1 /* 2 * Copyright (c) 1998, 2013, 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 #ifndef SHARE_VM_RUNTIME_OBJECTMONITOR_HPP 26 #define SHARE_VM_RUNTIME_OBJECTMONITOR_HPP 27 28 #include "runtime/os.hpp" 29 #include "runtime/park.hpp" 30 #include "runtime/perfData.hpp" 31 32 // ObjectWaiter serves as a "proxy" or surrogate thread. 33 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific 34 // ParkEvent instead. Beware, however, that the JVMTI code 35 // knows about ObjectWaiters, so we'll have to reconcile that code. 36 // See next_waiter(), first_waiter(), etc. 37 38 class ObjectWaiter : public StackObj { 39 public: 40 enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ; 41 enum Sorted { PREPEND, APPEND, SORTED } ; 42 ObjectWaiter * volatile _next; 43 ObjectWaiter * volatile _prev; 44 Thread* _thread; 45 jlong _notifier_tid; 46 ParkEvent * _event; 47 volatile int _notified ; 48 volatile TStates TState ; 49 Sorted _Sorted ; // List placement disposition 50 bool _active ; // Contention monitoring is enabled 51 public: 52 ObjectWaiter(Thread* thread); 53 54 void wait_reenter_begin(ObjectMonitor *mon); 55 void wait_reenter_end(ObjectMonitor *mon); 56 }; 57 58 // forward declaration to avoid include tracing.hpp 59 class EventJavaMonitorWait; 60 61 // WARNING: 62 // This is a very sensitive and fragile class. DO NOT make any 63 // change unless you are fully aware of the underlying semantics. 64 65 // This class can not inherit from any other class, because I have 66 // to let the displaced header be the very first word. Otherwise I 67 // have to let markOop include this file, which would export the 68 // monitor data structure to everywhere. 69 // 70 // The ObjectMonitor class is used to implement JavaMonitors which have 71 // transformed from the lightweight structure of the thread stack to a 72 // heavy weight lock due to contention 73 74 // It is also used as RawMonitor by the JVMTI 75 76 77 class ObjectMonitor { 78 public: 79 enum { 80 OM_OK, // no error 81 OM_SYSTEM_ERROR, // operating system error 82 OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException 83 OM_INTERRUPTED, // Thread.interrupt() 84 OM_TIMED_OUT // Object.wait() timed out 85 }; 86 87 public: 88 // TODO-FIXME: the "offset" routines should return a type of off_t instead of int ... 89 // ByteSize would also be an appropriate type. 90 static int header_offset_in_bytes() { return offset_of(ObjectMonitor, _header); } 91 static int object_offset_in_bytes() { return offset_of(ObjectMonitor, _object); } 92 static int owner_offset_in_bytes() { return offset_of(ObjectMonitor, _owner); } 93 static int count_offset_in_bytes() { return offset_of(ObjectMonitor, _count); } 94 static int recursions_offset_in_bytes() { return offset_of(ObjectMonitor, _recursions); } 95 static int cxq_offset_in_bytes() { return offset_of(ObjectMonitor, _cxq) ; } 96 static int succ_offset_in_bytes() { return offset_of(ObjectMonitor, _succ) ; } 97 static int EntryList_offset_in_bytes() { return offset_of(ObjectMonitor, _EntryList); } 98 static int FreeNext_offset_in_bytes() { return offset_of(ObjectMonitor, FreeNext); } 99 static int WaitSet_offset_in_bytes() { return offset_of(ObjectMonitor, _WaitSet) ; } 100 static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);} 101 static int Spinner_offset_in_bytes() { return offset_of(ObjectMonitor, _Spinner); } 102 103 public: 104 // Eventaully we'll make provisions for multiple callbacks, but 105 // now one will suffice. 106 static int (*SpinCallbackFunction)(intptr_t, int) ; 107 static intptr_t SpinCallbackArgument ; 108 109 110 public: 111 markOop header() const; 112 void set_header(markOop hdr); 113 114 intptr_t is_busy() const { 115 // TODO-FIXME: merge _count and _waiters. 116 // TODO-FIXME: assert _owner == null implies _recursions = 0 117 // TODO-FIXME: assert _WaitSet != null implies _count > 0 118 return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList ) ; 119 } 120 121 intptr_t is_entered(Thread* current) const; 122 123 void* owner() const; 124 void set_owner(void* owner); 125 126 intptr_t waiters() const; 127 128 intptr_t count() const; 129 void set_count(intptr_t count); 130 intptr_t contentions() const ; 131 intptr_t recursions() const { return _recursions; } 132 133 // JVM/DI GetMonitorInfo() needs this 134 ObjectWaiter* first_waiter() { return _WaitSet; } 135 ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; } 136 Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; } 137 138 // initialize the monitor, exception the semaphore, all other fields 139 // are simple integers or pointers 140 ObjectMonitor() { 141 _header = NULL; 142 _count = 0; 143 _waiters = 0, 144 _recursions = 0; 145 _object = NULL; 146 _owner = NULL; 147 _WaitSet = NULL; 148 _WaitSetLock = 0 ; 149 _Responsible = NULL ; 150 _succ = NULL ; 151 _cxq = NULL ; 152 FreeNext = NULL ; 153 _EntryList = NULL ; 154 _SpinFreq = 0 ; 155 _SpinClock = 0 ; 156 OwnerIsThread = 0 ; 157 _previous_owner_tid = 0; 158 } 159 160 ~ObjectMonitor() { 161 // TODO: Add asserts ... 162 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0 163 // _count == 0 _EntryList == NULL etc 164 } 165 166 private: 167 void Recycle () { 168 // TODO: add stronger asserts ... 169 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0 170 // _count == 0 EntryList == NULL 171 // _recursions == 0 _WaitSet == NULL 172 // TODO: assert (is_busy()|_recursions) == 0 173 _succ = NULL ; 174 _EntryList = NULL ; 175 _cxq = NULL ; 176 _WaitSet = NULL ; 177 _recursions = 0 ; 178 _SpinFreq = 0 ; 179 _SpinClock = 0 ; 180 OwnerIsThread = 0 ; 181 } 182 183 public: 184 185 void* object() const; 186 void* object_addr(); 187 void set_object(void* obj); 188 189 bool check(TRAPS); // true if the thread owns the monitor. 190 void check_slow(TRAPS); 191 void clear(); 192 #ifndef PRODUCT 193 void verify(); 194 void print(); 195 #endif 196 197 bool try_enter (TRAPS) ; 198 void enter(TRAPS); 199 void exit(bool not_suspended, TRAPS); 200 void wait(jlong millis, bool interruptable, TRAPS); 201 void notify(TRAPS); 202 void notifyAll(TRAPS); 203 204 // Use the following at your own risk 205 intptr_t complete_exit(TRAPS); 206 void reenter(intptr_t recursions, TRAPS); 207 208 private: 209 void AddWaiter (ObjectWaiter * waiter) ; 210 static void DeferredInitialize(); 211 212 ObjectWaiter * DequeueWaiter () ; 213 void DequeueSpecificWaiter (ObjectWaiter * waiter) ; 214 void EnterI (TRAPS) ; 215 void ReenterI (Thread * Self, ObjectWaiter * SelfNode) ; 216 void UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ; 217 int TryLock (Thread * Self) ; 218 int NotRunnable (Thread * Self, Thread * Owner) ; 219 int TrySpin_Fixed (Thread * Self) ; 220 int TrySpin_VaryFrequency (Thread * Self) ; 221 int TrySpin_VaryDuration (Thread * Self) ; 222 void ctAsserts () ; 223 void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ; 224 bool ExitSuspendEquivalent (JavaThread * Self) ; 225 void post_monitor_wait_event(EventJavaMonitorWait * event, 226 jlong notifier_tid, 227 jlong timeout, 228 bool timedout); 229 230 private: 231 friend class ObjectSynchronizer; 232 friend class ObjectWaiter; 233 friend class VMStructs; 234 235 // WARNING: this must be the very first word of ObjectMonitor 236 // This means this class can't use any virtual member functions. 237 // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the 238 // implicit 0 offset in emitted code. 239 240 volatile markOop _header; // displaced object header word - mark 241 void* volatile _object; // backward object pointer - strong root 242 243 double SharingPad [1] ; // temp to reduce false sharing 244 245 // All the following fields must be machine word aligned 246 // The VM assumes write ordering wrt these fields, which can be 247 // read from other threads. 248 249 protected: // protected for jvmtiRawMonitor 250 void * volatile _owner; // pointer to owning thread OR BasicLock 251 volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor 252 volatile intptr_t _recursions; // recursion count, 0 for first entry 253 private: 254 int OwnerIsThread ; // _owner is (Thread *) vs SP/BasicLock 255 ObjectWaiter * volatile _cxq ; // LL of recently-arrived threads blocked on entry. 256 // The list is actually composed of WaitNodes, acting 257 // as proxies for Threads. 258 protected: 259 ObjectWaiter * volatile _EntryList ; // Threads blocked on entry or reentry. 260 private: 261 Thread * volatile _succ ; // Heir presumptive thread - used for futile wakeup throttling 262 Thread * volatile _Responsible ; 263 int _PromptDrain ; // rqst to drain cxq into EntryList ASAP 264 265 volatile int _Spinner ; // for exit->spinner handoff optimization 266 volatile int _SpinFreq ; // Spin 1-out-of-N attempts: success rate 267 volatile int _SpinClock ; 268 volatile int _SpinDuration ; 269 volatile intptr_t _SpinState ; // MCS/CLH list of spinners 270 271 // TODO-FIXME: _count, _waiters and _recursions should be of 272 // type int, or int32_t but not intptr_t. There's no reason 273 // to use 64-bit fields for these variables on a 64-bit JVM. 274 275 volatile intptr_t _count; // reference count to prevent reclaimation/deflation 276 // at stop-the-world time. See deflate_idle_monitors(). 277 // _count is approximately |_WaitSet| + |_EntryList| 278 protected: 279 volatile intptr_t _waiters; // number of waiting threads 280 private: 281 protected: 282 ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor 283 private: 284 volatile int _WaitSetLock; // protects Wait Queue - simple spinlock 285 286 public: 287 int _QMix ; // Mixed prepend queue discipline 288 ObjectMonitor * FreeNext ; // Free list linkage 289 intptr_t StatA, StatsB ; 290 291 public: 292 static void Initialize () ; 293 static PerfCounter * _sync_ContendedLockAttempts ; 294 static PerfCounter * _sync_FutileWakeups ; 295 static PerfCounter * _sync_Parks ; 296 static PerfCounter * _sync_EmptyNotifications ; 297 static PerfCounter * _sync_Notifications ; 298 static PerfCounter * _sync_SlowEnter ; 299 static PerfCounter * _sync_SlowExit ; 300 static PerfCounter * _sync_SlowNotify ; 301 static PerfCounter * _sync_SlowNotifyAll ; 302 static PerfCounter * _sync_FailedSpins ; 303 static PerfCounter * _sync_SuccessfulSpins ; 304 static PerfCounter * _sync_PrivateA ; 305 static PerfCounter * _sync_PrivateB ; 306 static PerfCounter * _sync_MonInCirculation ; 307 static PerfCounter * _sync_MonScavenged ; 308 static PerfCounter * _sync_Inflations ; 309 static PerfCounter * _sync_Deflations ; 310 static PerfLongVariable * _sync_MonExtant ; 311 312 public: 313 static int Knob_Verbose; 314 static int Knob_SpinLimit; 315 void* operator new (size_t size) throw() { 316 return AllocateHeap(size, mtInternal); 317 } 318 void* operator new[] (size_t size) throw() { 319 return operator new (size); 320 } 321 void operator delete(void* p) { 322 FreeHeap(p, mtInternal); 323 } 324 void operator delete[] (void *p) { 325 operator delete(p); 326 } 327 }; 328 329 #undef TEVENT 330 #define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); } 331 332 #define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }} 333 334 #undef TEVENT 335 #define TEVENT(nom) {;} 336 337 338 #endif // SHARE_VM_RUNTIME_OBJECTMONITOR_HPP