoveredFinalRefs = &_discoveredWeakRefs[_max_num_q]; |
jmasa@2188 | 155 | _discoveredPhantomRefs = &_discoveredFinalRefs[_max_num_q]; |
coleenp@548 | 156 | assert(sentinel_ref() != NULL, "_sentinelRef is NULL"); |
duke@435 | 157 | // Initialized all entries to _sentinelRef |
jmasa@2188 | 158 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
coleenp@548 | 159 | _discoveredSoftRefs[i].set_head(sentinel_ref()); |
duke@435 | 160 | _discoveredSoftRefs[i].set_length(0); |
duke@435 | 161 | } |
ysr@777 | 162 | // If we do barreirs, cache a copy of the barrier set. |
ysr@777 | 163 | if (discovered_list_needs_barrier) { |
ysr@777 | 164 | _bs = Universe::heap()->barrier_set(); |
ysr@777 | 165 | } |
duke@435 | 166 | } |
duke@435 | 167 | |
duke@435 | 168 | #ifndef PRODUCT |
duke@435 | 169 | void ReferenceProcessor::verify_no_references_recorded() { |
duke@435 | 170 | guarantee(!_discovering_refs, "Discovering refs?"); |
jmasa@2188 | 171 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
duke@435 | 172 | guarantee(_discoveredSoftRefs[i].empty(), |
duke@435 | 173 | "Found non-empty discovered list"); |
duke@435 | 174 | } |
duke@435 | 175 | } |
duke@435 | 176 | #endif |
duke@435 | 177 | |
duke@435 | 178 | void ReferenceProcessor::weak_oops_do(OopClosure* f) { |
jmasa@2188 | 179 | // Should this instead be |
jmasa@2188 | 180 | // for (int i = 0; i < subclasses_of_ref; i++_ { |
jmasa@2188 | 181 | // for (int j = 0; j < _num_q; j++) { |
jmasa@2188 | 182 | // int index = i * _max_num_q + j; |
jmasa@2188 | 183 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
coleenp@548 | 184 | if (UseCompressedOops) { |
coleenp@548 | 185 | f->do_oop((narrowOop*)_discoveredSoftRefs[i].adr_head()); |
coleenp@548 | 186 | } else { |
coleenp@548 | 187 | f->do_oop((oop*)_discoveredSoftRefs[i].adr_head()); |
coleenp@548 | 188 | } |
duke@435 | 189 | } |
duke@435 | 190 | } |
duke@435 | 191 | |
duke@435 | 192 | void ReferenceProcessor::oops_do(OopClosure* f) { |
coleenp@548 | 193 | f->do_oop(adr_sentinel_ref()); |
duke@435 | 194 | } |
duke@435 | 195 | |
coleenp@548 | 196 | void ReferenceProcessor::update_soft_ref_master_clock() { |
duke@435 | 197 | // Update (advance) the soft ref master clock field. This must be done |
duke@435 | 198 | // after processing the soft ref list. |
duke@435 | 199 | jlong now = os::javaTimeMillis(); |
duke@435 | 200 | jlong clock = java_lang_ref_SoftReference::clock(); |
duke@435 | 201 | NOT_PRODUCT( |
duke@435 | 202 | if (now < clock) { |
duke@435 | 203 | warning("time warp: %d to %d", clock, now); |
duke@435 | 204 | } |
duke@435 | 205 | ) |
duke@435 | 206 | // In product mode, protect ourselves from system time being adjusted |
duke@435 | 207 | // externally and going backward; see note in the implementation of |
duke@435 | 208 | // GenCollectedHeap::time_since_last_gc() for the right way to fix |
duke@435 | 209 | // this uniformly throughout the VM; see bug-id 4741166. XXX |
duke@435 | 210 | if (now > clock) { |
duke@435 | 211 | java_lang_ref_SoftReference::set_clock(now); |
duke@435 | 212 | } |
duke@435 | 213 | // Else leave clock stalled at its old value until time progresses |
duke@435 | 214 | // past clock value. |
duke@435 | 215 | } |
duke@435 | 216 | |
coleenp@548 | 217 | void ReferenceProcessor::process_discovered_references( |
duke@435 | 218 | BoolObjectClosure* is_alive, |
duke@435 | 219 | OopClosure* keep_alive, |
duke@435 | 220 | VoidClosure* complete_gc, |
duke@435 | 221 | AbstractRefProcTaskExecutor* task_executor) { |
duke@435 | 222 | NOT_PRODUCT(verify_ok_to_handle_reflists()); |
duke@435 | 223 | |
duke@435 | 224 | assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); |
duke@435 | 225 | // Stop treating discovered references specially. |
duke@435 | 226 | disable_discovery(); |
duke@435 | 227 | |
duke@435 | 228 | bool trace_time = PrintGCDetails && PrintReferenceGC; |
duke@435 | 229 | // Soft references |
duke@435 | 230 | { |
duke@435 | 231 | TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); |
ysr@888 | 232 | process_discovered_reflist(_discoveredSoftRefs, _current_soft_ref_policy, true, |
duke@435 | 233 | is_alive, keep_alive, complete_gc, task_executor); |
duke@435 | 234 | } |
duke@435 | 235 | |
duke@435 | 236 | update_soft_ref_master_clock(); |
duke@435 | 237 | |
duke@435 | 238 | // Weak references |
duke@435 | 239 | { |
duke@435 | 240 | TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); |
duke@435 | 241 | process_discovered_reflist(_discoveredWeakRefs, NULL, true, |
duke@435 | 242 | is_alive, keep_alive, complete_gc, task_executor); |
duke@435 | 243 | } |
duke@435 | 244 | |
duke@435 | 245 | // Final references |
duke@435 | 246 | { |
duke@435 | 247 | TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); |
duke@435 | 248 | process_discovered_reflist(_discoveredFinalRefs, NULL, false, |
duke@435 | 249 | is_alive, keep_alive, complete_gc, task_executor); |
duke@435 | 250 | } |
duke@435 | 251 | |
duke@435 | 252 | // Phantom references |
duke@435 | 253 | { |
duke@435 | 254 | TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); |
duke@435 | 255 | process_discovered_reflist(_discoveredPhantomRefs, NULL, false, |
duke@435 | 256 | is_alive, keep_alive, complete_gc, task_executor); |
duke@435 | 257 | } |
duke@435 | 258 | |
duke@435 | 259 | // Weak global JNI references. It would make more sense (semantically) to |
duke@435 | 260 | // traverse these simultaneously with the regular weak references above, but |
duke@435 | 261 | // that is not how the JDK1.2 specification is. See #4126360. Native code can |
duke@435 | 262 | // thus use JNI weak references to circumvent the phantom references and |
duke@435 | 263 | // resurrect a "post-mortem" object. |
duke@435 | 264 | { |
duke@435 | 265 | TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); |
duke@435 | 266 | if (task_executor != NULL) { |
duke@435 | 267 | task_executor->set_single_threaded_mode(); |
duke@435 | 268 | } |
duke@435 | 269 | process_phaseJNI(is_alive, keep_alive, complete_gc); |
duke@435 | 270 | } |
duke@435 | 271 | } |
duke@435 | 272 | |
duke@435 | 273 | #ifndef PRODUCT |
duke@435 | 274 | // Calculate the number of jni handles. |
coleenp@548 | 275 | uint ReferenceProcessor::count_jni_refs() { |
duke@435 | 276 | class AlwaysAliveClosure: public BoolObjectClosure { |
duke@435 | 277 | public: |
coleenp@548 | 278 | virtual bool do_object_b(oop obj) { return true; } |
coleenp@548 | 279 | virtual void do_object(oop obj) { assert(false, "Don't call"); } |
duke@435 | 280 | }; |
duke@435 | 281 | |
duke@435 | 282 | class CountHandleClosure: public OopClosure { |
duke@435 | 283 | private: |
duke@435 | 284 | int _count; |
duke@435 | 285 | public: |
duke@435 | 286 | CountHandleClosure(): _count(0) {} |
coleenp@548 | 287 | void do_oop(oop* unused) { _count++; } |
coleenp@548 | 288 | void do_oop(narrowOop* unused) { ShouldNotReachHere(); } |
duke@435 | 289 | int count() { return _count; } |
duke@435 | 290 | }; |
duke@435 | 291 | CountHandleClosure global_handle_count; |
duke@435 | 292 | AlwaysAliveClosure always_alive; |
duke@435 | 293 | JNIHandles::weak_oops_do(&always_alive, &global_handle_count); |
duke@435 | 294 | return global_handle_count.count(); |
duke@435 | 295 | } |
duke@435 | 296 | #endif |
duke@435 | 297 | |
duke@435 | 298 | void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, |
duke@435 | 299 | OopClosure* keep_alive, |
duke@435 | 300 | VoidClosure* complete_gc) { |
duke@435 | 301 | #ifndef PRODUCT |
duke@435 | 302 | if (PrintGCDetails && PrintReferenceGC) { |
duke@435 | 303 | unsigned int count = count_jni_refs(); |
duke@435 | 304 | gclog_or_tty->print(", %u refs", count); |
duke@435 | 305 | } |
duke@435 | 306 | #endif |
duke@435 | 307 | JNIHandles::weak_oops_do(is_alive, keep_alive); |
duke@435 | 308 | // Finally remember to keep sentinel around |
coleenp@548 | 309 | keep_alive->do_oop(adr_sentinel_ref()); |
duke@435 | 310 | complete_gc->do_void(); |
duke@435 | 311 | } |
duke@435 | 312 | |
coleenp@548 | 313 | |
coleenp@548 | 314 | template <class T> |
phh@1558 | 315 | bool enqueue_discovered_ref_helper(ReferenceProcessor* ref, |
phh@1558 | 316 | AbstractRefProcTaskExecutor* task_executor) { |
coleenp@548 | 317 | |
duke@435 | 318 | // Remember old value of pending references list |
coleenp@548 | 319 | T* pending_list_addr = (T*)java_lang_ref_Reference::pending_list_addr(); |
coleenp@548 | 320 | T old_pending_list_value = *pending_list_addr; |
duke@435 | 321 | |
duke@435 | 322 | // Enqueue references that are not made active again, and |
duke@435 | 323 | // clear the decks for the next collection (cycle). |
coleenp@548 | 324 | ref->enqueue_discovered_reflists((HeapWord*)pending_list_addr, task_executor); |
duke@435 | 325 | // Do the oop-check on pending_list_addr missed in |
duke@435 | 326 | // enqueue_discovered_reflist. We should probably |
duke@435 | 327 | // do a raw oop_check so that future such idempotent |
duke@435 | 328 | // oop_stores relying on the oop-check side-effect |
duke@435 | 329 | // may be elided automatically and safely without |
duke@435 | 330 | // affecting correctness. |
coleenp@548 | 331 | oop_store(pending_list_addr, oopDesc::load_decode_heap_oop(pending_list_addr)); |
duke@435 | 332 | |
duke@435 | 333 | // Stop treating discovered references specially. |
coleenp@548 | 334 | ref->disable_discovery(); |
duke@435 | 335 | |
duke@435 | 336 | // Return true if new pending references were added |
duke@435 | 337 | return old_pending_list_value != *pending_list_addr; |
duke@435 | 338 | } |
duke@435 | 339 | |
coleenp@548 | 340 | bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
coleenp@548 | 341 | NOT_PRODUCT(verify_ok_to_handle_reflists()); |
coleenp@548 | 342 | if (UseCompressedOops) { |
coleenp@548 | 343 | return enqueue_discovered_ref_helper<narrowOop>(this, task_executor); |
coleenp@548 | 344 | } else { |
coleenp@548 | 345 | return enqueue_discovered_ref_helper<oop>(this, task_executor); |
coleenp@548 | 346 | } |
coleenp@548 | 347 | } |
coleenp@548 | 348 | |
duke@435 | 349 | void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
coleenp@548 | 350 | HeapWord* pending_list_addr) { |
duke@435 | 351 | // Given a list of refs linked through the "discovered" field |
duke@435 | 352 | // (java.lang.ref.Reference.discovered) chain them through the |
duke@435 | 353 | // "next" field (java.lang.ref.Reference.next) and prepend |
duke@435 | 354 | // to the pending list. |
duke@435 | 355 | if (TraceReferenceGC && PrintGCDetails) { |
duke@435 | 356 | gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " |
duke@435 | 357 | INTPTR_FORMAT, (address)refs_list.head()); |
duke@435 | 358 | } |
duke@435 | 359 | oop obj = refs_list.head(); |
duke@435 | 360 | // Walk down the list, copying the discovered field into |
duke@435 | 361 | // the next field and clearing it (except for the last |
duke@435 | 362 | // non-sentinel object which is treated specially to avoid |
duke@435 | 363 | // confusion with an active reference). |
coleenp@548 | 364 | while (obj != sentinel_ref()) { |
duke@435 | 365 | assert(obj->is_instanceRef(), "should be reference object"); |
duke@435 | 366 | oop next = java_lang_ref_Reference::discovered(obj); |
duke@435 | 367 | if (TraceReferenceGC && PrintGCDetails) { |
coleenp@548 | 368 | gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next " INTPTR_FORMAT, |
coleenp@548 | 369 | obj, next); |
duke@435 | 370 | } |
coleenp@548 | 371 | assert(java_lang_ref_Reference::next(obj) == NULL, |
coleenp@548 | 372 | "The reference should not be enqueued"); |
coleenp@548 | 373 | if (next == sentinel_ref()) { // obj is last |
duke@435 | 374 | // Swap refs_list into pendling_list_addr and |
duke@435 | 375 | // set obj's next to what we read from pending_list_addr. |
coleenp@548 | 376 | oop old = oopDesc::atomic_exchange_oop(refs_list.head(), pending_list_addr); |
duke@435 | 377 | // Need oop_check on pending_list_addr above; |
duke@435 | 378 | // see special oop-check code at the end of |
duke@435 | 379 | // enqueue_discovered_reflists() further below. |
duke@435 | 380 | if (old == NULL) { |
duke@435 | 381 | // obj should be made to point to itself, since |
duke@435 | 382 | // pending list was empty. |
duke@435 | 383 | java_lang_ref_Reference::set_next(obj, obj); |
duke@435 | 384 | } else { |
duke@435 | 385 | java_lang_ref_Reference::set_next(obj, old); |
duke@435 | 386 | } |
duke@435 | 387 | } else { |
duke@435 | 388 | java_lang_ref_Reference::set_next(obj, next); |
duke@435 | 389 | } |
duke@435 | 390 | java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
duke@435 | 391 | obj = next; |
duke@435 | 392 | } |
duke@435 | 393 | } |
duke@435 | 394 | |
duke@435 | 395 | // Parallel enqueue task |
duke@435 | 396 | class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { |
duke@435 | 397 | public: |
duke@435 | 398 | RefProcEnqueueTask(ReferenceProcessor& ref_processor, |
duke@435 | 399 | DiscoveredList discovered_refs[], |
coleenp@548 | 400 | HeapWord* pending_list_addr, |
duke@435 | 401 | oop sentinel_ref, |
duke@435 | 402 | int n_queues) |
duke@435 | 403 | : EnqueueTask(ref_processor, discovered_refs, |
duke@435 | 404 | pending_list_addr, sentinel_ref, n_queues) |
duke@435 | 405 | { } |
duke@435 | 406 | |
coleenp@548 | 407 | virtual void work(unsigned int work_id) { |
duke@435 | 408 | assert(work_id < (unsigned int)_ref_processor.num_q(), "Index out-of-bounds"); |
duke@435 | 409 | // Simplest first cut: static partitioning. |
duke@435 | 410 | int index = work_id; |
jmasa@2188 | 411 | // The increment on "index" must correspond to the maximum number of queues |
jmasa@2188 | 412 | // (n_queues) with which that ReferenceProcessor was created. That |
jmasa@2188 | 413 | // is because of the "clever" way the discovered references lists were |
jmasa@2188 | 414 | // allocated and are indexed into. That number is ParallelGCThreads |
jmasa@2188 | 415 | // currently. Assert that. |
jmasa@2188 | 416 | assert(_n_queues == (int) ParallelGCThreads, "Different number not expected"); |
jmasa@2188 | 417 | for (int j = 0; |
jmasa@2188 | 418 | j < subclasses_of_ref; |
jmasa@2188 | 419 | j++, index += _n_queues) { |
duke@435 | 420 | _ref_processor.enqueue_discovered_reflist( |
duke@435 | 421 | _refs_lists[index], _pending_list_addr); |
duke@435 | 422 | _refs_lists[index].set_head(_sentinel_ref); |
duke@435 | 423 | _refs_lists[index].set_length(0); |
duke@435 | 424 | } |
duke@435 | 425 | } |
duke@435 | 426 | }; |
duke@435 | 427 | |
duke@435 | 428 | // Enqueue references that are not made active again |
coleenp@548 | 429 | void ReferenceProcessor::enqueue_discovered_reflists(HeapWord* pending_list_addr, |
duke@435 | 430 | AbstractRefProcTaskExecutor* task_executor) { |
duke@435 | 431 | if (_processing_is_mt && task_executor != NULL) { |
duke@435 | 432 | // Parallel code |
duke@435 | 433 | RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, |
jmasa@2188 | 434 | pending_list_addr, sentinel_ref(), _max_num_q); |
duke@435 | 435 | task_executor->execute(tsk); |
duke@435 | 436 | } else { |
duke@435 | 437 | // Serial code: call the parent class's implementation |
jmasa@2188 | 438 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
duke@435 | 439 | enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
coleenp@548 | 440 | _discoveredSoftRefs[i].set_head(sentinel_ref()); |
duke@435 | 441 | _discoveredSoftRefs[i].set_length(0); |
duke@435 | 442 | } |
duke@435 | 443 | } |
duke@435 | 444 | } |
duke@435 | 445 | |
duke@435 | 446 | // Iterator for the list of discovered references. |
duke@435 | 447 | class DiscoveredListIterator { |
duke@435 | 448 | public: |
duke@435 | 449 | inline DiscoveredListIterator(DiscoveredList& refs_list, |
duke@435 | 450 | OopClosure* keep_alive, |
duke@435 | 451 | BoolObjectClosure* is_alive); |
duke@435 | 452 | |
duke@435 | 453 | // End Of List. |
coleenp@548 | 454 | inline bool has_next() const { return _next != ReferenceProcessor::sentinel_ref(); } |
duke@435 | 455 | |
duke@435 | 456 | // Get oop to the Reference object. |
coleenp@548 | 457 | inline oop obj() const { return _ref; } |
duke@435 | 458 | |
duke@435 | 459 | // Get oop to the referent object. |
coleenp@548 | 460 | inline oop referent() const { return _referent; } |
duke@435 | 461 | |
duke@435 | 462 | // Returns true if referent is alive. |
duke@435 | 463 | inline bool is_referent_alive() const; |
duke@435 | 464 | |
duke@435 | 465 | // Loads data for the current reference. |
duke@435 | 466 | // The "allow_null_referent" argument tells us to allow for the possibility |
duke@435 | 467 | // of a NULL referent in the discovered Reference object. This typically |
duke@435 | 468 | // happens in the case of concurrent collectors that may have done the |
ysr@887 | 469 | // discovery concurrently, or interleaved, with mutator execution. |
duke@435 | 470 | inline void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); |
duke@435 | 471 | |
duke@435 | 472 | // Move to the next discovered reference. |
duke@435 | 473 | inline void next(); |
duke@435 | 474 | |
ysr@887 | 475 | // Remove the current reference from the list |
duke@435 | 476 | inline void remove(); |
duke@435 | 477 | |
duke@435 | 478 | // Make the Reference object active again. |
duke@435 | 479 | inline void make_active() { java_lang_ref_Reference::set_next(_ref, NULL); } |
duke@435 | 480 | |
duke@435 | 481 | // Make the referent alive. |
coleenp@548 | 482 | inline void make_referent_alive() { |
coleenp@548 | 483 | if (UseCompressedOops) { |
coleenp@548 | 484 | _keep_alive->do_oop((narrowOop*)_referent_addr); |
coleenp@548 | 485 | } else { |
coleenp@548 | 486 | _keep_alive->do_oop((oop*)_referent_addr); |
coleenp@548 | 487 | } |
coleenp@548 | 488 | } |
duke@435 | 489 | |
duke@435 | 490 | // Update the discovered field. |
coleenp@548 | 491 | inline void update_discovered() { |
coleenp@548 | 492 | // First _prev_next ref actually points into DiscoveredList (gross). |
coleenp@548 | 493 | if (UseCompressedOops) { |
coleenp@548 | 494 | _keep_alive->do_oop((narrowOop*)_prev_next); |
coleenp@548 | 495 | } else { |
coleenp@548 | 496 | _keep_alive->do_oop((oop*)_prev_next); |
coleenp@548 | 497 | } |
coleenp@548 | 498 | } |
duke@435 | 499 | |
duke@435 | 500 | // NULL out referent pointer. |
coleenp@548 | 501 | inline void clear_referent() { oop_store_raw(_referent_addr, NULL); } |
duke@435 | 502 | |
duke@435 | 503 | // Statistics |
duke@435 | 504 | NOT_PRODUCT( |
duke@435 | 505 | inline size_t processed() const { return _processed; } |
duke@435 | 506 | inline size_t removed() const { return _removed; } |
duke@435 | 507 | ) |
duke@435 | 508 | |
duke@435 | 509 | inline void move_to_next(); |
duke@435 | 510 | |
duke@435 | 511 | private: |
duke@435 | 512 | DiscoveredList& _refs_list; |
coleenp@548 | 513 | HeapWord* _prev_next; |
duke@435 | 514 | oop _ref; |
coleenp@548 | 515 | HeapWord* _discovered_addr; |
duke@435 | 516 | oop _next; |
coleenp@548 | 517 | HeapWord* _referent_addr; |
duke@435 | 518 | oop _referent; |
duke@435 | 519 | OopClosure* _keep_alive; |
duke@435 | 520 | BoolObjectClosure* _is_alive; |
duke@435 | 521 | DEBUG_ONLY( |
duke@435 | 522 | oop _first_seen; // cyclic linked list check |
duke@435 | 523 | ) |
duke@435 | 524 | NOT_PRODUCT( |
duke@435 | 525 | size_t _processed; |
duke@435 | 526 | size_t _removed; |
duke@435 | 527 | ) |
duke@435 | 528 | }; |
duke@435 | 529 | |
duke@435 | 530 | inline DiscoveredListIterator::DiscoveredListIterator(DiscoveredList& refs_list, |
duke@435 | 531 | OopClosure* keep_alive, |
duke@435 | 532 | BoolObjectClosure* is_alive) |
duke@435 | 533 | : _refs_list(refs_list), |
coleenp@548 | 534 | _prev_next(refs_list.adr_head()), |
duke@435 | 535 | _ref(refs_list.head()), |
duke@435 | 536 | #ifdef ASSERT |
duke@435 | 537 | _first_seen(refs_list.head()), |
duke@435 | 538 | #endif |
duke@435 | 539 | #ifndef PRODUCT |
duke@435 | 540 | _processed(0), |
duke@435 | 541 | _removed(0), |
duke@435 | 542 | #endif |
duke@435 | 543 | _next(refs_list.head()), |
duke@435 | 544 | _keep_alive(keep_alive), |
duke@435 | 545 | _is_alive(is_alive) |
duke@435 | 546 | { } |
duke@435 | 547 | |
coleenp@548 | 548 | inline bool DiscoveredListIterator::is_referent_alive() const { |
duke@435 | 549 | return _is_alive->do_object_b(_referent); |
duke@435 | 550 | } |
duke@435 | 551 | |
coleenp@548 | 552 | inline void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) { |
duke@435 | 553 | _discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
coleenp@548 | 554 | oop discovered = java_lang_ref_Reference::discovered(_ref); |
coleenp@548 | 555 | assert(_discovered_addr && discovered->is_oop_or_null(), |
duke@435 | 556 | "discovered field is bad"); |
coleenp@548 | 557 | _next = discovered; |
duke@435 | 558 | _referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
coleenp@548 | 559 | _referent = java_lang_ref_Reference::referent(_ref); |
duke@435 | 560 | assert(Universe::heap()->is_in_reserved_or_null(_referent), |
duke@435 | 561 | "Wrong oop found in java.lang.Reference object"); |
duke@435 | 562 | assert(allow_null_referent ? |
duke@435 | 563 | _referent->is_oop_or_null() |
duke@435 | 564 | : _referent->is_oop(), |
duke@435 | 565 | "bad referent"); |
duke@435 | 566 | } |
duke@435 | 567 | |
coleenp@548 | 568 | inline void DiscoveredListIterator::next() { |
duke@435 | 569 | _prev_next = _discovered_addr; |
duke@435 | 570 | move_to_next(); |
duke@435 | 571 | } |
duke@435 | 572 | |
coleenp@548 | 573 | inline void DiscoveredListIterator::remove() { |
duke@435 | 574 | assert(_ref->is_oop(), "Dropping a bad reference"); |
coleenp@548 | 575 | oop_store_raw(_discovered_addr, NULL); |
coleenp@548 | 576 | // First _prev_next ref actually points into DiscoveredList (gross). |
coleenp@548 | 577 | if (UseCompressedOops) { |
coleenp@548 | 578 | // Remove Reference object from list. |
coleenp@548 | 579 | oopDesc::encode_store_heap_oop_not_null((narrowOop*)_prev_next, _next); |
coleenp@548 | 580 | } else { |
coleenp@548 | 581 | // Remove Reference object from list. |
coleenp@548 | 582 | oopDesc::store_heap_oop((oop*)_prev_next, _next); |
coleenp@548 | 583 | } |
duke@435 | 584 | NOT_PRODUCT(_removed++); |
ysr@887 | 585 | _refs_list.dec_length(1); |
duke@435 | 586 | } |
duke@435 | 587 | |
coleenp@548 | 588 | inline void DiscoveredListIterator::move_to_next() { |
duke@435 | 589 | _ref = _next; |
duke@435 | 590 | assert(_ref != _first_seen, "cyclic ref_list found"); |
duke@435 | 591 | NOT_PRODUCT(_processed++); |
duke@435 | 592 | } |
duke@435 | 593 | |
duke@435 | 594 | // NOTE: process_phase*() are largely similar, and at a high level |
duke@435 | 595 | // merely iterate over the extant list applying a predicate to |
duke@435 | 596 | // each of its elements and possibly removing that element from the |
duke@435 | 597 | // list and applying some further closures to that element. |
duke@435 | 598 | // We should consider the possibility of replacing these |
duke@435 | 599 | // process_phase*() methods by abstracting them into |
duke@435 | 600 | // a single general iterator invocation that receives appropriate |
duke@435 | 601 | // closures that accomplish this work. |
duke@435 | 602 | |
duke@435 | 603 | // (SoftReferences only) Traverse the list and remove any SoftReferences whose |
duke@435 | 604 | // referents are not alive, but that should be kept alive for policy reasons. |
duke@435 | 605 | // Keep alive the transitive closure of all such referents. |
duke@435 | 606 | void |
coleenp@548 | 607 | ReferenceProcessor::process_phase1(DiscoveredList& refs_list, |
duke@435 | 608 | ReferencePolicy* policy, |
duke@435 | 609 | BoolObjectClosure* is_alive, |
duke@435 | 610 | OopClosure* keep_alive, |
duke@435 | 611 | VoidClosure* complete_gc) { |
duke@435 | 612 | assert(policy != NULL, "Must have a non-NULL policy"); |
coleenp@548 | 613 | DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
duke@435 | 614 | // Decide which softly reachable refs should be kept alive. |
duke@435 | 615 | while (iter.has_next()) { |
duke@435 | 616 | iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); |
duke@435 | 617 | bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); |
duke@435 | 618 | if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { |
duke@435 | 619 | if (TraceReferenceGC) { |
duke@435 | 620 | gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", |
coleenp@548 | 621 | iter.obj(), iter.obj()->blueprint()->internal_name()); |
duke@435 | 622 | } |
ysr@887 | 623 | // Remove Reference object from list |
ysr@887 | 624 | iter.remove(); |
duke@435 | 625 | // Make the Reference object active again |
duke@435 | 626 | iter.make_active(); |
duke@435 | 627 | // keep the referent around |
duke@435 | 628 | iter.make_referent_alive(); |
ysr@887 | 629 | iter.move_to_next(); |
duke@435 | 630 | } else { |
duke@435 | 631 | iter.next(); |
duke@435 | 632 | } |
duke@435 | 633 | } |
duke@435 | 634 | // Close the reachable set |
duke@435 | 635 | complete_gc->do_void(); |
duke@435 | 636 | NOT_PRODUCT( |
duke@435 | 637 | if (PrintGCDetails && TraceReferenceGC) { |
jmasa@2188 | 638 | gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d " |
jmasa@2188 | 639 | "discovered Refs by policy list " INTPTR_FORMAT, |
jmasa@2188 | 640 | iter.removed(), iter.processed(), (address)refs_list.head()); |
duke@435 | 641 | } |
duke@435 | 642 | ) |
duke@435 | 643 | } |
duke@435 | 644 | |
duke@435 | 645 | // Traverse the list and remove any Refs that are not active, or |
duke@435 | 646 | // whose referents are either alive or NULL. |
duke@435 | 647 | void |
coleenp@548 | 648 | ReferenceProcessor::pp2_work(DiscoveredList& refs_list, |
duke@435 | 649 | BoolObjectClosure* is_alive, |
coleenp@548 | 650 | OopClosure* keep_alive) { |
duke@435 | 651 | assert(discovery_is_atomic(), "Error"); |
coleenp@548 | 652 | DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
duke@435 | 653 | while (iter.has_next()) { |
duke@435 | 654 | iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
coleenp@548 | 655 | DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());) |
coleenp@548 | 656 | assert(next == NULL, "Should not discover inactive Reference"); |
duke@435 | 657 | if (iter.is_referent_alive()) { |
duke@435 | 658 | if (TraceReferenceGC) { |
duke@435 | 659 | gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", |
coleenp@548 | 660 | iter.obj(), iter.obj()->blueprint()->internal_name()); |
duke@435 | 661 | } |
duke@435 | 662 | // The referent is reachable after all. |
ysr@887 | 663 | // Remove Reference object from list. |
ysr@887 | 664 | iter.remove(); |
duke@435 | 665 | // Update the referent pointer as necessary: Note that this |
duke@435 | 666 | // should not entail any recursive marking because the |
duke@435 | 667 | // referent must already have been traversed. |
duke@435 | 668 | iter.make_referent_alive(); |
ysr@887 | 669 | iter.move_to_next(); |
duke@435 | 670 | } else { |
duke@435 | 671 | iter.next(); |
duke@435 | 672 | } |
duke@435 | 673 | } |
duke@435 | 674 | NOT_PRODUCT( |
duke@435 | 675 | if (PrintGCDetails && TraceReferenceGC) { |
jmasa@2188 | 676 | gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
jmasa@2188 | 677 | "Refs in discovered list " INTPTR_FORMAT, |
jmasa@2188 | 678 | iter.removed(), iter.processed(), (address)refs_list.head()); |
duke@435 | 679 | } |
duke@435 | 680 | ) |
duke@435 | 681 | } |
duke@435 | 682 | |
duke@435 | 683 | void |
coleenp@548 | 684 | ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list, |
coleenp@548 | 685 | BoolObjectClosure* is_alive, |
coleenp@548 | 686 | OopClosure* keep_alive, |
coleenp@548 | 687 | VoidClosure* complete_gc) { |
duke@435 | 688 | assert(!discovery_is_atomic(), "Error"); |
coleenp@548 | 689 | DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
duke@435 | 690 | while (iter.has_next()) { |
duke@435 | 691 | iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
coleenp@548 | 692 | HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
coleenp@548 | 693 | oop next = java_lang_ref_Reference::next(iter.obj()); |
duke@435 | 694 | if ((iter.referent() == NULL || iter.is_referent_alive() || |
coleenp@548 | 695 | next != NULL)) { |
coleenp@548 | 696 | assert(next->is_oop_or_null(), "bad next field"); |
duke@435 | 697 | // Remove Reference object from list |
duke@435 | 698 | iter.remove(); |
duke@435 | 699 | // Trace the cohorts |
duke@435 | 700 | iter.make_referent_alive(); |
coleenp@548 | 701 | if (UseCompressedOops) { |
coleenp@548 | 702 | keep_alive->do_oop((narrowOop*)next_addr); |
coleenp@548 | 703 | } else { |
coleenp@548 | 704 | keep_alive->do_oop((oop*)next_addr); |
coleenp@548 | 705 | } |
ysr@887 | 706 | iter.move_to_next(); |
duke@435 | 707 | } else { |
duke@435 | 708 | iter.next(); |
duke@435 | 709 | } |
duke@435 | 710 | } |
duke@435 | 711 | // Now close the newly reachable set |
duke@435 | 712 | complete_gc->do_void(); |
duke@435 | 713 | NOT_PRODUCT( |
duke@435 | 714 | if (PrintGCDetails && TraceReferenceGC) { |
jmasa@2188 | 715 | gclog_or_tty->print_cr(" Dropped %d active Refs out of %d " |
jmasa@2188 | 716 | "Refs in discovered list " INTPTR_FORMAT, |
jmasa@2188 | 717 | iter.removed(), iter.processed(), (address)refs_list.head()); |
duke@435 | 718 | } |
duke@435 | 719 | ) |
duke@435 | 720 | } |
duke@435 | 721 | |
duke@435 | 722 | // Traverse the list and process the referents, by either |
coleenp@548 | 723 | // clearing them or keeping them (and their reachable |
duke@435 | 724 | // closure) alive. |
duke@435 | 725 | void |
coleenp@548 | 726 | ReferenceProcessor::process_phase3(DiscoveredList& refs_list, |
duke@435 | 727 | bool clear_referent, |
duke@435 | 728 | BoolObjectClosure* is_alive, |
duke@435 | 729 | OopClosure* keep_alive, |
duke@435 | 730 | VoidClosure* complete_gc) { |
jmasa@2188 | 731 | ResourceMark rm; |
coleenp@548 | 732 | DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
duke@435 | 733 | while (iter.has_next()) { |
duke@435 | 734 | iter.update_discovered(); |
duke@435 | 735 | iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
duke@435 | 736 | if (clear_referent) { |
duke@435 | 737 | // NULL out referent pointer |
duke@435 | 738 | iter.clear_referent(); |
duke@435 | 739 | } else { |
duke@435 | 740 | // keep the referent around |
duke@435 | 741 | iter.make_referent_alive(); |
duke@435 | 742 | } |
duke@435 | 743 | if (TraceReferenceGC) { |
duke@435 | 744 | gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", |
duke@435 | 745 | clear_referent ? "cleared " : "", |
coleenp@548 | 746 | iter.obj(), iter.obj()->blueprint()->internal_name()); |
duke@435 | 747 | } |
duke@435 | 748 | assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); |
duke@435 | 749 | iter.next(); |
duke@435 | 750 | } |
duke@435 | 751 | // Remember to keep sentinel pointer around |
duke@435 | 752 | iter.update_discovered(); |
duke@435 | 753 | // Close the reachable set |
duke@435 | 754 | complete_gc->do_void(); |
duke@435 | 755 | } |
duke@435 | 756 | |
duke@435 | 757 | void |
coleenp@548 | 758 | ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& refs_list) { |
coleenp@548 | 759 | oop obj = refs_list.head(); |
coleenp@548 | 760 | while (obj != sentinel_ref()) { |
coleenp@548 | 761 | oop discovered = java_lang_ref_Reference::discovered(obj); |
coleenp@548 | 762 | java_lang_ref_Reference::set_discovered_raw(obj, NULL); |
coleenp@548 | 763 | obj = discovered; |
duke@435 | 764 | } |
coleenp@548 | 765 | refs_list.set_head(sentinel_ref()); |
coleenp@548 | 766 | refs_list.set_length(0); |
duke@435 | 767 | } |
duke@435 | 768 | |
ysr@777 | 769 | void ReferenceProcessor::abandon_partial_discovery() { |
ysr@777 | 770 | // loop over the lists |
jmasa@2188 | 771 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
jmasa@2188 | 772 | if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) { |
johnc@2316 | 773 | gclog_or_tty->print_cr("\nAbandoning %s discovered list", |
johnc@2316 | 774 | list_name(i)); |
ysr@777 | 775 | } |
ysr@777 | 776 | abandon_partial_discovered_list(_discoveredSoftRefs[i]); |
duke@435 | 777 | } |
duke@435 | 778 | } |
duke@435 | 779 | |
duke@435 | 780 | class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { |
duke@435 | 781 | public: |
duke@435 | 782 | RefProcPhase1Task(ReferenceProcessor& ref_processor, |
duke@435 | 783 | DiscoveredList refs_lists[], |
duke@435 | 784 | ReferencePolicy* policy, |
duke@435 | 785 | bool marks_oops_alive) |
duke@435 | 786 | : ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
duke@435 | 787 | _policy(policy) |
duke@435 | 788 | { } |
duke@435 | 789 | virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
duke@435 | 790 | OopClosure& keep_alive, |
duke@435 | 791 | VoidClosure& complete_gc) |
duke@435 | 792 | { |
jmasa@2188 | 793 | Thread* thr = Thread::current(); |
jmasa@2188 | 794 | int refs_list_index = ((WorkerThread*)thr)->id(); |
jmasa@2188 | 795 | _ref_processor.process_phase1(_refs_lists[refs_list_index], _policy, |
duke@435 | 796 | &is_alive, &keep_alive, &complete_gc); |
duke@435 | 797 | } |
duke@435 | 798 | private: |
duke@435 | 799 | ReferencePolicy* _policy; |
duke@435 | 800 | }; |
duke@435 | 801 | |
duke@435 | 802 | class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { |
duke@435 | 803 | public: |
duke@435 | 804 | RefProcPhase2Task(ReferenceProcessor& ref_processor, |
duke@435 | 805 | DiscoveredList refs_lists[], |
duke@435 | 806 | bool marks_oops_alive) |
duke@435 | 807 | : ProcessTask(ref_processor, refs_lists, marks_oops_alive) |
duke@435 | 808 | { } |
duke@435 | 809 | virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
duke@435 | 810 | OopClosure& keep_alive, |
duke@435 | 811 | VoidClosure& complete_gc) |
duke@435 | 812 | { |
duke@435 | 813 | _ref_processor.process_phase2(_refs_lists[i], |
duke@435 | 814 | &is_alive, &keep_alive, &complete_gc); |
duke@435 | 815 | } |
duke@435 | 816 | }; |
duke@435 | 817 | |
duke@435 | 818 | class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { |
duke@435 | 819 | public: |
duke@435 | 820 | RefProcPhase3Task(ReferenceProcessor& ref_processor, |
duke@435 | 821 | DiscoveredList refs_lists[], |
duke@435 | 822 | bool clear_referent, |
duke@435 | 823 | bool marks_oops_alive) |
duke@435 | 824 | : ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
duke@435 | 825 | _clear_referent(clear_referent) |
duke@435 | 826 | { } |
duke@435 | 827 | virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
duke@435 | 828 | OopClosure& keep_alive, |
duke@435 | 829 | VoidClosure& complete_gc) |
duke@435 | 830 | { |
jmasa@2188 | 831 | // Don't use "refs_list_index" calculated in this way because |
jmasa@2188 | 832 | // balance_queues() has moved the Ref's into the first n queues. |
jmasa@2188 | 833 | // Thread* thr = Thread::current(); |
jmasa@2188 | 834 | // int refs_list_index = ((WorkerThread*)thr)->id(); |
jmasa@2188 | 835 | // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent, |
duke@435 | 836 | _ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
duke@435 | 837 | &is_alive, &keep_alive, &complete_gc); |
duke@435 | 838 | } |
duke@435 | 839 | private: |
duke@435 | 840 | bool _clear_referent; |
duke@435 | 841 | }; |
duke@435 | 842 | |
duke@435 | 843 | // Balances reference queues. |
jmasa@2188 | 844 | // Move entries from all queues[0, 1, ..., _max_num_q-1] to |
jmasa@2188 | 845 | // queues[0, 1, ..., _num_q-1] because only the first _num_q |
jmasa@2188 | 846 | // corresponding to the active workers will be processed. |
duke@435 | 847 | void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
duke@435 | 848 | { |
duke@435 | 849 | // calculate total length |
duke@435 | 850 | size_t total_refs = 0; |
jmasa@2188 | 851 | if (TraceReferenceGC && PrintGCDetails) { |
jmasa@2188 | 852 | gclog_or_tty->print_cr("\nBalance ref_lists "); |
jmasa@2188 | 853 | } |
jmasa@2188 | 854 | |
jmasa@2188 | 855 | for (int i = 0; i < _max_num_q; ++i) { |
duke@435 | 856 | total_refs += ref_lists[i].length(); |
jmasa@2188 | 857 | if (TraceReferenceGC && PrintGCDetails) { |
jmasa@2188 | 858 | gclog_or_tty->print("%d ", ref_lists[i].length()); |
jmasa@2188 | 859 | } |
jmasa@2188 | 860 | } |
jmasa@2188 | 861 | if (TraceReferenceGC && PrintGCDetails) { |
jmasa@2188 | 862 | gclog_or_tty->print_cr(" = %d", total_refs); |
duke@435 | 863 | } |
duke@435 | 864 | size_t avg_refs = total_refs / _num_q + 1; |
duke@435 | 865 | int to_idx = 0; |
jmasa@2188 | 866 | for (int from_idx = 0; from_idx < _max_num_q; from_idx++) { |
jmasa@2188 | 867 | bool move_all = false; |
jmasa@2188 | 868 | if (from_idx >= _num_q) { |
jmasa@2188 | 869 | move_all = ref_lists[from_idx].length() > 0; |
jmasa@2188 | 870 | } |
jmasa@2188 | 871 | while ((ref_lists[from_idx].length() > avg_refs) || |
jmasa@2188 | 872 | move_all) { |
duke@435 | 873 | assert(to_idx < _num_q, "Sanity Check!"); |
duke@435 | 874 | if (ref_lists[to_idx].length() < avg_refs) { |
duke@435 | 875 | // move superfluous refs |
jmasa@2188 | 876 | size_t refs_to_move; |
jmasa@2188 | 877 | // Move all the Ref's if the from queue will not be processed. |
jmasa@2188 | 878 | if (move_all) { |
jmasa@2188 | 879 | refs_to_move = MIN2(ref_lists[from_idx].length(), |
jmasa@2188 | 880 | avg_refs - ref_lists[to_idx].length()); |
jmasa@2188 | 881 | } else { |
jmasa@2188 | 882 | refs_to_move = MIN2(ref_lists[from_idx].length() - avg_refs, |
jmasa@2188 | 883 | avg_refs - ref_lists[to_idx].length()); |
jmasa@2188 | 884 | } |
duke@435 | 885 | oop move_head = ref_lists[from_idx].head(); |
duke@435 | 886 | oop move_tail = move_head; |
duke@435 | 887 | oop new_head = move_head; |
duke@435 | 888 | // find an element to split the list on |
duke@435 | 889 | for (size_t j = 0; j < refs_to_move; ++j) { |
duke@435 | 890 | move_tail = new_head; |
coleenp@548 | 891 | new_head = java_lang_ref_Reference::discovered(new_head); |
duke@435 | 892 | } |
duke@435 | 893 | java_lang_ref_Reference::set_discovered(move_tail, ref_lists[to_idx].head()); |
duke@435 | 894 | ref_lists[to_idx].set_head(move_head); |
ysr@887 | 895 | ref_lists[to_idx].inc_length(refs_to_move); |
duke@435 | 896 | ref_lists[from_idx].set_head(new_head); |
ysr@887 | 897 | ref_lists[from_idx].dec_length(refs_to_move); |
jmasa@2188 | 898 | if (ref_lists[from_idx].length() == 0) { |
jmasa@2188 | 899 | break; |
jmasa@2188 | 900 | } |
duke@435 | 901 | } else { |
jmasa@2188 | 902 | to_idx = (to_idx + 1) % _num_q; |
duke@435 | 903 | } |
duke@435 | 904 | } |
duke@435 | 905 | } |
jmasa@2188 | 906 | #ifdef ASSERT |
jmasa@2188 | 907 | size_t balanced_total_refs = 0; |
jmasa@2188 | 908 | for (int i = 0; i < _max_num_q; ++i) { |
jmasa@2188 | 909 | balanced_total_refs += ref_lists[i].length(); |
jmasa@2188 | 910 | if (TraceReferenceGC && PrintGCDetails) { |
jmasa@2188 | 911 | gclog_or_tty->print("%d ", ref_lists[i].length()); |
jmasa@2188 | 912 | } |
jmasa@2188 | 913 | } |
jmasa@2188 | 914 | if (TraceReferenceGC && PrintGCDetails) { |
jmasa@2188 | 915 | gclog_or_tty->print_cr(" = %d", balanced_total_refs); |
jmasa@2188 | 916 | gclog_or_tty->flush(); |
jmasa@2188 | 917 | } |
jmasa@2188 | 918 | assert(total_refs == balanced_total_refs, "Balancing was incomplete"); |
jmasa@2188 | 919 | #endif |
jmasa@2188 | 920 | } |
jmasa@2188 | 921 | |
jmasa@2188 | 922 | void ReferenceProcessor::balance_all_queues() { |
jmasa@2188 | 923 | balance_queues(_discoveredSoftRefs); |
jmasa@2188 | 924 | balance_queues(_discoveredWeakRefs); |
jmasa@2188 | 925 | balance_queues(_discoveredFinalRefs); |
jmasa@2188 | 926 | balance_queues(_discoveredPhantomRefs); |
duke@435 | 927 | } |
duke@435 | 928 | |
duke@435 | 929 | void |
duke@435 | 930 | ReferenceProcessor::process_discovered_reflist( |
duke@435 | 931 | DiscoveredList refs_lists[], |
duke@435 | 932 | ReferencePolicy* policy, |
duke@435 | 933 | bool clear_referent, |
duke@435 | 934 | BoolObjectClosure* is_alive, |
duke@435 | 935 | OopClosure* keep_alive, |
duke@435 | 936 | VoidClosure* complete_gc, |
duke@435 | 937 | AbstractRefProcTaskExecutor* task_executor) |
duke@435 | 938 | { |
jmasa@2188 | 939 | bool mt_processing = task_executor != NULL && _processing_is_mt; |
jmasa@2188 | 940 | // If discovery used MT and a dynamic number of GC threads, then |
jmasa@2188 | 941 | // the queues must be balanced for correctness if fewer than the |
jmasa@2188 | 942 | // maximum number of queues were used. The number of queue used |
jmasa@2188 | 943 | // during discovery may be different than the number to be used |
jmasa@2188 | 944 | // for processing so don't depend of _num_q < _max_num_q as part |
jmasa@2188 | 945 | // of the test. |
jmasa@2188 | 946 | bool must_balance = _discovery_is_mt; |
jmasa@2188 | 947 | |
jmasa@2188 | 948 | if ((mt_processing && ParallelRefProcBalancingEnabled) || |
jmasa@2188 | 949 | must_balance) { |
duke@435 | 950 | balance_queues(refs_lists); |
duke@435 | 951 | } |
duke@435 | 952 | if (PrintReferenceGC && PrintGCDetails) { |
duke@435 | 953 | size_t total = 0; |
duke@435 | 954 | for (int i = 0; i < _num_q; ++i) { |
duke@435 | 955 | total += refs_lists[i].length(); |
duke@435 | 956 | } |
duke@435 | 957 | gclog_or_tty->print(", %u refs", total); |
duke@435 | 958 | } |
duke@435 | 959 | |
duke@435 | 960 | // Phase 1 (soft refs only): |
duke@435 | 961 | // . Traverse the list and remove any SoftReferences whose |
duke@435 | 962 | // referents are not alive, but that should be kept alive for |
duke@435 | 963 | // policy reasons. Keep alive the transitive closure of all |
duke@435 | 964 | // such referents. |
duke@435 | 965 | if (policy != NULL) { |
jmasa@2188 | 966 | if (mt_processing) { |
duke@435 | 967 | RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
duke@435 | 968 | task_executor->execute(phase1); |
duke@435 | 969 | } else { |
duke@435 | 970 | for (int i = 0; i < _num_q; i++) { |
duke@435 | 971 | process_phase1(refs_lists[i], policy, |
duke@435 | 972 | is_alive, keep_alive, complete_gc); |
duke@435 | 973 | } |
duke@435 | 974 | } |
duke@435 | 975 | } else { // policy == NULL |
duke@435 | 976 | assert(refs_lists != _discoveredSoftRefs, |
duke@435 | 977 | "Policy must be specified for soft references."); |
duke@435 | 978 | } |
duke@435 | 979 | |
duke@435 | 980 | // Phase 2: |
duke@435 | 981 | // . Traverse the list and remove any refs whose referents are alive. |
jmasa@2188 | 982 | if (mt_processing) { |
duke@435 | 983 | RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
duke@435 | 984 | task_executor->execute(phase2); |
duke@435 | 985 | } else { |
duke@435 | 986 | for (int i = 0; i < _num_q; i++) { |
duke@435 | 987 | process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); |
duke@435 | 988 | } |
duke@435 | 989 | } |
duke@435 | 990 | |
duke@435 | 991 | // Phase 3: |
duke@435 | 992 | // . Traverse the list and process referents as appropriate. |
jmasa@2188 | 993 | if (mt_processing) { |
duke@435 | 994 | RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
duke@435 | 995 | task_executor->execute(phase3); |
duke@435 | 996 | } else { |
duke@435 | 997 | for (int i = 0; i < _num_q; i++) { |
duke@435 | 998 | process_phase3(refs_lists[i], clear_referent, |
duke@435 | 999 | is_alive, keep_alive, complete_gc); |
duke@435 | 1000 | } |
duke@435 | 1001 | } |
duke@435 | 1002 | } |
duke@435 | 1003 | |
duke@435 | 1004 | void ReferenceProcessor::clean_up_discovered_references() { |
duke@435 | 1005 | // loop over the lists |
jmasa@2188 | 1006 | // Should this instead be |
jmasa@2188 | 1007 | // for (int i = 0; i < subclasses_of_ref; i++_ { |
jmasa@2188 | 1008 | // for (int j = 0; j < _num_q; j++) { |
jmasa@2188 | 1009 | // int index = i * _max_num_q + j; |
jmasa@2188 | 1010 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
duke@435 | 1011 | if (TraceReferenceGC && PrintGCDetails && ((i % _num_q) == 0)) { |
duke@435 | 1012 | gclog_or_tty->print_cr( |
duke@435 | 1013 | "\nScrubbing %s discovered list of Null referents", |
duke@435 | 1014 | list_name(i)); |
duke@435 | 1015 | } |
duke@435 | 1016 | clean_up_discovered_reflist(_discoveredSoftRefs[i]); |
duke@435 | 1017 | } |
duke@435 | 1018 | } |
duke@435 | 1019 | |
duke@435 | 1020 | void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { |
duke@435 | 1021 | assert(!discovery_is_atomic(), "Else why call this method?"); |
duke@435 | 1022 | DiscoveredListIterator iter(refs_list, NULL, NULL); |
duke@435 | 1023 | while (iter.has_next()) { |
duke@435 | 1024 | iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
coleenp@548 | 1025 | oop next = java_lang_ref_Reference::next(iter.obj()); |
coleenp@548 | 1026 | assert(next->is_oop_or_null(), "bad next field"); |
duke@435 | 1027 | // If referent has been cleared or Reference is not active, |
duke@435 | 1028 | // drop it. |
coleenp@548 | 1029 | if (iter.referent() == NULL || next != NULL) { |
duke@435 | 1030 | debug_only( |
duke@435 | 1031 | if (PrintGCDetails && TraceReferenceGC) { |
duke@435 | 1032 | gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " |
duke@435 | 1033 | INTPTR_FORMAT " with next field: " INTPTR_FORMAT |
duke@435 | 1034 | " and referent: " INTPTR_FORMAT, |
coleenp@548 | 1035 | iter.obj(), next, iter.referent()); |
duke@435 | 1036 | } |
duke@435 | 1037 | ) |
duke@435 | 1038 | // Remove Reference object from list |
duke@435 | 1039 | iter.remove(); |
ysr@887 | 1040 | iter.move_to_next(); |
duke@435 | 1041 | } else { |
duke@435 | 1042 | iter.next(); |
duke@435 | 1043 | } |
duke@435 | 1044 | } |
duke@435 | 1045 | NOT_PRODUCT( |
duke@435 | 1046 | if (PrintGCDetails && TraceReferenceGC) { |
duke@435 | 1047 | gclog_or_tty->print( |
duke@435 | 1048 | " Removed %d Refs with NULL referents out of %d discovered Refs", |
duke@435 | 1049 | iter.removed(), iter.processed()); |
duke@435 | 1050 | } |
duke@435 | 1051 | ) |
duke@435 | 1052 | } |
duke@435 | 1053 | |
duke@435 | 1054 | inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { |
duke@435 | 1055 | int id = 0; |
duke@435 | 1056 | // Determine the queue index to use for this object. |
duke@435 | 1057 | if (_discovery_is_mt) { |
duke@435 | 1058 | // During a multi-threaded discovery phase, |
duke@435 | 1059 | // each thread saves to its "own" list. |
duke@435 | 1060 | Thread* thr = Thread::current(); |
johnc@2316 | 1061 | id = thr->as_Worker_thread()->id(); |
duke@435 | 1062 | } else { |
duke@435 | 1063 | // single-threaded discovery, we save in round-robin |
duke@435 | 1064 | // fashion to each of the lists. |
duke@435 | 1065 | if (_processing_is_mt) { |
duke@435 | 1066 | id = next_id(); |
duke@435 | 1067 | } |
duke@435 | 1068 | } |
jmasa@2188 | 1069 | assert(0 <= id && id < _max_num_q, "Id is out-of-bounds (call Freud?)"); |
duke@435 | 1070 | |
duke@435 | 1071 | // Get the discovered queue to which we will add |
duke@435 | 1072 | DiscoveredList* list = NULL; |
duke@435 | 1073 | switch (rt) { |
duke@435 | 1074 | case REF_OTHER: |
duke@435 | 1075 | // Unknown reference type, no special treatment |
duke@435 | 1076 | break; |
duke@435 | 1077 | case REF_SOFT: |
duke@435 | 1078 | list = &_discoveredSoftRefs[id]; |
duke@435 | 1079 | break; |
duke@435 | 1080 | case REF_WEAK: |
duke@435 | 1081 | list = &_discoveredWeakRefs[id]; |
duke@435 | 1082 | break; |
duke@435 | 1083 | case REF_FINAL: |
duke@435 | 1084 | list = &_discoveredFinalRefs[id]; |
duke@435 | 1085 | break; |
duke@435 | 1086 | case REF_PHANTOM: |
duke@435 | 1087 | list = &_discoveredPhantomRefs[id]; |
duke@435 | 1088 | break; |
duke@435 | 1089 | case REF_NONE: |
duke@435 | 1090 | // we should not reach here if we are an instanceRefKlass |
duke@435 | 1091 | default: |
duke@435 | 1092 | ShouldNotReachHere(); |
duke@435 | 1093 | } |
jmasa@2188 | 1094 | if (TraceReferenceGC && PrintGCDetails) { |
johnc@2316 | 1095 | gclog_or_tty->print_cr("Thread %d gets list " INTPTR_FORMAT, id, list); |
jmasa@2188 | 1096 | } |
duke@435 | 1097 | return list; |
duke@435 | 1098 | } |
duke@435 | 1099 | |
coleenp@548 | 1100 | inline void |
coleenp@548 | 1101 | ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& refs_list, |
coleenp@548 | 1102 | oop obj, |
coleenp@548 | 1103 | HeapWord* discovered_addr) { |
duke@435 | 1104 | assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
duke@435 | 1105 | // First we must make sure this object is only enqueued once. CAS in a non null |
duke@435 | 1106 | // discovered_addr. |
ysr@777 | 1107 | oop current_head = refs_list.head(); |
ysr@777 | 1108 | |
ysr@1280 | 1109 | // Note: In the case of G1, this specific pre-barrier is strictly |
ysr@777 | 1110 | // not necessary because the only case we are interested in |
ysr@1280 | 1111 | // here is when *discovered_addr is NULL (see the CAS further below), |
ysr@1280 | 1112 | // so this will expand to nothing. As a result, we have manually |
ysr@1280 | 1113 | // elided this out for G1, but left in the test for some future |
ysr@1280 | 1114 | // collector that might have need for a pre-barrier here. |
ysr@777 | 1115 | if (_discovered_list_needs_barrier && !UseG1GC) { |
ysr@1280 | 1116 | if (UseCompressedOops) { |
ysr@1280 | 1117 | _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
ysr@1280 | 1118 | } else { |
ysr@1280 | 1119 | _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
ysr@1280 | 1120 | } |
ysr@1280 | 1121 | guarantee(false, "Need to check non-G1 collector"); |
ysr@777 | 1122 | } |
ysr@777 | 1123 | oop retest = oopDesc::atomic_compare_exchange_oop(current_head, discovered_addr, |
coleenp@548 | 1124 | NULL); |
duke@435 | 1125 | if (retest == NULL) { |
duke@435 | 1126 | // This thread just won the right to enqueue the object. |
duke@435 | 1127 | // We have separate lists for enqueueing so no synchronization |
duke@435 | 1128 | // is necessary. |
coleenp@548 | 1129 | refs_list.set_head(obj); |
ysr@887 | 1130 | refs_list.inc_length(1); |
ysr@777 | 1131 | if (_discovered_list_needs_barrier) { |
ysr@1280 | 1132 | _bs->write_ref_field((void*)discovered_addr, current_head); |
ysr@777 | 1133 | } |
johnc@2316 | 1134 | |
johnc@2316 | 1135 | if (TraceReferenceGC) { |
johnc@2316 | 1136 | gclog_or_tty->print_cr("Enqueued reference (mt) (" INTPTR_FORMAT ": %s)", |
johnc@2316 | 1137 | obj, obj->blueprint()->internal_name()); |
johnc@2316 | 1138 | } |
duke@435 | 1139 | } else { |
duke@435 | 1140 | // If retest was non NULL, another thread beat us to it: |
duke@435 | 1141 | // The reference has already been discovered... |
duke@435 | 1142 | if (TraceReferenceGC) { |
duke@435 | 1143 | gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
duke@435 | 1144 | obj, obj->blueprint()->internal_name()); |
duke@435 | 1145 | } |
duke@435 | 1146 | } |
duke@435 | 1147 | } |
duke@435 | 1148 | |
ysr@2337 | 1149 | #ifndef PRODUCT |
ysr@2337 | 1150 | // Non-atomic (i.e. concurrent) discovery might allow us |
ysr@2337 | 1151 | // to observe j.l.References with NULL referents, being those |
ysr@2337 | 1152 | // cleared concurrently by mutators during (or after) discovery. |
ysr@2337 | 1153 | void ReferenceProcessor::verify_referent(oop obj) { |
ysr@2337 | 1154 | bool da = discovery_is_atomic(); |
ysr@2337 | 1155 | oop referent = java_lang_ref_Reference::referent(obj); |
ysr@2337 | 1156 | assert(da ? referent->is_oop() : referent->is_oop_or_null(), |
ysr@2337 | 1157 | err_msg("Bad referent " INTPTR_FORMAT " found in Reference " |
ysr@2337 | 1158 | INTPTR_FORMAT " during %satomic discovery ", |
ysr@2337 | 1159 | (intptr_t)referent, (intptr_t)obj, da ? "" : "non-")); |
ysr@2337 | 1160 | } |
ysr@2337 | 1161 | #endif |
ysr@2337 | 1162 | |
duke@435 | 1163 | // We mention two of several possible choices here: |
duke@435 | 1164 | // #0: if the reference object is not in the "originating generation" |
duke@435 | 1165 | // (or part of the heap being collected, indicated by our "span" |
duke@435 | 1166 | // we don't treat it specially (i.e. we scan it as we would |
duke@435 | 1167 | // a normal oop, treating its references as strong references). |
duke@435 | 1168 | // This means that references can't be enqueued unless their |
duke@435 | 1169 | // referent is also in the same span. This is the simplest, |
duke@435 | 1170 | // most "local" and most conservative approach, albeit one |
duke@435 | 1171 | // that may cause weak references to be enqueued least promptly. |
duke@435 | 1172 | // We call this choice the "ReferenceBasedDiscovery" policy. |
duke@435 | 1173 | // #1: the reference object may be in any generation (span), but if |
duke@435 | 1174 | // the referent is in the generation (span) being currently collected |
duke@435 | 1175 | // then we can discover the reference object, provided |
duke@435 | 1176 | // the object has not already been discovered by |
duke@435 | 1177 | // a different concurrently running collector (as may be the |
duke@435 | 1178 | // case, for instance, if the reference object is in CMS and |
duke@435 | 1179 | // the referent in DefNewGeneration), and provided the processing |
duke@435 | 1180 | // of this reference object by the current collector will |
duke@435 | 1181 | // appear atomic to every other collector in the system. |
duke@435 | 1182 | // (Thus, for instance, a concurrent collector may not |
duke@435 | 1183 | // discover references in other generations even if the |
duke@435 | 1184 | // referent is in its own generation). This policy may, |
duke@435 | 1185 | // in certain cases, enqueue references somewhat sooner than |
duke@435 | 1186 | // might Policy #0 above, but at marginally increased cost |
duke@435 | 1187 | // and complexity in processing these references. |
duke@435 | 1188 | // We call this choice the "RefeferentBasedDiscovery" policy. |
duke@435 | 1189 | bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { |
duke@435 | 1190 | // We enqueue references only if we are discovering refs |
duke@435 | 1191 | // (rather than processing discovered refs). |
duke@435 | 1192 | if (!_discovering_refs || !RegisterReferences) { |
duke@435 | 1193 | return false; |
duke@435 | 1194 | } |
duke@435 | 1195 | // We only enqueue active references. |
coleenp@548 | 1196 | oop next = java_lang_ref_Reference::next(obj); |
coleenp@548 | 1197 | if (next != NULL) { |
duke@435 | 1198 | return false; |
duke@435 | 1199 | } |
duke@435 | 1200 | |
duke@435 | 1201 | HeapWord* obj_addr = (HeapWord*)obj; |
duke@435 | 1202 | if (RefDiscoveryPolicy == ReferenceBasedDiscovery && |
duke@435 | 1203 | !_span.contains(obj_addr)) { |
duke@435 | 1204 | // Reference is not in the originating generation; |
duke@435 | 1205 | // don't treat it specially (i.e. we want to scan it as a normal |
duke@435 | 1206 | // object with strong references). |
duke@435 | 1207 | return false; |
duke@435 | 1208 | } |
duke@435 | 1209 | |
duke@435 | 1210 | // We only enqueue references whose referents are not (yet) strongly |
duke@435 | 1211 | // reachable. |
duke@435 | 1212 | if (is_alive_non_header() != NULL) { |
ysr@2337 | 1213 | verify_referent(obj); |
ysr@2337 | 1214 | if (is_alive_non_header()->do_object_b(java_lang_ref_Reference::referent(obj))) { |
duke@435 | 1215 | return false; // referent is reachable |
duke@435 | 1216 | } |
duke@435 | 1217 | } |
ysr@888 | 1218 | if (rt == REF_SOFT) { |
ysr@888 | 1219 | // For soft refs we can decide now if these are not |
ysr@888 | 1220 | // current candidates for clearing, in which case we |
ysr@888 | 1221 | // can mark through them now, rather than delaying that |
ysr@888 | 1222 | // to the reference-processing phase. Since all current |
ysr@888 | 1223 | // time-stamp policies advance the soft-ref clock only |
ysr@888 | 1224 | // at a major collection cycle, this is always currently |
ysr@888 | 1225 | // accurate. |
ysr@888 | 1226 | if (!_current_soft_ref_policy->should_clear_reference(obj)) { |
ysr@888 | 1227 | return false; |
ysr@888 | 1228 | } |
ysr@888 | 1229 | } |
duke@435 | 1230 | |
ysr@777 | 1231 | HeapWord* const discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
ysr@777 | 1232 | const oop discovered = java_lang_ref_Reference::discovered(obj); |
coleenp@548 | 1233 | assert(discovered->is_oop_or_null(), "bad discovered field"); |
coleenp@548 | 1234 | if (discovered != NULL) { |
duke@435 | 1235 | // The reference has already been discovered... |
duke@435 | 1236 | if (TraceReferenceGC) { |
duke@435 | 1237 | gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
coleenp@548 | 1238 | obj, obj->blueprint()->internal_name()); |
duke@435 | 1239 | } |
duke@435 | 1240 | if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
duke@435 | 1241 | // assumes that an object is not processed twice; |
duke@435 | 1242 | // if it's been already discovered it must be on another |
duke@435 | 1243 | // generation's discovered list; so we won't discover it. |
duke@435 | 1244 | return false; |
duke@435 | 1245 | } else { |
duke@435 | 1246 | assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, |
duke@435 | 1247 | "Unrecognized policy"); |
duke@435 | 1248 | // Check assumption that an object is not potentially |
duke@435 | 1249 | // discovered twice except by concurrent collectors that potentially |
duke@435 | 1250 | // trace the same Reference object twice. |
johnc@2316 | 1251 | assert(UseConcMarkSweepGC || UseG1GC, |
johnc@2316 | 1252 | "Only possible with a concurrent marking collector"); |
duke@435 | 1253 | return true; |
duke@435 | 1254 | } |
duke@435 | 1255 | } |
duke@435 | 1256 | |
duke@435 | 1257 | if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
ysr@2337 | 1258 | verify_referent(obj); |
duke@435 | 1259 | // enqueue if and only if either: |
duke@435 | 1260 | // reference is in our span or |
duke@435 | 1261 | // we are an atomic collector and referent is in our span |
duke@435 | 1262 | if (_span.contains(obj_addr) || |
ysr@2337 | 1263 | (discovery_is_atomic() && |
ysr@2337 | 1264 | _span.contains(java_lang_ref_Reference::referent(obj)))) { |
duke@435 | 1265 | // should_enqueue = true; |
duke@435 | 1266 | } else { |
duke@435 | 1267 | return false; |
duke@435 | 1268 | } |
duke@435 | 1269 | } else { |
duke@435 | 1270 | assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && |
duke@435 | 1271 | _span.contains(obj_addr), "code inconsistency"); |
duke@435 | 1272 | } |
duke@435 | 1273 | |
duke@435 | 1274 | // Get the right type of discovered queue head. |
duke@435 | 1275 | DiscoveredList* list = get_discovered_list(rt); |
duke@435 | 1276 | if (list == NULL) { |
duke@435 | 1277 | return false; // nothing special needs to be done |
duke@435 | 1278 | } |
duke@435 | 1279 | |
duke@435 | 1280 | if (_discovery_is_mt) { |
duke@435 | 1281 | add_to_discovered_list_mt(*list, obj, discovered_addr); |
duke@435 | 1282 | } else { |
ysr@777 | 1283 | // If "_discovered_list_needs_barrier", we do write barriers when |
ysr@777 | 1284 | // updating the discovered reference list. Otherwise, we do a raw store |
ysr@777 | 1285 | // here: the field will be visited later when processing the discovered |
ysr@777 | 1286 | // references. |
ysr@777 | 1287 | oop current_head = list->head(); |
ysr@777 | 1288 | // As in the case further above, since we are over-writing a NULL |
ysr@777 | 1289 | // pre-value, we can safely elide the pre-barrier here for the case of G1. |
ysr@777 | 1290 | assert(discovered == NULL, "control point invariant"); |
ysr@777 | 1291 | if (_discovered_list_needs_barrier && !UseG1GC) { // safe to elide for G1 |
ysr@1280 | 1292 | if (UseCompressedOops) { |
ysr@1280 | 1293 | _bs->write_ref_field_pre((narrowOop*)discovered_addr, current_head); |
ysr@1280 | 1294 | } else { |
ysr@1280 | 1295 | _bs->write_ref_field_pre((oop*)discovered_addr, current_head); |
ysr@1280 | 1296 | } |
ysr@1280 | 1297 | guarantee(false, "Need to check non-G1 collector"); |
ysr@777 | 1298 | } |
ysr@777 | 1299 | oop_store_raw(discovered_addr, current_head); |
ysr@777 | 1300 | if (_discovered_list_needs_barrier) { |
ysr@1280 | 1301 | _bs->write_ref_field((void*)discovered_addr, current_head); |
ysr@777 | 1302 | } |
duke@435 | 1303 | list->set_head(obj); |
ysr@887 | 1304 | list->inc_length(1); |
duke@435 | 1305 | |
johnc@2316 | 1306 | if (TraceReferenceGC) { |
duke@435 | 1307 | gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)", |
johnc@2316 | 1308 | obj, obj->blueprint()->internal_name()); |
duke@435 | 1309 | } |
duke@435 | 1310 | } |
duke@435 | 1311 | assert(obj->is_oop(), "Enqueued a bad reference"); |
ysr@2337 | 1312 | verify_referent(obj); |
duke@435 | 1313 | return true; |
duke@435 | 1314 | } |
duke@435 | 1315 | |
duke@435 | 1316 | // Preclean the discovered references by removing those |
duke@435 | 1317 | // whose referents are alive, and by marking from those that |
duke@435 | 1318 | // are not active. These lists can be handled here |
duke@435 | 1319 | // in any order and, indeed, concurrently. |
duke@435 | 1320 | void ReferenceProcessor::preclean_discovered_references( |
duke@435 | 1321 | BoolObjectClosure* is_alive, |
duke@435 | 1322 | OopClosure* keep_alive, |
duke@435 | 1323 | VoidClosure* complete_gc, |
jmasa@1625 | 1324 | YieldClosure* yield, |
jmasa@1625 | 1325 | bool should_unload_classes) { |
duke@435 | 1326 | |
duke@435 | 1327 | NOT_PRODUCT(verify_ok_to_handle_reflists()); |
duke@435 | 1328 | |
jmasa@1370 | 1329 | #ifdef ASSERT |
jmasa@1370 | 1330 | bool must_remember_klasses = ClassUnloading && !UseConcMarkSweepGC || |
jmasa@1625 | 1331 | CMSClassUnloadingEnabled && UseConcMarkSweepGC || |
jmasa@1625 | 1332 | ExplicitGCInvokesConcurrentAndUnloadsClasses && |
jmasa@1625 | 1333 | UseConcMarkSweepGC && should_unload_classes; |
jmasa@1370 | 1334 | RememberKlassesChecker mx(must_remember_klasses); |
jmasa@1370 | 1335 | #endif |
duke@435 | 1336 | // Soft references |
duke@435 | 1337 | { |
duke@435 | 1338 | TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, |
duke@435 | 1339 | false, gclog_or_tty); |
jmasa@2188 | 1340 | for (int i = 0; i < _max_num_q; i++) { |
ysr@887 | 1341 | if (yield->should_return()) { |
ysr@887 | 1342 | return; |
ysr@887 | 1343 | } |
duke@435 | 1344 | preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
duke@435 | 1345 | keep_alive, complete_gc, yield); |
duke@435 | 1346 | } |
duke@435 | 1347 | } |
duke@435 | 1348 | |
duke@435 | 1349 | // Weak references |
duke@435 | 1350 | { |
duke@435 | 1351 | TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, |
duke@435 | 1352 | false, gclog_or_tty); |
duke@435 | 1353 | for (int i = 0; i < _num_q; i++) { |
ysr@887 | 1354 | if (yield->should_return()) { |
ysr@887 | 1355 | return; |
ysr@887 | 1356 | } |
duke@435 | 1357 | preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
duke@435 | 1358 | keep_alive, complete_gc, yield); |
duke@435 | 1359 | } |
duke@435 | 1360 | } |
duke@435 | 1361 | |
duke@435 | 1362 | // Final references |
duke@435 | 1363 | { |
duke@435 | 1364 | TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, |
duke@435 | 1365 | false, gclog_or_tty); |
duke@435 | 1366 | for (int i = 0; i < _num_q; i++) { |
ysr@887 | 1367 | if (yield->should_return()) { |
ysr@887 | 1368 | return; |
ysr@887 | 1369 | } |
duke@435 | 1370 | preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
duke@435 | 1371 | keep_alive, complete_gc, yield); |
duke@435 | 1372 | } |
duke@435 | 1373 | } |
duke@435 | 1374 | |
duke@435 | 1375 | // Phantom references |
duke@435 | 1376 | { |
duke@435 | 1377 | TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, |
duke@435 | 1378 | false, gclog_or_tty); |
duke@435 | 1379 | for (int i = 0; i < _num_q; i++) { |
ysr@887 | 1380 | if (yield->should_return()) { |
ysr@887 | 1381 | return; |
ysr@887 | 1382 | } |
duke@435 | 1383 | preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
duke@435 | 1384 | keep_alive, complete_gc, yield); |
duke@435 | 1385 | } |
duke@435 | 1386 | } |
duke@435 | 1387 | } |
duke@435 | 1388 | |
duke@435 | 1389 | // Walk the given discovered ref list, and remove all reference objects |
duke@435 | 1390 | // whose referents are still alive, whose referents are NULL or which |
ysr@887 | 1391 | // are not active (have a non-NULL next field). NOTE: When we are |
ysr@887 | 1392 | // thus precleaning the ref lists (which happens single-threaded today), |
ysr@887 | 1393 | // we do not disable refs discovery to honour the correct semantics of |
ysr@887 | 1394 | // java.lang.Reference. As a result, we need to be careful below |
ysr@887 | 1395 | // that ref removal steps interleave safely with ref discovery steps |
ysr@887 | 1396 | // (in this thread). |
coleenp@548 | 1397 | void |
coleenp@548 | 1398 | ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list, |
coleenp@548 | 1399 | BoolObjectClosure* is_alive, |
coleenp@548 | 1400 | OopClosure* keep_alive, |
coleenp@548 | 1401 | VoidClosure* complete_gc, |
coleenp@548 | 1402 | YieldClosure* yield) { |
duke@435 | 1403 | DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
duke@435 | 1404 | while (iter.has_next()) { |
duke@435 | 1405 | iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
coleenp@548 | 1406 | oop obj = iter.obj(); |
coleenp@548 | 1407 | oop next = java_lang_ref_Reference::next(obj); |
duke@435 | 1408 | if (iter.referent() == NULL || iter.is_referent_alive() || |
coleenp@548 | 1409 | next != NULL) { |
duke@435 | 1410 | // The referent has been cleared, or is alive, or the Reference is not |
duke@435 | 1411 | // active; we need to trace and mark its cohort. |
duke@435 | 1412 | if (TraceReferenceGC) { |
duke@435 | 1413 | gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", |
duke@435 | 1414 | iter.obj(), iter.obj()->blueprint()->internal_name()); |
duke@435 | 1415 | } |
duke@435 | 1416 | // Remove Reference object from list |
duke@435 | 1417 | iter.remove(); |
duke@435 | 1418 | // Keep alive its cohort. |
duke@435 | 1419 | iter.make_referent_alive(); |
coleenp@548 | 1420 | if (UseCompressedOops) { |
coleenp@548 | 1421 | narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj); |
coleenp@548 | 1422 | keep_alive->do_oop(next_addr); |
coleenp@548 | 1423 | } else { |
coleenp@548 | 1424 | oop* next_addr = (oop*)java_lang_ref_Reference::next_addr(obj); |
coleenp@548 | 1425 | keep_alive->do_oop(next_addr); |
coleenp@548 | 1426 | } |
ysr@887 | 1427 | iter.move_to_next(); |
duke@435 | 1428 | } else { |
duke@435 | 1429 | iter.next(); |
duke@435 | 1430 | } |
duke@435 | 1431 | } |
duke@435 | 1432 | // Close the reachable set |
duke@435 | 1433 | complete_gc->do_void(); |
duke@435 | 1434 | |
duke@435 | 1435 | NOT_PRODUCT( |
duke@435 | 1436 | if (PrintGCDetails && PrintReferenceGC) { |
jmasa@2188 | 1437 | gclog_or_tty->print_cr(" Dropped %d Refs out of %d " |
jmasa@2188 | 1438 | "Refs in discovered list " INTPTR_FORMAT, |
jmasa@2188 | 1439 | iter.removed(), iter.processed(), (address)refs_list.head()); |
duke@435 | 1440 | } |
duke@435 | 1441 | ) |
duke@435 | 1442 | } |
duke@435 | 1443 | |
duke@435 | 1444 | const char* ReferenceProcessor::list_name(int i) { |
jmasa@2188 | 1445 | assert(i >= 0 && i <= _max_num_q * subclasses_of_ref, "Out of bounds index"); |
jmasa@2188 | 1446 | int j = i / _max_num_q; |
duke@435 | 1447 | switch (j) { |
duke@435 | 1448 | case 0: return "SoftRef"; |
duke@435 | 1449 | case 1: return "WeakRef"; |
duke@435 | 1450 | case 2: return "FinalRef"; |
duke@435 | 1451 | case 3: return "PhantomRef"; |
duke@435 | 1452 | } |
duke@435 | 1453 | ShouldNotReachHere(); |
duke@435 | 1454 | return NULL; |
duke@435 | 1455 | } |
duke@435 | 1456 | |
duke@435 | 1457 | #ifndef PRODUCT |
duke@435 | 1458 | void ReferenceProcessor::verify_ok_to_handle_reflists() { |
duke@435 | 1459 | // empty for now |
duke@435 | 1460 | } |
duke@435 | 1461 | #endif |
duke@435 | 1462 | |
duke@435 | 1463 | void ReferenceProcessor::verify() { |
coleenp@548 | 1464 | guarantee(sentinel_ref() != NULL && sentinel_ref()->is_oop(), "Lost _sentinelRef"); |
duke@435 | 1465 | } |
duke@435 | 1466 | |
duke@435 | 1467 | #ifndef PRODUCT |
duke@435 | 1468 | void ReferenceProcessor::clear_discovered_references() { |
duke@435 | 1469 | guarantee(!_discovering_refs, "Discovering refs?"); |
jmasa@2188 | 1470 | for (int i = 0; i < _max_num_q * subclasses_of_ref; i++) { |
duke@435 | 1471 | oop obj = _discoveredSoftRefs[i].head(); |
coleenp@548 | 1472 | while (obj != sentinel_ref()) { |
duke@435 | 1473 | oop next = java_lang_ref_Reference::discovered(obj); |
duke@435 | 1474 | java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
duke@435 | 1475 | obj = next; |
duke@435 | 1476 | } |
coleenp@548 | 1477 | _discoveredSoftRefs[i].set_head(sentinel_ref()); |
duke@435 | 1478 | _discoveredSoftRefs[i].set_length(0); |
duke@435 | 1479 | } |
duke@435 | 1480 | } |
duke@435 | 1481 | #endif // PRODUCT |