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 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "gc/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 #include "runtime/os.hpp"
35
36 ConcurrentGCThread::ConcurrentGCThread() :
37 _should_terminate(false), _has_terminated(false) {
38 };
39
40 void ConcurrentGCThread::create_and_start() {
41 if (os::create_thread(this, os::cgc_thread)) {
42 // XXX: need to set this to low priority
43 // unless "aggressive mode" set; priority
44 // should be just less than that of VMThread.
45 os::set_priority(this, NearMaxPriority);
46 if (!_should_terminate && !DisableStartThread) {
47 os::start_thread(this);
48 }
49 }
50 }
51
52 void ConcurrentGCThread::initialize_in_thread() {
53 this->record_stack_base_and_size();
54 this->initialize_named_thread();
55 this->set_active_handles(JNIHandleBlock::allocate_block());
56 // From this time Thread::current() should be working.
57 assert(this == Thread::current(), "just checking");
58 }
59
60 void ConcurrentGCThread::wait_for_universe_init() {
61 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
62 while (!is_init_completed() && !_should_terminate) {
63 CGC_lock->wait(Mutex::_no_safepoint_check_flag, 1);
64 }
65 }
66
67 void ConcurrentGCThread::terminate() {
68 assert(_should_terminate, "Should only be called on terminate request.");
69 // Signal that it is terminated
70 {
71 MutexLockerEx mu(Terminator_lock,
72 Mutex::_no_safepoint_check_flag);
73 _has_terminated = true;
74 Terminator_lock->notify();
75 }
76 }
77
78 void ConcurrentGCThread::run() {
79 initialize_in_thread();
80 wait_for_universe_init();
81
82 run_service();
83
84 terminate();
85 }
86
87 void ConcurrentGCThread::stop() {
88 // it is ok to take late safepoints here, if needed
89 {
90 MutexLockerEx mu(Terminator_lock);
91 _should_terminate = true;
92 }
93
94 stop_service();
95
96 {
97 MutexLockerEx mu(Terminator_lock);
98 while (!_has_terminated) {
99 Terminator_lock->wait();
100 }
101 }
102 }
103
104 static void _sltLoop(JavaThread* thread, TRAPS) {
105 SurrogateLockerThread* slt = (SurrogateLockerThread*)thread;
106 slt->loop();
107 }
108
109 SurrogateLockerThread::SurrogateLockerThread() :
110 JavaThread(&_sltLoop),
111 _monitor(Mutex::nonleaf, "SLTMonitor", false,
112 Monitor::_safepoint_check_sometimes),
113 _buffer(empty)
114 {}
115
116 SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) {
117 Klass* k =
118 SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(),
119 true, CHECK_NULL);
120 instanceKlassHandle klass (THREAD, k);
121 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
122
123 const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)";
124 Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL);
125
126 // Initialize thread_oop to put it into the system threadGroup
127 Handle thread_group (THREAD, Universe::system_thread_group());
128 JavaValue result(T_VOID);
129 JavaCalls::call_special(&result, thread_oop,
130 klass,
131 vmSymbols::object_initializer_name(),
132 vmSymbols::threadgroup_string_void_signature(),
133 thread_group,
134 string,
135 CHECK_NULL);
136
137 SurrogateLockerThread* res;
138 {
139 MutexLocker mu(Threads_lock);
140 res = new SurrogateLockerThread();
141
142 // At this point it may be possible that no osthread was created for the
143 // JavaThread due to lack of memory. We would have to throw an exception
144 // in that case. However, since this must work and we do not allow
145 // exceptions anyway, check and abort if this fails.
146 if (res == NULL || res->osthread() == NULL) {
147 vm_exit_during_initialization("java.lang.OutOfMemoryError",
148 os::native_thread_creation_failed_msg());
149 }
150 java_lang_Thread::set_thread(thread_oop(), res);
151 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
152 java_lang_Thread::set_daemon(thread_oop());
153
154 res->set_threadObj(thread_oop());
155 Threads::add(res);
156 Thread::start(res);
157 }
158 os::naked_yield(); // This seems to help with initial start-up of SLT
159 return res;
160 }
161
162 void SurrogateLockerThread::report_missing_slt() {
163 vm_exit_during_initialization(
164 "GC before GC support fully initialized: "
165 "SLT is needed but has not yet been created.");
166 ShouldNotReachHere();
167 }
168
169 void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) {
170 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag);
171 assert(_buffer == empty, "Should be empty");
172 assert(msg != empty, "empty message");
173 assert(!Heap_lock->owned_by_self(), "Heap_lock owned by requesting thread");
174
175 _buffer = msg;
176 while (_buffer != empty) {
177 _monitor.notify();
178 _monitor.wait(Mutex::_no_safepoint_check_flag);
179 }
180 }
181
182 // ======= Surrogate Locker Thread =============
183
184 void SurrogateLockerThread::loop() {
185 BasicLock pll_basic_lock;
186 SLT_msg_type msg;
187 debug_only(unsigned int owned = 0;)
188
189 while (/* !isTerminated() */ 1) {
190 {
191 MutexLocker x(&_monitor);
192 // Since we are a JavaThread, we can't be here at a safepoint.
193 assert(!SafepointSynchronize::is_at_safepoint(),
194 "SLT is a JavaThread");
195 // wait for msg buffer to become non-empty
196 while (_buffer == empty) {
197 _monitor.notify();
198 _monitor.wait();
199 }
200 msg = _buffer;
201 }
202 switch(msg) {
203 case acquirePLL: {
204 InstanceRefKlass::acquire_pending_list_lock(&pll_basic_lock);
205 debug_only(owned++;)
206 break;
207 }
208 case releaseAndNotifyPLL: {
209 assert(owned > 0, "Don't have PLL");
210 InstanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock);
211 debug_only(owned--;)
212 break;
213 }
214 case empty:
215 default: {
216 guarantee(false,"Unexpected message in _buffer");
217 break;
218 }
219 }
220 {
221 MutexLocker x(&_monitor);
222 // Since we are a JavaThread, we can't be here at a safepoint.
223 assert(!SafepointSynchronize::is_at_safepoint(),
224 "SLT is a JavaThread");
225 _buffer = empty;
226 _monitor.notify();
227 }
228 }
229 assert(!_monitor.owned_by_self(), "Should unlock before exit.");
230 }