1 /*
2 * Copyright (c) 2001, 2011, 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/systemDictionary.hpp"
27 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepGeneration.inline.hpp"
28 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
29 #include "memory/genCollectedHeap.hpp"
30 #include "oops/instanceRefKlass.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/init.hpp"
33 #include "runtime/interfaceSupport.hpp"
34 #include "runtime/java.hpp"
35 #include "runtime/javaCalls.hpp"
36 #include "runtime/mutexLocker.hpp"
37 #include "runtime/os.hpp"
38 #include "runtime/vmThread.hpp"
39
40 // ======= Concurrent Mark Sweep Thread ========
41
42 // The CMS thread is created when Concurrent Mark Sweep is used in the
43 // older of two generations in a generational memory system.
44
45 ConcurrentMarkSweepThread*
46 ConcurrentMarkSweepThread::_cmst = NULL;
47 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
48 bool ConcurrentMarkSweepThread::_should_terminate = false;
49 int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
50
51 volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
52 volatile jint ConcurrentMarkSweepThread::_pending_decrements = 0;
53
54 volatile jint ConcurrentMarkSweepThread::_icms_disabled = 0;
55 volatile bool ConcurrentMarkSweepThread::_should_run = false;
56 // When icms is enabled, the icms thread is stopped until explicitly
57 // started.
58 volatile bool ConcurrentMarkSweepThread::_should_stop = true;
59
60 SurrogateLockerThread*
61 ConcurrentMarkSweepThread::_slt = NULL;
62 SurrogateLockerThread::SLT_msg_type
63 ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
64 Monitor*
65 ConcurrentMarkSweepThread::_sltMonitor = NULL;
66
67 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
68 : ConcurrentGCThread() {
69 assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
70 assert(_cmst == NULL, "CMS thread already created");
71 _cmst = this;
72 assert(_collector == NULL, "Collector already set");
73 _collector = collector;
74
75 set_name("Concurrent Mark-Sweep GC Thread");
76
77 if (os::create_thread(this, os::cgc_thread)) {
78 // XXX: need to set this to low priority
79 // unless "agressive mode" set; priority
80 // should be just less than that of VMThread.
81 os::set_priority(this, NearMaxPriority);
82 if (!DisableStartThread) {
83 os::start_thread(this);
84 }
85 }
86 _sltMonitor = SLT_lock;
87 assert(!CMSIncrementalMode || icms_is_enabled(), "Error");
88 }
89
90 void ConcurrentMarkSweepThread::run() {
91 assert(this == cmst(), "just checking");
92
93 this->record_stack_base_and_size();
94 this->initialize_thread_local_storage();
95 this->set_active_handles(JNIHandleBlock::allocate_block());
96 // From this time Thread::current() should be working.
97 assert(this == Thread::current(), "just checking");
98 if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
99 warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
100 }
101 // Wait until Universe::is_fully_initialized()
102 {
103 CMSLoopCountWarn loopX("CMS::run", "waiting for "
104 "Universe::is_fully_initialized()", 2);
105 MutexLockerEx x(CGC_lock, true);
106 set_CMS_flag(CMS_cms_wants_token);
107 // Wait until Universe is initialized and all initialization is completed.
108 while (!is_init_completed() && !Universe::is_fully_initialized() &&
109 !_should_terminate) {
110 CGC_lock->wait(true, 200);
111 loopX.tick();
112 }
113 // Wait until the surrogate locker thread that will do
114 // pending list locking on our behalf has been created.
115 // We cannot start the SLT thread ourselves since we need
116 // to be a JavaThread to do so.
117 CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
118 while (_slt == NULL && !_should_terminate) {
119 CGC_lock->wait(true, 200);
120 loopY.tick();
121 }
122 clear_CMS_flag(CMS_cms_wants_token);
123 }
124
125 while (!_should_terminate) {
126 sleepBeforeNextCycle();
127 if (_should_terminate) break;
128 _collector->collect_in_background(false); // !clear_all_soft_refs
129 }
130 assert(_should_terminate, "just checking");
131 // Check that the state of any protocol for synchronization
132 // between background (CMS) and foreground collector is "clean"
133 // (i.e. will not potentially block the foreground collector,
134 // requiring action by us).
135 verify_ok_to_terminate();
136 // Signal that it is terminated
137 {
138 MutexLockerEx mu(Terminator_lock,
139 Mutex::_no_safepoint_check_flag);
140 assert(_cmst == this, "Weird!");
141 _cmst = NULL;
142 Terminator_lock->notify();
143 }
144
145 // Thread destructor usually does this..
146 ThreadLocalStorage::set_thread(NULL);
147 }
148
149 #ifndef PRODUCT
150 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
151 assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
152 cms_thread_wants_cms_token()),
153 "Must renounce all worldly possessions and desires for nirvana");
154 _collector->verify_ok_to_terminate();
155 }
156 #endif
157
158 // create and start a new ConcurrentMarkSweep Thread for given CMS generation
159 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
160 if (!_should_terminate) {
161 assert(cmst() == NULL, "start() called twice?");
162 ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
163 assert(cmst() == th, "Where did the just-created CMS thread go?");
164 return th;
165 }
166 return NULL;
167 }
168
169 void ConcurrentMarkSweepThread::stop() {
170 if (CMSIncrementalMode) {
171 // Disable incremental mode and wake up the thread so it notices the change.
172 disable_icms();
173 start_icms();
174 }
175 // it is ok to take late safepoints here, if needed
176 {
177 MutexLockerEx x(Terminator_lock);
178 _should_terminate = true;
179 }
180 { // Now post a notify on CGC_lock so as to nudge
181 // CMS thread(s) that might be slumbering in
182 // sleepBeforeNextCycle.
183 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
184 CGC_lock->notify_all();
185 }
186 { // Now wait until (all) CMS thread(s) have exited
187 MutexLockerEx x(Terminator_lock);
188 while(cmst() != NULL) {
189 Terminator_lock->wait();
190 }
191 }
192 }
193
194 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
195 assert(tc != NULL, "Null ThreadClosure");
196 if (_cmst != NULL) {
197 tc->do_thread(_cmst);
198 }
199 assert(Universe::is_fully_initialized(),
200 "Called too early, make sure heap is fully initialized");
201 if (_collector != NULL) {
202 AbstractWorkGang* gang = _collector->conc_workers();
203 if (gang != NULL) {
204 gang->threads_do(tc);
205 }
206 }
207 }
208
209 void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
210 st->print("\"%s\" ", name());
211 Thread::print_on(st);
212 st->cr();
213 }
214
215 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
216 if (_cmst != NULL) {
217 _cmst->print_on(st);
218 }
219 if (_collector != NULL) {
220 AbstractWorkGang* gang = _collector->conc_workers();
221 if (gang != NULL) {
222 gang->print_worker_threads_on(st);
223 }
224 }
225 }
226
227 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
228 assert(UseConcMarkSweepGC, "just checking");
229
230 MutexLockerEx x(CGC_lock,
231 Mutex::_no_safepoint_check_flag);
232 if (!is_cms_thread) {
233 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
234 CMSSynchronousYieldRequest yr;
235 while (CMS_flag_is_set(CMS_cms_has_token)) {
236 // indicate that we want to get the token
237 set_CMS_flag(CMS_vm_wants_token);
238 CGC_lock->wait(true);
239 }
240 // claim the token and proceed
241 clear_CMS_flag(CMS_vm_wants_token);
242 set_CMS_flag(CMS_vm_has_token);
243 } else {
244 assert(Thread::current()->is_ConcurrentGC_thread(),
245 "Not a CMS thread");
246 // The following barrier assumes there's only one CMS thread.
247 // This will need to be modified is there are more CMS threads than one.
248 while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
249 set_CMS_flag(CMS_cms_wants_token);
250 CGC_lock->wait(true);
251 }
252 // claim the token
253 clear_CMS_flag(CMS_cms_wants_token);
254 set_CMS_flag(CMS_cms_has_token);
255 }
256 }
257
258 void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
259 assert(UseConcMarkSweepGC, "just checking");
260
261 MutexLockerEx x(CGC_lock,
262 Mutex::_no_safepoint_check_flag);
263 if (!is_cms_thread) {
264 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
265 assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
266 clear_CMS_flag(CMS_vm_has_token);
267 if (CMS_flag_is_set(CMS_cms_wants_token)) {
268 // wake-up a waiting CMS thread
269 CGC_lock->notify();
270 }
271 assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
272 "Should have been cleared");
273 } else {
274 assert(Thread::current()->is_ConcurrentGC_thread(),
275 "Not a CMS thread");
276 assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
277 clear_CMS_flag(CMS_cms_has_token);
278 if (CMS_flag_is_set(CMS_vm_wants_token)) {
279 // wake-up a waiting VM thread
280 CGC_lock->notify();
281 }
282 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
283 "Should have been cleared");
284 }
285 }
286
287 // Wait until the next synchronous GC, a concurrent full gc request,
288 // or a timeout, whichever is earlier.
289 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
290 MutexLockerEx x(CGC_lock,
291 Mutex::_no_safepoint_check_flag);
292 if (_should_terminate || _collector->_full_gc_requested) {
293 return;
294 }
295 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
296 CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
297 clear_CMS_flag(CMS_cms_wants_token);
298 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
299 "Should not be set");
300 }
301
302 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
303 while (!_should_terminate) {
304 if (CMSIncrementalMode) {
305 icms_wait();
306 return;
307 } else {
308 // Wait until the next synchronous GC, a concurrent full gc
309 // request or a timeout, whichever is earlier.
310 wait_on_cms_lock(CMSWaitDuration);
311 }
312 // Check if we should start a CMS collection cycle
313 if (_collector->shouldConcurrentCollect()) {
314 return;
315 }
316 // .. collection criterion not yet met, let's go back
317 // and wait some more
318 }
319 }
320
321 // Incremental CMS
322 void ConcurrentMarkSweepThread::start_icms() {
323 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
324 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
325 trace_state("start_icms");
326 _should_run = true;
327 iCMS_lock->notify_all();
328 }
329
330 void ConcurrentMarkSweepThread::stop_icms() {
331 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
332 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
333 if (!_should_stop) {
334 trace_state("stop_icms");
335 _should_stop = true;
336 _should_run = false;
337 asynchronous_yield_request();
338 iCMS_lock->notify_all();
339 }
340 }
341
342 void ConcurrentMarkSweepThread::icms_wait() {
343 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
344 if (_should_stop && icms_is_enabled()) {
345 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
346 trace_state("pause_icms");
347 _collector->stats().stop_cms_timer();
348 while(!_should_run && icms_is_enabled()) {
349 iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
350 }
351 _collector->stats().start_cms_timer();
352 _should_stop = false;
353 trace_state("pause_icms end");
354 }
355 }
356
357 // Note: this method, although exported by the ConcurrentMarkSweepThread,
358 // which is a non-JavaThread, can only be called by a JavaThread.
359 // Currently this is done at vm creation time (post-vm-init) by the
360 // main/Primordial (Java)Thread.
361 // XXX Consider changing this in the future to allow the CMS thread
362 // itself to create this thread?
363 void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
364 assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
365 assert(_slt == NULL, "SLT already created");
366 _slt = SurrogateLockerThread::make(THREAD);
367 }