author | ysr |
Tue, 12 Feb 2008 16:07:46 -0800 | |
changeset 178 | 3f20890fb323 |
parent 1 | 489c9b5090e2 |
child 360 | 21d113ecbf6a |
permissions | -rw-r--r-- |
1 | 1 |
/* |
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* Copyright 2001-2007 Sun Microsystems, Inc. All Rights Reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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* CA 95054 USA or visit www.sun.com if you need additional information or |
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* have any questions. |
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* |
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*/ |
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# include "incls/_precompiled.incl" |
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# include "incls/_referenceProcessor.cpp.incl" |
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// List of discovered references. |
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class DiscoveredList { |
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public: |
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DiscoveredList() : _head(NULL), _len(0) { } |
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oop head() const { return _head; } |
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oop* head_ptr() { return &_head; } |
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void set_head(oop o) { _head = o; } |
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bool empty() const { return _head == ReferenceProcessor::_sentinelRef; } |
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size_t length() { return _len; } |
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void set_length(size_t len) { _len = len; } |
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private: |
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size_t _len; |
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oop _head; |
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}; |
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oop ReferenceProcessor::_sentinelRef = NULL; |
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const int subclasses_of_ref = REF_PHANTOM - REF_OTHER; |
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void referenceProcessor_init() { |
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ReferenceProcessor::init_statics(); |
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} |
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void ReferenceProcessor::init_statics() { |
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assert(_sentinelRef == NULL, "should be initialized precsiely once"); |
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EXCEPTION_MARK; |
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_sentinelRef = instanceKlass::cast( |
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SystemDictionary::object_klass())-> |
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allocate_permanent_instance(THREAD); |
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// Initialize the master soft ref clock. |
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java_lang_ref_SoftReference::set_clock(os::javaTimeMillis()); |
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if (HAS_PENDING_EXCEPTION) { |
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Handle ex(THREAD, PENDING_EXCEPTION); |
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vm_exit_during_initialization(ex); |
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} |
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assert(_sentinelRef != NULL && _sentinelRef->is_oop(), |
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"Just constructed it!"); |
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guarantee(RefDiscoveryPolicy == ReferenceBasedDiscovery || |
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RefDiscoveryPolicy == ReferentBasedDiscovery, |
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"Unrecongnized RefDiscoveryPolicy"); |
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} |
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ReferenceProcessor* ReferenceProcessor::create_ref_processor( |
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MemRegion span, |
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bool atomic_discovery, |
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bool mt_discovery, |
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BoolObjectClosure* is_alive_non_header, |
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int parallel_gc_threads, |
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bool mt_processing) |
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{ |
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int mt_degree = 1; |
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if (parallel_gc_threads > 1) { |
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mt_degree = parallel_gc_threads; |
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} |
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ReferenceProcessor* rp = |
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new ReferenceProcessor(span, atomic_discovery, |
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mt_discovery, mt_degree, |
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3f20890fb323
6659981: +ParallelRefProcEnabled crashes on single core platform
ysr
parents:
1
diff
changeset
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mt_processing && (parallel_gc_threads > 0)); |
1 | 89 |
if (rp == NULL) { |
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vm_exit_during_initialization("Could not allocate ReferenceProcessor object"); |
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} |
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rp->set_is_alive_non_header(is_alive_non_header); |
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return rp; |
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} |
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ReferenceProcessor::ReferenceProcessor(MemRegion span, |
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bool atomic_discovery, bool mt_discovery, int mt_degree, |
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bool mt_processing) : |
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_discovering_refs(false), |
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_enqueuing_is_done(false), |
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_is_alive_non_header(NULL), |
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_processing_is_mt(mt_processing), |
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_next_id(0) |
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{ |
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_span = span; |
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_discovery_is_atomic = atomic_discovery; |
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_discovery_is_mt = mt_discovery; |
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_num_q = mt_degree; |
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_discoveredSoftRefs = NEW_C_HEAP_ARRAY(DiscoveredList, _num_q * subclasses_of_ref); |
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if (_discoveredSoftRefs == NULL) { |
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vm_exit_during_initialization("Could not allocated RefProc Array"); |
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} |
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_discoveredWeakRefs = &_discoveredSoftRefs[_num_q]; |
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_discoveredFinalRefs = &_discoveredWeakRefs[_num_q]; |
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_discoveredPhantomRefs = &_discoveredFinalRefs[_num_q]; |
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assert(_sentinelRef != NULL, "_sentinelRef is NULL"); |
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// Initialized all entries to _sentinelRef |
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for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
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_discoveredSoftRefs[i].set_head(_sentinelRef); |
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_discoveredSoftRefs[i].set_length(0); |
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} |
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} |
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#ifndef PRODUCT |
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void ReferenceProcessor::verify_no_references_recorded() { |
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guarantee(!_discovering_refs, "Discovering refs?"); |
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for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
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guarantee(_discoveredSoftRefs[i].empty(), |
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"Found non-empty discovered list"); |
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} |
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} |
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#endif |
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void ReferenceProcessor::weak_oops_do(OopClosure* f) { |
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for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
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f->do_oop(_discoveredSoftRefs[i].head_ptr()); |
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} |
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} |
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void ReferenceProcessor::oops_do(OopClosure* f) { |
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f->do_oop(&_sentinelRef); |
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} |
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void ReferenceProcessor::update_soft_ref_master_clock() |
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{ |
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// Update (advance) the soft ref master clock field. This must be done |
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// after processing the soft ref list. |
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jlong now = os::javaTimeMillis(); |
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jlong clock = java_lang_ref_SoftReference::clock(); |
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NOT_PRODUCT( |
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if (now < clock) { |
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warning("time warp: %d to %d", clock, now); |
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} |
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) |
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// In product mode, protect ourselves from system time being adjusted |
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// externally and going backward; see note in the implementation of |
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// GenCollectedHeap::time_since_last_gc() for the right way to fix |
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// this uniformly throughout the VM; see bug-id 4741166. XXX |
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if (now > clock) { |
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java_lang_ref_SoftReference::set_clock(now); |
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} |
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// Else leave clock stalled at its old value until time progresses |
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// past clock value. |
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} |
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void |
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ReferenceProcessor::process_discovered_references( |
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ReferencePolicy* policy, |
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BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc, |
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AbstractRefProcTaskExecutor* task_executor) { |
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NOT_PRODUCT(verify_ok_to_handle_reflists()); |
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assert(!enqueuing_is_done(), "If here enqueuing should not be complete"); |
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// Stop treating discovered references specially. |
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disable_discovery(); |
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bool trace_time = PrintGCDetails && PrintReferenceGC; |
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// Soft references |
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{ |
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TraceTime tt("SoftReference", trace_time, false, gclog_or_tty); |
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process_discovered_reflist(_discoveredSoftRefs, policy, true, |
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is_alive, keep_alive, complete_gc, task_executor); |
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} |
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update_soft_ref_master_clock(); |
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// Weak references |
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{ |
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TraceTime tt("WeakReference", trace_time, false, gclog_or_tty); |
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process_discovered_reflist(_discoveredWeakRefs, NULL, true, |
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is_alive, keep_alive, complete_gc, task_executor); |
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} |
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// Final references |
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{ |
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TraceTime tt("FinalReference", trace_time, false, gclog_or_tty); |
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process_discovered_reflist(_discoveredFinalRefs, NULL, false, |
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is_alive, keep_alive, complete_gc, task_executor); |
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} |
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// Phantom references |
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{ |
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TraceTime tt("PhantomReference", trace_time, false, gclog_or_tty); |
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process_discovered_reflist(_discoveredPhantomRefs, NULL, false, |
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is_alive, keep_alive, complete_gc, task_executor); |
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} |
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// Weak global JNI references. It would make more sense (semantically) to |
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// traverse these simultaneously with the regular weak references above, but |
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// that is not how the JDK1.2 specification is. See #4126360. Native code can |
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// thus use JNI weak references to circumvent the phantom references and |
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// resurrect a "post-mortem" object. |
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{ |
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TraceTime tt("JNI Weak Reference", trace_time, false, gclog_or_tty); |
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if (task_executor != NULL) { |
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task_executor->set_single_threaded_mode(); |
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} |
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process_phaseJNI(is_alive, keep_alive, complete_gc); |
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} |
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} |
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225 |
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226 |
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227 |
#ifndef PRODUCT |
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// Calculate the number of jni handles. |
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unsigned int ReferenceProcessor::count_jni_refs() |
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{ |
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class AlwaysAliveClosure: public BoolObjectClosure { |
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public: |
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bool do_object_b(oop obj) { return true; } |
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void do_object(oop obj) { assert(false, "Don't call"); } |
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}; |
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237 |
class CountHandleClosure: public OopClosure { |
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private: |
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int _count; |
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public: |
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CountHandleClosure(): _count(0) {} |
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void do_oop(oop* unused) { |
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_count++; |
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} |
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int count() { return _count; } |
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}; |
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CountHandleClosure global_handle_count; |
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AlwaysAliveClosure always_alive; |
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JNIHandles::weak_oops_do(&always_alive, &global_handle_count); |
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return global_handle_count.count(); |
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} |
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#endif |
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void ReferenceProcessor::process_phaseJNI(BoolObjectClosure* is_alive, |
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OopClosure* keep_alive, |
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VoidClosure* complete_gc) { |
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#ifndef PRODUCT |
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if (PrintGCDetails && PrintReferenceGC) { |
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unsigned int count = count_jni_refs(); |
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gclog_or_tty->print(", %u refs", count); |
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} |
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#endif |
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JNIHandles::weak_oops_do(is_alive, keep_alive); |
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// Finally remember to keep sentinel around |
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keep_alive->do_oop(&_sentinelRef); |
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complete_gc->do_void(); |
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} |
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bool ReferenceProcessor::enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor) { |
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NOT_PRODUCT(verify_ok_to_handle_reflists()); |
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// Remember old value of pending references list |
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oop* pending_list_addr = java_lang_ref_Reference::pending_list_addr(); |
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oop old_pending_list_value = *pending_list_addr; |
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// Enqueue references that are not made active again, and |
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// clear the decks for the next collection (cycle). |
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enqueue_discovered_reflists(pending_list_addr, task_executor); |
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// Do the oop-check on pending_list_addr missed in |
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// enqueue_discovered_reflist. We should probably |
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// do a raw oop_check so that future such idempotent |
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// oop_stores relying on the oop-check side-effect |
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// may be elided automatically and safely without |
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// affecting correctness. |
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oop_store(pending_list_addr, *(pending_list_addr)); |
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// Stop treating discovered references specially. |
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disable_discovery(); |
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288 |
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289 |
// Return true if new pending references were added |
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return old_pending_list_value != *pending_list_addr; |
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} |
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void ReferenceProcessor::enqueue_discovered_reflist(DiscoveredList& refs_list, |
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oop* pending_list_addr) { |
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// Given a list of refs linked through the "discovered" field |
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// (java.lang.ref.Reference.discovered) chain them through the |
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// "next" field (java.lang.ref.Reference.next) and prepend |
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298 |
// to the pending list. |
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299 |
if (TraceReferenceGC && PrintGCDetails) { |
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300 |
gclog_or_tty->print_cr("ReferenceProcessor::enqueue_discovered_reflist list " |
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INTPTR_FORMAT, (address)refs_list.head()); |
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} |
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oop obj = refs_list.head(); |
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// Walk down the list, copying the discovered field into |
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// the next field and clearing it (except for the last |
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// non-sentinel object which is treated specially to avoid |
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307 |
// confusion with an active reference). |
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308 |
while (obj != _sentinelRef) { |
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309 |
assert(obj->is_instanceRef(), "should be reference object"); |
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310 |
oop next = java_lang_ref_Reference::discovered(obj); |
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if (TraceReferenceGC && PrintGCDetails) { |
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gclog_or_tty->print_cr(" obj " INTPTR_FORMAT "/next " INTPTR_FORMAT, |
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313 |
(oopDesc*) obj, (oopDesc*) next); |
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314 |
} |
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315 |
assert(*java_lang_ref_Reference::next_addr(obj) == NULL, |
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316 |
"The reference should not be enqueued"); |
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317 |
if (next == _sentinelRef) { // obj is last |
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318 |
// Swap refs_list into pendling_list_addr and |
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// set obj's next to what we read from pending_list_addr. |
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320 |
oop old = (oop)Atomic::xchg_ptr(refs_list.head(), pending_list_addr); |
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321 |
// Need oop_check on pending_list_addr above; |
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322 |
// see special oop-check code at the end of |
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323 |
// enqueue_discovered_reflists() further below. |
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324 |
if (old == NULL) { |
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325 |
// obj should be made to point to itself, since |
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// pending list was empty. |
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327 |
java_lang_ref_Reference::set_next(obj, obj); |
|
328 |
} else { |
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329 |
java_lang_ref_Reference::set_next(obj, old); |
|
330 |
} |
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331 |
} else { |
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332 |
java_lang_ref_Reference::set_next(obj, next); |
|
333 |
} |
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334 |
java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
|
335 |
obj = next; |
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336 |
} |
|
337 |
} |
|
338 |
||
339 |
// Parallel enqueue task |
|
340 |
class RefProcEnqueueTask: public AbstractRefProcTaskExecutor::EnqueueTask { |
|
341 |
public: |
|
342 |
RefProcEnqueueTask(ReferenceProcessor& ref_processor, |
|
343 |
DiscoveredList discovered_refs[], |
|
344 |
oop* pending_list_addr, |
|
345 |
oop sentinel_ref, |
|
346 |
int n_queues) |
|
347 |
: EnqueueTask(ref_processor, discovered_refs, |
|
348 |
pending_list_addr, sentinel_ref, n_queues) |
|
349 |
{ } |
|
350 |
||
351 |
virtual void work(unsigned int work_id) |
|
352 |
{ |
|
353 |
assert(work_id < (unsigned int)_ref_processor.num_q(), "Index out-of-bounds"); |
|
354 |
// Simplest first cut: static partitioning. |
|
355 |
int index = work_id; |
|
356 |
for (int j = 0; j < subclasses_of_ref; j++, index += _n_queues) { |
|
357 |
_ref_processor.enqueue_discovered_reflist( |
|
358 |
_refs_lists[index], _pending_list_addr); |
|
359 |
_refs_lists[index].set_head(_sentinel_ref); |
|
360 |
_refs_lists[index].set_length(0); |
|
361 |
} |
|
362 |
} |
|
363 |
}; |
|
364 |
||
365 |
// Enqueue references that are not made active again |
|
366 |
void ReferenceProcessor::enqueue_discovered_reflists(oop* pending_list_addr, |
|
367 |
AbstractRefProcTaskExecutor* task_executor) { |
|
368 |
if (_processing_is_mt && task_executor != NULL) { |
|
369 |
// Parallel code |
|
370 |
RefProcEnqueueTask tsk(*this, _discoveredSoftRefs, |
|
371 |
pending_list_addr, _sentinelRef, _num_q); |
|
372 |
task_executor->execute(tsk); |
|
373 |
} else { |
|
374 |
// Serial code: call the parent class's implementation |
|
375 |
for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
|
376 |
enqueue_discovered_reflist(_discoveredSoftRefs[i], pending_list_addr); |
|
377 |
_discoveredSoftRefs[i].set_head(_sentinelRef); |
|
378 |
_discoveredSoftRefs[i].set_length(0); |
|
379 |
} |
|
380 |
} |
|
381 |
} |
|
382 |
||
383 |
// Iterator for the list of discovered references. |
|
384 |
class DiscoveredListIterator { |
|
385 |
public: |
|
386 |
inline DiscoveredListIterator(DiscoveredList& refs_list, |
|
387 |
OopClosure* keep_alive, |
|
388 |
BoolObjectClosure* is_alive); |
|
389 |
||
390 |
// End Of List. |
|
391 |
inline bool has_next() const |
|
392 |
{ return _next != ReferenceProcessor::_sentinelRef; } |
|
393 |
||
394 |
// Get oop to the Reference object. |
|
395 |
inline oop obj() const { return _ref; } |
|
396 |
||
397 |
// Get oop to the referent object. |
|
398 |
inline oop referent() const { return _referent; } |
|
399 |
||
400 |
// Returns true if referent is alive. |
|
401 |
inline bool is_referent_alive() const; |
|
402 |
||
403 |
// Loads data for the current reference. |
|
404 |
// The "allow_null_referent" argument tells us to allow for the possibility |
|
405 |
// of a NULL referent in the discovered Reference object. This typically |
|
406 |
// happens in the case of concurrent collectors that may have done the |
|
407 |
// discovery concurrently or interleaved with mutator execution. |
|
408 |
inline void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); |
|
409 |
||
410 |
// Move to the next discovered reference. |
|
411 |
inline void next(); |
|
412 |
||
413 |
// Remove the current reference from the list and move to the next. |
|
414 |
inline void remove(); |
|
415 |
||
416 |
// Make the Reference object active again. |
|
417 |
inline void make_active() { java_lang_ref_Reference::set_next(_ref, NULL); } |
|
418 |
||
419 |
// Make the referent alive. |
|
420 |
inline void make_referent_alive() { _keep_alive->do_oop(_referent_addr); } |
|
421 |
||
422 |
// Update the discovered field. |
|
423 |
inline void update_discovered() { _keep_alive->do_oop(_prev_next); } |
|
424 |
||
425 |
// NULL out referent pointer. |
|
426 |
inline void clear_referent() { *_referent_addr = NULL; } |
|
427 |
||
428 |
// Statistics |
|
429 |
NOT_PRODUCT( |
|
430 |
inline size_t processed() const { return _processed; } |
|
431 |
inline size_t removed() const { return _removed; } |
|
432 |
) |
|
433 |
||
434 |
private: |
|
435 |
inline void move_to_next(); |
|
436 |
||
437 |
private: |
|
438 |
DiscoveredList& _refs_list; |
|
439 |
oop* _prev_next; |
|
440 |
oop _ref; |
|
441 |
oop* _discovered_addr; |
|
442 |
oop _next; |
|
443 |
oop* _referent_addr; |
|
444 |
oop _referent; |
|
445 |
OopClosure* _keep_alive; |
|
446 |
BoolObjectClosure* _is_alive; |
|
447 |
DEBUG_ONLY( |
|
448 |
oop _first_seen; // cyclic linked list check |
|
449 |
) |
|
450 |
NOT_PRODUCT( |
|
451 |
size_t _processed; |
|
452 |
size_t _removed; |
|
453 |
) |
|
454 |
}; |
|
455 |
||
456 |
inline DiscoveredListIterator::DiscoveredListIterator(DiscoveredList& refs_list, |
|
457 |
OopClosure* keep_alive, |
|
458 |
BoolObjectClosure* is_alive) |
|
459 |
: _refs_list(refs_list), |
|
460 |
_prev_next(refs_list.head_ptr()), |
|
461 |
_ref(refs_list.head()), |
|
462 |
#ifdef ASSERT |
|
463 |
_first_seen(refs_list.head()), |
|
464 |
#endif |
|
465 |
#ifndef PRODUCT |
|
466 |
_processed(0), |
|
467 |
_removed(0), |
|
468 |
#endif |
|
469 |
_next(refs_list.head()), |
|
470 |
_keep_alive(keep_alive), |
|
471 |
_is_alive(is_alive) |
|
472 |
{ } |
|
473 |
||
474 |
inline bool DiscoveredListIterator::is_referent_alive() const |
|
475 |
{ |
|
476 |
return _is_alive->do_object_b(_referent); |
|
477 |
} |
|
478 |
||
479 |
inline void DiscoveredListIterator::load_ptrs(DEBUG_ONLY(bool allow_null_referent)) |
|
480 |
{ |
|
481 |
_discovered_addr = java_lang_ref_Reference::discovered_addr(_ref); |
|
482 |
assert(_discovered_addr && (*_discovered_addr)->is_oop_or_null(), |
|
483 |
"discovered field is bad"); |
|
484 |
_next = *_discovered_addr; |
|
485 |
_referent_addr = java_lang_ref_Reference::referent_addr(_ref); |
|
486 |
_referent = *_referent_addr; |
|
487 |
assert(Universe::heap()->is_in_reserved_or_null(_referent), |
|
488 |
"Wrong oop found in java.lang.Reference object"); |
|
489 |
assert(allow_null_referent ? |
|
490 |
_referent->is_oop_or_null() |
|
491 |
: _referent->is_oop(), |
|
492 |
"bad referent"); |
|
493 |
} |
|
494 |
||
495 |
inline void DiscoveredListIterator::next() |
|
496 |
{ |
|
497 |
_prev_next = _discovered_addr; |
|
498 |
move_to_next(); |
|
499 |
} |
|
500 |
||
501 |
inline void DiscoveredListIterator::remove() |
|
502 |
{ |
|
503 |
assert(_ref->is_oop(), "Dropping a bad reference"); |
|
504 |
// Clear the discovered_addr field so that the object does |
|
505 |
// not look like it has been discovered. |
|
506 |
*_discovered_addr = NULL; |
|
507 |
// Remove Reference object from list. |
|
508 |
*_prev_next = _next; |
|
509 |
NOT_PRODUCT(_removed++); |
|
510 |
move_to_next(); |
|
511 |
} |
|
512 |
||
513 |
inline void DiscoveredListIterator::move_to_next() |
|
514 |
{ |
|
515 |
_ref = _next; |
|
516 |
assert(_ref != _first_seen, "cyclic ref_list found"); |
|
517 |
NOT_PRODUCT(_processed++); |
|
518 |
} |
|
519 |
||
520 |
||
521 |
// NOTE: process_phase*() are largely similar, and at a high level |
|
522 |
// merely iterate over the extant list applying a predicate to |
|
523 |
// each of its elements and possibly removing that element from the |
|
524 |
// list and applying some further closures to that element. |
|
525 |
// We should consider the possibility of replacing these |
|
526 |
// process_phase*() methods by abstracting them into |
|
527 |
// a single general iterator invocation that receives appropriate |
|
528 |
// closures that accomplish this work. |
|
529 |
||
530 |
// (SoftReferences only) Traverse the list and remove any SoftReferences whose |
|
531 |
// referents are not alive, but that should be kept alive for policy reasons. |
|
532 |
// Keep alive the transitive closure of all such referents. |
|
533 |
void |
|
534 |
ReferenceProcessor::process_phase1(DiscoveredList& refs_list_addr, |
|
535 |
ReferencePolicy* policy, |
|
536 |
BoolObjectClosure* is_alive, |
|
537 |
OopClosure* keep_alive, |
|
538 |
VoidClosure* complete_gc) { |
|
539 |
assert(policy != NULL, "Must have a non-NULL policy"); |
|
540 |
DiscoveredListIterator iter(refs_list_addr, keep_alive, is_alive); |
|
541 |
// Decide which softly reachable refs should be kept alive. |
|
542 |
while (iter.has_next()) { |
|
543 |
iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */)); |
|
544 |
bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive(); |
|
545 |
if (referent_is_dead && !policy->should_clear_reference(iter.obj())) { |
|
546 |
if (TraceReferenceGC) { |
|
547 |
gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy", |
|
548 |
(address)iter.obj(), iter.obj()->blueprint()->internal_name()); |
|
549 |
} |
|
550 |
// Make the Reference object active again |
|
551 |
iter.make_active(); |
|
552 |
// keep the referent around |
|
553 |
iter.make_referent_alive(); |
|
554 |
// Remove Reference object from list |
|
555 |
iter.remove(); |
|
556 |
} else { |
|
557 |
iter.next(); |
|
558 |
} |
|
559 |
} |
|
560 |
// Close the reachable set |
|
561 |
complete_gc->do_void(); |
|
562 |
NOT_PRODUCT( |
|
563 |
if (PrintGCDetails && TraceReferenceGC) { |
|
564 |
gclog_or_tty->print(" Dropped %d dead Refs out of %d " |
|
565 |
"discovered Refs by policy ", iter.removed(), iter.processed()); |
|
566 |
} |
|
567 |
) |
|
568 |
} |
|
569 |
||
570 |
// Traverse the list and remove any Refs that are not active, or |
|
571 |
// whose referents are either alive or NULL. |
|
572 |
void |
|
573 |
ReferenceProcessor::pp2_work(DiscoveredList& refs_list_addr, |
|
574 |
BoolObjectClosure* is_alive, |
|
575 |
OopClosure* keep_alive) |
|
576 |
{ |
|
577 |
assert(discovery_is_atomic(), "Error"); |
|
578 |
DiscoveredListIterator iter(refs_list_addr, keep_alive, is_alive); |
|
579 |
while (iter.has_next()) { |
|
580 |
iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
|
581 |
DEBUG_ONLY(oop* next_addr = java_lang_ref_Reference::next_addr(iter.obj());) |
|
582 |
assert(*next_addr == NULL, "Should not discover inactive Reference"); |
|
583 |
if (iter.is_referent_alive()) { |
|
584 |
if (TraceReferenceGC) { |
|
585 |
gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)", |
|
586 |
(address)iter.obj(), iter.obj()->blueprint()->internal_name()); |
|
587 |
} |
|
588 |
// The referent is reachable after all. |
|
589 |
// Update the referent pointer as necessary: Note that this |
|
590 |
// should not entail any recursive marking because the |
|
591 |
// referent must already have been traversed. |
|
592 |
iter.make_referent_alive(); |
|
593 |
// Remove Reference object from list |
|
594 |
iter.remove(); |
|
595 |
} else { |
|
596 |
iter.next(); |
|
597 |
} |
|
598 |
} |
|
599 |
NOT_PRODUCT( |
|
600 |
if (PrintGCDetails && TraceReferenceGC) { |
|
601 |
gclog_or_tty->print(" Dropped %d active Refs out of %d " |
|
602 |
"Refs in discovered list ", iter.removed(), iter.processed()); |
|
603 |
} |
|
604 |
) |
|
605 |
} |
|
606 |
||
607 |
void |
|
608 |
ReferenceProcessor::pp2_work_concurrent_discovery( |
|
609 |
DiscoveredList& refs_list_addr, |
|
610 |
BoolObjectClosure* is_alive, |
|
611 |
OopClosure* keep_alive, |
|
612 |
VoidClosure* complete_gc) |
|
613 |
{ |
|
614 |
assert(!discovery_is_atomic(), "Error"); |
|
615 |
DiscoveredListIterator iter(refs_list_addr, keep_alive, is_alive); |
|
616 |
while (iter.has_next()) { |
|
617 |
iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
|
618 |
oop* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
|
619 |
if ((iter.referent() == NULL || iter.is_referent_alive() || |
|
620 |
*next_addr != NULL)) { |
|
621 |
assert((*next_addr)->is_oop_or_null(), "bad next field"); |
|
622 |
// Remove Reference object from list |
|
623 |
iter.remove(); |
|
624 |
// Trace the cohorts |
|
625 |
iter.make_referent_alive(); |
|
626 |
keep_alive->do_oop(next_addr); |
|
627 |
} else { |
|
628 |
iter.next(); |
|
629 |
} |
|
630 |
} |
|
631 |
// Now close the newly reachable set |
|
632 |
complete_gc->do_void(); |
|
633 |
NOT_PRODUCT( |
|
634 |
if (PrintGCDetails && TraceReferenceGC) { |
|
635 |
gclog_or_tty->print(" Dropped %d active Refs out of %d " |
|
636 |
"Refs in discovered list ", iter.removed(), iter.processed()); |
|
637 |
} |
|
638 |
) |
|
639 |
} |
|
640 |
||
641 |
// Traverse the list and process the referents, by either |
|
642 |
// either clearing them or keeping them (and their reachable |
|
643 |
// closure) alive. |
|
644 |
void |
|
645 |
ReferenceProcessor::process_phase3(DiscoveredList& refs_list_addr, |
|
646 |
bool clear_referent, |
|
647 |
BoolObjectClosure* is_alive, |
|
648 |
OopClosure* keep_alive, |
|
649 |
VoidClosure* complete_gc) { |
|
650 |
DiscoveredListIterator iter(refs_list_addr, keep_alive, is_alive); |
|
651 |
while (iter.has_next()) { |
|
652 |
iter.update_discovered(); |
|
653 |
iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */)); |
|
654 |
if (clear_referent) { |
|
655 |
// NULL out referent pointer |
|
656 |
iter.clear_referent(); |
|
657 |
} else { |
|
658 |
// keep the referent around |
|
659 |
iter.make_referent_alive(); |
|
660 |
} |
|
661 |
if (TraceReferenceGC) { |
|
662 |
gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending", |
|
663 |
clear_referent ? "cleared " : "", |
|
664 |
(address)iter.obj(), iter.obj()->blueprint()->internal_name()); |
|
665 |
} |
|
666 |
assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference"); |
|
667 |
// If discovery is concurrent, we may have objects with null referents, |
|
668 |
// being those that were concurrently cleared after they were discovered |
|
669 |
// (and not subsequently precleaned). |
|
670 |
assert( (discovery_is_atomic() && iter.referent()->is_oop()) |
|
671 |
|| (!discovery_is_atomic() && iter.referent()->is_oop_or_null(UseConcMarkSweepGC)), |
|
672 |
"Adding a bad referent"); |
|
673 |
iter.next(); |
|
674 |
} |
|
675 |
// Remember to keep sentinel pointer around |
|
676 |
iter.update_discovered(); |
|
677 |
// Close the reachable set |
|
678 |
complete_gc->do_void(); |
|
679 |
} |
|
680 |
||
681 |
void |
|
682 |
ReferenceProcessor::abandon_partial_discovered_list(DiscoveredList& ref_list) { |
|
683 |
oop obj = ref_list.head(); |
|
684 |
while (obj != _sentinelRef) { |
|
685 |
oop* discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
|
686 |
obj = *discovered_addr; |
|
687 |
*discovered_addr = NULL; |
|
688 |
} |
|
689 |
ref_list.set_head(_sentinelRef); |
|
690 |
ref_list.set_length(0); |
|
691 |
} |
|
692 |
||
693 |
void |
|
694 |
ReferenceProcessor::abandon_partial_discovered_list_arr(DiscoveredList refs_lists[]) { |
|
695 |
for (int i = 0; i < _num_q; i++) { |
|
696 |
abandon_partial_discovered_list(refs_lists[i]); |
|
697 |
} |
|
698 |
} |
|
699 |
||
700 |
class RefProcPhase1Task: public AbstractRefProcTaskExecutor::ProcessTask { |
|
701 |
public: |
|
702 |
RefProcPhase1Task(ReferenceProcessor& ref_processor, |
|
703 |
DiscoveredList refs_lists[], |
|
704 |
ReferencePolicy* policy, |
|
705 |
bool marks_oops_alive) |
|
706 |
: ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
|
707 |
_policy(policy) |
|
708 |
{ } |
|
709 |
virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
|
710 |
OopClosure& keep_alive, |
|
711 |
VoidClosure& complete_gc) |
|
712 |
{ |
|
713 |
_ref_processor.process_phase1(_refs_lists[i], _policy, |
|
714 |
&is_alive, &keep_alive, &complete_gc); |
|
715 |
} |
|
716 |
private: |
|
717 |
ReferencePolicy* _policy; |
|
718 |
}; |
|
719 |
||
720 |
class RefProcPhase2Task: public AbstractRefProcTaskExecutor::ProcessTask { |
|
721 |
public: |
|
722 |
RefProcPhase2Task(ReferenceProcessor& ref_processor, |
|
723 |
DiscoveredList refs_lists[], |
|
724 |
bool marks_oops_alive) |
|
725 |
: ProcessTask(ref_processor, refs_lists, marks_oops_alive) |
|
726 |
{ } |
|
727 |
virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
|
728 |
OopClosure& keep_alive, |
|
729 |
VoidClosure& complete_gc) |
|
730 |
{ |
|
731 |
_ref_processor.process_phase2(_refs_lists[i], |
|
732 |
&is_alive, &keep_alive, &complete_gc); |
|
733 |
} |
|
734 |
}; |
|
735 |
||
736 |
class RefProcPhase3Task: public AbstractRefProcTaskExecutor::ProcessTask { |
|
737 |
public: |
|
738 |
RefProcPhase3Task(ReferenceProcessor& ref_processor, |
|
739 |
DiscoveredList refs_lists[], |
|
740 |
bool clear_referent, |
|
741 |
bool marks_oops_alive) |
|
742 |
: ProcessTask(ref_processor, refs_lists, marks_oops_alive), |
|
743 |
_clear_referent(clear_referent) |
|
744 |
{ } |
|
745 |
virtual void work(unsigned int i, BoolObjectClosure& is_alive, |
|
746 |
OopClosure& keep_alive, |
|
747 |
VoidClosure& complete_gc) |
|
748 |
{ |
|
749 |
_ref_processor.process_phase3(_refs_lists[i], _clear_referent, |
|
750 |
&is_alive, &keep_alive, &complete_gc); |
|
751 |
} |
|
752 |
private: |
|
753 |
bool _clear_referent; |
|
754 |
}; |
|
755 |
||
756 |
// Balances reference queues. |
|
757 |
void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[]) |
|
758 |
{ |
|
759 |
// calculate total length |
|
760 |
size_t total_refs = 0; |
|
761 |
for (int i = 0; i < _num_q; ++i) { |
|
762 |
total_refs += ref_lists[i].length(); |
|
763 |
} |
|
764 |
size_t avg_refs = total_refs / _num_q + 1; |
|
765 |
int to_idx = 0; |
|
766 |
for (int from_idx = 0; from_idx < _num_q; from_idx++) { |
|
767 |
while (ref_lists[from_idx].length() > avg_refs) { |
|
768 |
assert(to_idx < _num_q, "Sanity Check!"); |
|
769 |
if (ref_lists[to_idx].length() < avg_refs) { |
|
770 |
// move superfluous refs |
|
771 |
size_t refs_to_move = |
|
772 |
MIN2(ref_lists[from_idx].length() - avg_refs, |
|
773 |
avg_refs - ref_lists[to_idx].length()); |
|
774 |
oop move_head = ref_lists[from_idx].head(); |
|
775 |
oop move_tail = move_head; |
|
776 |
oop new_head = move_head; |
|
777 |
// find an element to split the list on |
|
778 |
for (size_t j = 0; j < refs_to_move; ++j) { |
|
779 |
move_tail = new_head; |
|
780 |
new_head = *java_lang_ref_Reference::discovered_addr(new_head); |
|
781 |
} |
|
782 |
java_lang_ref_Reference::set_discovered(move_tail, ref_lists[to_idx].head()); |
|
783 |
ref_lists[to_idx].set_head(move_head); |
|
784 |
ref_lists[to_idx].set_length(ref_lists[to_idx].length() + refs_to_move); |
|
785 |
ref_lists[from_idx].set_head(new_head); |
|
786 |
ref_lists[from_idx].set_length(ref_lists[from_idx].length() - refs_to_move); |
|
787 |
} else { |
|
788 |
++to_idx; |
|
789 |
} |
|
790 |
} |
|
791 |
} |
|
792 |
} |
|
793 |
||
794 |
void |
|
795 |
ReferenceProcessor::process_discovered_reflist( |
|
796 |
DiscoveredList refs_lists[], |
|
797 |
ReferencePolicy* policy, |
|
798 |
bool clear_referent, |
|
799 |
BoolObjectClosure* is_alive, |
|
800 |
OopClosure* keep_alive, |
|
801 |
VoidClosure* complete_gc, |
|
802 |
AbstractRefProcTaskExecutor* task_executor) |
|
803 |
{ |
|
804 |
bool mt = task_executor != NULL && _processing_is_mt; |
|
805 |
if (mt && ParallelRefProcBalancingEnabled) { |
|
806 |
balance_queues(refs_lists); |
|
807 |
} |
|
808 |
if (PrintReferenceGC && PrintGCDetails) { |
|
809 |
size_t total = 0; |
|
810 |
for (int i = 0; i < _num_q; ++i) { |
|
811 |
total += refs_lists[i].length(); |
|
812 |
} |
|
813 |
gclog_or_tty->print(", %u refs", total); |
|
814 |
} |
|
815 |
||
816 |
// Phase 1 (soft refs only): |
|
817 |
// . Traverse the list and remove any SoftReferences whose |
|
818 |
// referents are not alive, but that should be kept alive for |
|
819 |
// policy reasons. Keep alive the transitive closure of all |
|
820 |
// such referents. |
|
821 |
if (policy != NULL) { |
|
822 |
if (mt) { |
|
823 |
RefProcPhase1Task phase1(*this, refs_lists, policy, true /*marks_oops_alive*/); |
|
824 |
task_executor->execute(phase1); |
|
825 |
} else { |
|
826 |
for (int i = 0; i < _num_q; i++) { |
|
827 |
process_phase1(refs_lists[i], policy, |
|
828 |
is_alive, keep_alive, complete_gc); |
|
829 |
} |
|
830 |
} |
|
831 |
} else { // policy == NULL |
|
832 |
assert(refs_lists != _discoveredSoftRefs, |
|
833 |
"Policy must be specified for soft references."); |
|
834 |
} |
|
835 |
||
836 |
// Phase 2: |
|
837 |
// . Traverse the list and remove any refs whose referents are alive. |
|
838 |
if (mt) { |
|
839 |
RefProcPhase2Task phase2(*this, refs_lists, !discovery_is_atomic() /*marks_oops_alive*/); |
|
840 |
task_executor->execute(phase2); |
|
841 |
} else { |
|
842 |
for (int i = 0; i < _num_q; i++) { |
|
843 |
process_phase2(refs_lists[i], is_alive, keep_alive, complete_gc); |
|
844 |
} |
|
845 |
} |
|
846 |
||
847 |
// Phase 3: |
|
848 |
// . Traverse the list and process referents as appropriate. |
|
849 |
if (mt) { |
|
850 |
RefProcPhase3Task phase3(*this, refs_lists, clear_referent, true /*marks_oops_alive*/); |
|
851 |
task_executor->execute(phase3); |
|
852 |
} else { |
|
853 |
for (int i = 0; i < _num_q; i++) { |
|
854 |
process_phase3(refs_lists[i], clear_referent, |
|
855 |
is_alive, keep_alive, complete_gc); |
|
856 |
} |
|
857 |
} |
|
858 |
} |
|
859 |
||
860 |
void ReferenceProcessor::clean_up_discovered_references() { |
|
861 |
// loop over the lists |
|
862 |
for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
|
863 |
if (TraceReferenceGC && PrintGCDetails && ((i % _num_q) == 0)) { |
|
864 |
gclog_or_tty->print_cr( |
|
865 |
"\nScrubbing %s discovered list of Null referents", |
|
866 |
list_name(i)); |
|
867 |
} |
|
868 |
clean_up_discovered_reflist(_discoveredSoftRefs[i]); |
|
869 |
} |
|
870 |
} |
|
871 |
||
872 |
void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) { |
|
873 |
assert(!discovery_is_atomic(), "Else why call this method?"); |
|
874 |
DiscoveredListIterator iter(refs_list, NULL, NULL); |
|
875 |
size_t length = refs_list.length(); |
|
876 |
while (iter.has_next()) { |
|
877 |
iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
|
878 |
oop* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
|
879 |
assert((*next_addr)->is_oop_or_null(), "bad next field"); |
|
880 |
// If referent has been cleared or Reference is not active, |
|
881 |
// drop it. |
|
882 |
if (iter.referent() == NULL || *next_addr != NULL) { |
|
883 |
debug_only( |
|
884 |
if (PrintGCDetails && TraceReferenceGC) { |
|
885 |
gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: " |
|
886 |
INTPTR_FORMAT " with next field: " INTPTR_FORMAT |
|
887 |
" and referent: " INTPTR_FORMAT, |
|
888 |
(address)iter.obj(), (address)*next_addr, (address)iter.referent()); |
|
889 |
} |
|
890 |
) |
|
891 |
// Remove Reference object from list |
|
892 |
iter.remove(); |
|
893 |
--length; |
|
894 |
} else { |
|
895 |
iter.next(); |
|
896 |
} |
|
897 |
} |
|
898 |
refs_list.set_length(length); |
|
899 |
NOT_PRODUCT( |
|
900 |
if (PrintGCDetails && TraceReferenceGC) { |
|
901 |
gclog_or_tty->print( |
|
902 |
" Removed %d Refs with NULL referents out of %d discovered Refs", |
|
903 |
iter.removed(), iter.processed()); |
|
904 |
} |
|
905 |
) |
|
906 |
} |
|
907 |
||
908 |
inline DiscoveredList* ReferenceProcessor::get_discovered_list(ReferenceType rt) { |
|
909 |
int id = 0; |
|
910 |
// Determine the queue index to use for this object. |
|
911 |
if (_discovery_is_mt) { |
|
912 |
// During a multi-threaded discovery phase, |
|
913 |
// each thread saves to its "own" list. |
|
914 |
Thread* thr = Thread::current(); |
|
915 |
assert(thr->is_GC_task_thread(), |
|
916 |
"Dubious cast from Thread* to WorkerThread*?"); |
|
917 |
id = ((WorkerThread*)thr)->id(); |
|
918 |
} else { |
|
919 |
// single-threaded discovery, we save in round-robin |
|
920 |
// fashion to each of the lists. |
|
921 |
if (_processing_is_mt) { |
|
922 |
id = next_id(); |
|
923 |
} |
|
924 |
} |
|
925 |
assert(0 <= id && id < _num_q, "Id is out-of-bounds (call Freud?)"); |
|
926 |
||
927 |
// Get the discovered queue to which we will add |
|
928 |
DiscoveredList* list = NULL; |
|
929 |
switch (rt) { |
|
930 |
case REF_OTHER: |
|
931 |
// Unknown reference type, no special treatment |
|
932 |
break; |
|
933 |
case REF_SOFT: |
|
934 |
list = &_discoveredSoftRefs[id]; |
|
935 |
break; |
|
936 |
case REF_WEAK: |
|
937 |
list = &_discoveredWeakRefs[id]; |
|
938 |
break; |
|
939 |
case REF_FINAL: |
|
940 |
list = &_discoveredFinalRefs[id]; |
|
941 |
break; |
|
942 |
case REF_PHANTOM: |
|
943 |
list = &_discoveredPhantomRefs[id]; |
|
944 |
break; |
|
945 |
case REF_NONE: |
|
946 |
// we should not reach here if we are an instanceRefKlass |
|
947 |
default: |
|
948 |
ShouldNotReachHere(); |
|
949 |
} |
|
950 |
return list; |
|
951 |
} |
|
952 |
||
953 |
inline void ReferenceProcessor::add_to_discovered_list_mt(DiscoveredList& list, |
|
954 |
oop obj, oop* discovered_addr) { |
|
955 |
assert(_discovery_is_mt, "!_discovery_is_mt should have been handled by caller"); |
|
956 |
// First we must make sure this object is only enqueued once. CAS in a non null |
|
957 |
// discovered_addr. |
|
958 |
oop retest = (oop)Atomic::cmpxchg_ptr(list.head(), discovered_addr, NULL); |
|
959 |
if (retest == NULL) { |
|
960 |
// This thread just won the right to enqueue the object. |
|
961 |
// We have separate lists for enqueueing so no synchronization |
|
962 |
// is necessary. |
|
963 |
list.set_head(obj); |
|
964 |
list.set_length(list.length() + 1); |
|
965 |
} else { |
|
966 |
// If retest was non NULL, another thread beat us to it: |
|
967 |
// The reference has already been discovered... |
|
968 |
if (TraceReferenceGC) { |
|
969 |
gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
|
970 |
obj, obj->blueprint()->internal_name()); |
|
971 |
} |
|
972 |
} |
|
973 |
} |
|
974 |
||
975 |
||
976 |
// We mention two of several possible choices here: |
|
977 |
// #0: if the reference object is not in the "originating generation" |
|
978 |
// (or part of the heap being collected, indicated by our "span" |
|
979 |
// we don't treat it specially (i.e. we scan it as we would |
|
980 |
// a normal oop, treating its references as strong references). |
|
981 |
// This means that references can't be enqueued unless their |
|
982 |
// referent is also in the same span. This is the simplest, |
|
983 |
// most "local" and most conservative approach, albeit one |
|
984 |
// that may cause weak references to be enqueued least promptly. |
|
985 |
// We call this choice the "ReferenceBasedDiscovery" policy. |
|
986 |
// #1: the reference object may be in any generation (span), but if |
|
987 |
// the referent is in the generation (span) being currently collected |
|
988 |
// then we can discover the reference object, provided |
|
989 |
// the object has not already been discovered by |
|
990 |
// a different concurrently running collector (as may be the |
|
991 |
// case, for instance, if the reference object is in CMS and |
|
992 |
// the referent in DefNewGeneration), and provided the processing |
|
993 |
// of this reference object by the current collector will |
|
994 |
// appear atomic to every other collector in the system. |
|
995 |
// (Thus, for instance, a concurrent collector may not |
|
996 |
// discover references in other generations even if the |
|
997 |
// referent is in its own generation). This policy may, |
|
998 |
// in certain cases, enqueue references somewhat sooner than |
|
999 |
// might Policy #0 above, but at marginally increased cost |
|
1000 |
// and complexity in processing these references. |
|
1001 |
// We call this choice the "RefeferentBasedDiscovery" policy. |
|
1002 |
bool ReferenceProcessor::discover_reference(oop obj, ReferenceType rt) { |
|
1003 |
// We enqueue references only if we are discovering refs |
|
1004 |
// (rather than processing discovered refs). |
|
1005 |
if (!_discovering_refs || !RegisterReferences) { |
|
1006 |
return false; |
|
1007 |
} |
|
1008 |
// We only enqueue active references. |
|
1009 |
oop* next_addr = java_lang_ref_Reference::next_addr(obj); |
|
1010 |
if (*next_addr != NULL) { |
|
1011 |
return false; |
|
1012 |
} |
|
1013 |
||
1014 |
HeapWord* obj_addr = (HeapWord*)obj; |
|
1015 |
if (RefDiscoveryPolicy == ReferenceBasedDiscovery && |
|
1016 |
!_span.contains(obj_addr)) { |
|
1017 |
// Reference is not in the originating generation; |
|
1018 |
// don't treat it specially (i.e. we want to scan it as a normal |
|
1019 |
// object with strong references). |
|
1020 |
return false; |
|
1021 |
} |
|
1022 |
||
1023 |
// We only enqueue references whose referents are not (yet) strongly |
|
1024 |
// reachable. |
|
1025 |
if (is_alive_non_header() != NULL) { |
|
1026 |
oop referent = java_lang_ref_Reference::referent(obj); |
|
1027 |
// We'd like to assert the following: |
|
1028 |
// assert(referent != NULL, "Refs with null referents already filtered"); |
|
1029 |
// However, since this code may be executed concurrently with |
|
1030 |
// mutators, which can clear() the referent, it is not |
|
1031 |
// guaranteed that the referent is non-NULL. |
|
1032 |
if (is_alive_non_header()->do_object_b(referent)) { |
|
1033 |
return false; // referent is reachable |
|
1034 |
} |
|
1035 |
} |
|
1036 |
||
1037 |
oop* discovered_addr = java_lang_ref_Reference::discovered_addr(obj); |
|
1038 |
assert(discovered_addr != NULL && (*discovered_addr)->is_oop_or_null(), |
|
1039 |
"bad discovered field"); |
|
1040 |
if (*discovered_addr != NULL) { |
|
1041 |
// The reference has already been discovered... |
|
1042 |
if (TraceReferenceGC) { |
|
1043 |
gclog_or_tty->print_cr("Already enqueued reference (" INTPTR_FORMAT ": %s)", |
|
1044 |
(oopDesc*)obj, obj->blueprint()->internal_name()); |
|
1045 |
} |
|
1046 |
if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
|
1047 |
// assumes that an object is not processed twice; |
|
1048 |
// if it's been already discovered it must be on another |
|
1049 |
// generation's discovered list; so we won't discover it. |
|
1050 |
return false; |
|
1051 |
} else { |
|
1052 |
assert(RefDiscoveryPolicy == ReferenceBasedDiscovery, |
|
1053 |
"Unrecognized policy"); |
|
1054 |
// Check assumption that an object is not potentially |
|
1055 |
// discovered twice except by concurrent collectors that potentially |
|
1056 |
// trace the same Reference object twice. |
|
1057 |
assert(UseConcMarkSweepGC, |
|
1058 |
"Only possible with a concurrent collector"); |
|
1059 |
return true; |
|
1060 |
} |
|
1061 |
} |
|
1062 |
||
1063 |
if (RefDiscoveryPolicy == ReferentBasedDiscovery) { |
|
1064 |
oop referent = java_lang_ref_Reference::referent(obj); |
|
1065 |
assert(referent->is_oop(), "bad referent"); |
|
1066 |
// enqueue if and only if either: |
|
1067 |
// reference is in our span or |
|
1068 |
// we are an atomic collector and referent is in our span |
|
1069 |
if (_span.contains(obj_addr) || |
|
1070 |
(discovery_is_atomic() && _span.contains(referent))) { |
|
1071 |
// should_enqueue = true; |
|
1072 |
} else { |
|
1073 |
return false; |
|
1074 |
} |
|
1075 |
} else { |
|
1076 |
assert(RefDiscoveryPolicy == ReferenceBasedDiscovery && |
|
1077 |
_span.contains(obj_addr), "code inconsistency"); |
|
1078 |
} |
|
1079 |
||
1080 |
// Get the right type of discovered queue head. |
|
1081 |
DiscoveredList* list = get_discovered_list(rt); |
|
1082 |
if (list == NULL) { |
|
1083 |
return false; // nothing special needs to be done |
|
1084 |
} |
|
1085 |
||
1086 |
// We do a raw store here, the field will be visited later when |
|
1087 |
// processing the discovered references. |
|
1088 |
if (_discovery_is_mt) { |
|
1089 |
add_to_discovered_list_mt(*list, obj, discovered_addr); |
|
1090 |
} else { |
|
1091 |
*discovered_addr = list->head(); |
|
1092 |
list->set_head(obj); |
|
1093 |
list->set_length(list->length() + 1); |
|
1094 |
} |
|
1095 |
||
1096 |
// In the MT discovery case, it is currently possible to see |
|
1097 |
// the following message multiple times if several threads |
|
1098 |
// discover a reference about the same time. Only one will |
|
1099 |
// however have actually added it to the disocvered queue. |
|
1100 |
// One could let add_to_discovered_list_mt() return an |
|
1101 |
// indication for success in queueing (by 1 thread) or |
|
1102 |
// failure (by all other threads), but I decided the extra |
|
1103 |
// code was not worth the effort for something that is |
|
1104 |
// only used for debugging support. |
|
1105 |
if (TraceReferenceGC) { |
|
1106 |
oop referent = java_lang_ref_Reference::referent(obj); |
|
1107 |
if (PrintGCDetails) { |
|
1108 |
gclog_or_tty->print_cr("Enqueued reference (" INTPTR_FORMAT ": %s)", |
|
1109 |
(oopDesc*) obj, obj->blueprint()->internal_name()); |
|
1110 |
} |
|
1111 |
assert(referent->is_oop(), "Enqueued a bad referent"); |
|
1112 |
} |
|
1113 |
assert(obj->is_oop(), "Enqueued a bad reference"); |
|
1114 |
return true; |
|
1115 |
} |
|
1116 |
||
1117 |
// Preclean the discovered references by removing those |
|
1118 |
// whose referents are alive, and by marking from those that |
|
1119 |
// are not active. These lists can be handled here |
|
1120 |
// in any order and, indeed, concurrently. |
|
1121 |
void ReferenceProcessor::preclean_discovered_references( |
|
1122 |
BoolObjectClosure* is_alive, |
|
1123 |
OopClosure* keep_alive, |
|
1124 |
VoidClosure* complete_gc, |
|
1125 |
YieldClosure* yield) { |
|
1126 |
||
1127 |
NOT_PRODUCT(verify_ok_to_handle_reflists()); |
|
1128 |
||
1129 |
// Soft references |
|
1130 |
{ |
|
1131 |
TraceTime tt("Preclean SoftReferences", PrintGCDetails && PrintReferenceGC, |
|
1132 |
false, gclog_or_tty); |
|
1133 |
for (int i = 0; i < _num_q; i++) { |
|
1134 |
preclean_discovered_reflist(_discoveredSoftRefs[i], is_alive, |
|
1135 |
keep_alive, complete_gc, yield); |
|
1136 |
} |
|
1137 |
} |
|
1138 |
if (yield->should_return()) { |
|
1139 |
return; |
|
1140 |
} |
|
1141 |
||
1142 |
// Weak references |
|
1143 |
{ |
|
1144 |
TraceTime tt("Preclean WeakReferences", PrintGCDetails && PrintReferenceGC, |
|
1145 |
false, gclog_or_tty); |
|
1146 |
for (int i = 0; i < _num_q; i++) { |
|
1147 |
preclean_discovered_reflist(_discoveredWeakRefs[i], is_alive, |
|
1148 |
keep_alive, complete_gc, yield); |
|
1149 |
} |
|
1150 |
} |
|
1151 |
if (yield->should_return()) { |
|
1152 |
return; |
|
1153 |
} |
|
1154 |
||
1155 |
// Final references |
|
1156 |
{ |
|
1157 |
TraceTime tt("Preclean FinalReferences", PrintGCDetails && PrintReferenceGC, |
|
1158 |
false, gclog_or_tty); |
|
1159 |
for (int i = 0; i < _num_q; i++) { |
|
1160 |
preclean_discovered_reflist(_discoveredFinalRefs[i], is_alive, |
|
1161 |
keep_alive, complete_gc, yield); |
|
1162 |
} |
|
1163 |
} |
|
1164 |
if (yield->should_return()) { |
|
1165 |
return; |
|
1166 |
} |
|
1167 |
||
1168 |
// Phantom references |
|
1169 |
{ |
|
1170 |
TraceTime tt("Preclean PhantomReferences", PrintGCDetails && PrintReferenceGC, |
|
1171 |
false, gclog_or_tty); |
|
1172 |
for (int i = 0; i < _num_q; i++) { |
|
1173 |
preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive, |
|
1174 |
keep_alive, complete_gc, yield); |
|
1175 |
} |
|
1176 |
} |
|
1177 |
} |
|
1178 |
||
1179 |
// Walk the given discovered ref list, and remove all reference objects |
|
1180 |
// whose referents are still alive, whose referents are NULL or which |
|
1181 |
// are not active (have a non-NULL next field). NOTE: For this to work |
|
1182 |
// correctly, refs discovery can not be happening concurrently with this |
|
1183 |
// step. |
|
1184 |
void ReferenceProcessor::preclean_discovered_reflist( |
|
1185 |
DiscoveredList& refs_list, BoolObjectClosure* is_alive, |
|
1186 |
OopClosure* keep_alive, VoidClosure* complete_gc, YieldClosure* yield) { |
|
1187 |
||
1188 |
DiscoveredListIterator iter(refs_list, keep_alive, is_alive); |
|
1189 |
size_t length = refs_list.length(); |
|
1190 |
while (iter.has_next()) { |
|
1191 |
iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */)); |
|
1192 |
oop* next_addr = java_lang_ref_Reference::next_addr(iter.obj()); |
|
1193 |
if (iter.referent() == NULL || iter.is_referent_alive() || |
|
1194 |
*next_addr != NULL) { |
|
1195 |
// The referent has been cleared, or is alive, or the Reference is not |
|
1196 |
// active; we need to trace and mark its cohort. |
|
1197 |
if (TraceReferenceGC) { |
|
1198 |
gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)", |
|
1199 |
iter.obj(), iter.obj()->blueprint()->internal_name()); |
|
1200 |
} |
|
1201 |
// Remove Reference object from list |
|
1202 |
iter.remove(); |
|
1203 |
--length; |
|
1204 |
// Keep alive its cohort. |
|
1205 |
iter.make_referent_alive(); |
|
1206 |
keep_alive->do_oop(next_addr); |
|
1207 |
} else { |
|
1208 |
iter.next(); |
|
1209 |
} |
|
1210 |
} |
|
1211 |
refs_list.set_length(length); |
|
1212 |
||
1213 |
// Close the reachable set |
|
1214 |
complete_gc->do_void(); |
|
1215 |
||
1216 |
NOT_PRODUCT( |
|
1217 |
if (PrintGCDetails && PrintReferenceGC) { |
|
1218 |
gclog_or_tty->print(" Dropped %d Refs out of %d " |
|
1219 |
"Refs in discovered list ", iter.removed(), iter.processed()); |
|
1220 |
} |
|
1221 |
) |
|
1222 |
} |
|
1223 |
||
1224 |
const char* ReferenceProcessor::list_name(int i) { |
|
1225 |
assert(i >= 0 && i <= _num_q * subclasses_of_ref, "Out of bounds index"); |
|
1226 |
int j = i / _num_q; |
|
1227 |
switch (j) { |
|
1228 |
case 0: return "SoftRef"; |
|
1229 |
case 1: return "WeakRef"; |
|
1230 |
case 2: return "FinalRef"; |
|
1231 |
case 3: return "PhantomRef"; |
|
1232 |
} |
|
1233 |
ShouldNotReachHere(); |
|
1234 |
return NULL; |
|
1235 |
} |
|
1236 |
||
1237 |
#ifndef PRODUCT |
|
1238 |
void ReferenceProcessor::verify_ok_to_handle_reflists() { |
|
1239 |
// empty for now |
|
1240 |
} |
|
1241 |
#endif |
|
1242 |
||
1243 |
void ReferenceProcessor::verify() { |
|
1244 |
guarantee(_sentinelRef != NULL && _sentinelRef->is_oop(), "Lost _sentinelRef"); |
|
1245 |
} |
|
1246 |
||
1247 |
#ifndef PRODUCT |
|
1248 |
void ReferenceProcessor::clear_discovered_references() { |
|
1249 |
guarantee(!_discovering_refs, "Discovering refs?"); |
|
1250 |
for (int i = 0; i < _num_q * subclasses_of_ref; i++) { |
|
1251 |
oop obj = _discoveredSoftRefs[i].head(); |
|
1252 |
while (obj != _sentinelRef) { |
|
1253 |
oop next = java_lang_ref_Reference::discovered(obj); |
|
1254 |
java_lang_ref_Reference::set_discovered(obj, (oop) NULL); |
|
1255 |
obj = next; |
|
1256 |
} |
|
1257 |
_discoveredSoftRefs[i].set_head(_sentinelRef); |
|
1258 |
_discoveredSoftRefs[i].set_length(0); |
|
1259 |
} |
|
1260 |
} |
|
1261 |
#endif // PRODUCT |