1 /*
2 * Copyright (c) 1998, 2010, 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
33 // ObjectWaiter serves as a "proxy" or surrogate thread.
34 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
35 // ParkEvent instead. Beware, however, that the JVMTI code
36 // knows about ObjectWaiters, so we'll have to reconcile that code.
37 // See next_waiter(), first_waiter(), etc.
38
39 class ObjectWaiter : public StackObj {
40 public:
41 enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ;
42 enum Sorted { PREPEND, APPEND, SORTED } ;
43 ObjectWaiter * volatile _next;
44 ObjectWaiter * volatile _prev;
45 Thread* _thread;
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 }
155
156 ~ObjectMonitor() {
157 // TODO: Add asserts ...
158 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
159 // _count == 0 _EntryList == NULL etc
160 }
161
162 private:
163 void Recycle () {
164 // TODO: add stronger asserts ...
165 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
166 // _count == 0 EntryList == NULL
167 // _recursions == 0 _WaitSet == NULL
168 // TODO: assert (is_busy()|_recursions) == 0
169 _succ = NULL ;
170 _EntryList = NULL ;
171 _cxq = NULL ;
172 _WaitSet = NULL ;
173 _recursions = 0 ;
174 _SpinFreq = 0 ;
175 _SpinClock = 0 ;
176 OwnerIsThread = 0 ;
177 }
178
179 public:
180
181 void* object() const;
182 void* object_addr();
183 void set_object(void* obj);
184
185 bool check(TRAPS); // true if the thread owns the monitor.
186 void check_slow(TRAPS);
187 void clear();
188 #ifndef PRODUCT
189 void verify();
190 void print();
191 #endif
192
193 bool try_enter (TRAPS) ;
194 void enter(TRAPS);
195 void exit(TRAPS);
196 void wait(jlong millis, bool interruptable, TRAPS);
197 void notify(TRAPS);
198 void notifyAll(TRAPS);
199
200 // Use the following at your own risk
201 intptr_t complete_exit(TRAPS);
202 void reenter(intptr_t recursions, TRAPS);
203
204 private:
205 void AddWaiter (ObjectWaiter * waiter) ;
206 static void DeferredInitialize();
207
208 ObjectWaiter * DequeueWaiter () ;
209 void DequeueSpecificWaiter (ObjectWaiter * waiter) ;
210 void EnterI (TRAPS) ;
211 void ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;
212 void UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;
213 int TryLock (Thread * Self) ;
214 int NotRunnable (Thread * Self, Thread * Owner) ;
215 int TrySpin_Fixed (Thread * Self) ;
216 int TrySpin_VaryFrequency (Thread * Self) ;
217 int TrySpin_VaryDuration (Thread * Self) ;
218 void ctAsserts () ;
219 void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;
220 bool ExitSuspendEquivalent (JavaThread * Self) ;
221
222 private:
223 friend class ObjectSynchronizer;
224 friend class ObjectWaiter;
225 friend class VMStructs;
226
227 // WARNING: this must be the very first word of ObjectMonitor
228 // This means this class can't use any virtual member functions.
229 // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the
230 // implicit 0 offset in emitted code.
231
232 volatile markOop _header; // displaced object header word - mark
233 void* volatile _object; // backward object pointer - strong root
234
235 double SharingPad [1] ; // temp to reduce false sharing
236
237 // All the following fields must be machine word aligned
238 // The VM assumes write ordering wrt these fields, which can be
239 // read from other threads.
240
241 protected: // protected for jvmtiRawMonitor
242 void * volatile _owner; // pointer to owning thread OR BasicLock
243 volatile intptr_t _recursions; // recursion count, 0 for first entry
244 private:
245 int OwnerIsThread ; // _owner is (Thread *) vs SP/BasicLock
246 ObjectWaiter * volatile _cxq ; // LL of recently-arrived threads blocked on entry.
247 // The list is actually composed of WaitNodes, acting
248 // as proxies for Threads.
249 protected:
250 ObjectWaiter * volatile _EntryList ; // Threads blocked on entry or reentry.
251 private:
252 Thread * volatile _succ ; // Heir presumptive thread - used for futile wakeup throttling
253 Thread * volatile _Responsible ;
254 int _PromptDrain ; // rqst to drain cxq into EntryList ASAP
255
256 volatile int _Spinner ; // for exit->spinner handoff optimization
257 volatile int _SpinFreq ; // Spin 1-out-of-N attempts: success rate
258 volatile int _SpinClock ;
259 volatile int _SpinDuration ;
260 volatile intptr_t _SpinState ; // MCS/CLH list of spinners
261
262 // TODO-FIXME: _count, _waiters and _recursions should be of
263 // type int, or int32_t but not intptr_t. There's no reason
264 // to use 64-bit fields for these variables on a 64-bit JVM.
265
266 volatile intptr_t _count; // reference count to prevent reclaimation/deflation
267 // at stop-the-world time. See deflate_idle_monitors().
268 // _count is approximately |_WaitSet| + |_EntryList|
269 protected:
270 volatile intptr_t _waiters; // number of waiting threads
271 private:
272 protected:
273 ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor
274 private:
275 volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
276
277 public:
278 int _QMix ; // Mixed prepend queue discipline
279 ObjectMonitor * FreeNext ; // Free list linkage
280 intptr_t StatA, StatsB ;
281
282 public:
283 static void Initialize () ;
284 static PerfCounter * _sync_ContendedLockAttempts ;
285 static PerfCounter * _sync_FutileWakeups ;
286 static PerfCounter * _sync_Parks ;
287 static PerfCounter * _sync_EmptyNotifications ;
288 static PerfCounter * _sync_Notifications ;
289 static PerfCounter * _sync_SlowEnter ;
290 static PerfCounter * _sync_SlowExit ;
291 static PerfCounter * _sync_SlowNotify ;
292 static PerfCounter * _sync_SlowNotifyAll ;
293 static PerfCounter * _sync_FailedSpins ;
294 static PerfCounter * _sync_SuccessfulSpins ;
295 static PerfCounter * _sync_PrivateA ;
296 static PerfCounter * _sync_PrivateB ;
297 static PerfCounter * _sync_MonInCirculation ;
298 static PerfCounter * _sync_MonScavenged ;
299 static PerfCounter * _sync_Inflations ;
300 static PerfCounter * _sync_Deflations ;
301 static PerfLongVariable * _sync_MonExtant ;
302
303 public:
304 static int Knob_Verbose;
305 static int Knob_SpinLimit;
306 void* operator new (size_t size) {
307 return AllocateHeap(size, mtInternal);
308 }
309 void* operator new[] (size_t size) {
310 return operator new (size);
311 }
312 void operator delete(void* p) {
313 FreeHeap(p, mtInternal);
314 }
315 void operator delete[] (void *p) {
316 operator delete(p);
317 }
318 };
319
320 #undef TEVENT
321 #define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); }
322
323 #define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }}
324
325 #undef TEVENT
326 #define TEVENT(nom) {;}
327
328
329 #endif // SHARE_VM_RUNTIME_OBJECTMONITOR_HPP