/*

 * Copyright (c) 1998, 2010, 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

 * questions.

 *

 */

#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;

  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 ;

  }

  ~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();

#ifndef PRODUCT

  void      verify();

  void      print();

#endif

  bool      try_enter (TRAPS) ;

  void      enter(TRAPS);

  void      exit(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.

  // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the

  // implicit 0 offset in emitted code.

  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 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;

};

#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