Mercurial > hg > truffle
annotate src/share/vm/gc_implementation/g1/g1StringDedupQueue.cpp @ 20652:e8bf410d5e23
8058209: Race in G1 card scanning could allow scanning of memory covered by PLABs
Summary: Read _top before _gc_time_stamp in saved_mark_word() with LoadLoad order to ensure we get a consistent view
Reviewed-by: brutisso, dcubed, dholmes, stefank
| author | mgerdin |
|---|---|
| date | Fri, 14 Nov 2014 14:23:25 +0100 |
| parents | 1772223a25a2 |
| children |
| rev | line source |
|---|---|
| 17764 | 1 /* |
| 2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved. | |
| 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 * | |
| 5 * This code is free software; you can redistribute it and/or modify it | |
| 6 * under the terms of the GNU General Public License version 2 only, as | |
| 7 * published by the Free Software Foundation. | |
| 8 * | |
| 9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 12 * version 2 for more details (a copy is included in the LICENSE file that | |
| 13 * accompanied this code). | |
| 14 * | |
| 15 * You should have received a copy of the GNU General Public License version | |
| 16 * 2 along with this work; if not, write to the Free Software Foundation, | |
| 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 18 * | |
| 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 20 * or visit www.oracle.com if you need additional information or have any | |
| 21 * questions. | |
| 22 * | |
| 23 */ | |
| 24 | |
| 25 #include "precompiled.hpp" | |
| 26 #include "classfile/javaClasses.hpp" | |
| 27 #include "gc_implementation/g1/g1StringDedupQueue.hpp" | |
| 28 #include "memory/gcLocker.hpp" | |
| 29 #include "runtime/mutexLocker.hpp" | |
| 30 #include "utilities/stack.inline.hpp" | |
| 31 | |
| 32 G1StringDedupQueue* G1StringDedupQueue::_queue = NULL; | |
| 33 const size_t G1StringDedupQueue::_max_size = 1000000; // Max number of elements per queue | |
| 34 const size_t G1StringDedupQueue::_max_cache_size = 0; // Max cache size per queue | |
| 35 | |
| 36 G1StringDedupQueue::G1StringDedupQueue() : | |
| 37 _cursor(0), | |
|
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38 _cancel(false), |
| 17764 | 39 _empty(true), |
| 40 _dropped(0) { | |
| 41 _nqueues = MAX2(ParallelGCThreads, (size_t)1); | |
| 42 _queues = NEW_C_HEAP_ARRAY(G1StringDedupWorkerQueue, _nqueues, mtGC); | |
| 43 for (size_t i = 0; i < _nqueues; i++) { | |
| 44 new (_queues + i) G1StringDedupWorkerQueue(G1StringDedupWorkerQueue::default_segment_size(), _max_cache_size, _max_size); | |
| 45 } | |
| 46 } | |
| 47 | |
| 48 G1StringDedupQueue::~G1StringDedupQueue() { | |
| 49 ShouldNotReachHere(); | |
| 50 } | |
| 51 | |
| 52 void G1StringDedupQueue::create() { | |
| 53 assert(_queue == NULL, "One string deduplication queue allowed"); | |
| 54 _queue = new G1StringDedupQueue(); | |
| 55 } | |
| 56 | |
| 57 void G1StringDedupQueue::wait() { | |
| 58 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); | |
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59 while (_queue->_empty && !_queue->_cancel) { |
| 17764 | 60 ml.wait(Mutex::_no_safepoint_check_flag); |
| 61 } | |
| 62 } | |
| 63 | |
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64 void G1StringDedupQueue::cancel_wait() { |
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65 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); |
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66 _queue->_cancel = true; |
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67 ml.notify(); |
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68 } |
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69 |
| 17764 | 70 void G1StringDedupQueue::push(uint worker_id, oop java_string) { |
| 71 assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint"); | |
| 72 assert(worker_id < _queue->_nqueues, "Invalid queue"); | |
| 73 | |
| 74 // Push and notify waiter | |
| 75 G1StringDedupWorkerQueue& worker_queue = _queue->_queues[worker_id]; | |
| 76 if (!worker_queue.is_full()) { | |
| 77 worker_queue.push(java_string); | |
| 78 if (_queue->_empty) { | |
| 79 MonitorLockerEx ml(StringDedupQueue_lock, Mutex::_no_safepoint_check_flag); | |
| 80 if (_queue->_empty) { | |
| 81 // Mark non-empty and notify waiter | |
| 82 _queue->_empty = false; | |
| 83 ml.notify(); | |
| 84 } | |
| 85 } | |
| 86 } else { | |
| 87 // Queue is full, drop the string and update the statistics | |
| 88 Atomic::inc_ptr(&_queue->_dropped); | |
| 89 } | |
| 90 } | |
| 91 | |
| 92 oop G1StringDedupQueue::pop() { | |
| 93 assert(!SafepointSynchronize::is_at_safepoint(), "Must not be at safepoint"); | |
| 94 No_Safepoint_Verifier nsv; | |
| 95 | |
| 96 // Try all queues before giving up | |
| 97 for (size_t tries = 0; tries < _queue->_nqueues; tries++) { | |
| 98 // The cursor indicates where we left of last time | |
| 99 G1StringDedupWorkerQueue* queue = &_queue->_queues[_queue->_cursor]; | |
| 100 while (!queue->is_empty()) { | |
| 101 oop obj = queue->pop(); | |
| 102 // The oop we pop can be NULL if it was marked | |
| 103 // dead. Just ignore those and pop the next oop. | |
| 104 if (obj != NULL) { | |
| 105 return obj; | |
| 106 } | |
| 107 } | |
| 108 | |
| 109 // Try next queue | |
| 110 _queue->_cursor = (_queue->_cursor + 1) % _queue->_nqueues; | |
| 111 } | |
| 112 | |
| 113 // Mark empty | |
| 114 _queue->_empty = true; | |
| 115 | |
| 116 return NULL; | |
| 117 } | |
| 118 | |
| 119 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl) { | |
| 120 // A worker thread first claims a queue, which ensures exclusive | |
| 121 // access to that queue, then continues to process it. | |
| 122 for (;;) { | |
| 123 // Grab next queue to scan | |
| 124 size_t queue = cl->claim_queue(); | |
| 125 if (queue >= _queue->_nqueues) { | |
| 126 // End of queues | |
| 127 break; | |
| 128 } | |
| 129 | |
| 130 // Scan the queue | |
| 131 unlink_or_oops_do(cl, queue); | |
| 132 } | |
| 133 } | |
| 134 | |
| 135 void G1StringDedupQueue::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, size_t queue) { | |
| 136 assert(queue < _queue->_nqueues, "Invalid queue"); | |
| 137 StackIterator<oop, mtGC> iter(_queue->_queues[queue]); | |
| 138 while (!iter.is_empty()) { | |
| 139 oop* p = iter.next_addr(); | |
| 140 if (*p != NULL) { | |
| 141 if (cl->is_alive(*p)) { | |
| 142 cl->keep_alive(p); | |
| 143 } else { | |
| 144 // Clear dead reference | |
| 145 *p = NULL; | |
| 146 } | |
| 147 } | |
| 148 } | |
| 149 } | |
| 150 | |
| 151 void G1StringDedupQueue::print_statistics(outputStream* st) { | |
| 152 st->print_cr( | |
| 153 " [Queue]\n" | |
| 154 " [Dropped: "UINTX_FORMAT"]", _queue->_dropped); | |
| 155 } | |
| 156 | |
| 157 void G1StringDedupQueue::verify() { | |
| 158 for (size_t i = 0; i < _queue->_nqueues; i++) { | |
| 159 StackIterator<oop, mtGC> iter(_queue->_queues[i]); | |
| 160 while (!iter.is_empty()) { | |
| 161 oop obj = iter.next(); | |
| 162 if (obj != NULL) { | |
| 163 guarantee(Universe::heap()->is_in_reserved(obj), "Object must be on the heap"); | |
| 164 guarantee(!obj->is_forwarded(), "Object must not be forwarded"); | |
| 165 guarantee(java_lang_String::is_instance(obj), "Object must be a String"); | |
| 166 } | |
| 167 } | |
| 168 } | |
| 169 } |