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 // Priority should be just less than that of VMThread.
79 int native_prio;
80 if (UseCriticalCMSThreadPriority) {
81 native_prio = os::java_to_os_priority[CriticalPriority];
82 } else {
83 native_prio = os::java_to_os_priority[NearMaxPriority];
84 }
85 os::set_native_priority(this, native_prio);
86
87 if (!DisableStartThread) {
88 os::start_thread(this);
89 }
90 }
91 _sltMonitor = SLT_lock;
92 assert(!CMSIncrementalMode || icms_is_enabled(), "Error");
93 }
94
95 void ConcurrentMarkSweepThread::run() {
96 assert(this == cmst(), "just checking");
97
98 this->record_stack_base_and_size();
99 this->initialize_thread_local_storage();
100 this->set_active_handles(JNIHandleBlock::allocate_block());
101 // From this time Thread::current() should be working.
102 assert(this == Thread::current(), "just checking");
103 if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
104 warning("Couldn't bind CMS thread to processor %u", CPUForCMSThread);
105 }
106 // Wait until Universe::is_fully_initialized()
107 {
108 CMSLoopCountWarn loopX("CMS::run", "waiting for "
109 "Universe::is_fully_initialized()", 2);
110 MutexLockerEx x(CGC_lock, true);
111 set_CMS_flag(CMS_cms_wants_token);
112 // Wait until Universe is initialized and all initialization is completed.
113 while (!is_init_completed() && !Universe::is_fully_initialized() &&
114 !_should_terminate) {
115 CGC_lock->wait(true, 200);
116 loopX.tick();
117 }
118 // Wait until the surrogate locker thread that will do
119 // pending list locking on our behalf has been created.
120 // We cannot start the SLT thread ourselves since we need
121 // to be a JavaThread to do so.
122 CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
123 while (_slt == NULL && !_should_terminate) {
124 CGC_lock->wait(true, 200);
125 loopY.tick();
126 }
127 clear_CMS_flag(CMS_cms_wants_token);
128 }
129
130 while (!_should_terminate) {
131 sleepBeforeNextCycle();
132 if (_should_terminate) break;
133 _collector->collect_in_background(false); // !clear_all_soft_refs
134 }
135 assert(_should_terminate, "just checking");
136 // Check that the state of any protocol for synchronization
137 // between background (CMS) and foreground collector is "clean"
138 // (i.e. will not potentially block the foreground collector,
139 // requiring action by us).
140 verify_ok_to_terminate();
141 // Signal that it is terminated
142 {
143 MutexLockerEx mu(Terminator_lock,
144 Mutex::_no_safepoint_check_flag);
145 assert(_cmst == this, "Weird!");
146 _cmst = NULL;
147 Terminator_lock->notify();
148 }
149
150 // Thread destructor usually does this..
151 ThreadLocalStorage::set_thread(NULL);
152 }
153
154 #ifndef PRODUCT
155 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
156 assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
157 cms_thread_wants_cms_token()),
158 "Must renounce all worldly possessions and desires for nirvana");
159 _collector->verify_ok_to_terminate();
160 }
161 #endif
162
163 // create and start a new ConcurrentMarkSweep Thread for given CMS generation
164 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
165 if (!_should_terminate) {
166 assert(cmst() == NULL, "start() called twice?");
167 ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
168 assert(cmst() == th, "Where did the just-created CMS thread go?");
169 return th;
170 }
171 return NULL;
172 }
173
174 void ConcurrentMarkSweepThread::stop() {
175 if (CMSIncrementalMode) {
176 // Disable incremental mode and wake up the thread so it notices the change.
177 disable_icms();
178 start_icms();
179 }
180 // it is ok to take late safepoints here, if needed
181 {
182 MutexLockerEx x(Terminator_lock);
183 _should_terminate = true;
184 }
185 { // Now post a notify on CGC_lock so as to nudge
186 // CMS thread(s) that might be slumbering in
187 // sleepBeforeNextCycle.
188 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
189 CGC_lock->notify_all();
190 }
191 { // Now wait until (all) CMS thread(s) have exited
192 MutexLockerEx x(Terminator_lock);
193 while(cmst() != NULL) {
194 Terminator_lock->wait();
195 }
196 }
197 }
198
199 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
200 assert(tc != NULL, "Null ThreadClosure");
201 if (_cmst != NULL) {
202 tc->do_thread(_cmst);
203 }
204 assert(Universe::is_fully_initialized(),
205 "Called too early, make sure heap is fully initialized");
206 if (_collector != NULL) {
207 AbstractWorkGang* gang = _collector->conc_workers();
208 if (gang != NULL) {
209 gang->threads_do(tc);
210 }
211 }
212 }
213
214 void ConcurrentMarkSweepThread::print_on(outputStream* st) const {
215 st->print("\"%s\" ", name());
216 Thread::print_on(st);
217 st->cr();
218 }
219
220 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
221 if (_cmst != NULL) {
222 _cmst->print_on(st);
223 }
224 if (_collector != NULL) {
225 AbstractWorkGang* gang = _collector->conc_workers();
226 if (gang != NULL) {
227 gang->print_worker_threads_on(st);
228 }
229 }
230 }
231
232 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
233 assert(UseConcMarkSweepGC, "just checking");
234
235 MutexLockerEx x(CGC_lock,
236 Mutex::_no_safepoint_check_flag);
237 if (!is_cms_thread) {
238 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
239 CMSSynchronousYieldRequest yr;
240 while (CMS_flag_is_set(CMS_cms_has_token)) {
241 // indicate that we want to get the token
242 set_CMS_flag(CMS_vm_wants_token);
243 CGC_lock->wait(true);
244 }
245 // claim the token and proceed
246 clear_CMS_flag(CMS_vm_wants_token);
247 set_CMS_flag(CMS_vm_has_token);
248 } else {
249 assert(Thread::current()->is_ConcurrentGC_thread(),
250 "Not a CMS thread");
251 // The following barrier assumes there's only one CMS thread.
252 // This will need to be modified is there are more CMS threads than one.
253 while (CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token)) {
254 set_CMS_flag(CMS_cms_wants_token);
255 CGC_lock->wait(true);
256 }
257 // claim the token
258 clear_CMS_flag(CMS_cms_wants_token);
259 set_CMS_flag(CMS_cms_has_token);
260 }
261 }
262
263 void ConcurrentMarkSweepThread::desynchronize(bool is_cms_thread) {
264 assert(UseConcMarkSweepGC, "just checking");
265
266 MutexLockerEx x(CGC_lock,
267 Mutex::_no_safepoint_check_flag);
268 if (!is_cms_thread) {
269 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
270 assert(CMS_flag_is_set(CMS_vm_has_token), "just checking");
271 clear_CMS_flag(CMS_vm_has_token);
272 if (CMS_flag_is_set(CMS_cms_wants_token)) {
273 // wake-up a waiting CMS thread
274 CGC_lock->notify();
275 }
276 assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
277 "Should have been cleared");
278 } else {
279 assert(Thread::current()->is_ConcurrentGC_thread(),
280 "Not a CMS thread");
281 assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
282 clear_CMS_flag(CMS_cms_has_token);
283 if (CMS_flag_is_set(CMS_vm_wants_token)) {
284 // wake-up a waiting VM thread
285 CGC_lock->notify();
286 }
287 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
288 "Should have been cleared");
289 }
290 }
291
292 // Wait until the next synchronous GC, a concurrent full gc request,
293 // or a timeout, whichever is earlier.
294 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
295 MutexLockerEx x(CGC_lock,
296 Mutex::_no_safepoint_check_flag);
297 if (_should_terminate || _collector->_full_gc_requested) {
298 return;
299 }
300 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
301 CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
302 clear_CMS_flag(CMS_cms_wants_token);
303 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
304 "Should not be set");
305 }
306
307 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
308 while (!_should_terminate) {
309 if (CMSIncrementalMode) {
310 icms_wait();
311 return;
312 } else {
313 // Wait until the next synchronous GC, a concurrent full gc
314 // request or a timeout, whichever is earlier.
315 wait_on_cms_lock(CMSWaitDuration);
316 }
317 // Check if we should start a CMS collection cycle
318 if (_collector->shouldConcurrentCollect()) {
319 return;
320 }
321 // .. collection criterion not yet met, let's go back
322 // and wait some more
323 }
324 }
325
326 // Incremental CMS
327 void ConcurrentMarkSweepThread::start_icms() {
328 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
329 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
330 trace_state("start_icms");
331 _should_run = true;
332 iCMS_lock->notify_all();
333 }
334
335 void ConcurrentMarkSweepThread::stop_icms() {
336 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
337 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
338 if (!_should_stop) {
339 trace_state("stop_icms");
340 _should_stop = true;
341 _should_run = false;
342 asynchronous_yield_request();
343 iCMS_lock->notify_all();
344 }
345 }
346
347 void ConcurrentMarkSweepThread::icms_wait() {
348 assert(UseConcMarkSweepGC && CMSIncrementalMode, "just checking");
349 if (_should_stop && icms_is_enabled()) {
350 MutexLockerEx x(iCMS_lock, Mutex::_no_safepoint_check_flag);
351 trace_state("pause_icms");
352 _collector->stats().stop_cms_timer();
353 while(!_should_run && icms_is_enabled()) {
354 iCMS_lock->wait(Mutex::_no_safepoint_check_flag);
355 }
356 _collector->stats().start_cms_timer();
357 _should_stop = false;
358 trace_state("pause_icms end");
359 }
360 }
361
362 // Note: this method, although exported by the ConcurrentMarkSweepThread,
363 // which is a non-JavaThread, can only be called by a JavaThread.
364 // Currently this is done at vm creation time (post-vm-init) by the
365 // main/Primordial (Java)Thread.
366 // XXX Consider changing this in the future to allow the CMS thread
367 // itself to create this thread?
368 void ConcurrentMarkSweepThread::makeSurrogateLockerThread(TRAPS) {
369 assert(UseConcMarkSweepGC, "SLT thread needed only for CMS GC");
370 assert(_slt == NULL, "SLT already created");
371 _slt = SurrogateLockerThread::make(THREAD);
372 }