1 /*
2 * Copyright (c) 2005, 2010, 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 "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
28 #include "gc_implementation/concurrentMarkSweep/vmCMSOperations.hpp"
29 #include "gc_implementation/shared/isGCActiveMark.hpp"
30 #include "memory/gcLocker.inline.hpp"
31 #include "runtime/interfaceSupport.hpp"
32 #include "utilities/dtrace.hpp"
33 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
34 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
35
36 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
37 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
38
39 //////////////////////////////////////////////////////////
40 // Methods in abstract class VM_CMS_Operation
41 //////////////////////////////////////////////////////////
42 void VM_CMS_Operation::acquire_pending_list_lock() {
43 // The caller may block while communicating
44 // with the SLT thread in order to acquire/release the PLL.
45 ConcurrentMarkSweepThread::slt()->
46 manipulatePLL(SurrogateLockerThread::acquirePLL);
47 }
48
49 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
50 // The caller may block while communicating
51 // with the SLT thread in order to acquire/release the PLL.
52 ConcurrentMarkSweepThread::slt()->
53 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
54 }
55
56 void VM_CMS_Operation::verify_before_gc() {
57 if (VerifyBeforeGC &&
58 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
59 HandleMark hm;
60 FreelistLocker x(_collector);
61 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
62 Universe::heap()->prepare_for_verify();
63 Universe::verify(true);
64 }
65 }
66
67 void VM_CMS_Operation::verify_after_gc() {
68 if (VerifyAfterGC &&
69 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
70 HandleMark hm;
71 FreelistLocker x(_collector);
72 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
73 Universe::verify(true);
74 }
75 }
76
77 bool VM_CMS_Operation::lost_race() const {
78 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
79 // We lost a race to a foreground collection
80 // -- there's nothing to do
81 return true;
82 }
83 assert(CMSCollector::abstract_state() == legal_state(),
84 "Inconsistent collector state?");
85 return false;
86 }
87
88 bool VM_CMS_Operation::doit_prologue() {
89 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
90 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
91 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
92 "Possible deadlock");
93
94 if (needs_pll()) {
95 acquire_pending_list_lock();
96 }
97 // Get the Heap_lock after the pending_list_lock.
98 Heap_lock->lock();
99 if (lost_race()) {
100 assert(_prologue_succeeded == false, "Initialized in c'tor");
101 Heap_lock->unlock();
102 if (needs_pll()) {
103 release_and_notify_pending_list_lock();
104 }
105 } else {
106 _prologue_succeeded = true;
107 }
108 return _prologue_succeeded;
109 }
110
111 void VM_CMS_Operation::doit_epilogue() {
112 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
113 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
114 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
115 "Possible deadlock");
116
117 // Release the Heap_lock first.
118 Heap_lock->unlock();
119 if (needs_pll()) {
120 release_and_notify_pending_list_lock();
121 }
122 }
123
124 //////////////////////////////////////////////////////////
125 // Methods in class VM_CMS_Initial_Mark
126 //////////////////////////////////////////////////////////
127 void VM_CMS_Initial_Mark::doit() {
128 if (lost_race()) {
129 // Nothing to do.
130 return;
131 }
132 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
133
134 GenCollectedHeap* gch = GenCollectedHeap::heap();
135 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
136
137 VM_CMS_Operation::verify_before_gc();
138
139 IsGCActiveMark x; // stop-world GC active
140 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial);
141
142 VM_CMS_Operation::verify_after_gc();
143 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
144 }
145
146 //////////////////////////////////////////////////////////
147 // Methods in class VM_CMS_Final_Remark_Operation
148 //////////////////////////////////////////////////////////
149 void VM_CMS_Final_Remark::doit() {
150 if (lost_race()) {
151 // Nothing to do.
152 return;
153 }
154 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
155
156 GenCollectedHeap* gch = GenCollectedHeap::heap();
157 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
158
159 VM_CMS_Operation::verify_before_gc();
160
161 IsGCActiveMark x; // stop-world GC active
162 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal);
163
164 VM_CMS_Operation::verify_after_gc();
165 HS_DTRACE_PROBE(hs_private, cms__remark__end);
166 }
167
168 // VM operation to invoke a concurrent collection of a
169 // GenCollectedHeap heap.
170 void VM_GenCollectFullConcurrent::doit() {
171 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
172 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
173
174 GenCollectedHeap* gch = GenCollectedHeap::heap();
175 if (_gc_count_before == gch->total_collections()) {
176 // The "full" of do_full_collection call below "forces"
177 // a collection; the second arg, 0, below ensures that
178 // only the young gen is collected. XXX In the future,
179 // we'll probably need to have something in this interface
180 // to say do this only if we are sure we will not bail
181 // out to a full collection in this attempt, but that's
182 // for the future.
183 assert(SafepointSynchronize::is_at_safepoint(),
184 "We can only be executing this arm of if at a safepoint");
185 GCCauseSetter gccs(gch, _gc_cause);
186 gch->do_full_collection(gch->must_clear_all_soft_refs(),
187 0 /* collect only youngest gen */);
188 } // Else no need for a foreground young gc
189 assert((_gc_count_before < gch->total_collections()) ||
190 (GC_locker::is_active() /* gc may have been skipped */
191 && (_gc_count_before == gch->total_collections())),
192 "total_collections() should be monotonically increasing");
193
194 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
195 if (gch->total_full_collections() == _full_gc_count_before) {
196 // Disable iCMS until the full collection is done.
197 CMSCollector::disable_icms();
198 // In case CMS thread was in icms_wait(), wake it up.
199 CMSCollector::start_icms();
200 // Nudge the CMS thread to start a concurrent collection.
201 CMSCollector::request_full_gc(_full_gc_count_before);
202 } else {
203 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
204 }
205 }
206
207 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
208 Thread* thr = Thread::current();
209 assert(thr != NULL, "Unexpected tid");
210 if (!thr->is_Java_thread()) {
211 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
212 GenCollectedHeap* gch = GenCollectedHeap::heap();
213 if (_gc_count_before != gch->total_collections()) {
214 // No need to do a young gc, we'll just nudge the CMS thread
215 // in the doit() method above, to be executed soon.
216 assert(_gc_count_before < gch->total_collections(),
217 "total_collections() should be monotnically increasing");
218 return false; // no need for foreground young gc
219 }
220 }
221 return true; // may still need foreground young gc
222 }
223
224
225 void VM_GenCollectFullConcurrent::doit_epilogue() {
226 Thread* thr = Thread::current();
227 assert(thr->is_Java_thread(), "just checking");
228 JavaThread* jt = (JavaThread*)thr;
229 // Release the Heap_lock first.
230 Heap_lock->unlock();
231 release_and_notify_pending_list_lock();
232
233 // It is fine to test whether completed collections has
234 // exceeded our request count without locking because
235 // the completion count is monotonically increasing;
236 // this will break for very long-running apps when the
237 // count overflows and wraps around. XXX fix me !!!
238 // e.g. at the rate of 1 full gc per ms, this could
239 // overflow in about 1000 years.
240 GenCollectedHeap* gch = GenCollectedHeap::heap();
241 if (_gc_cause != GCCause::_gc_locker &&
242 gch->total_full_collections_completed() <= _full_gc_count_before) {
243 // maybe we should change the condition to test _gc_cause ==
244 // GCCause::_java_lang_system_gc, instead of
245 // _gc_cause != GCCause::_gc_locker
246 assert(_gc_cause == GCCause::_java_lang_system_gc,
247 "the only way to get here if this was a System.gc()-induced GC");
248 assert(ExplicitGCInvokesConcurrent, "Error");
249 // Now, wait for witnessing concurrent gc cycle to complete,
250 // but do so in native mode, because we want to lock the
251 // FullGCEvent_lock, which may be needed by the VM thread
252 // or by the CMS thread, so we do not want to be suspended
253 // while holding that lock.
254 ThreadToNativeFromVM native(jt);
255 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
256 // Either a concurrent or a stop-world full gc is sufficient
257 // witness to our request.
258 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
259 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
260 }
261 }
262 // Enable iCMS back.
263 CMSCollector::enable_icms();
264 }