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, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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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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.
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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/concurrentMarkThread.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
29 #include "gc_implementation/g1/g1Log.hpp"
30 #include "gc_implementation/g1/g1MMUTracker.hpp"
31 #include "gc_implementation/g1/vm_operations_g1.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "runtime/vmThread.hpp"
35 // ======= Concurrent Mark Thread ========
37 // The CM thread is created when the G1 garbage collector is used
39 SurrogateLockerThread*
40 ConcurrentMarkThread::_slt = NULL;
42 ConcurrentMarkThread::ConcurrentMarkThread(ConcurrentMark* cm) :
43 ConcurrentGCThread(),
44 _cm(cm),
45 _started(false),
46 _in_progress(false),
47 _vtime_accum(0.0),
48 _vtime_mark_accum(0.0) {
49 create_and_start();
50 }
52 class CMCheckpointRootsFinalClosure: public VoidClosure {
54 ConcurrentMark* _cm;
55 public:
57 CMCheckpointRootsFinalClosure(ConcurrentMark* cm) :
58 _cm(cm) {}
60 void do_void(){
61 _cm->checkpointRootsFinal(false); // !clear_all_soft_refs
62 }
63 };
65 class CMCleanUp: public VoidClosure {
66 ConcurrentMark* _cm;
67 public:
69 CMCleanUp(ConcurrentMark* cm) :
70 _cm(cm) {}
72 void do_void(){
73 _cm->cleanup();
74 }
75 };
79 void ConcurrentMarkThread::run() {
80 initialize_in_thread();
81 _vtime_start = os::elapsedVTime();
82 wait_for_universe_init();
84 G1CollectedHeap* g1h = G1CollectedHeap::heap();
85 G1CollectorPolicy* g1_policy = g1h->g1_policy();
86 G1MMUTracker *mmu_tracker = g1_policy->mmu_tracker();
87 Thread *current_thread = Thread::current();
89 while (!_should_terminate) {
90 // wait until started is set.
91 sleepBeforeNextCycle();
92 if (_should_terminate) {
93 break;
94 }
96 {
97 ResourceMark rm;
98 HandleMark hm;
99 double cycle_start = os::elapsedVTime();
101 // We have to ensure that we finish scanning the root regions
102 // before the next GC takes place. To ensure this we have to
103 // make sure that we do not join the STS until the root regions
104 // have been scanned. If we did then it's possible that a
105 // subsequent GC could block us from joining the STS and proceed
106 // without the root regions have been scanned which would be a
107 // correctness issue.
109 double scan_start = os::elapsedTime();
110 if (!cm()->has_aborted()) {
111 if (G1Log::fine()) {
112 gclog_or_tty->date_stamp(PrintGCDateStamps);
113 gclog_or_tty->stamp(PrintGCTimeStamps);
114 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-start]");
115 }
117 _cm->scanRootRegions();
119 double scan_end = os::elapsedTime();
120 if (G1Log::fine()) {
121 gclog_or_tty->date_stamp(PrintGCDateStamps);
122 gclog_or_tty->stamp(PrintGCTimeStamps);
123 gclog_or_tty->print_cr("[GC concurrent-root-region-scan-end, %1.7lf secs]",
124 scan_end - scan_start);
125 }
126 }
128 double mark_start_sec = os::elapsedTime();
129 if (G1Log::fine()) {
130 gclog_or_tty->date_stamp(PrintGCDateStamps);
131 gclog_or_tty->stamp(PrintGCTimeStamps);
132 gclog_or_tty->print_cr("[GC concurrent-mark-start]");
133 }
135 int iter = 0;
136 do {
137 iter++;
138 if (!cm()->has_aborted()) {
139 _cm->markFromRoots();
140 }
142 double mark_end_time = os::elapsedVTime();
143 double mark_end_sec = os::elapsedTime();
144 _vtime_mark_accum += (mark_end_time - cycle_start);
145 if (!cm()->has_aborted()) {
146 if (g1_policy->adaptive_young_list_length()) {
147 double now = os::elapsedTime();
148 double remark_prediction_ms = g1_policy->predict_remark_time_ms();
149 jlong sleep_time_ms = mmu_tracker->when_ms(now, remark_prediction_ms);
150 os::sleep(current_thread, sleep_time_ms, false);
151 }
153 if (G1Log::fine()) {
154 gclog_or_tty->date_stamp(PrintGCDateStamps);
155 gclog_or_tty->stamp(PrintGCTimeStamps);
156 gclog_or_tty->print_cr("[GC concurrent-mark-end, %1.7lf secs]",
157 mark_end_sec - mark_start_sec);
158 }
160 CMCheckpointRootsFinalClosure final_cl(_cm);
161 VM_CGC_Operation op(&final_cl, "GC remark", true /* needs_pll */);
162 VMThread::execute(&op);
163 }
164 if (cm()->restart_for_overflow()) {
165 if (G1TraceMarkStackOverflow) {
166 gclog_or_tty->print_cr("Restarting conc marking because of MS overflow "
167 "in remark (restart #%d).", iter);
168 }
169 if (G1Log::fine()) {
170 gclog_or_tty->date_stamp(PrintGCDateStamps);
171 gclog_or_tty->stamp(PrintGCTimeStamps);
172 gclog_or_tty->print_cr("[GC concurrent-mark-restart-for-overflow]");
173 }
174 }
175 } while (cm()->restart_for_overflow());
177 double end_time = os::elapsedVTime();
178 // Update the total virtual time before doing this, since it will try
179 // to measure it to get the vtime for this marking. We purposely
180 // neglect the presumably-short "completeCleanup" phase here.
181 _vtime_accum = (end_time - _vtime_start);
183 if (!cm()->has_aborted()) {
184 if (g1_policy->adaptive_young_list_length()) {
185 double now = os::elapsedTime();
186 double cleanup_prediction_ms = g1_policy->predict_cleanup_time_ms();
187 jlong sleep_time_ms = mmu_tracker->when_ms(now, cleanup_prediction_ms);
188 os::sleep(current_thread, sleep_time_ms, false);
189 }
191 CMCleanUp cl_cl(_cm);
192 VM_CGC_Operation op(&cl_cl, "GC cleanup", false /* needs_pll */);
193 VMThread::execute(&op);
194 } else {
195 // We don't want to update the marking status if a GC pause
196 // is already underway.
197 _sts.join();
198 g1h->set_marking_complete();
199 _sts.leave();
200 }
202 // Check if cleanup set the free_regions_coming flag. If it
203 // hasn't, we can just skip the next step.
204 if (g1h->free_regions_coming()) {
205 // The following will finish freeing up any regions that we
206 // found to be empty during cleanup. We'll do this part
207 // without joining the suspendible set. If an evacuation pause
208 // takes place, then we would carry on freeing regions in
209 // case they are needed by the pause. If a Full GC takes
210 // place, it would wait for us to process the regions
211 // reclaimed by cleanup.
213 double cleanup_start_sec = os::elapsedTime();
214 if (G1Log::fine()) {
215 gclog_or_tty->date_stamp(PrintGCDateStamps);
216 gclog_or_tty->stamp(PrintGCTimeStamps);
217 gclog_or_tty->print_cr("[GC concurrent-cleanup-start]");
218 }
220 // Now do the concurrent cleanup operation.
221 _cm->completeCleanup();
223 // Notify anyone who's waiting that there are no more free
224 // regions coming. We have to do this before we join the STS
225 // (in fact, we should not attempt to join the STS in the
226 // interval between finishing the cleanup pause and clearing
227 // the free_regions_coming flag) otherwise we might deadlock:
228 // a GC worker could be blocked waiting for the notification
229 // whereas this thread will be blocked for the pause to finish
230 // while it's trying to join the STS, which is conditional on
231 // the GC workers finishing.
232 g1h->reset_free_regions_coming();
234 double cleanup_end_sec = os::elapsedTime();
235 if (G1Log::fine()) {
236 gclog_or_tty->date_stamp(PrintGCDateStamps);
237 gclog_or_tty->stamp(PrintGCTimeStamps);
238 gclog_or_tty->print_cr("[GC concurrent-cleanup-end, %1.7lf secs]",
239 cleanup_end_sec - cleanup_start_sec);
240 }
241 }
242 guarantee(cm()->cleanup_list_is_empty(),
243 "at this point there should be no regions on the cleanup list");
245 // There is a tricky race before recording that the concurrent
246 // cleanup has completed and a potential Full GC starting around
247 // the same time. We want to make sure that the Full GC calls
248 // abort() on concurrent mark after
249 // record_concurrent_mark_cleanup_completed(), since abort() is
250 // the method that will reset the concurrent mark state. If we
251 // end up calling record_concurrent_mark_cleanup_completed()
252 // after abort() then we might incorrectly undo some of the work
253 // abort() did. Checking the has_aborted() flag after joining
254 // the STS allows the correct ordering of the two methods. There
255 // are two scenarios:
256 //
257 // a) If we reach here before the Full GC, the fact that we have
258 // joined the STS means that the Full GC cannot start until we
259 // leave the STS, so record_concurrent_mark_cleanup_completed()
260 // will complete before abort() is called.
261 //
262 // b) If we reach here during the Full GC, we'll be held up from
263 // joining the STS until the Full GC is done, which means that
264 // abort() will have completed and has_aborted() will return
265 // true to prevent us from calling
266 // record_concurrent_mark_cleanup_completed() (and, in fact, it's
267 // not needed any more as the concurrent mark state has been
268 // already reset).
269 _sts.join();
270 if (!cm()->has_aborted()) {
271 g1_policy->record_concurrent_mark_cleanup_completed();
272 }
273 _sts.leave();
275 if (cm()->has_aborted()) {
276 if (G1Log::fine()) {
277 gclog_or_tty->date_stamp(PrintGCDateStamps);
278 gclog_or_tty->stamp(PrintGCTimeStamps);
279 gclog_or_tty->print_cr("[GC concurrent-mark-abort]");
280 }
281 }
283 // We now want to allow clearing of the marking bitmap to be
284 // suspended by a collection pause.
285 _sts.join();
286 _cm->clearNextBitmap();
287 _sts.leave();
288 }
290 // Update the number of full collections that have been
291 // completed. This will also notify the FullGCCount_lock in case a
292 // Java thread is waiting for a full GC to happen (e.g., it
293 // called System.gc() with +ExplicitGCInvokesConcurrent).
294 _sts.join();
295 g1h->increment_old_marking_cycles_completed(true /* concurrent */);
296 g1h->register_concurrent_cycle_end();
297 _sts.leave();
298 }
299 assert(_should_terminate, "just checking");
301 terminate();
302 }
305 void ConcurrentMarkThread::yield() {
306 _sts.yield("Concurrent Mark");
307 }
309 void ConcurrentMarkThread::stop() {
310 {
311 MutexLockerEx ml(Terminator_lock);
312 _should_terminate = true;
313 }
315 {
316 MutexLockerEx ml(CGC_lock, Mutex::_no_safepoint_check_flag);
317 CGC_lock->notify_all();
318 }
320 {
321 MutexLockerEx ml(Terminator_lock);
322 while (!_has_terminated) {
323 Terminator_lock->wait();
324 }
325 }
326 }
328 void ConcurrentMarkThread::print() const {
329 print_on(tty);
330 }
332 void ConcurrentMarkThread::print_on(outputStream* st) const {
333 st->print("\"G1 Main Concurrent Mark GC Thread\" ");
334 Thread::print_on(st);
335 st->cr();
336 }
338 void ConcurrentMarkThread::sleepBeforeNextCycle() {
339 // We join here because we don't want to do the "shouldConcurrentMark()"
340 // below while the world is otherwise stopped.
341 assert(!in_progress(), "should have been cleared");
343 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
344 while (!started() && !_should_terminate) {
345 CGC_lock->wait(Mutex::_no_safepoint_check_flag);
346 }
348 if (started()) {
349 set_in_progress();
350 clear_started();
351 }
352 }
354 // Note: As is the case with CMS - this method, although exported
355 // by the ConcurrentMarkThread, which is a non-JavaThread, can only
356 // be called by a JavaThread. Currently this is done at vm creation
357 // time (post-vm-init) by the main/Primordial (Java)Thread.
358 // XXX Consider changing this in the future to allow the CM thread
359 // itself to create this thread?
360 void ConcurrentMarkThread::makeSurrogateLockerThread(TRAPS) {
361 assert(UseG1GC, "SLT thread needed only for concurrent GC");
362 assert(THREAD->is_Java_thread(), "must be a Java thread");
363 assert(_slt == NULL, "SLT already created");
364 _slt = SurrogateLockerThread::make(THREAD);
365 }