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 * 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, 200); 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 static void _sltLoop(JavaThread* thread, TRAPS) { 79 SurrogateLockerThread* slt = (SurrogateLockerThread*)thread; 80 slt->loop(); 81 } 82 83 SurrogateLockerThread::SurrogateLockerThread() : 84 JavaThread(&_sltLoop), 85 _monitor(Mutex::nonleaf, "SLTMonitor", false, 86 Monitor::_safepoint_check_sometimes), 87 _buffer(empty) 88 {} 89 90 SurrogateLockerThread* SurrogateLockerThread::make(TRAPS) { 91 Klass* k = 92 SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), 93 true, CHECK_NULL); 94 instanceKlassHandle klass (THREAD, k); 95 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL); 96 97 const char thread_name[] = "Surrogate Locker Thread (Concurrent GC)"; 98 Handle string = java_lang_String::create_from_str(thread_name, CHECK_NULL); 99 100 // Initialize thread_oop to put it into the system threadGroup 101 Handle thread_group (THREAD, Universe::system_thread_group()); 102 JavaValue result(T_VOID); 103 JavaCalls::call_special(&result, thread_oop, 104 klass, 105 vmSymbols::object_initializer_name(), 106 vmSymbols::threadgroup_string_void_signature(), 107 thread_group, 108 string, 109 CHECK_NULL); 110 111 SurrogateLockerThread* res; 112 { 113 MutexLocker mu(Threads_lock); 114 res = new SurrogateLockerThread(); 115 116 // At this point it may be possible that no osthread was created for the 117 // JavaThread due to lack of memory. We would have to throw an exception 118 // in that case. However, since this must work and we do not allow 119 // exceptions anyway, check and abort if this fails. 120 if (res == NULL || res->osthread() == NULL) { 121 vm_exit_during_initialization("java.lang.OutOfMemoryError", 122 os::native_thread_creation_failed_msg()); 123 } 124 java_lang_Thread::set_thread(thread_oop(), res); 125 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority); 126 java_lang_Thread::set_daemon(thread_oop()); 127 128 res->set_threadObj(thread_oop()); 129 Threads::add(res); 130 Thread::start(res); 131 } 132 os::naked_yield(); // This seems to help with initial start-up of SLT 133 return res; 134 } 135 136 void SurrogateLockerThread::report_missing_slt() { 137 vm_exit_during_initialization( 138 "GC before GC support fully initialized: " 139 "SLT is needed but has not yet been created."); 140 ShouldNotReachHere(); 141 } 142 143 void SurrogateLockerThread::manipulatePLL(SLT_msg_type msg) { 144 MutexLockerEx x(&_monitor, Mutex::_no_safepoint_check_flag); 145 assert(_buffer == empty, "Should be empty"); 146 assert(msg != empty, "empty message"); 147 assert(!Heap_lock->owned_by_self(), "Heap_lock owned by requesting thread"); 148 149 _buffer = msg; 150 while (_buffer != empty) { 151 _monitor.notify(); 152 _monitor.wait(Mutex::_no_safepoint_check_flag); 153 } 154 } 155 156 // ======= Surrogate Locker Thread ============= 157 158 void SurrogateLockerThread::loop() { 159 BasicLock pll_basic_lock; 160 SLT_msg_type msg; 161 debug_only(unsigned int owned = 0;) 162 163 while (/* !isTerminated() */ 1) { 164 { 165 MutexLocker x(&_monitor); 166 // Since we are a JavaThread, we can't be here at a safepoint. 167 assert(!SafepointSynchronize::is_at_safepoint(), 168 "SLT is a JavaThread"); 169 // wait for msg buffer to become non-empty 170 while (_buffer == empty) { 171 _monitor.notify(); 172 _monitor.wait(); 173 } 174 msg = _buffer; 175 } 176 switch(msg) { 177 case acquirePLL: { 178 InstanceRefKlass::acquire_pending_list_lock(&pll_basic_lock); 179 debug_only(owned++;) 180 break; 181 } 182 case releaseAndNotifyPLL: { 183 assert(owned > 0, "Don't have PLL"); 184 InstanceRefKlass::release_and_notify_pending_list_lock(&pll_basic_lock); 185 debug_only(owned--;) 186 break; 187 } 188 case empty: 189 default: { 190 guarantee(false,"Unexpected message in _buffer"); 191 break; 192 } 193 } 194 { 195 MutexLocker x(&_monitor); 196 // Since we are a JavaThread, we can't be here at a safepoint. 197 assert(!SafepointSynchronize::is_at_safepoint(), 198 "SLT is a JavaThread"); 199 _buffer = empty; 200 _monitor.notify(); 201 } 202 } 203 assert(!_monitor.owned_by_self(), "Should unlock before exit."); 204 }