1 /*
2 * Copyright (c) 2005, 2006, 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 # include "incls/_precompiled.incl"
25 # include "incls/_vmCMSOperations.cpp.incl"
26
27 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__begin);
28 HS_DTRACE_PROBE_DECL(hs_private, cms__initmark__end);
29
30 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__begin);
31 HS_DTRACE_PROBE_DECL(hs_private, cms__remark__end);
32
33 //////////////////////////////////////////////////////////
34 // Methods in abstract class VM_CMS_Operation
35 //////////////////////////////////////////////////////////
36 void VM_CMS_Operation::acquire_pending_list_lock() {
37 // The caller may block while communicating
38 // with the SLT thread in order to acquire/release the PLL.
39 ConcurrentMarkSweepThread::slt()->
40 manipulatePLL(SurrogateLockerThread::acquirePLL);
41 }
42
43 void VM_CMS_Operation::release_and_notify_pending_list_lock() {
44 // The caller may block while communicating
45 // with the SLT thread in order to acquire/release the PLL.
46 ConcurrentMarkSweepThread::slt()->
47 manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
48 }
49
50 void VM_CMS_Operation::verify_before_gc() {
51 if (VerifyBeforeGC &&
52 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
53 HandleMark hm;
54 FreelistLocker x(_collector);
55 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
56 Universe::heap()->prepare_for_verify();
57 Universe::verify(true);
58 }
59 }
60
61 void VM_CMS_Operation::verify_after_gc() {
62 if (VerifyAfterGC &&
63 GenCollectedHeap::heap()->total_collections() >= VerifyGCStartAt) {
64 HandleMark hm;
65 FreelistLocker x(_collector);
66 MutexLockerEx y(_collector->bitMapLock(), Mutex::_no_safepoint_check_flag);
67 Universe::verify(true);
68 }
69 }
70
71 bool VM_CMS_Operation::lost_race() const {
72 if (CMSCollector::abstract_state() == CMSCollector::Idling) {
73 // We lost a race to a foreground collection
74 // -- there's nothing to do
75 return true;
76 }
77 assert(CMSCollector::abstract_state() == legal_state(),
78 "Inconsistent collector state?");
79 return false;
80 }
81
82 bool VM_CMS_Operation::doit_prologue() {
83 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
84 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
85 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
86 "Possible deadlock");
87
88 if (needs_pll()) {
89 acquire_pending_list_lock();
90 }
91 // Get the Heap_lock after the pending_list_lock.
92 Heap_lock->lock();
93 if (lost_race()) {
94 assert(_prologue_succeeded == false, "Initialized in c'tor");
95 Heap_lock->unlock();
96 if (needs_pll()) {
97 release_and_notify_pending_list_lock();
98 }
99 } else {
100 _prologue_succeeded = true;
101 }
102 return _prologue_succeeded;
103 }
104
105 void VM_CMS_Operation::doit_epilogue() {
106 assert(Thread::current()->is_ConcurrentGC_thread(), "just checking");
107 assert(!CMSCollector::foregroundGCShouldWait(), "Possible deadlock");
108 assert(!ConcurrentMarkSweepThread::cms_thread_has_cms_token(),
109 "Possible deadlock");
110
111 // Release the Heap_lock first.
112 Heap_lock->unlock();
113 if (needs_pll()) {
114 release_and_notify_pending_list_lock();
115 }
116 }
117
118 //////////////////////////////////////////////////////////
119 // Methods in class VM_CMS_Initial_Mark
120 //////////////////////////////////////////////////////////
121 void VM_CMS_Initial_Mark::doit() {
122 if (lost_race()) {
123 // Nothing to do.
124 return;
125 }
126 HS_DTRACE_PROBE(hs_private, cms__initmark__begin);
127
128 GenCollectedHeap* gch = GenCollectedHeap::heap();
129 GCCauseSetter gccs(gch, GCCause::_cms_initial_mark);
130
131 VM_CMS_Operation::verify_before_gc();
132
133 IsGCActiveMark x; // stop-world GC active
134 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsInitial);
135
136 VM_CMS_Operation::verify_after_gc();
137 HS_DTRACE_PROBE(hs_private, cms__initmark__end);
138 }
139
140 //////////////////////////////////////////////////////////
141 // Methods in class VM_CMS_Final_Remark_Operation
142 //////////////////////////////////////////////////////////
143 void VM_CMS_Final_Remark::doit() {
144 if (lost_race()) {
145 // Nothing to do.
146 return;
147 }
148 HS_DTRACE_PROBE(hs_private, cms__remark__begin);
149
150 GenCollectedHeap* gch = GenCollectedHeap::heap();
151 GCCauseSetter gccs(gch, GCCause::_cms_final_remark);
152
153 VM_CMS_Operation::verify_before_gc();
154
155 IsGCActiveMark x; // stop-world GC active
156 _collector->do_CMS_operation(CMSCollector::CMS_op_checkpointRootsFinal);
157
158 VM_CMS_Operation::verify_after_gc();
159 HS_DTRACE_PROBE(hs_private, cms__remark__end);
160 }
161
162 // VM operation to invoke a concurrent collection of a
163 // GenCollectedHeap heap.
164 void VM_GenCollectFullConcurrent::doit() {
165 assert(Thread::current()->is_VM_thread(), "Should be VM thread");
166 assert(GCLockerInvokesConcurrent || ExplicitGCInvokesConcurrent, "Unexpected");
167
168 GenCollectedHeap* gch = GenCollectedHeap::heap();
169 if (_gc_count_before == gch->total_collections()) {
170 // The "full" of do_full_collection call below "forces"
171 // a collection; the second arg, 0, below ensures that
172 // only the young gen is collected. XXX In the future,
173 // we'll probably need to have something in this interface
174 // to say do this only if we are sure we will not bail
175 // out to a full collection in this attempt, but that's
176 // for the future.
177 assert(SafepointSynchronize::is_at_safepoint(),
178 "We can only be executing this arm of if at a safepoint");
179 GCCauseSetter gccs(gch, _gc_cause);
180 gch->do_full_collection(gch->must_clear_all_soft_refs(),
181 0 /* collect only youngest gen */);
182 } // Else no need for a foreground young gc
183 assert((_gc_count_before < gch->total_collections()) ||
184 (GC_locker::is_active() /* gc may have been skipped */
185 && (_gc_count_before == gch->total_collections())),
186 "total_collections() should be monotonically increasing");
187
188 MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
189 if (gch->total_full_collections() == _full_gc_count_before) {
190 // Disable iCMS until the full collection is done.
191 CMSCollector::disable_icms();
192 // In case CMS thread was in icms_wait(), wake it up.
193 CMSCollector::start_icms();
194 // Nudge the CMS thread to start a concurrent collection.
195 CMSCollector::request_full_gc(_full_gc_count_before);
196 } else {
197 FullGCCount_lock->notify_all(); // Inform the Java thread its work is done
198 }
199 }
200
201 bool VM_GenCollectFullConcurrent::evaluate_at_safepoint() const {
202 Thread* thr = Thread::current();
203 assert(thr != NULL, "Unexpected tid");
204 if (!thr->is_Java_thread()) {
205 assert(thr->is_VM_thread(), "Expected to be evaluated by VM thread");
206 GenCollectedHeap* gch = GenCollectedHeap::heap();
207 if (_gc_count_before != gch->total_collections()) {
208 // No need to do a young gc, we'll just nudge the CMS thread
209 // in the doit() method above, to be executed soon.
210 assert(_gc_count_before < gch->total_collections(),
211 "total_collections() should be monotnically increasing");
212 return false; // no need for foreground young gc
213 }
214 }
215 return true; // may still need foreground young gc
216 }
217
218
219 void VM_GenCollectFullConcurrent::doit_epilogue() {
220 Thread* thr = Thread::current();
221 assert(thr->is_Java_thread(), "just checking");
222 JavaThread* jt = (JavaThread*)thr;
223 // Release the Heap_lock first.
224 Heap_lock->unlock();
225 release_and_notify_pending_list_lock();
226
227 // It is fine to test whether completed collections has
228 // exceeded our request count without locking because
229 // the completion count is monotonically increasing;
230 // this will break for very long-running apps when the
231 // count overflows and wraps around. XXX fix me !!!
232 // e.g. at the rate of 1 full gc per ms, this could
233 // overflow in about 1000 years.
234 GenCollectedHeap* gch = GenCollectedHeap::heap();
235 if (_gc_cause != GCCause::_gc_locker &&
236 gch->total_full_collections_completed() <= _full_gc_count_before) {
237 // maybe we should change the condition to test _gc_cause ==
238 // GCCause::_java_lang_system_gc, instead of
239 // _gc_cause != GCCause::_gc_locker
240 assert(_gc_cause == GCCause::_java_lang_system_gc,
241 "the only way to get here if this was a System.gc()-induced GC");
242 assert(ExplicitGCInvokesConcurrent, "Error");
243 // Now, wait for witnessing concurrent gc cycle to complete,
244 // but do so in native mode, because we want to lock the
245 // FullGCEvent_lock, which may be needed by the VM thread
246 // or by the CMS thread, so we do not want to be suspended
247 // while holding that lock.
248 ThreadToNativeFromVM native(jt);
249 MutexLockerEx ml(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
250 // Either a concurrent or a stop-world full gc is sufficient
251 // witness to our request.
252 while (gch->total_full_collections_completed() <= _full_gc_count_before) {
253 FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
254 }
255 }
256 // Enable iCMS back.
257 CMSCollector::enable_icms();
258 }