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/shared/concurrentGCThread.hpp"
28 #include "oops/instanceRefKlass.hpp"
29 #include "oops/oop.inline.hpp"
30 #include "runtime/init.hpp"
31 #include "runtime/interfaceSupport.hpp"
32 #include "runtime/java.hpp"
33 #include "runtime/javaCalls.hpp"
34
35 // CopyrightVersion 1.2
36
37 int ConcurrentGCThread::_CGC_flag = CGC_nil;
38
39 SuspendibleThreadSet ConcurrentGCThread::_sts;
40
41 ConcurrentGCThread::ConcurrentGCThread() :
42 _should_terminate(false), _has_terminated(false) {
43 _sts.initialize();
44 };
45
46 void ConcurrentGCThread::safepoint_synchronize() {
47 _sts.suspend_all();
48 }
49
50 void ConcurrentGCThread::safepoint_desynchronize() {
51 _sts.resume_all();
52 }
53
54 void ConcurrentGCThread::create_and_start() {
55 if (os::create_thread(this, os::cgc_thread)) {
56 // XXX: need to set this to low priority
57 // unless "agressive mode" set; priority
58 // should be just less than that of VMThread.
59 os::set_priority(this, NearMaxPriority);
60 if (!_should_terminate && !DisableStartThread) {
61 os::start_thread(this);
62 }
63 }
64 }
65
66 void ConcurrentGCThread::initialize_in_thread() {
67 this->record_stack_base_and_size();
68 this->initialize_thread_local_storage();
69 this->set_active_handles(JNIHandleBlock::allocate_block());
70 // From this time Thread::current() should be working.
71 assert(this == Thread::current(), "just checking");
72 }
73
74 void ConcurrentGCThread::wait_for_universe_init() {
75 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
76 while (!is_init_completed() && !_should_terminate) {
77 CGC_lock->wait(Mutex::_no_safepoint_check_flag, 200);
78 }
79 }
80
81 void ConcurrentGCThread::terminate() {
82 // Signal that it is terminated
83 {
84 MutexLockerEx mu(Terminator_lock,
85 Mutex::_no_safepoint_check_flag);
86 _has_terminated = true;
87 Terminator_lock->notify();
88 }
89
90 // Thread destructor usually does this..
91 ThreadLocalStorage::set_thread(NULL);
92 }
93
94
95 void SuspendibleThreadSet::initialize_work() {
96 MutexLocker x(STS_init_lock);
97 if (!_initialized) {
98 _m = new Monitor(Mutex::leaf,
99 "SuspendibleThreadSetLock", true);
100 _async = 0;
101 _async_stop = false;
102 _async_stopped = 0;
103 _initialized = true;
104 }
105 }
106
107 void SuspendibleThreadSet::join() {
108 initialize();
109 MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
110 while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
111 _async++;
112 assert(_async > 0, "Huh.");
113 }
114
115 void SuspendibleThreadSet::leave() {
116 assert(_initialized, "Must be initialized.");
117 MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
118 _async--;
119 assert(_async >= 0, "Huh.");
120 if (_async_stop) _m->notify_all();
121 }
122
123 void SuspendibleThreadSet::yield(const char* id) {
124 assert(_initialized, "Must be initialized.");
125 if (_async_stop) {
126 MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
127 if (_async_stop) {
128 _async_stopped++;
129 assert(_async_stopped > 0, "Huh.");
130 if (_async_stopped == _async) {
131 if (ConcGCYieldTimeout > 0) {
132 double now = os::elapsedTime();
133 guarantee((now - _suspend_all_start) * 1000.0 <
134 (double)ConcGCYieldTimeout,
135 "Long delay; whodunit?");
136 }
137 }
138 _m->notify_all();
139 while (_async_stop) _m->wait(Mutex::_no_safepoint_check_flag);
140 _async_stopped--;
141 assert(_async >= 0, "Huh");
142 _m->notify_all();
143 }
144 }
145 }
146
147 void SuspendibleThreadSet::suspend_all() {
148 initialize(); // If necessary.
149 if (ConcGCYieldTimeout > 0) {
150 _suspend_all_start = os::elapsedTime();
151 }
152 MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
153 assert(!_async_stop, "Only one at a time.");
154 _async_stop = true;
155 while (_async_stopped < _async) _m->wait(Mutex::_no_safepoint_check_flag);
156 }
157
158 void SuspendibleThreadSet::resume_all() {
159 assert(_initialized, "Must be initialized.");
160 MutexLockerEx x(_m, Mutex::_no_safepoint_check_flag);
161 assert(_async_stopped == _async, "Huh.");
162 _async_stop = false;
163 _m->notify_all();
164 }
165
166 static void _sltLoop(JavaThread* thread, TRAPS) {
167 SurrogateLockerThread* slt = (SurrogateLockerThread*)thread;
168 slt->loop();
169 }
170
171 SurrogateLockerThread::SurrogateLockerThread() :
172 JavaThread(&_sltLoop),
173 _monitor(Mutex::nonleaf, "SLTMonitor"),
174 _buffer(empty)
175 {}
176
177 SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) {
178 klassOop k =
179 SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(),
180 true, CHECK_NULL);
181 instanceKlassHandle klass (THREAD, k);
182 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
183
184 const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)";
185 Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL);
186
187 // Initialize thread_oop to put it into the system threadGroup
188 Handle thread_group (THREAD, Universe::system_thread_group());
189 JavaValue result(T_VOID);
190 JavaCalls::call_special(&result, thread_oop,
191 klass,
192 vmSymbols::object_initializer_name(),
193 vmSymbols::threadgroup_string_void_signature(),
194 thread_group,
195 string,
196 CHECK_NULL);
197
198 SurrogateLockerThread* res;
199 {
200 MutexLocker mu(Threads_lock);
201 res = new SurrogateLockerThread();
202
203 // At this point it may be possible that no osthread was created for the
204 // JavaThread due to lack of memory. We would have to throw an exception
205 // in that case. However, since this must work and we do not allow
206 // exceptions anyway, check and abort if this fails.
207 if (res == NULL || res->osthread() == NULL) {
208 vm_exit_during_initialization("java.lang.OutOfMemoryError",
209 "unable to create new native thread");
210 }
211 java_lang_Thread::set_thread(thread_oop(), res);
212 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
213 java_lang_Thread::set_daemon(thread_oop());
214
215 res->set_threadObj(thread_oop());
216 Threads::add(res);
217 Thread::start(res);
218 }
219 os::yield(); // This seems to help with initial start-up of SLT
220 return res;
221 }
222
223 void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) {
224 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
225 assert(_buffer == empty, "Should be empty");
226 assert(msg != empty, "empty message");
227 _buffer = msg;
228 while (_buffer != empty) {
229 _monitor.notify();
230 _monitor.wait(Mutex::_no_safepoint_check_flag);
231 }
232 }
233
234 // ======= Surrogate Locker Thread =============
235
236 void SurrogateLockerThread::loop() {
237 BasicLock pll_basic_lock;
238 SLT_msg_type msg;
239 debug_only(unsigned int owned = 0;)
240
241 while (/* !isTerminated() */ 1) {
242 {
243 MutexLocker x(&_monitor);
244 // Since we are a JavaThread, we can't be here at a safepoint.
245 assert(!SafepointSynchronize::is_at_safepoint(),
246 "SLT is a JavaThread");
247 // wait for msg buffer to become non-empty
248 while (_buffer == empty) {
249 _monitor.notify();
250 _monitor.wait();
251 }
252 msg = _buffer;
253 }
254 switch(msg) {
255 case acquirePLL: {
256 instanceRefKlass::acquire_pending_list_lock(&pll_basic_lock);
257 debug_only(owned++;)
258 break;
259 }
260 case releaseAndNotifyPLL: {
261 assert(owned > 0, "Don't have PLL");
262 instanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock);
263 debug_only(owned--;)
264 break;
265 }
266 case empty:
267 default: {
268 guarantee(false,"Unexpected message in _buffer");
269 break;
270 }
271 }
272 {
273 MutexLocker x(&_monitor);
274 // Since we are a JavaThread, we can't be here at a safepoint.
275 assert(!SafepointSynchronize::is_at_safepoint(),
276 "SLT is a JavaThread");
277 _buffer = empty;
278 _monitor.notify();
279 }
280 }
281 assert(!_monitor.owned_by_self(), "Should unlock before exit.");
282 }
283
284
285 // ===== STS Access From Outside CGCT =====
286
287 void ConcurrentGCThread::stsYield(const char* id) {
288 assert( Thread::current()->is_ConcurrentGC_thread(),
289 "only a conc GC thread can call this" );
290 _sts.yield(id);
291 }
292
293 bool ConcurrentGCThread::stsShouldYield() {
294 assert( Thread::current()->is_ConcurrentGC_thread(),
295 "only a conc GC thread can call this" );
296 return _sts.should_yield();
297 }
298
299 void ConcurrentGCThread::stsJoin() {
300 assert( Thread::current()->is_ConcurrentGC_thread(),
301 "only a conc GC thread can call this" );
302 _sts.join();
303 }
304
305 void ConcurrentGCThread::stsLeave() {
306 assert( Thread::current()->is_ConcurrentGC_thread(),
307 "only a conc GC thread can call this" );
308 _sts.leave();
309 }