1 /*
2 * Copyright (c) 2001, 2015, 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 *
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
28 #include "gc/cms/concurrentMarkSweepThread.hpp"
29 #include "gc/shared/gcId.hpp"
30 #include "gc/shared/genCollectedHeap.hpp"
31 #include "oops/instanceRefKlass.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/init.hpp"
34 #include "runtime/interfaceSupport.hpp"
35 #include "runtime/java.hpp"
36 #include "runtime/javaCalls.hpp"
37 #include "runtime/mutexLocker.hpp"
38 #include "runtime/os.hpp"
39 #include "runtime/vmThread.hpp"
40
41 // ======= Concurrent Mark Sweep Thread ========
42
43 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::_cmst = NULL;
44 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
45 bool ConcurrentMarkSweepThread::_should_terminate = false;
46 int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
47
48 volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
49
50 SurrogateLockerThread* ConcurrentMarkSweepThread::_slt = NULL;
51 SurrogateLockerThread::SLT_msg_type
52 ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
53 Monitor* ConcurrentMarkSweepThread::_sltMonitor = NULL;
54
55 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
56 : ConcurrentGCThread() {
57 assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
58 assert(_cmst == NULL, "CMS thread already created");
59 _cmst = this;
60 assert(_collector == NULL, "Collector already set");
61 _collector = collector;
62
63 set_name("CMS Main Thread");
64
65 if (os::create_thread(this, os::cgc_thread)) {
66 // An old comment here said: "Priority should be just less
67 // than that of VMThread". Since the VMThread runs at
68 // NearMaxPriority, the old comment was inaccurate, but
69 // changing the default priority to NearMaxPriority-1
70 // could change current behavior, so the default of
71 // NearMaxPriority stays in place.
72 //
73 // Note that there's a possibility of the VMThread
74 // starving if UseCriticalCMSThreadPriority is on.
75 // That won't happen on Solaris for various reasons,
76 // but may well happen on non-Solaris platforms.
77 int native_prio;
78 if (UseCriticalCMSThreadPriority) {
79 native_prio = os::java_to_os_priority[CriticalPriority];
80 } else {
81 native_prio = os::java_to_os_priority[NearMaxPriority];
82 }
83 os::set_native_priority(this, native_prio);
84
85 if (!DisableStartThread) {
86 os::start_thread(this);
87 }
88 }
89 _sltMonitor = SLT_lock;
90 }
91
92 void ConcurrentMarkSweepThread::run() {
93 assert(this == cmst(), "just checking");
94
95 initialize_in_thread();
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 " UINTX_FORMAT, 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 GCIdMark gc_id_mark;
129 GCCause::Cause cause = _collector->_full_gc_requested ?
130 _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;
131 _collector->collect_in_background(cause);
132 }
133 assert(_should_terminate, "just checking");
134 // Check that the state of any protocol for synchronization
135 // between background (CMS) and foreground collector is "clean"
136 // (i.e. will not potentially block the foreground collector,
137 // requiring action by us).
138 verify_ok_to_terminate();
139 // Signal that it is terminated
140 {
141 MutexLockerEx mu(Terminator_lock,
142 Mutex::_no_safepoint_check_flag);
143 assert(_cmst == this, "Weird!");
144 _cmst = NULL;
145 Terminator_lock->notify();
146 }
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 // it is ok to take late safepoints here, if needed
171 {
172 MutexLockerEx x(Terminator_lock);
173 _should_terminate = true;
174 }
175 { // Now post a notify on CGC_lock so as to nudge
176 // CMS thread(s) that might be slumbering in
177 // sleepBeforeNextCycle.
178 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
179 CGC_lock->notify_all();
180 }
181 { // Now wait until (all) CMS thread(s) have exited
182 MutexLockerEx x(Terminator_lock);
183 while(cmst() != NULL) {
184 Terminator_lock->wait();
185 }
186 }
187 }
188
189 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
190 assert(tc != NULL, "Null ThreadClosure");
191 if (_cmst != NULL) {
192 tc->do_thread(_cmst);
193 }
194 assert(Universe::is_fully_initialized(),
195 "Called too early, make sure heap is fully initialized");
196 if (_collector != NULL) {
197 AbstractWorkGang* gang = _collector->conc_workers();
198 if (gang != NULL) {
199 gang->threads_do(tc);
200 }
201 }
202 }
203
204 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
205 if (_cmst != NULL) {
206 _cmst->print_on(st);
207 st->cr();
208 }
209 if (_collector != NULL) {
210 AbstractWorkGang* gang = _collector->conc_workers();
211 if (gang != NULL) {
212 gang->print_worker_threads_on(st);
213 }
214 }
215 }
216
217 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
218 assert(UseConcMarkSweepGC, "just checking");
219
220 MutexLockerEx x(CGC_lock,
221 Mutex::_no_safepoint_check_flag);
222 if (!is_cms_thread) {
223 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
224 CMSSynchronousYieldRequest yr;
225 while (CMS_flag_is_set(CMS_cms_has_token)) {
226 // indicate that we want to get the token
261 assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
262 "Should have been cleared");
263 } else {
264 assert(Thread::current()->is_ConcurrentGC_thread(),
265 "Not a CMS thread");
266 assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
267 clear_CMS_flag(CMS_cms_has_token);
268 if (CMS_flag_is_set(CMS_vm_wants_token)) {
269 // wake-up a waiting VM thread
270 CGC_lock->notify();
271 }
272 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
273 "Should have been cleared");
274 }
275 }
276
277 // Wait until any cms_lock event
278 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
279 MutexLockerEx x(CGC_lock,
280 Mutex::_no_safepoint_check_flag);
281 if (_should_terminate || _collector->_full_gc_requested) {
282 return;
283 }
284 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
285 CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
286 clear_CMS_flag(CMS_cms_wants_token);
287 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
288 "Should not be set");
289 }
290
291 // Wait until the next synchronous GC, a concurrent full gc request,
292 // or a timeout, whichever is earlier.
293 void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {
294 // Wait time in millis or 0 value representing infinite wait for a scavenge
295 assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");
296
297 GenCollectedHeap* gch = GenCollectedHeap::heap();
298 double start_time_secs = os::elapsedTime();
299 double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));
300
301 // Total collections count before waiting loop
302 unsigned int before_count;
303 {
304 MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
305 before_count = gch->total_collections();
306 }
307
308 unsigned int loop_count = 0;
309
310 while(!_should_terminate) {
311 double now_time = os::elapsedTime();
312 long wait_time_millis;
313
314 if(t_millis != 0) {
315 // New wait limit
316 wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);
317 if(wait_time_millis <= 0) {
318 // Wait time is over
319 break;
320 }
321 } else {
322 // No wait limit, wait if necessary forever
323 wait_time_millis = 0;
324 }
325
326 // Wait until the next event or the remaining timeout
327 {
328 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
329
330 if (_should_terminate || _collector->_full_gc_requested) {
331 return;
332 }
333 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
334 assert(t_millis == 0 || wait_time_millis > 0, "Sanity");
335 CGC_lock->wait(Mutex::_no_safepoint_check_flag, wait_time_millis);
336 clear_CMS_flag(CMS_cms_wants_token);
337 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
338 "Should not be set");
339 }
340
341 // Extra wait time check before entering the heap lock to get the collection count
342 if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {
343 // Wait time is over
344 break;
345 }
346
347 // Total collections count after the event
348 unsigned int after_count;
349 {
350 MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
351 after_count = gch->total_collections();
352 }
353
354 if(before_count != after_count) {
355 // There was a collection - success
356 break;
357 }
358
359 // Too many loops warning
360 if(++loop_count == 0) {
361 warning("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);
362 }
363 }
364 }
365
366 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
367 while (!_should_terminate) {
368 if(CMSWaitDuration >= 0) {
369 // Wait until the next synchronous GC, a concurrent full gc
370 // request or a timeout, whichever is earlier.
371 wait_on_cms_lock_for_scavenge(CMSWaitDuration);
372 } else {
373 // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently
374 wait_on_cms_lock(CMSCheckInterval);
375 }
376 // Check if we should start a CMS collection cycle
377 if (_collector->shouldConcurrentCollect()) {
378 return;
379 }
380 // .. collection criterion not yet met, let's go back
381 // and wait some more
382 }
383 }
384
385 // Note: this method, although exported by the ConcurrentMarkSweepThread,
386 // which is a non-JavaThread, can only be called by a JavaThread.
387 // Currently this is done at vm creation time (post-vm-init) by the
|
1 /*
2 * Copyright (c) 2001, 2016, 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 *
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "gc/cms/concurrentMarkSweepGeneration.inline.hpp"
28 #include "gc/cms/concurrentMarkSweepThread.hpp"
29 #include "gc/shared/gcId.hpp"
30 #include "gc/shared/genCollectedHeap.hpp"
31 #include "oops/instanceRefKlass.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/init.hpp"
34 #include "runtime/interfaceSupport.hpp"
35 #include "runtime/java.hpp"
36 #include "runtime/javaCalls.hpp"
37 #include "runtime/mutexLocker.hpp"
38 #include "runtime/os.hpp"
39 #include "runtime/vmThread.hpp"
40
41 // ======= Concurrent Mark Sweep Thread ========
42
43 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::_cmst = NULL;
44 CMSCollector* ConcurrentMarkSweepThread::_collector = NULL;
45 int ConcurrentMarkSweepThread::_CMS_flag = CMS_nil;
46
47 volatile jint ConcurrentMarkSweepThread::_pending_yields = 0;
48
49 SurrogateLockerThread* ConcurrentMarkSweepThread::_slt = NULL;
50 SurrogateLockerThread::SLT_msg_type
51 ConcurrentMarkSweepThread::_sltBuffer = SurrogateLockerThread::empty;
52 Monitor* ConcurrentMarkSweepThread::_sltMonitor = NULL;
53
54 ConcurrentMarkSweepThread::ConcurrentMarkSweepThread(CMSCollector* collector)
55 : ConcurrentGCThread() {
56 assert(UseConcMarkSweepGC, "UseConcMarkSweepGC should be set");
57 assert(_cmst == NULL, "CMS thread already created");
58 _cmst = this;
59 assert(_collector == NULL, "Collector already set");
60 _collector = collector;
61
62 set_name("CMS Main Thread");
63
64 // An old comment here said: "Priority should be just less
65 // than that of VMThread". Since the VMThread runs at
66 // NearMaxPriority, the old comment was inaccurate, but
67 // changing the default priority to NearMaxPriority-1
68 // could change current behavior, so the default of
69 // NearMaxPriority stays in place.
70 //
71 // Note that there's a possibility of the VMThread
72 // starving if UseCriticalCMSThreadPriority is on.
73 // That won't happen on Solaris for various reasons,
74 // but may well happen on non-Solaris platforms.
75 create_and_start(UseCriticalCMSThreadPriority ? CriticalPriority : NearMaxPriority);
76
77 _sltMonitor = SLT_lock;
78 }
79
80 void ConcurrentMarkSweepThread::run_service() {
81 assert(this == cmst(), "just checking");
82
83 if (BindCMSThreadToCPU && !os::bind_to_processor(CPUForCMSThread)) {
84 warning("Couldn't bind CMS thread to processor " UINTX_FORMAT, CPUForCMSThread);
85 }
86
87 {
88 MutexLockerEx x(CGC_lock, true);
89 set_CMS_flag(CMS_cms_wants_token);
90 assert(is_init_completed() && Universe::is_fully_initialized(), "ConcurrentGCThread::run() should have waited for this.");
91
92 // Wait until the surrogate locker thread that will do
93 // pending list locking on our behalf has been created.
94 // We cannot start the SLT thread ourselves since we need
95 // to be a JavaThread to do so.
96 CMSLoopCountWarn loopY("CMS::run", "waiting for SLT installation", 2);
97 while (_slt == NULL && !should_terminate()) {
98 CGC_lock->wait(true, 200);
99 loopY.tick();
100 }
101 clear_CMS_flag(CMS_cms_wants_token);
102 }
103
104 while (!should_terminate()) {
105 sleepBeforeNextCycle();
106 if (should_terminate()) break;
107 GCIdMark gc_id_mark;
108 GCCause::Cause cause = _collector->_full_gc_requested ?
109 _collector->_full_gc_cause : GCCause::_cms_concurrent_mark;
110 _collector->collect_in_background(cause);
111 }
112
113 // Check that the state of any protocol for synchronization
114 // between background (CMS) and foreground collector is "clean"
115 // (i.e. will not potentially block the foreground collector,
116 // requiring action by us).
117 verify_ok_to_terminate();
118 }
119
120 #ifndef PRODUCT
121 void ConcurrentMarkSweepThread::verify_ok_to_terminate() const {
122 assert(!(CGC_lock->owned_by_self() || cms_thread_has_cms_token() ||
123 cms_thread_wants_cms_token()),
124 "Must renounce all worldly possessions and desires for nirvana");
125 _collector->verify_ok_to_terminate();
126 }
127 #endif
128
129 // create and start a new ConcurrentMarkSweep Thread for given CMS generation
130 ConcurrentMarkSweepThread* ConcurrentMarkSweepThread::start(CMSCollector* collector) {
131 guarantee(_cmst == NULL, "start() called twice!");
132 ConcurrentMarkSweepThread* th = new ConcurrentMarkSweepThread(collector);
133 assert(_cmst == th, "Where did the just-created CMS thread go?");
134 return th;
135 }
136
137 void ConcurrentMarkSweepThread::stop_all() {
138 assert(_cmst != NULL, "stop_all should be called after initialization");
139 _cmst->stop();
140 }
141
142 void ConcurrentMarkSweepThread::stop_service() {
143 // Now post a notify on CGC_lock so as to nudge
144 // CMS thread(s) that might be slumbering in
145 // sleepBeforeNextCycle.
146 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
147 CGC_lock->notify_all();
148 }
149
150 void ConcurrentMarkSweepThread::threads_do(ThreadClosure* tc) {
151 assert(tc != NULL, "Null ThreadClosure");
152 if (cmst() != NULL && !cmst()->has_terminated()) {
153 tc->do_thread(cmst());
154 }
155 assert(Universe::is_fully_initialized(),
156 "Called too early, make sure heap is fully initialized");
157 if (_collector != NULL) {
158 AbstractWorkGang* gang = _collector->conc_workers();
159 if (gang != NULL) {
160 gang->threads_do(tc);
161 }
162 }
163 }
164
165 void ConcurrentMarkSweepThread::print_all_on(outputStream* st) {
166 if (cmst() != NULL && !cmst()->has_terminated()) {
167 cmst()->print_on(st);
168 st->cr();
169 }
170 if (_collector != NULL) {
171 AbstractWorkGang* gang = _collector->conc_workers();
172 if (gang != NULL) {
173 gang->print_worker_threads_on(st);
174 }
175 }
176 }
177
178 void ConcurrentMarkSweepThread::synchronize(bool is_cms_thread) {
179 assert(UseConcMarkSweepGC, "just checking");
180
181 MutexLockerEx x(CGC_lock,
182 Mutex::_no_safepoint_check_flag);
183 if (!is_cms_thread) {
184 assert(Thread::current()->is_VM_thread(), "Not a VM thread");
185 CMSSynchronousYieldRequest yr;
186 while (CMS_flag_is_set(CMS_cms_has_token)) {
187 // indicate that we want to get the token
222 assert(!CMS_flag_is_set(CMS_vm_has_token | CMS_vm_wants_token),
223 "Should have been cleared");
224 } else {
225 assert(Thread::current()->is_ConcurrentGC_thread(),
226 "Not a CMS thread");
227 assert(CMS_flag_is_set(CMS_cms_has_token), "just checking");
228 clear_CMS_flag(CMS_cms_has_token);
229 if (CMS_flag_is_set(CMS_vm_wants_token)) {
230 // wake-up a waiting VM thread
231 CGC_lock->notify();
232 }
233 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
234 "Should have been cleared");
235 }
236 }
237
238 // Wait until any cms_lock event
239 void ConcurrentMarkSweepThread::wait_on_cms_lock(long t_millis) {
240 MutexLockerEx x(CGC_lock,
241 Mutex::_no_safepoint_check_flag);
242 if (should_terminate() || _collector->_full_gc_requested) {
243 return;
244 }
245 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
246 CGC_lock->wait(Mutex::_no_safepoint_check_flag, t_millis);
247 clear_CMS_flag(CMS_cms_wants_token);
248 assert(!CMS_flag_is_set(CMS_cms_has_token | CMS_cms_wants_token),
249 "Should not be set");
250 }
251
252 // Wait until the next synchronous GC, a concurrent full gc request,
253 // or a timeout, whichever is earlier.
254 void ConcurrentMarkSweepThread::wait_on_cms_lock_for_scavenge(long t_millis) {
255 // Wait time in millis or 0 value representing infinite wait for a scavenge
256 assert(t_millis >= 0, "Wait time for scavenge should be 0 or positive");
257
258 GenCollectedHeap* gch = GenCollectedHeap::heap();
259 double start_time_secs = os::elapsedTime();
260 double end_time_secs = start_time_secs + (t_millis / ((double) MILLIUNITS));
261
262 // Total collections count before waiting loop
263 unsigned int before_count;
264 {
265 MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
266 before_count = gch->total_collections();
267 }
268
269 unsigned int loop_count = 0;
270
271 while(!should_terminate()) {
272 double now_time = os::elapsedTime();
273 long wait_time_millis;
274
275 if(t_millis != 0) {
276 // New wait limit
277 wait_time_millis = (long) ((end_time_secs - now_time) * MILLIUNITS);
278 if(wait_time_millis <= 0) {
279 // Wait time is over
280 break;
281 }
282 } else {
283 // No wait limit, wait if necessary forever
284 wait_time_millis = 0;
285 }
286
287 // Wait until the next event or the remaining timeout
288 {
289 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
290
291 if (should_terminate() || _collector->_full_gc_requested) {
292 return;
293 }
294 set_CMS_flag(CMS_cms_wants_token); // to provoke notifies
295 assert(t_millis == 0 || wait_time_millis > 0, "Sanity");
296 CGC_lock->wait(Mutex::_no_safepoint_check_flag, wait_time_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 // Extra wait time check before entering the heap lock to get the collection count
303 if(t_millis != 0 && os::elapsedTime() >= end_time_secs) {
304 // Wait time is over
305 break;
306 }
307
308 // Total collections count after the event
309 unsigned int after_count;
310 {
311 MutexLockerEx hl(Heap_lock, Mutex::_no_safepoint_check_flag);
312 after_count = gch->total_collections();
313 }
314
315 if(before_count != after_count) {
316 // There was a collection - success
317 break;
318 }
319
320 // Too many loops warning
321 if(++loop_count == 0) {
322 warning("wait_on_cms_lock_for_scavenge() has looped %u times", loop_count - 1);
323 }
324 }
325 }
326
327 void ConcurrentMarkSweepThread::sleepBeforeNextCycle() {
328 while (!should_terminate()) {
329 if(CMSWaitDuration >= 0) {
330 // Wait until the next synchronous GC, a concurrent full gc
331 // request or a timeout, whichever is earlier.
332 wait_on_cms_lock_for_scavenge(CMSWaitDuration);
333 } else {
334 // Wait until any cms_lock event or check interval not to call shouldConcurrentCollect permanently
335 wait_on_cms_lock(CMSCheckInterval);
336 }
337 // Check if we should start a CMS collection cycle
338 if (_collector->shouldConcurrentCollect()) {
339 return;
340 }
341 // .. collection criterion not yet met, let's go back
342 // and wait some more
343 }
344 }
345
346 // Note: this method, although exported by the ConcurrentMarkSweepThread,
347 // which is a non-JavaThread, can only be called by a JavaThread.
348 // Currently this is done at vm creation time (post-vm-init) by the
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