1 /*
2 * Copyright (c) 1998, 2022, 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 *
128 #endif
129
130 class ObjectMonitor : public CHeapObj<mtObjectMonitor> {
131 friend class ObjectSynchronizer;
132 friend class ObjectWaiter;
133 friend class VMStructs;
134 JVMCI_ONLY(friend class JVMCIVMStructs;)
135
136 static OopStorage* _oop_storage;
137
138 // The sync code expects the header field to be at offset zero (0).
139 // Enforced by the assert() in header_addr().
140 volatile markWord _header; // displaced object header word - mark
141 WeakHandle _object; // backward object pointer
142 // Separate _header and _owner on different cache lines since both can
143 // have busy multi-threaded access. _header and _object are set at initial
144 // inflation. The _object does not change, so it is a good choice to share
145 // its cache line with _header.
146 DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
147 sizeof(WeakHandle));
148 // Used by async deflation as a marker in the _owner field:
149 #define DEFLATER_MARKER reinterpret_cast<void*>(-1)
150 void* volatile _owner; // pointer to owning thread OR BasicLock
151 volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
152 // Separate _owner and _next_om on different cache lines since
153 // both can have busy multi-threaded access. _previous_owner_tid is only
154 // changed by ObjectMonitor::exit() so it is a good choice to share the
155 // cache line with _owner.
156 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
157 sizeof(volatile jlong));
158 ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
159 volatile intx _recursions; // recursion count, 0 for first entry
160 ObjectWaiter* volatile _EntryList; // Threads blocked on entry or reentry.
161 // The list is actually composed of WaitNodes,
162 // acting as proxies for Threads.
163
164 ObjectWaiter* volatile _cxq; // LL of recently-arrived threads blocked on entry.
165 JavaThread* volatile _succ; // Heir presumptive thread - used for futile wakeup throttling
166 JavaThread* volatile _Responsible;
167
168 volatile int _Spinner; // for exit->spinner handoff optimization
169 volatile int _SpinDuration;
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 bool is_busy() const {
235 // TODO-FIXME: assert _owner == null implies _recursions = 0
236 intptr_t ret_code = _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
237 if (contentions() > 0) {
238 ret_code |= contentions();
239 }
240 if (!owner_is_DEFLATER_MARKER()) {
241 ret_code |= intptr_t(owner_raw());
242 }
243 return ret_code != 0;
244 }
245 const char* is_busy_to_string(stringStream* ss);
246
247 intptr_t is_entered(JavaThread* current) const;
248
249 void* owner() const; // Returns NULL if DEFLATER_MARKER is observed.
250 void* owner_raw() const;
251 // Returns true if owner field == DEFLATER_MARKER and false otherwise.
252 bool owner_is_DEFLATER_MARKER() const;
253 // Returns true if 'this' is being async deflated and false otherwise.
254 bool is_being_async_deflated();
255 // Clear _owner field; current value must match old_value.
256 void release_clear_owner(void* old_value);
257 // Simply set _owner field to new_value; current value must match old_value.
258 void set_owner_from(void* old_value, void* new_value);
259 // Simply set _owner field to current; current value must match basic_lock_p.
260 void set_owner_from_BasicLock(void* basic_lock_p, JavaThread* current);
261 // Try to set _owner field to new_value if the current value matches
262 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
263 // _owner field. Returns the prior value of the _owner field.
264 void* try_set_owner_from(void* old_value, void* new_value);
265
266 // Simply get _next_om field.
267 ObjectMonitor* next_om() const;
268 // Get _next_om field with acquire semantics.
269 ObjectMonitor* next_om_acquire() const;
270 // Simply set _next_om field to new_value.
271 void set_next_om(ObjectMonitor* new_value);
272 // Set _next_om field to new_value with release semantics.
273 void release_set_next_om(ObjectMonitor* new_value);
274 // Try to set _next_om field to new_value if the current value matches
275 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
276 // _next_om field. Returns the prior value of the _next_om field.
277 ObjectMonitor* try_set_next_om(ObjectMonitor* old_value, ObjectMonitor* new_value);
278
279 jint waiters() const;
280
281 jint contentions() const;
282 void add_to_contentions(jint value);
283 intx recursions() const { return _recursions; }
284
285 // JVM/TI GetObjectMonitorUsage() needs this:
286 ObjectWaiter* first_waiter() { return _WaitSet; }
287 ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; }
288 JavaThread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; }
289
290 ObjectMonitor(oop object);
291 ~ObjectMonitor();
292
293 oop object() const;
294 oop object_peek() const;
295
296 // Returns true if the specified thread owns the ObjectMonitor. Otherwise
297 // returns false and throws IllegalMonitorStateException (IMSE).
298 bool check_owner(TRAPS);
299
300 private:
301 class ExitOnSuspend {
302 protected:
303 ObjectMonitor* _om;
304 bool _om_exited;
305 public:
306 ExitOnSuspend(ObjectMonitor* om) : _om(om), _om_exited(false) {}
307 void operator()(JavaThread* current);
308 bool exited() { return _om_exited; }
309 };
310 class ClearSuccOnSuspend {
311 protected:
312 ObjectMonitor* _om;
313 public:
314 ClearSuccOnSuspend(ObjectMonitor* om) : _om(om) {}
315 void operator()(JavaThread* current);
316 };
317 public:
318 bool enter(JavaThread* current);
319 void exit(JavaThread* current, bool not_suspended = true);
320 void wait(jlong millis, bool interruptible, TRAPS);
321 void notify(TRAPS);
322 void notifyAll(TRAPS);
323
324 void print() const;
325 #ifdef ASSERT
326 void print_debug_style_on(outputStream* st) const;
327 #endif
328 void print_on(outputStream* st) const;
329
330 // Use the following at your own risk
331 intx complete_exit(JavaThread* current);
332 bool reenter(intx recursions, JavaThread* current);
333
334 private:
335 void AddWaiter(ObjectWaiter* waiter);
336 void INotify(JavaThread* current);
337 ObjectWaiter* DequeueWaiter();
338 void DequeueSpecificWaiter(ObjectWaiter* waiter);
339 void EnterI(JavaThread* current);
340 void ReenterI(JavaThread* current, ObjectWaiter* current_node);
341 void UnlinkAfterAcquire(JavaThread* current, ObjectWaiter* current_node);
342 int TryLock(JavaThread* current);
343 int NotRunnable(JavaThread* current, JavaThread* Owner);
344 int TrySpin(JavaThread* current);
345 void ExitEpilog(JavaThread* current, ObjectWaiter* Wakee);
346
347 // Deflation support
348 bool deflate_monitor();
349 void install_displaced_markword_in_object(const oop obj);
350 };
351
352 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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1 /*
2 * Copyright (c) 1998, 2024, 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 *
128 #endif
129
130 class ObjectMonitor : public CHeapObj<mtObjectMonitor> {
131 friend class ObjectSynchronizer;
132 friend class ObjectWaiter;
133 friend class VMStructs;
134 JVMCI_ONLY(friend class JVMCIVMStructs;)
135
136 static OopStorage* _oop_storage;
137
138 // The sync code expects the header field to be at offset zero (0).
139 // Enforced by the assert() in header_addr().
140 volatile markWord _header; // displaced object header word - mark
141 WeakHandle _object; // backward object pointer
142 // Separate _header and _owner on different cache lines since both can
143 // have busy multi-threaded access. _header and _object are set at initial
144 // inflation. The _object does not change, so it is a good choice to share
145 // its cache line with _header.
146 DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
147 sizeof(WeakHandle));
148 // Used by async deflation as a marker in the _owner field.
149 // Note that the choice of the two markers is peculiar:
150 // - They need to represent values that cannot be pointers. In particular,
151 // we achieve this by using the lowest two bits.
152 // - ANONYMOUS_OWNER should be a small value, it is used in generated code
153 // and small values encode much better.
154 // - We test for anonymous owner by testing for the lowest bit, therefore
155 // DEFLATER_MARKER must *not* have that bit set.
156 #define DEFLATER_MARKER reinterpret_cast<void*>(2)
157 public:
158 // NOTE: Typed as uintptr_t so that we can pick it up in SA, via vmStructs.
159 static const uintptr_t ANONYMOUS_OWNER = 1;
160
161 private:
162 static void* anon_owner_ptr() { return reinterpret_cast<void*>(ANONYMOUS_OWNER); }
163
164 void* volatile _owner; // pointer to owning thread OR BasicLock
165 volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
166 // Separate _owner and _next_om on different cache lines since
167 // both can have busy multi-threaded access. _previous_owner_tid is only
168 // changed by ObjectMonitor::exit() so it is a good choice to share the
169 // cache line with _owner.
170 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
171 sizeof(volatile jlong));
172 ObjectMonitor* _next_om; // Next ObjectMonitor* linkage
173 volatile intx _recursions; // recursion count, 0 for first entry
174 ObjectWaiter* volatile _EntryList; // Threads blocked on entry or reentry.
175 // The list is actually composed of WaitNodes,
176 // acting as proxies for Threads.
177
178 ObjectWaiter* volatile _cxq; // LL of recently-arrived threads blocked on entry.
179 JavaThread* volatile _succ; // Heir presumptive thread - used for futile wakeup throttling
180 JavaThread* volatile _Responsible;
181
182 volatile int _Spinner; // for exit->spinner handoff optimization
183 volatile int _SpinDuration;
241 #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
242 ((ObjectMonitor::f ## _offset_in_bytes()) - markWord::monitor_value)
243
244 markWord header() const;
245 volatile markWord* header_addr();
246 void set_header(markWord hdr);
247
248 bool is_busy() const {
249 // TODO-FIXME: assert _owner == null implies _recursions = 0
250 intptr_t ret_code = _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
251 if (contentions() > 0) {
252 ret_code |= contentions();
253 }
254 if (!owner_is_DEFLATER_MARKER()) {
255 ret_code |= intptr_t(owner_raw());
256 }
257 return ret_code != 0;
258 }
259 const char* is_busy_to_string(stringStream* ss);
260
261 bool is_entered(JavaThread* current) const;
262
263 bool has_owner() const;
264 void* owner() const; // Returns NULL if DEFLATER_MARKER is observed.
265 void* owner_raw() const;
266 // Returns true if owner field == DEFLATER_MARKER and false otherwise.
267 bool owner_is_DEFLATER_MARKER() const;
268 // Returns true if 'this' is being async deflated and false otherwise.
269 bool is_being_async_deflated();
270 // Clear _owner field; current value must match old_value.
271 void release_clear_owner(void* old_value);
272 // Simply set _owner field to new_value; current value must match old_value.
273 void set_owner_from(void* old_value, void* new_value);
274 // Simply set _owner field to current; current value must match basic_lock_p.
275 void set_owner_from_BasicLock(void* basic_lock_p, JavaThread* current);
276 // Try to set _owner field to new_value if the current value matches
277 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
278 // _owner field. Returns the prior value of the _owner field.
279 void* try_set_owner_from(void* old_value, void* new_value);
280
281 void set_owner_anonymous() {
282 set_owner_from(NULL, anon_owner_ptr());
283 }
284
285 bool is_owner_anonymous() const {
286 return owner_raw() == anon_owner_ptr();
287 }
288
289 void set_owner_from_anonymous(Thread* owner) {
290 set_owner_from(anon_owner_ptr(), owner);
291 }
292
293 // Simply get _next_om field.
294 ObjectMonitor* next_om() const;
295 // Get _next_om field with acquire semantics.
296 ObjectMonitor* next_om_acquire() const;
297 // Simply set _next_om field to new_value.
298 void set_next_om(ObjectMonitor* new_value);
299 // Set _next_om field to new_value with release semantics.
300 void release_set_next_om(ObjectMonitor* new_value);
301 // Try to set _next_om field to new_value if the current value matches
302 // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
303 // _next_om field. Returns the prior value of the _next_om field.
304 ObjectMonitor* try_set_next_om(ObjectMonitor* old_value, ObjectMonitor* new_value);
305
306 jint waiters() const;
307
308 jint contentions() const;
309 void add_to_contentions(jint value);
310 intx recursions() const { return _recursions; }
311 void set_recursions(size_t recursions);
312
313 // JVM/TI GetObjectMonitorUsage() needs this:
314 ObjectWaiter* first_waiter() { return _WaitSet; }
315 ObjectWaiter* next_waiter(ObjectWaiter* o) { return o->_next; }
316 JavaThread* thread_of_waiter(ObjectWaiter* o) { return o->_thread; }
317
318 ObjectMonitor(oop object);
319 ~ObjectMonitor();
320
321 oop object() const;
322 oop object_peek() const;
323
324 // Returns true if the specified thread owns the ObjectMonitor. Otherwise
325 // returns false and throws IllegalMonitorStateException (IMSE).
326 bool check_owner(TRAPS);
327
328 private:
329 class ExitOnSuspend {
330 protected:
331 ObjectMonitor* _om;
332 bool _om_exited;
333 public:
334 ExitOnSuspend(ObjectMonitor* om) : _om(om), _om_exited(false) {}
335 void operator()(JavaThread* current);
336 bool exited() { return _om_exited; }
337 };
338 class ClearSuccOnSuspend {
339 protected:
340 ObjectMonitor* _om;
341 public:
342 ClearSuccOnSuspend(ObjectMonitor* om) : _om(om) {}
343 void operator()(JavaThread* current);
344 };
345 public:
346 bool enter_for(JavaThread* locking_thread);
347 bool enter(JavaThread* current);
348 void exit(JavaThread* current, bool not_suspended = true);
349 void wait(jlong millis, bool interruptible, TRAPS);
350 void notify(TRAPS);
351 void notifyAll(TRAPS);
352
353 void print() const;
354 #ifdef ASSERT
355 void print_debug_style_on(outputStream* st) const;
356 #endif
357 void print_on(outputStream* st) const;
358
359 // Use the following at your own risk
360 intx complete_exit(JavaThread* current);
361 bool reenter(intx recursions, JavaThread* current);
362
363 static void maybe_deflate_dead(oop* p);
364
365 private:
366 void AddWaiter(ObjectWaiter* waiter);
367 void INotify(JavaThread* current);
368 ObjectWaiter* DequeueWaiter();
369 void DequeueSpecificWaiter(ObjectWaiter* waiter);
370 void EnterI(JavaThread* current);
371 void ReenterI(JavaThread* current, ObjectWaiter* current_node);
372 void UnlinkAfterAcquire(JavaThread* current, ObjectWaiter* current_node);
373 int TryLock(JavaThread* current);
374 int NotRunnable(JavaThread* current, JavaThread* Owner);
375 int TrySpin(JavaThread* current);
376 void ExitEpilog(JavaThread* current, ObjectWaiter* Wakee);
377
378 // Deflation support
379 bool deflate_monitor();
380 void install_displaced_markword_in_object(const oop obj);
381 };
382
383 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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