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 static void sanity_checks(); // public for -XX:+ExecuteInternalVMTests
193 // in PRODUCT for -XX:SyncKnobs=Verbose=1
194 #ifndef PRODUCT
195 void verify();
196 void print();
197 #endif
198
199 bool try_enter (TRAPS) ;
200 void enter(TRAPS);
201 void exit(bool not_suspended, TRAPS);
202 void wait(jlong millis, bool interruptable, TRAPS);
203 void notify(TRAPS);
204 void notifyAll(TRAPS);
205
206 // Use the following at your own risk
207 intptr_t complete_exit(TRAPS);
208 void reenter(intptr_t recursions, TRAPS);
209
210 private:
211 void AddWaiter (ObjectWaiter * waiter) ;
212 static void DeferredInitialize();
213
214 ObjectWaiter * DequeueWaiter () ;
215 void DequeueSpecificWaiter (ObjectWaiter * waiter) ;
216 void EnterI (TRAPS) ;
217 void ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;
218 void UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;
219 int TryLock (Thread * Self) ;
220 int NotRunnable (Thread * Self, Thread * Owner) ;
221 int TrySpin_Fixed (Thread * Self) ;
222 int TrySpin_VaryFrequency (Thread * Self) ;
223 int TrySpin_VaryDuration (Thread * Self) ;
224 void ctAsserts () ;
225 void ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;
226 bool ExitSuspendEquivalent (JavaThread * Self) ;
227 void post_monitor_wait_event(EventJavaMonitorWait * event,
228 jlong notifier_tid,
229 jlong timeout,
230 bool timedout);
231
232 private:
233 friend class ObjectSynchronizer;
234 friend class ObjectWaiter;
235 friend class VMStructs;
236
237 // WARNING: this must be the very first word of ObjectMonitor
238 // This means this class can't use any virtual member functions.
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