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src/hotspot/share/runtime/objectMonitor.hpp

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 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_RUNTIME_OBJECTMONITOR_HPP
 26 #define SHARE_RUNTIME_OBJECTMONITOR_HPP
 27 
 28 #include "memory/allocation.hpp"
 29 #include "memory/padded.hpp"
 30 #include "oops/markWord.hpp"

 31 #include "oops/weakHandle.hpp"

 32 #include "runtime/perfDataTypes.hpp"
 33 #include "utilities/checkedCast.hpp"
 34 
 35 class ObjectMonitor;
 36 class ParkEvent;

 37 
 38 // ObjectWaiter serves as a "proxy" or surrogate thread.
 39 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
 40 // ParkEvent instead.  Beware, however, that the JVMTI code
 41 // knows about ObjectWaiters, so we'll have to reconcile that code.
 42 // See next_waiter(), first_waiter(), etc.
 43 
 44 class ObjectWaiter : public StackObj {
 45  public:
 46   enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ };
 47   ObjectWaiter* volatile _next;
 48   ObjectWaiter* volatile _prev;
 49   JavaThread*   _thread;

 50   uint64_t      _notifier_tid;
 51   ParkEvent *   _event;
 52   volatile int  _notified;
 53   volatile TStates TState;
 54   bool          _active;           // Contention monitoring is enabled
 55  public:
 56   ObjectWaiter(JavaThread* current);
 57 








 58   void wait_reenter_begin(ObjectMonitor *mon);
 59   void wait_reenter_end(ObjectMonitor *mon);
 60 };
 61 
 62 // The ObjectMonitor class implements the heavyweight version of a
 63 // JavaMonitor. The lightweight BasicLock/stack lock version has been
 64 // inflated into an ObjectMonitor. This inflation is typically due to
 65 // contention or use of Object.wait().
 66 //
 67 // WARNING: This is a very sensitive and fragile class. DO NOT make any
 68 // changes unless you are fully aware of the underlying semantics.
 69 //
 70 // ObjectMonitor Layout Overview/Highlights/Restrictions:
 71 //
 72 // - The _header field must be at offset 0 because the displaced header
 73 //   from markWord is stored there. We do not want markWord.hpp to include
 74 //   ObjectMonitor.hpp to avoid exposing ObjectMonitor everywhere. This
 75 //   means that ObjectMonitor cannot inherit from any other class nor can
 76 //   it use any virtual member functions. This restriction is critical to
 77 //   the proper functioning of the VM.

110 //     avoid false sharing might be profitable. Given
111 //     http://blogs.oracle.com/dave/entry/cas_and_cache_trivia_invalidate
112 //     we know that the CAS in monitorenter will invalidate the line
113 //     underlying _owner. We want to avoid an L1 data cache miss on that
114 //     same line for monitorexit. Putting these <remaining_fields>:
115 //     _recursions, _EntryList, _cxq, and _succ, all of which may be
116 //     fetched in the inflated unlock path, on a different cache line
117 //     would make them immune to CAS-based invalidation from the _owner
118 //     field.
119 //
120 //   - The _recursions field should be of type int, or int32_t but not
121 //     intptr_t. There's no reason to use a 64-bit type for this field
122 //     in a 64-bit JVM.
123 
124 #define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
125 
126 class ObjectMonitor : public CHeapObj<mtObjectMonitor> {
127   friend class ObjectSynchronizer;
128   friend class ObjectWaiter;
129   friend class VMStructs;

130   JVMCI_ONLY(friend class JVMCIVMStructs;)
131 
132   static OopStorage* _oop_storage;
133 



134   // The sync code expects the header field to be at offset zero (0).
135   // Enforced by the assert() in header_addr().
136   volatile markWord _header;        // displaced object header word - mark
137   WeakHandle _object;               // backward object pointer
138   // Separate _header and _owner on different cache lines since both can
139   // have busy multi-threaded access. _header and _object are set at initial
140   // inflation. The _object does not change, so it is a good choice to share
141   // its cache line with _header.
142   DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
143                         sizeof(WeakHandle));
144   // Used by async deflation as a marker in the _owner field.
145   // Note that the choice of the two markers is peculiar:
146   // - They need to represent values that cannot be pointers. In particular,
147   //   we achieve this by using the lowest two bits.
148   // - ANONYMOUS_OWNER should be a small value, it is used in generated code
149   //   and small values encode much better.
150   // - We test for anonymous owner by testing for the lowest bit, therefore
151   //   DEFLATER_MARKER must *not* have that bit set.
152   #define DEFLATER_MARKER reinterpret_cast<void*>(2)
153 public:
154   // NOTE: Typed as uintptr_t so that we can pick it up in SA, via vmStructs.
155   static const uintptr_t ANONYMOUS_OWNER = 1;
156 
157 private:
158   static void* anon_owner_ptr() { return reinterpret_cast<void*>(ANONYMOUS_OWNER); }
159 
160   void* volatile _owner;            // pointer to owning thread OR BasicLock

161   volatile uint64_t _previous_owner_tid;  // thread id of the previous owner of the monitor
162   // Separate _owner and _next_om on different cache lines since
163   // both can have busy multi-threaded access. _previous_owner_tid is only
164   // changed by ObjectMonitor::exit() so it is a good choice to share the
165   // cache line with _owner.
166   DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(void* volatile) +
167                         sizeof(volatile uint64_t));
168   ObjectMonitor* _next_om;          // Next ObjectMonitor* linkage
169   volatile intx _recursions;        // recursion count, 0 for first entry
170   ObjectWaiter* volatile _EntryList;  // Threads blocked on entry or reentry.
171                                       // The list is actually composed of WaitNodes,
172                                       // acting as proxies for Threads.
173 
174   ObjectWaiter* volatile _cxq;      // LL of recently-arrived threads blocked on entry.
175   JavaThread* volatile _succ;       // Heir presumptive thread - used for futile wakeup throttling
176   JavaThread* volatile _Responsible;
177 
178   volatile int _Spinner;            // for exit->spinner handoff optimization
179   volatile int _SpinDuration;
180 
181   int _contentions;                 // Number of active contentions in enter(). It is used by is_busy()
182                                     // along with other fields to determine if an ObjectMonitor can be
183                                     // deflated. It is also used by the async deflation protocol. See
184                                     // ObjectMonitor::deflate_monitor().
185  protected:
186   ObjectWaiter* volatile _WaitSet;  // LL of threads wait()ing on the monitor
187   volatile int  _waiters;           // number of waiting threads
188  private:
189   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock
190 
191  public:
192 
193   static void Initialize();




194 
195   // Only perform a PerfData operation if the PerfData object has been
196   // allocated and if the PerfDataManager has not freed the PerfData
197   // objects which can happen at normal VM shutdown.
198   //
199   #define OM_PERFDATA_OP(f, op_str)                 \
200     do {                                            \
201       if (ObjectMonitor::_sync_ ## f != nullptr &&  \
202           PerfDataManager::has_PerfData()) {        \
203         ObjectMonitor::_sync_ ## f->op_str;         \
204       }                                             \
205     } while (0)
206 
207   static PerfCounter * _sync_ContendedLockAttempts;
208   static PerfCounter * _sync_FutileWakeups;
209   static PerfCounter * _sync_Parks;
210   static PerfCounter * _sync_Notifications;
211   static PerfCounter * _sync_Inflations;
212   static PerfCounter * _sync_Deflations;
213   static PerfLongVariable * _sync_MonExtant;
214 
215   static int Knob_SpinLimit;
216 
217   static ByteSize owner_offset()       { return byte_offset_of(ObjectMonitor, _owner); }
218   static ByteSize recursions_offset()  { return byte_offset_of(ObjectMonitor, _recursions); }
219   static ByteSize cxq_offset()         { return byte_offset_of(ObjectMonitor, _cxq); }
220   static ByteSize succ_offset()        { return byte_offset_of(ObjectMonitor, _succ); }
221   static ByteSize EntryList_offset()   { return byte_offset_of(ObjectMonitor, _EntryList); }

222 
223   // ObjectMonitor references can be ORed with markWord::monitor_value
224   // as part of the ObjectMonitor tagging mechanism. When we combine an
225   // ObjectMonitor reference with an offset, we need to remove the tag
226   // value in order to generate the proper address.
227   //
228   // We can either adjust the ObjectMonitor reference and then add the
229   // offset or we can adjust the offset that is added to the ObjectMonitor
230   // reference. The latter avoids an AGI (Address Generation Interlock)
231   // stall so the helper macro adjusts the offset value that is returned
232   // to the ObjectMonitor reference manipulation code:
233   //
234   #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
235     ((in_bytes(ObjectMonitor::f ## _offset())) - checked_cast<int>(markWord::monitor_value))
236 
237   markWord           header() const;
238   volatile markWord* header_addr();
239   void               set_header(markWord hdr);
240 
241   bool is_busy() const {
242     // TODO-FIXME: assert _owner == null implies _recursions = 0
243     intptr_t ret_code = intptr_t(_waiters) | intptr_t(_cxq) | intptr_t(_EntryList);
244     int cnts = contentions(); // read once
245     if (cnts > 0) {
246       ret_code |= intptr_t(cnts);
247     }
248     if (!owner_is_DEFLATER_MARKER()) {
249       ret_code |= intptr_t(owner_raw());
250     }
251     return ret_code != 0;
252   }
253   const char* is_busy_to_string(stringStream* ss);
254 
255   bool is_entered(JavaThread* current) const;

256 
257   // Returns true if this OM has an owner, false otherwise.
258   bool      has_owner() const;
259   void*     owner() const;  // Returns null if DEFLATER_MARKER is observed.






260   void*     owner_raw() const;

261   // Returns true if owner field == DEFLATER_MARKER and false otherwise.
262   bool      owner_is_DEFLATER_MARKER() const;
263   // Returns true if 'this' is being async deflated and false otherwise.
264   bool      is_being_async_deflated();
265   // Clear _owner field; current value must match old_value.
266   void      release_clear_owner(void* old_value);
267   // Simply set _owner field to new_value; current value must match old_value.
268   void      set_owner_from(void* old_value, void* new_value);

269   // Simply set _owner field to current; current value must match basic_lock_p.
270   void      set_owner_from_BasicLock(void* basic_lock_p, JavaThread* current);
271   // Try to set _owner field to new_value if the current value matches
272   // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
273   // _owner field. Returns the prior value of the _owner field.
274   void*     try_set_owner_from(void* old_value, void* new_value);

275 
276   void set_owner_anonymous() {
277     set_owner_from(nullptr, anon_owner_ptr());
278   }
279 
280   bool is_owner_anonymous() const {
281     return owner_raw() == anon_owner_ptr();
282   }
283 
284   void set_owner_from_anonymous(Thread* owner) {
285     set_owner_from(anon_owner_ptr(), owner);
286   }
287 
288   // Simply get _next_om field.
289   ObjectMonitor* next_om() const;
290   // Simply set _next_om field to new_value.
291   void set_next_om(ObjectMonitor* new_value);
292 
293   int       waiters() const;
294 
295   int       contentions() const;
296   void      add_to_contentions(int value);
297   intx      recursions() const                                         { return _recursions; }
298   void      set_recursions(size_t recursions);
299 

300   // JVM/TI GetObjectMonitorUsage() needs this:

301   ObjectWaiter* first_waiter()                                         { return _WaitSet; }
302   ObjectWaiter* next_waiter(ObjectWaiter* o)                           { return o->_next; }
303   JavaThread* thread_of_waiter(ObjectWaiter* o)                        { return o->_thread; }
304 
305   ObjectMonitor(oop object);
306   ~ObjectMonitor();
307 
308   oop       object() const;
309   oop       object_peek() const;
310 
311   // Returns true if the specified thread owns the ObjectMonitor. Otherwise
312   // returns false and throws IllegalMonitorStateException (IMSE).
313   bool      check_owner(TRAPS);
314 
315  private:
316   class ExitOnSuspend {
317    protected:
318     ObjectMonitor* _om;
319     bool _om_exited;
320    public:
321     ExitOnSuspend(ObjectMonitor* om) : _om(om), _om_exited(false) {}
322     void operator()(JavaThread* current);
323     bool exited() { return _om_exited; }
324   };
325   class ClearSuccOnSuspend {
326    protected:
327     ObjectMonitor* _om;
328    public:
329     ClearSuccOnSuspend(ObjectMonitor* om) : _om(om)  {}
330     void operator()(JavaThread* current);
331   };
332  public:
333   bool      enter_for(JavaThread* locking_thread);
334   bool      enter(JavaThread* current);

335   void      exit(JavaThread* current, bool not_suspended = true);
336   void      wait(jlong millis, bool interruptible, TRAPS);
337   void      notify(TRAPS);
338   void      notifyAll(TRAPS);
339 
340   void      print() const;
341 #ifdef ASSERT
342   void      print_debug_style_on(outputStream* st) const;
343 #endif
344   void      print_on(outputStream* st) const;
345 
346   // Use the following at your own risk
347   intx      complete_exit(JavaThread* current);
348 
349  private:
350   void      AddWaiter(ObjectWaiter* waiter);
351   void      INotify(JavaThread* current);
352   ObjectWaiter* DequeueWaiter();
353   void      DequeueSpecificWaiter(ObjectWaiter* waiter);
354   void      EnterI(JavaThread* current);
355   void      ReenterI(JavaThread* current, ObjectWaiter* current_node);
356   void      UnlinkAfterAcquire(JavaThread* current, ObjectWaiter* current_node);



357   int       TryLock(JavaThread* current);
358   int       TrySpin(JavaThread* current);
359   void      ExitEpilog(JavaThread* current, ObjectWaiter* Wakee);
360 
361   // Deflation support
362   bool      deflate_monitor();
363   void      install_displaced_markword_in_object(const oop obj);
364 };
365 
366 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP

 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_RUNTIME_OBJECTMONITOR_HPP
 26 #define SHARE_RUNTIME_OBJECTMONITOR_HPP
 27 
 28 #include "memory/allocation.hpp"
 29 #include "memory/padded.hpp"
 30 #include "oops/markWord.hpp"
 31 #include "oops/oopHandle.inline.hpp"
 32 #include "oops/weakHandle.hpp"
 33 #include "runtime/javaThread.hpp"
 34 #include "runtime/perfDataTypes.hpp"
 35 #include "utilities/checkedCast.hpp"
 36 
 37 class ObjectMonitor;
 38 class ParkEvent;
 39 class BasicLock;
 40 
 41 // ObjectWaiter serves as a "proxy" or surrogate thread.
 42 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
 43 // ParkEvent instead.  Beware, however, that the JVMTI code
 44 // knows about ObjectWaiters, so we'll have to reconcile that code.
 45 // See next_waiter(), first_waiter(), etc.
 46 
 47 class ObjectWaiter : public CHeapObj<mtThread> {
 48  public:
 49   enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ };
 50   ObjectWaiter* volatile _next;
 51   ObjectWaiter* volatile _prev;
 52   JavaThread*   _thread;
 53   OopHandle _vthread;
 54   uint64_t      _notifier_tid;
 55   ParkEvent *   _event;
 56   volatile int  _notified;
 57   volatile TStates TState;
 58   bool          _active;           // Contention monitoring is enabled
 59  public:
 60   ObjectWaiter(JavaThread* current);
 61   ObjectWaiter(oop vthread);
 62   ~ObjectWaiter() {
 63     if (is_vthread()) {
 64       assert(_vthread.resolve() != nullptr, "invariant");
 65       _vthread.release(JavaThread::thread_oop_storage());
 66     }
 67   }
 68   oop vthread() { return _vthread.resolve(); }
 69   bool is_vthread() { return _thread == nullptr; }
 70   void wait_reenter_begin(ObjectMonitor *mon);
 71   void wait_reenter_end(ObjectMonitor *mon);
 72 };
 73 
 74 // The ObjectMonitor class implements the heavyweight version of a
 75 // JavaMonitor. The lightweight BasicLock/stack lock version has been
 76 // inflated into an ObjectMonitor. This inflation is typically due to
 77 // contention or use of Object.wait().
 78 //
 79 // WARNING: This is a very sensitive and fragile class. DO NOT make any
 80 // changes unless you are fully aware of the underlying semantics.
 81 //
 82 // ObjectMonitor Layout Overview/Highlights/Restrictions:
 83 //
 84 // - The _header field must be at offset 0 because the displaced header
 85 //   from markWord is stored there. We do not want markWord.hpp to include
 86 //   ObjectMonitor.hpp to avoid exposing ObjectMonitor everywhere. This
 87 //   means that ObjectMonitor cannot inherit from any other class nor can
 88 //   it use any virtual member functions. This restriction is critical to
 89 //   the proper functioning of the VM.

122 //     avoid false sharing might be profitable. Given
123 //     http://blogs.oracle.com/dave/entry/cas_and_cache_trivia_invalidate
124 //     we know that the CAS in monitorenter will invalidate the line
125 //     underlying _owner. We want to avoid an L1 data cache miss on that
126 //     same line for monitorexit. Putting these <remaining_fields>:
127 //     _recursions, _EntryList, _cxq, and _succ, all of which may be
128 //     fetched in the inflated unlock path, on a different cache line
129 //     would make them immune to CAS-based invalidation from the _owner
130 //     field.
131 //
132 //   - The _recursions field should be of type int, or int32_t but not
133 //     intptr_t. There's no reason to use a 64-bit type for this field
134 //     in a 64-bit JVM.
135 
136 #define OM_CACHE_LINE_SIZE DEFAULT_CACHE_LINE_SIZE
137 
138 class ObjectMonitor : public CHeapObj<mtObjectMonitor> {
139   friend class ObjectSynchronizer;
140   friend class ObjectWaiter;
141   friend class VMStructs;
142   friend class MonitorList;
143   JVMCI_ONLY(friend class JVMCIVMStructs;)
144 
145   static OopStorage* _oop_storage;
146 
147   static OopHandle _vthread_cxq_head;
148   static ParkEvent* _vthread_unparker_ParkEvent;
149 
150   // The sync code expects the header field to be at offset zero (0).
151   // Enforced by the assert() in header_addr().
152   volatile markWord _header;        // displaced object header word - mark
153   WeakHandle _object;               // backward object pointer
154   // Separate _header and _owner on different cache lines since both can
155   // have busy multi-threaded access. _header and _object are set at initial
156   // inflation. The _object does not change, so it is a good choice to share
157   // its cache line with _header.
158   DEFINE_PAD_MINUS_SIZE(0, OM_CACHE_LINE_SIZE, sizeof(volatile markWord) +
159                         sizeof(WeakHandle));
160   // Used by async deflation as a marker in the _owner field.
161   // Note that the choice of the two markers is peculiar:
162   // - They need to represent values that cannot be pointers. In particular,
163   //   we achieve this by using the lowest two bits.
164   // - ANONYMOUS_OWNER should be a small value, it is used in generated code
165   //   and small values encode much better.
166   // - We test for anonymous owner by testing for the lowest bit, therefore
167   //   DEFLATER_MARKER must *not* have that bit set.
168   #define DEFLATER_MARKER reinterpret_cast<void*>(2)
169 public:
170   // NOTE: Typed as uintptr_t so that we can pick it up in SA, via vmStructs.
171   static const uintptr_t ANONYMOUS_OWNER = 1;
172 
173 private:
174   static void* anon_owner_ptr() { return reinterpret_cast<void*>(ANONYMOUS_OWNER); }
175 
176   void* volatile _owner;            // pointer to owning thread OR BasicLock
177   BasicLock* volatile _stack_locker;      // can this share a cache line with owner? they're used together
178   volatile uint64_t _previous_owner_tid;  // thread id of the previous owner of the monitor
179   // Separate _owner and _next_om on different cache lines since
180   // both can have busy multi-threaded access. _previous_owner_tid is only
181   // changed by ObjectMonitor::exit() so it is a good choice to share the
182   // cache line with _owner.
183   DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, 2 * sizeof(void* volatile) +
184                         sizeof(volatile uint64_t));
185   ObjectMonitor* _next_om;          // Next ObjectMonitor* linkage
186   volatile intx _recursions;        // recursion count, 0 for first entry
187   ObjectWaiter* volatile _EntryList;  // Threads blocked on entry or reentry.
188                                       // The list is actually composed of WaitNodes,
189                                       // acting as proxies for Threads.
190 
191   ObjectWaiter* volatile _cxq;      // LL of recently-arrived threads blocked on entry.
192   JavaThread* volatile _succ;       // Heir presumptive thread - used for futile wakeup throttling
193   JavaThread* volatile _Responsible;
194 
195   volatile int _Spinner;            // for exit->spinner handoff optimization
196   volatile int _SpinDuration;
197 
198   int _contentions;                 // Number of active contentions in enter(). It is used by is_busy()
199                                     // along with other fields to determine if an ObjectMonitor can be
200                                     // deflated. It is also used by the async deflation protocol. See
201                                     // ObjectMonitor::deflate_monitor().
202  protected:
203   ObjectWaiter* volatile _WaitSet;  // LL of threads wait()ing on the monitor
204   volatile int  _waiters;           // number of waiting threads
205  private:
206   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock
207 
208  public:
209 
210   static void Initialize();
211   static void Initialize2();
212 
213   static OopHandle& vthread_cxq_head() { return _vthread_cxq_head; }
214   static ParkEvent* vthread_unparker_ParkEvent() { return _vthread_unparker_ParkEvent; }
215 
216   // Only perform a PerfData operation if the PerfData object has been
217   // allocated and if the PerfDataManager has not freed the PerfData
218   // objects which can happen at normal VM shutdown.
219   //
220   #define OM_PERFDATA_OP(f, op_str)                 \
221     do {                                            \
222       if (ObjectMonitor::_sync_ ## f != nullptr &&  \
223           PerfDataManager::has_PerfData()) {        \
224         ObjectMonitor::_sync_ ## f->op_str;         \
225       }                                             \
226     } while (0)
227 
228   static PerfCounter * _sync_ContendedLockAttempts;
229   static PerfCounter * _sync_FutileWakeups;
230   static PerfCounter * _sync_Parks;
231   static PerfCounter * _sync_Notifications;
232   static PerfCounter * _sync_Inflations;
233   static PerfCounter * _sync_Deflations;
234   static PerfLongVariable * _sync_MonExtant;
235 
236   static int Knob_SpinLimit;
237 
238   static ByteSize owner_offset()       { return byte_offset_of(ObjectMonitor, _owner); }
239   static ByteSize recursions_offset()  { return byte_offset_of(ObjectMonitor, _recursions); }
240   static ByteSize cxq_offset()         { return byte_offset_of(ObjectMonitor, _cxq); }
241   static ByteSize succ_offset()        { return byte_offset_of(ObjectMonitor, _succ); }
242   static ByteSize EntryList_offset()   { return byte_offset_of(ObjectMonitor, _EntryList); }
243   static ByteSize stack_locker_offset(){ return byte_offset_of(ObjectMonitor, _stack_locker); }
244 
245   // ObjectMonitor references can be ORed with markWord::monitor_value
246   // as part of the ObjectMonitor tagging mechanism. When we combine an
247   // ObjectMonitor reference with an offset, we need to remove the tag
248   // value in order to generate the proper address.
249   //
250   // We can either adjust the ObjectMonitor reference and then add the
251   // offset or we can adjust the offset that is added to the ObjectMonitor
252   // reference. The latter avoids an AGI (Address Generation Interlock)
253   // stall so the helper macro adjusts the offset value that is returned
254   // to the ObjectMonitor reference manipulation code:
255   //
256   #define OM_OFFSET_NO_MONITOR_VALUE_TAG(f) \
257     ((in_bytes(ObjectMonitor::f ## _offset())) - checked_cast<int>(markWord::monitor_value))
258 
259   markWord           header() const;
260   volatile markWord* header_addr();
261   void               set_header(markWord hdr);
262 
263   bool is_busy() const {
264     // TODO-FIXME: assert _owner == null implies _recursions = 0
265     intptr_t ret_code = intptr_t(_waiters) | intptr_t(_cxq) | intptr_t(_EntryList);
266     int cnts = contentions(); // read once
267     if (cnts > 0) {
268       ret_code |= intptr_t(cnts);
269     }
270     if (!owner_is_DEFLATER_MARKER()) {
271       ret_code |= intptr_t(owner_raw());
272     }
273     return ret_code != 0;
274   }
275   const char* is_busy_to_string(stringStream* ss);
276 
277   bool is_entered(JavaThread* current) const;
278   int contentions() const;
279 
280   // Returns true if this OM has an owner, false otherwise.
281   bool   has_owner() const;
282   void*  owner() const;  // Returns null if DEFLATER_MARKER is observed.
283   bool   is_owner(JavaThread* thread) const { return owner() == owner_for(thread); }
284   bool   is_owner_anonymous() const { return owner_raw() == anon_owner_ptr(); }
285   bool   is_stack_locker(JavaThread* current);
286   BasicLock* stack_locker() const;
287 
288  private:
289   void*     owner_raw() const;
290   void*     owner_for(JavaThread* thread) const;
291   // Returns true if owner field == DEFLATER_MARKER and false otherwise.
292   bool      owner_is_DEFLATER_MARKER() const;
293   // Returns true if 'this' is being async deflated and false otherwise.
294   bool      is_being_async_deflated();
295   // Clear _owner field; current value must match old_value.
296   void      release_clear_owner(JavaThread* old_value);
297   // Simply set _owner field to new_value; current value must match old_value.
298   void      set_owner_from_raw(void* old_value, void* new_value);
299   void      set_owner_from(void* old_value, JavaThread* current);
300   // Simply set _owner field to current; current value must match basic_lock_p.
301   void      set_owner_from_BasicLock(JavaThread* current);
302   // Try to set _owner field to new_value if the current value matches
303   // old_value, using Atomic::cmpxchg(). Otherwise, does not change the
304   // _owner field. Returns the prior value of the _owner field.
305   void*     try_set_owner_from_raw(void* old_value, void* new_value);
306   void*     try_set_owner_from(void* old_value, JavaThread* current);
307 
308   void set_stack_locker(BasicLock* locker);


309 
310   void set_owner_anonymous() {
311     set_owner_from_raw(nullptr, anon_owner_ptr());
312   }
313 
314   void set_owner_from_anonymous(JavaThread* owner) {
315     set_owner_from(anon_owner_ptr(), owner);
316   }
317 
318   // Simply get _next_om field.
319   ObjectMonitor* next_om() const;
320   // Simply set _next_om field to new_value.
321   void set_next_om(ObjectMonitor* new_value);
322 



323   void      add_to_contentions(int value);
324   intx      recursions() const                                         { return _recursions; }
325   void      set_recursions(size_t recursions);
326 
327  public:
328   // JVM/TI GetObjectMonitorUsage() needs this:
329   int waiters() const;
330   ObjectWaiter* first_waiter()                                         { return _WaitSet; }
331   ObjectWaiter* next_waiter(ObjectWaiter* o)                           { return o->_next; }
332   JavaThread* thread_of_waiter(ObjectWaiter* o)                        { return o->_thread; }
333 
334   ObjectMonitor(oop object);
335   ~ObjectMonitor();
336 
337   oop       object() const;
338   oop       object_peek() const;
339 
340   // Returns true if the specified thread owns the ObjectMonitor. Otherwise
341   // returns false and throws IllegalMonitorStateException (IMSE).
342   bool      check_owner(TRAPS);
343 
344  private:
345   class ExitOnSuspend {
346    protected:
347     ObjectMonitor* _om;
348     bool _om_exited;
349    public:
350     ExitOnSuspend(ObjectMonitor* om) : _om(om), _om_exited(false) {}
351     void operator()(JavaThread* current);
352     bool exited() { return _om_exited; }
353   };
354   class ClearSuccOnSuspend {
355    protected:
356     ObjectMonitor* _om;
357    public:
358     ClearSuccOnSuspend(ObjectMonitor* om) : _om(om)  {}
359     void operator()(JavaThread* current);
360   };
361  public:
362   bool      enter_for(JavaThread* locking_thread);
363   bool      enter(JavaThread* current);
364   void      redo_enter(JavaThread* current);
365   void      exit(JavaThread* current, bool not_suspended = true);
366   void      wait(jlong millis, bool interruptible, TRAPS);
367   void      notify(TRAPS);
368   void      notifyAll(TRAPS);
369 
370   void      print() const;
371 #ifdef ASSERT
372   void      print_debug_style_on(outputStream* st) const;
373 #endif
374   void      print_on(outputStream* st) const;
375 
376   // Use the following at your own risk
377   intx      complete_exit(JavaThread* current);
378 
379  private:
380   void      AddWaiter(ObjectWaiter* waiter);
381   void      INotify(JavaThread* current);
382   ObjectWaiter* DequeueWaiter();
383   void      DequeueSpecificWaiter(ObjectWaiter* waiter);
384   void      EnterI(JavaThread* current);
385   void      ReenterI(JavaThread* current, ObjectWaiter* current_node);
386   bool      HandlePreemptedVThread(JavaThread* current);
387   void      VThreadEpilog(JavaThread* current);
388   void      UnlinkAfterAcquire(JavaThread* current, ObjectWaiter* current_node, oop vthread = nullptr);
389   ObjectWaiter* LookupWaiter(int64_t threadid);
390   int       TryLock(JavaThread* current);
391   int       TrySpin(JavaThread* current);
392   void      ExitEpilog(JavaThread* current, ObjectWaiter* Wakee);
393 
394   // Deflation support
395   bool      deflate_monitor();
396   void      install_displaced_markword_in_object(const oop obj);
397 };
398 
399 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP
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