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