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