Tue, 19 Aug 2014 02:05:49 -0700
8044406: JVM crash with JDK8 (build 1.8.0-b132) with G1 GC
Summary: Fill the last card that has been allocated into with a dummy object
Reviewed-by: tschatzl, mgerdin
1 /*
2 * Copyright (c) 2001, 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
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7 * published by the Free Software Foundation.
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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).
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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.
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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
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/ptrQueue.hpp"
27 #include "memory/allocation.hpp"
28 #include "memory/allocation.inline.hpp"
29 #include "runtime/mutex.hpp"
30 #include "runtime/mutexLocker.hpp"
31 #include "runtime/thread.inline.hpp"
33 PtrQueue::PtrQueue(PtrQueueSet* qset, bool perm, bool active) :
34 _qset(qset), _buf(NULL), _index(0), _sz(0), _active(active),
35 _perm(perm), _lock(NULL)
36 {}
38 PtrQueue::~PtrQueue() {
39 assert(_perm || (_buf == NULL), "queue must be flushed before delete");
40 }
42 void PtrQueue::flush_impl() {
43 if (!_perm && _buf != NULL) {
44 if (_index == _sz) {
45 // No work to do.
46 qset()->deallocate_buffer(_buf);
47 } else {
48 // We must NULL out the unused entries, then enqueue.
49 for (size_t i = 0; i < _index; i += oopSize) {
50 _buf[byte_index_to_index((int)i)] = NULL;
51 }
52 qset()->enqueue_complete_buffer(_buf);
53 }
54 _buf = NULL;
55 _index = 0;
56 }
57 }
60 void PtrQueue::enqueue_known_active(void* ptr) {
61 assert(0 <= _index && _index <= _sz, "Invariant.");
62 assert(_index == 0 || _buf != NULL, "invariant");
64 while (_index == 0) {
65 handle_zero_index();
66 }
68 assert(_index > 0, "postcondition");
69 _index -= oopSize;
70 _buf[byte_index_to_index((int)_index)] = ptr;
71 assert(0 <= _index && _index <= _sz, "Invariant.");
72 }
74 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
75 assert(_lock->owned_by_self(), "Required.");
77 // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
78 // we acquire DirtyCardQ_CBL_mon inside enqeue_complete_buffer as they
79 // have the same rank and we may get the "possible deadlock" message
80 _lock->unlock();
82 qset()->enqueue_complete_buffer(buf);
83 // We must relock only because the caller will unlock, for the normal
84 // case.
85 _lock->lock_without_safepoint_check();
86 }
89 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
90 _max_completed_queue(0),
91 _cbl_mon(NULL), _fl_lock(NULL),
92 _notify_when_complete(notify_when_complete),
93 _sz(0),
94 _completed_buffers_head(NULL),
95 _completed_buffers_tail(NULL),
96 _n_completed_buffers(0),
97 _process_completed_threshold(0), _process_completed(false),
98 _buf_free_list(NULL), _buf_free_list_sz(0)
99 {
100 _fl_owner = this;
101 }
103 void** PtrQueueSet::allocate_buffer() {
104 assert(_sz > 0, "Didn't set a buffer size.");
105 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
106 if (_fl_owner->_buf_free_list != NULL) {
107 void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
108 _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
109 _fl_owner->_buf_free_list_sz--;
110 return res;
111 } else {
112 // Allocate space for the BufferNode in front of the buffer.
113 char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
114 return BufferNode::make_buffer_from_block(b);
115 }
116 }
118 void PtrQueueSet::deallocate_buffer(void** buf) {
119 assert(_sz > 0, "Didn't set a buffer size.");
120 MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
121 BufferNode *node = BufferNode::make_node_from_buffer(buf);
122 node->set_next(_fl_owner->_buf_free_list);
123 _fl_owner->_buf_free_list = node;
124 _fl_owner->_buf_free_list_sz++;
125 }
127 void PtrQueueSet::reduce_free_list() {
128 assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
129 // For now we'll adopt the strategy of deleting half.
130 MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
131 size_t n = _buf_free_list_sz / 2;
132 while (n > 0) {
133 assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
134 void* b = BufferNode::make_block_from_node(_buf_free_list);
135 _buf_free_list = _buf_free_list->next();
136 FREE_C_HEAP_ARRAY(char, b, mtGC);
137 _buf_free_list_sz --;
138 n--;
139 }
140 }
142 void PtrQueue::handle_zero_index() {
143 assert(_index == 0, "Precondition.");
145 // This thread records the full buffer and allocates a new one (while
146 // holding the lock if there is one).
147 if (_buf != NULL) {
148 if (!should_enqueue_buffer()) {
149 assert(_index > 0, "the buffer can only be re-used if it's not full");
150 return;
151 }
153 if (_lock) {
154 assert(_lock->owned_by_self(), "Required.");
156 // The current PtrQ may be the shared dirty card queue and
157 // may be being manipulated by more than one worker thread
158 // during a pause. Since the enqueuing of the completed
159 // buffer unlocks the Shared_DirtyCardQ_lock more than one
160 // worker thread can 'race' on reading the shared queue attributes
161 // (_buf and _index) and multiple threads can call into this
162 // routine for the same buffer. This will cause the completed
163 // buffer to be added to the CBL multiple times.
165 // We "claim" the current buffer by caching value of _buf in
166 // a local and clearing the field while holding _lock. When
167 // _lock is released (while enqueueing the completed buffer)
168 // the thread that acquires _lock will skip this code,
169 // preventing the subsequent the multiple enqueue, and
170 // install a newly allocated buffer below.
172 void** buf = _buf; // local pointer to completed buffer
173 _buf = NULL; // clear shared _buf field
175 locking_enqueue_completed_buffer(buf); // enqueue completed buffer
177 // While the current thread was enqueuing the buffer another thread
178 // may have a allocated a new buffer and inserted it into this pointer
179 // queue. If that happens then we just return so that the current
180 // thread doesn't overwrite the buffer allocated by the other thread
181 // and potentially losing some dirtied cards.
183 if (_buf != NULL) return;
184 } else {
185 if (qset()->process_or_enqueue_complete_buffer(_buf)) {
186 // Recycle the buffer. No allocation.
187 _sz = qset()->buffer_size();
188 _index = _sz;
189 return;
190 }
191 }
192 }
193 // Reallocate the buffer
194 _buf = qset()->allocate_buffer();
195 _sz = qset()->buffer_size();
196 _index = _sz;
197 assert(0 <= _index && _index <= _sz, "Invariant.");
198 }
200 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
201 if (Thread::current()->is_Java_thread()) {
202 // We don't lock. It is fine to be epsilon-precise here.
203 if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
204 _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
205 bool b = mut_process_buffer(buf);
206 if (b) {
207 // True here means that the buffer hasn't been deallocated and the caller may reuse it.
208 return true;
209 }
210 }
211 }
212 // The buffer will be enqueued. The caller will have to get a new one.
213 enqueue_complete_buffer(buf);
214 return false;
215 }
217 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
218 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
219 BufferNode* cbn = BufferNode::new_from_buffer(buf);
220 cbn->set_index(index);
221 if (_completed_buffers_tail == NULL) {
222 assert(_completed_buffers_head == NULL, "Well-formedness");
223 _completed_buffers_head = cbn;
224 _completed_buffers_tail = cbn;
225 } else {
226 _completed_buffers_tail->set_next(cbn);
227 _completed_buffers_tail = cbn;
228 }
229 _n_completed_buffers++;
231 if (!_process_completed && _process_completed_threshold >= 0 &&
232 _n_completed_buffers >= _process_completed_threshold) {
233 _process_completed = true;
234 if (_notify_when_complete)
235 _cbl_mon->notify();
236 }
237 debug_only(assert_completed_buffer_list_len_correct_locked());
238 }
240 int PtrQueueSet::completed_buffers_list_length() {
241 int n = 0;
242 BufferNode* cbn = _completed_buffers_head;
243 while (cbn != NULL) {
244 n++;
245 cbn = cbn->next();
246 }
247 return n;
248 }
250 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
251 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
252 assert_completed_buffer_list_len_correct_locked();
253 }
255 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
256 guarantee(completed_buffers_list_length() == _n_completed_buffers,
257 "Completed buffer length is wrong.");
258 }
260 void PtrQueueSet::set_buffer_size(size_t sz) {
261 assert(_sz == 0 && sz > 0, "Should be called only once.");
262 _sz = sz * oopSize;
263 }
265 // Merge lists of buffers. Notify the processing threads.
266 // The source queue is emptied as a result. The queues
267 // must share the monitor.
268 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
269 assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
270 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
271 if (_completed_buffers_tail == NULL) {
272 assert(_completed_buffers_head == NULL, "Well-formedness");
273 _completed_buffers_head = src->_completed_buffers_head;
274 _completed_buffers_tail = src->_completed_buffers_tail;
275 } else {
276 assert(_completed_buffers_head != NULL, "Well formedness");
277 if (src->_completed_buffers_head != NULL) {
278 _completed_buffers_tail->set_next(src->_completed_buffers_head);
279 _completed_buffers_tail = src->_completed_buffers_tail;
280 }
281 }
282 _n_completed_buffers += src->_n_completed_buffers;
284 src->_n_completed_buffers = 0;
285 src->_completed_buffers_head = NULL;
286 src->_completed_buffers_tail = NULL;
288 assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
289 _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
290 "Sanity");
291 }
293 void PtrQueueSet::notify_if_necessary() {
294 MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
295 if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
296 _process_completed = true;
297 if (_notify_when_complete)
298 _cbl_mon->notify();
299 }
300 }