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 /*

  * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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 #ifndef SHARE_VM_RUNTIME_OBJECTMONITOR_HPP

 #define SHARE_VM_RUNTIME_OBJECTMONITOR_HPP

 #include "runtime/os.hpp"

 #include "runtime/park.hpp"

 #include "runtime/perfData.hpp"

 // ObjectWaiter serves as a "proxy" or surrogate thread.

 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific

 // ParkEvent instead.  Beware, however, that the JVMTI code

 // knows about ObjectWaiters, so we'll have to reconcile that code.

 // See next_waiter(), first_waiter(), etc.

 class ObjectWaiter : public StackObj {

  public:

   enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ;

   enum Sorted  { PREPEND, APPEND, SORTED } ;

   ObjectWaiter * volatile _next;

   ObjectWaiter * volatile _prev;

   Thread*       _thread;

   jlong         _notifier_tid;

   ParkEvent *   _event;

   volatile int  _notified ;

   volatile TStates TState ;

   Sorted        _Sorted ;           // List placement disposition

   bool          _active ;           // Contention monitoring is enabled

  public:

   ObjectWaiter(Thread* thread);

   void wait_reenter_begin(ObjectMonitor *mon);

   void wait_reenter_end(ObjectMonitor *mon);

 };

 // WARNING:

 //   This is a very sensitive and fragile class. DO NOT make any

 // change unless you are fully aware of the underlying semantics.

 //   This class can not inherit from any other class, because I have

 // to let the displaced header be the very first word. Otherwise I

 // have to let markOop include this file, which would export the

 // monitor data structure to everywhere.

 //

 // The ObjectMonitor class is used to implement JavaMonitors which have

 // transformed from the lightweight structure of the thread stack to a

 // heavy weight lock due to contention

 // It is also used as RawMonitor by the JVMTI

 class ObjectMonitor {

  public:

   enum {

     OM_OK,                    // no error

     OM_SYSTEM_ERROR,          // operating system error

     OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException

     OM_INTERRUPTED,           // Thread.interrupt()

     OM_TIMED_OUT              // Object.wait() timed out

   };

  public:

   // TODO-FIXME: the "offset" routines should return a type of off_t instead of int ...

   // ByteSize would also be an appropriate type.

   static int header_offset_in_bytes()      { return offset_of(ObjectMonitor, _header);     }

   static int object_offset_in_bytes()      { return offset_of(ObjectMonitor, _object);     }

   static int owner_offset_in_bytes()       { return offset_of(ObjectMonitor, _owner);      }

   static int count_offset_in_bytes()       { return offset_of(ObjectMonitor, _count);      }

   static int recursions_offset_in_bytes()  { return offset_of(ObjectMonitor, _recursions); }

   static int cxq_offset_in_bytes()         { return offset_of(ObjectMonitor, _cxq) ;       }

   static int succ_offset_in_bytes()        { return offset_of(ObjectMonitor, _succ) ;      }

   static int EntryList_offset_in_bytes()   { return offset_of(ObjectMonitor, _EntryList);  }

   static int FreeNext_offset_in_bytes()    { return offset_of(ObjectMonitor, FreeNext);    }

   static int WaitSet_offset_in_bytes()     { return offset_of(ObjectMonitor, _WaitSet) ;   }

   static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);}

   static int Spinner_offset_in_bytes()     { return offset_of(ObjectMonitor, _Spinner);    }

  public:

   // Eventaully we'll make provisions for multiple callbacks, but

   // now one will suffice.

   static int (*SpinCallbackFunction)(intptr_t, int) ;

   static intptr_t SpinCallbackArgument ;

  public:

   markOop   header() const;

   void      set_header(markOop hdr);

   intptr_t is_busy() const {

     // TODO-FIXME: merge _count and _waiters.

     // TODO-FIXME: assert _owner == null implies _recursions = 0

     // TODO-FIXME: assert _WaitSet != null implies _count > 0

     return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList ) ;

   }

   intptr_t  is_entered(Thread* current) const;

   void*     owner() const;

   void      set_owner(void* owner);

   intptr_t  waiters() const;

   intptr_t  count() const;

   void      set_count(intptr_t count);

   intptr_t  contentions() const ;

   intptr_t  recursions() const                                         { return _recursions; }

   // JVM/DI GetMonitorInfo() needs this

   ObjectWaiter* first_waiter()                                         { return _WaitSet; }

   ObjectWaiter* next_waiter(ObjectWaiter* o)                           { return o->_next; }

   Thread* thread_of_waiter(ObjectWaiter* o)                            { return o->_thread; }

   // initialize the monitor, exception the semaphore, all other fields

   // are simple integers or pointers

   ObjectMonitor() {

     _header       = NULL;

     _count        = 0;

     _waiters      = 0,

     _recursions   = 0;

     _object       = NULL;

     _owner        = NULL;

     _WaitSet      = NULL;

     _WaitSetLock  = 0 ;

     _Responsible  = NULL ;

     _succ         = NULL ;

     _cxq          = NULL ;

     FreeNext      = NULL ;

     _EntryList    = NULL ;

     _SpinFreq     = 0 ;

     _SpinClock    = 0 ;

     OwnerIsThread = 0 ;

     _previous_owner_tid = 0;

   }

   ~ObjectMonitor() {

    // TODO: Add asserts ...

    // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0

    // _count == 0 _EntryList  == NULL etc

   }

 private:

   void Recycle () {

     // TODO: add stronger asserts ...

     // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0

     // _count == 0 EntryList  == NULL

     // _recursions == 0 _WaitSet == NULL

     // TODO: assert (is_busy()|_recursions) == 0

     _succ          = NULL ;

     _EntryList     = NULL ;

     _cxq           = NULL ;

     _WaitSet       = NULL ;

     _recursions    = 0 ;

     _SpinFreq      = 0 ;

     _SpinClock     = 0 ;

     OwnerIsThread  = 0 ;

   }

 public:

   void*     object() const;

   void*     object_addr();

   void      set_object(void* obj);

   bool      check(TRAPS);       // true if the thread owns the monitor.

   void      check_slow(TRAPS);

   void      clear();

   static void sanity_checks();  // public for -XX:+ExecuteInternalVMTests

                                 // in PRODUCT for -XX:SyncKnobs=Verbose=1

 #ifndef PRODUCT

   void      verify();

   void      print();

 #endif

   bool      try_enter (TRAPS) ;

   void      enter(TRAPS);

   void      exit(bool not_suspended, TRAPS);

   void      wait(jlong millis, bool interruptable, TRAPS);

   void      notify(TRAPS);

   void      notifyAll(TRAPS);

 // Use the following at your own risk

   intptr_t  complete_exit(TRAPS);

   void      reenter(intptr_t recursions, TRAPS);

  private:

   void      AddWaiter (ObjectWaiter * waiter) ;

   static    void DeferredInitialize();

   ObjectWaiter * DequeueWaiter () ;

   void      DequeueSpecificWaiter (ObjectWaiter * waiter) ;

   void      EnterI (TRAPS) ;

   void      ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;

   void      UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;

   int       TryLock (Thread * Self) ;

   int       NotRunnable (Thread * Self, Thread * Owner) ;

   int       TrySpin_Fixed (Thread * Self) ;

   int       TrySpin_VaryFrequency (Thread * Self) ;

   int       TrySpin_VaryDuration  (Thread * Self) ;

   void      ctAsserts () ;

   void      ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;

   bool      ExitSuspendEquivalent (JavaThread * Self) ;

  private:

   friend class ObjectSynchronizer;

   friend class ObjectWaiter;

   friend class VMStructs;

   // WARNING: this must be the very first word of ObjectMonitor

   // This means this class can't use any virtual member functions.

   volatile markOop   _header;       // displaced object header word - mark

   void*     volatile _object;       // backward object pointer - strong root

   double SharingPad [1] ;           // temp to reduce false sharing

   // All the following fields must be machine word aligned

   // The VM assumes write ordering wrt these fields, which can be

   // read from other threads.

  protected:                         // protected for jvmtiRawMonitor

   void *  volatile _owner;          // pointer to owning thread OR BasicLock

   volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor

   volatile intptr_t  _recursions;   // recursion count, 0 for first entry

  private:

   int OwnerIsThread ;               // _owner is (Thread *) vs SP/BasicLock

   ObjectWaiter * volatile _cxq ;    // LL of recently-arrived threads blocked on entry.

                                     // The list is actually composed of WaitNodes, acting

                                     // as proxies for Threads.

  protected:

   ObjectWaiter * volatile _EntryList ;     // Threads blocked on entry or reentry.

  private:

   Thread * volatile _succ ;          // Heir presumptive thread - used for futile wakeup throttling

   Thread * volatile _Responsible ;

   int _PromptDrain ;                // rqst to drain cxq into EntryList ASAP

   volatile int _Spinner ;           // for exit->spinner handoff optimization

   volatile int _SpinFreq ;          // Spin 1-out-of-N attempts: success rate

   volatile int _SpinClock ;

   volatile int _SpinDuration ;

   volatile intptr_t _SpinState ;    // MCS/CLH list of spinners

   // TODO-FIXME: _count, _waiters and _recursions should be of

   // type int, or int32_t but not intptr_t.  There's no reason

   // to use 64-bit fields for these variables on a 64-bit JVM.

   volatile intptr_t  _count;        // reference count to prevent reclaimation/deflation

                                     // at stop-the-world time.  See deflate_idle_monitors().

                                     // _count is approximately |_WaitSet| + |_EntryList|

  protected:

   volatile intptr_t  _waiters;      // number of waiting threads

  private:

  protected:

   ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor

  private:

   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock

  public:

   int _QMix ;                       // Mixed prepend queue discipline

   ObjectMonitor * FreeNext ;        // Free list linkage

   intptr_t StatA, StatsB ;

  public:

   static void Initialize () ;

   static PerfCounter * _sync_ContendedLockAttempts ;

   static PerfCounter * _sync_FutileWakeups ;

   static PerfCounter * _sync_Parks ;

   static PerfCounter * _sync_EmptyNotifications ;

   static PerfCounter * _sync_Notifications ;

   static PerfCounter * _sync_SlowEnter ;

   static PerfCounter * _sync_SlowExit ;

   static PerfCounter * _sync_SlowNotify ;

   static PerfCounter * _sync_SlowNotifyAll ;

   static PerfCounter * _sync_FailedSpins ;

   static PerfCounter * _sync_SuccessfulSpins ;

   static PerfCounter * _sync_PrivateA ;

   static PerfCounter * _sync_PrivateB ;

   static PerfCounter * _sync_MonInCirculation ;

   static PerfCounter * _sync_MonScavenged ;

   static PerfCounter * _sync_Inflations ;

   static PerfCounter * _sync_Deflations ;

   static PerfLongVariable * _sync_MonExtant ;

  public:

   static int Knob_Verbose;

   static int Knob_SpinLimit;

   void* operator new (size_t size) throw() {

     return AllocateHeap(size, mtInternal);

   }

   void* operator new[] (size_t size) throw() {

     return operator new (size);

   }

   void operator delete(void* p) {

     FreeHeap(p, mtInternal);

   }

   void operator delete[] (void *p) {

     operator delete(p);

   }

 };

 #undef TEVENT

 #define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); }

 #define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }}

 #undef  TEVENT

 #define TEVENT(nom) {;}

 #endif // SHARE_VM_RUNTIME_OBJECTMONITOR_HPP