119 // - The _recursions field should be of type int, or int32_t but not
120 // intptr_t. There's no reason to use a 64-bit type for this field
121 // in a 64-bit JVM.
122
123 #ifndef OM_CACHE_LINE_SIZE
124 // Use DEFAULT_CACHE_LINE_SIZE if not already specified for
125 // the current build platform.
126 #define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
127 #endif
128
129 class ObjectMonitor {
130 friend class ObjectSynchronizer;
131 friend class ObjectWaiter;
132 friend class VMStructs;
133 JVMCI_ONLY(friend class JVMCIVMStructs;)
134
135 // The sync code expects the header field to be at offset zero (0).
136 // Enforced by the assert() in header_addr().
137 volatile markWord _header; // displaced object header word - mark
138 void* volatile _object; // backward object pointer - strong root
139 private:
140 // Separate _header and _owner on different cache lines since both can
141 // have busy multi-threaded access. _header and _object are set at
142 // initial inflation and _object doesn't change until deflation so
143 // _object is a good choice to share the cache line with _header.
144 DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE,
145 sizeof(volatile markWord) + sizeof(void* volatile));
146 void* volatile _owner; // pointer to owning thread OR BasicLock
147 volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
148 // Separate _owner and _next_om on different cache lines since
149 // both can have busy multi-threaded access. _previous_owner_tid is only
150 // changed by ObjectMonitor::exit() so it is a good choice to share the
151 // cache line with _owner.
152 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
153 sizeof(volatile jlong));
154 ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
155 volatile intx _recursions; // recursion count, 0 for first entry
156 ObjectWaiter* volatile _EntryList; // Threads blocked on entry or reentry.
157 // The list is actually composed of WaitNodes,
158 // acting as proxies for Threads.
159
160 ObjectWaiter* volatile _cxq; // LL of recently-arrived threads blocked on entry.
161 Thread* volatile _succ; // Heir presumptive thread - used for futile wakeup throttling
162 Thread* volatile _Responsible;
163
164 volatile int _Spinner; // for exit->spinner handoff optimization
165 volatile int _SpinDuration;
166
167 volatile jint _contentions; // Number of active contentions in enter(). It is used by is_busy()
168 // along with other fields to determine if an ObjectMonitor can be
169 // deflated. See ObjectSynchronizer::deflate_monitor().
170 protected:
171 ObjectWaiter* volatile _WaitSet; // LL of threads wait()ing on the monitor
172 volatile jint _waiters; // number of waiting threads
173 private:
174 volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
175
176 public:
177 static void Initialize();
178
179 // Only perform a PerfData operation if the PerfData object has been
180 // allocated and if the PerfDataManager has not freed the PerfData
181 // objects which can happen at normal VM shutdown.
182 //
183 #define OM_PERFDATA_OP(f, op_str) \
184 do { \
185 if (ObjectMonitor::_sync_ ## f != NULL && \
186 PerfDataManager::has_PerfData()) { \
187 ObjectMonitor::_sync_ ## f->op_str; \
188 } \
189 } while (0)
216 // ObjectMonitor references can be ORed with markWord::monitor_value
217 // as part of the ObjectMonitor tagging mechanism. When we combine an
218 // ObjectMonitor reference with an offset, we need to remove the tag
219 // value in order to generate the proper address.
220 //
221 // We can either adjust the ObjectMonitor reference and then add the
222 // offset or we can adjust the offset that is added to the ObjectMonitor
223 // reference. The latter avoids an AGI (Address Generation Interlock)
224 // stall so the helper macro adjusts the offset value that is returned
225 // to the ObjectMonitor reference manipulation code:
226 //
227 #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
228 ((ObjectMonitor::f ## _offset_in_bytes()) - markWord::monitor_value)
229
230 markWord header() const;
231 volatile markWord* header_addr();
232 void set_header(markWord hdr);
233
234 intptr_t is_busy() const {
235 // TODO-FIXME: assert _owner == null implies _recursions = 0
236 return _contentions|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList);
237 }
238 const char* is_busy_to_string(stringStream* ss);
239
240 intptr_t is_entered(Thread* current) const;
241
242 void* owner() const;
243 // Clear _owner field; current value must match old_value.
244 void release_clear_owner(void* old_value);
245 // Simply set _owner field to new_value; current value must match old_value.
246 void set_owner_from(void* old_value, void* new_value);
247 // Simply set _owner field to self; current value must match basic_lock_p.
248 void set_owner_from_BasicLock(void* basic_lock_p, Thread* self);
249 // Try to set _owner field to new_value if the current value matches
250 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
251 // _owner field. Returns the prior value of the _owner field.
252 void* try_set_owner_from(void* old_value, void* new_value);
253
254 ObjectMonitor* next_om() const;
255 // Simply set _next_om field to new_value.
256 void set_next_om(ObjectMonitor* new_value);
257 // Try to set _next_om field to new_value if the current value matches
258 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
259 // _next_om field. Returns the prior value of the _next_om field.
260 ObjectMonitor* try_set_next_om(ObjectMonitor* old_value, ObjectMonitor* new_value);
261
262 jint waiters() const;
263
264 jint contentions() const;
265 intx recursions() const { return _recursions; }
266
267 // JVM/TI GetObjectMonitorUsage() needs this:
268 ObjectWaiter* first_waiter() { return _WaitSet; }
269 ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; }
270 Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; }
271
272 protected:
273 // We don't typically expect or want the ctors or dtors to run.
274 // normal ObjectMonitors are type-stable and immortal.
275 ObjectMonitor() { ::memset((void*)this, 0, sizeof(*this)); }
276
277 ~ObjectMonitor() {
278 // TODO: Add asserts ...
279 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
280 // _contentions == 0 _EntryList == NULL etc
281 }
282
283 private:
284 void Recycle() {
285 // TODO: add stronger asserts ...
286 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
287 // _contentions == 0 EntryList == NULL
288 // _recursions == 0 _WaitSet == NULL
289 DEBUG_ONLY(stringStream ss;)
290 assert((is_busy() | _recursions) == 0, "freeing in-use monitor: %s, "
291 "recursions=" INTX_FORMAT, is_busy_to_string(&ss), _recursions);
292 _succ = NULL;
293 _EntryList = NULL;
294 _cxq = NULL;
295 _WaitSet = NULL;
296 _recursions = 0;
297 }
298
299 public:
300
301 void* object() const;
302 void* object_addr();
303 void set_object(void* obj);
304
305 // Returns true if the specified thread owns the ObjectMonitor. Otherwise
306 // returns false and throws IllegalMonitorStateException (IMSE).
307 bool check_owner(Thread* THREAD);
308 void clear();
309
310 void enter(TRAPS);
311 void exit(bool not_suspended, TRAPS);
312 void wait(jlong millis, bool interruptable, TRAPS);
313 void notify(TRAPS);
314 void notifyAll(TRAPS);
315
316 void print() const;
317 #ifdef ASSERT
318 void print_debug_style_on(outputStream* st) const;
319 #endif
320 void print_on(outputStream* st) const;
321
322 // Use the following at your own risk
323 intx complete_exit(TRAPS);
324 void reenter(intx recursions, TRAPS);
325
326 private:
327 void AddWaiter(ObjectWaiter* waiter);
328 void INotify(Thread* self);
329 ObjectWaiter* DequeueWaiter();
330 void DequeueSpecificWaiter(ObjectWaiter* waiter);
331 void EnterI(TRAPS);
332 void ReenterI(Thread* self, ObjectWaiter* self_node);
333 void UnlinkAfterAcquire(Thread* self, ObjectWaiter* self_node);
334 int TryLock(Thread* self);
335 int NotRunnable(Thread* self, Thread * Owner);
336 int TrySpin(Thread* self);
337 void ExitEpilog(Thread* self, ObjectWaiter* Wakee);
338 bool ExitSuspendEquivalent(JavaThread* self);
339 };
340
341 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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119 // - The _recursions field should be of type int, or int32_t but not
120 // intptr_t. There's no reason to use a 64-bit type for this field
121 // in a 64-bit JVM.
122
123 #ifndef OM_CACHE_LINE_SIZE
124 // Use DEFAULT_CACHE_LINE_SIZE if not already specified for
125 // the current build platform.
126 #define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
127 #endif
128
129 class ObjectMonitor {
130 friend class ObjectSynchronizer;
131 friend class ObjectWaiter;
132 friend class VMStructs;
133 JVMCI_ONLY(friend class JVMCIVMStructs;)
134
135 // The sync code expects the header field to be at offset zero (0).
136 // Enforced by the assert() in header_addr().
137 volatile markWord _header; // displaced object header word - mark
138 void* volatile _object; // backward object pointer - strong root
139 typedef enum {
140 Free = 0, // Free must be 0 for monitor to be free after memset(..,0,..).
141 New,
142 Old
143 } AllocationState;
144 AllocationState _allocation_state;
145 // Separate _header and _owner on different cache lines since both can
146 // have busy multi-threaded access. _header, _object and _allocation_state
147 // are set at initial inflation. _object and _allocation_state don't
148 // change until deflation so _object and _allocation_state are good
149 // choices to share the cache line with _header.
150 DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
151 sizeof(void* volatile) + sizeof(AllocationState));
152 // Used by async deflation as a marker in the _owner field:
153 #define DEFLATER_MARKER reinterpret_cast<void*>(-1)
154 void* volatile _owner; // pointer to owning thread OR BasicLock
155 volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
156 // Separate _owner and _next_om on different cache lines since
157 // both can have busy multi-threaded access. _previous_owner_tid is only
158 // changed by ObjectMonitor::exit() so it is a good choice to share the
159 // cache line with _owner.
160 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
161 sizeof(volatile jlong));
162 ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
163 volatile intx _recursions; // recursion count, 0 for first entry
164 ObjectWaiter* volatile _EntryList; // Threads blocked on entry or reentry.
165 // The list is actually composed of WaitNodes,
166 // acting as proxies for Threads.
167
168 ObjectWaiter* volatile _cxq; // LL of recently-arrived threads blocked on entry.
169 Thread* volatile _succ; // Heir presumptive thread - used for futile wakeup throttling
170 Thread* volatile _Responsible;
171
172 volatile int _Spinner; // for exit->spinner handoff optimization
173 volatile int _SpinDuration;
174
175 jint _contentions; // Number of active contentions in enter(). It is used by is_busy()
176 // along with other fields to determine if an ObjectMonitor can be
177 // deflated. It is also used by the async deflation protocol. See
178 // ObjectSynchronizer::deflate_monitor() and deflate_monitor_using_JT().
179 protected:
180 ObjectWaiter* volatile _WaitSet; // LL of threads wait()ing on the monitor
181 volatile jint _waiters; // number of waiting threads
182 private:
183 volatile int _WaitSetLock; // protects Wait Queue - simple spinlock
184
185 public:
186 static void Initialize();
187
188 // Only perform a PerfData operation if the PerfData object has been
189 // allocated and if the PerfDataManager has not freed the PerfData
190 // objects which can happen at normal VM shutdown.
191 //
192 #define OM_PERFDATA_OP(f, op_str) \
193 do { \
194 if (ObjectMonitor::_sync_ ## f != NULL && \
195 PerfDataManager::has_PerfData()) { \
196 ObjectMonitor::_sync_ ## f->op_str; \
197 } \
198 } while (0)
225 // ObjectMonitor references can be ORed with markWord::monitor_value
226 // as part of the ObjectMonitor tagging mechanism. When we combine an
227 // ObjectMonitor reference with an offset, we need to remove the tag
228 // value in order to generate the proper address.
229 //
230 // We can either adjust the ObjectMonitor reference and then add the
231 // offset or we can adjust the offset that is added to the ObjectMonitor
232 // reference. The latter avoids an AGI (Address Generation Interlock)
233 // stall so the helper macro adjusts the offset value that is returned
234 // to the ObjectMonitor reference manipulation code:
235 //
236 #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
237 ((ObjectMonitor::f ## _offset_in_bytes()) - markWord::monitor_value)
238
239 markWord header() const;
240 volatile markWord* header_addr();
241 void set_header(markWord hdr);
242
243 intptr_t is_busy() const {
244 // TODO-FIXME: assert _owner == null implies _recursions = 0
245 intptr_t ret_code = _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
246 if (!AsyncDeflateIdleMonitors) {
247 ret_code |= contentions() | intptr_t(_owner);
248 } else {
249 if (contentions() > 0) {
250 ret_code |= contentions();
251 }
252 if (_owner != DEFLATER_MARKER) {
253 ret_code |= intptr_t(_owner);
254 }
255 }
256 return ret_code;
257 }
258 const char* is_busy_to_string(stringStream* ss);
259
260 intptr_t is_entered(Thread* current) const;
261
262 void* owner() const; // Returns NULL if DEFLATER_MARKER is observed.
263 // Returns true if owner field == DEFLATER_MARKER and false otherwise.
264 bool owner_is_DEFLATER_MARKER();
265 // Returns true if 'this' is being async deflated and false otherwise.
266 bool is_being_async_deflated();
267 // Clear _owner field; current value must match old_value.
268 void release_clear_owner(void* old_value);
269 // Simply set _owner field to new_value; current value must match old_value.
270 void set_owner_from(void* old_value, void* new_value);
271 // Simply set _owner field to new_value; current value must match old_value1 or old_value2.
272 void set_owner_from(void* old_value1, void* old_value2, void* new_value);
273 // Simply set _owner field to self; current value must match basic_lock_p.
274 void set_owner_from_BasicLock(void* basic_lock_p, Thread* self);
275 // Try to set _owner field to new_value if the current value matches
276 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
277 // _owner field. Returns the prior value of the _owner field.
278 void* try_set_owner_from(void* old_value, void* new_value);
279
280 ObjectMonitor* next_om() const;
281 // Simply set _next_om field to new_value.
282 void set_next_om(ObjectMonitor* new_value);
283 // Try to set _next_om field to new_value if the current value matches
284 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
285 // _next_om field. Returns the prior value of the _next_om field.
286 ObjectMonitor* try_set_next_om(ObjectMonitor* old_value, ObjectMonitor* new_value);
287
288 jint waiters() const;
289
290 jint contentions() const;
291 void add_to_contentions(jint value);
292 intx recursions() const { return _recursions; }
293
294 // JVM/TI GetObjectMonitorUsage() needs this:
295 ObjectWaiter* first_waiter() { return _WaitSet; }
296 ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; }
297 Thread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; }
298
299 protected:
300 // We don't typically expect or want the ctors or dtors to run.
301 // normal ObjectMonitors are type-stable and immortal.
302 ObjectMonitor() { ::memset((void*)this, 0, sizeof(*this)); }
303
304 ~ObjectMonitor() {
305 // TODO: Add asserts ...
306 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
307 // _contentions == 0 _EntryList == NULL etc
308 }
309
310 private:
311 void Recycle() {
312 // TODO: add stronger asserts ...
313 // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
314 // _contentions == 0 EntryList == NULL
315 // _recursions == 0 _WaitSet == NULL
316 #ifdef ASSERT
317 stringStream ss;
318 #endif
319 assert((is_busy() | _recursions) == 0, "freeing in-use monitor: %s, "
320 "recursions=" INTX_FORMAT, is_busy_to_string(&ss), _recursions);
321 _succ = NULL;
322 _EntryList = NULL;
323 _cxq = NULL;
324 _WaitSet = NULL;
325 _recursions = 0;
326 }
327
328 public:
329
330 void* object() const;
331 void* object_addr();
332 void set_object(void* obj);
333 void set_allocation_state(AllocationState s);
334 AllocationState allocation_state() const;
335 bool is_free() const;
336 bool is_old() const;
337 bool is_new() const;
338
339 // Returns true if the specified thread owns the ObjectMonitor. Otherwise
340 // returns false and throws IllegalMonitorStateException (IMSE).
341 bool check_owner(Thread* THREAD);
342 void clear();
343 void clear_common();
344
345 bool enter(TRAPS);
346 void exit(bool not_suspended, TRAPS);
347 void wait(jlong millis, bool interruptable, TRAPS);
348 void notify(TRAPS);
349 void notifyAll(TRAPS);
350
351 void print() const;
352 #ifdef ASSERT
353 void print_debug_style_on(outputStream* st) const;
354 #endif
355 void print_on(outputStream* st) const;
356
357 // Use the following at your own risk
358 intx complete_exit(TRAPS);
359 bool reenter(intx recursions, TRAPS);
360
361 private:
362 void AddWaiter(ObjectWaiter* waiter);
363 void INotify(Thread* self);
364 ObjectWaiter* DequeueWaiter();
365 void DequeueSpecificWaiter(ObjectWaiter* waiter);
366 void EnterI(TRAPS);
367 void ReenterI(Thread* self, ObjectWaiter* self_node);
368 void UnlinkAfterAcquire(Thread* self, ObjectWaiter* self_node);
369 int TryLock(Thread* self);
370 int NotRunnable(Thread* self, Thread* Owner);
371 int TrySpin(Thread* self);
372 void ExitEpilog(Thread* self, ObjectWaiter* Wakee);
373 bool ExitSuspendEquivalent(JavaThread* self);
374 void install_displaced_markword_in_object(const oop obj);
375 };
376
377 // Macro to use guarantee() for more strict AsyncDeflateIdleMonitors
378 // checks and assert() otherwise.
379 #define ADIM_guarantee(p, ...) \
380 do { \
381 if (AsyncDeflateIdleMonitors) { \
382 guarantee(p, __VA_ARGS__); \
383 } else { \
384 assert(p, __VA_ARGS__); \
385 } \
386 } while (0)
387
388 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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