1 /*
   2  * Copyright (c) 1998, 2013, 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  *
  23  */
  24 
  25 #ifndef SHARE_VM_RUNTIME_OBJECTMONITOR_HPP
  26 #define SHARE_VM_RUNTIME_OBJECTMONITOR_HPP
  27 
  28 #include "runtime/os.hpp"
  29 #include "runtime/park.hpp"
  30 #include "runtime/perfData.hpp"
  31 
  32 // ObjectWaiter serves as a "proxy" or surrogate thread.
  33 // TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
  34 // ParkEvent instead.  Beware, however, that the JVMTI code
  35 // knows about ObjectWaiters, so we'll have to reconcile that code.
  36 // See next_waiter(), first_waiter(), etc.
  37 
  38 class ObjectWaiter : public StackObj {
  39  public:
  40   enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ;
  41   enum Sorted  { PREPEND, APPEND, SORTED } ;
  42   ObjectWaiter * volatile _next;
  43   ObjectWaiter * volatile _prev;
  44   Thread*       _thread;
  45   jlong         _notifier_tid;
  46   ParkEvent *   _event;
  47   volatile int  _notified ;
  48   volatile TStates TState ;
  49   Sorted        _Sorted ;           // List placement disposition
  50   bool          _active ;           // Contention monitoring is enabled
  51  public:
  52   ObjectWaiter(Thread* thread);
  53 
  54   void wait_reenter_begin(ObjectMonitor *mon);
  55   void wait_reenter_end(ObjectMonitor *mon);
  56 };
  57 
  58 // forward declaration to avoid include tracing.hpp
  59 class EventJavaMonitorWait;
  60 
  61 // WARNING:
  62 //   This is a very sensitive and fragile class. DO NOT make any
  63 // change unless you are fully aware of the underlying semantics.
  64 
  65 //   This class can not inherit from any other class, because I have
  66 // to let the displaced header be the very first word. Otherwise I
  67 // have to let markOop include this file, which would export the
  68 // monitor data structure to everywhere.
  69 //
  70 // The ObjectMonitor class is used to implement JavaMonitors which have
  71 // transformed from the lightweight structure of the thread stack to a
  72 // heavy weight lock due to contention
  73 
  74 // It is also used as RawMonitor by the JVMTI
  75 
  76 
  77 class ObjectMonitor {
  78  public:
  79   enum {
  80     OM_OK,                    // no error
  81     OM_SYSTEM_ERROR,          // operating system error
  82     OM_ILLEGAL_MONITOR_STATE, // IllegalMonitorStateException
  83     OM_INTERRUPTED,           // Thread.interrupt()
  84     OM_TIMED_OUT              // Object.wait() timed out
  85   };
  86 
  87  public:
  88   // TODO-FIXME: the "offset" routines should return a type of off_t instead of int ...
  89   // ByteSize would also be an appropriate type.
  90   static int header_offset_in_bytes()      { return offset_of(ObjectMonitor, _header);     }
  91   static int object_offset_in_bytes()      { return offset_of(ObjectMonitor, _object);     }
  92   static int owner_offset_in_bytes()       { return offset_of(ObjectMonitor, _owner);      }
  93   static int count_offset_in_bytes()       { return offset_of(ObjectMonitor, _count);      }
  94   static int recursions_offset_in_bytes()  { return offset_of(ObjectMonitor, _recursions); }
  95   static int cxq_offset_in_bytes()         { return offset_of(ObjectMonitor, _cxq) ;       }
  96   static int succ_offset_in_bytes()        { return offset_of(ObjectMonitor, _succ) ;      }
  97   static int EntryList_offset_in_bytes()   { return offset_of(ObjectMonitor, _EntryList);  }
  98   static int FreeNext_offset_in_bytes()    { return offset_of(ObjectMonitor, FreeNext);    }
  99   static int WaitSet_offset_in_bytes()     { return offset_of(ObjectMonitor, _WaitSet) ;   }
 100   static int Responsible_offset_in_bytes() { return offset_of(ObjectMonitor, _Responsible);}
 101   static int Spinner_offset_in_bytes()     { return offset_of(ObjectMonitor, _Spinner);    }
 102 
 103  public:
 104   // Eventaully we'll make provisions for multiple callbacks, but
 105   // now one will suffice.
 106   static int (*SpinCallbackFunction)(intptr_t, int) ;
 107   static intptr_t SpinCallbackArgument ;
 108 
 109 
 110  public:
 111   markOop   header() const;
 112   void      set_header(markOop hdr);
 113 
 114   intptr_t is_busy() const {
 115     // TODO-FIXME: merge _count and _waiters.
 116     // TODO-FIXME: assert _owner == null implies _recursions = 0
 117     // TODO-FIXME: assert _WaitSet != null implies _count > 0
 118     return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList ) ;
 119   }
 120 
 121   intptr_t  is_entered(Thread* current) const;
 122 
 123   void*     owner() const;
 124   void      set_owner(void* owner);
 125 
 126   intptr_t  waiters() const;
 127 
 128   intptr_t  count() const;
 129   void      set_count(intptr_t count);
 130   intptr_t  contentions() const ;
 131   intptr_t  recursions() const                                         { return _recursions; }
 132 
 133   // JVM/DI GetMonitorInfo() needs this
 134   ObjectWaiter* first_waiter()                                         { return _WaitSet; }
 135   ObjectWaiter* next_waiter(ObjectWaiter* o)                           { return o->_next; }
 136   Thread* thread_of_waiter(ObjectWaiter* o)                            { return o->_thread; }
 137 
 138   // initialize the monitor, exception the semaphore, all other fields
 139   // are simple integers or pointers
 140   ObjectMonitor() {
 141     _header       = NULL;
 142     _count        = 0;
 143     _waiters      = 0,
 144     _recursions   = 0;
 145     _object       = NULL;
 146     _owner        = NULL;
 147     _WaitSet      = NULL;
 148     _WaitSetLock  = 0 ;
 149     _Responsible  = NULL ;
 150     _succ         = NULL ;
 151     _cxq          = NULL ;
 152     FreeNext      = NULL ;
 153     _EntryList    = NULL ;
 154     _SpinFreq     = 0 ;
 155     _SpinClock    = 0 ;
 156     OwnerIsThread = 0 ;
 157     _previous_owner_tid = 0;
 158   }
 159 
 160   ~ObjectMonitor() {
 161    // TODO: Add asserts ...
 162    // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
 163    // _count == 0 _EntryList  == NULL etc
 164   }
 165 
 166 private:
 167   void Recycle () {
 168     // TODO: add stronger asserts ...
 169     // _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
 170     // _count == 0 EntryList  == NULL
 171     // _recursions == 0 _WaitSet == NULL
 172     // TODO: assert (is_busy()|_recursions) == 0
 173     _succ          = NULL ;
 174     _EntryList     = NULL ;
 175     _cxq           = NULL ;
 176     _WaitSet       = NULL ;
 177     _recursions    = 0 ;
 178     _SpinFreq      = 0 ;
 179     _SpinClock     = 0 ;
 180     OwnerIsThread  = 0 ;
 181   }
 182 
 183 public:
 184 
 185   void*     object() const;
 186   void*     object_addr();
 187   void      set_object(void* obj);
 188 
 189   bool      check(TRAPS);       // true if the thread owns the monitor.
 190   void      check_slow(TRAPS);
 191   void      clear();
 192 #ifndef PRODUCT
 193   void      verify();
 194   void      print();
 195 #endif
 196 
 197   bool      try_enter (TRAPS) ;
 198   void      enter(TRAPS);
 199   void      exit(bool not_suspended, TRAPS);
 200   void      wait(jlong millis, bool interruptable, TRAPS);
 201   void      notify(TRAPS);
 202   void      notifyAll(TRAPS);
 203 
 204 // Use the following at your own risk
 205   intptr_t  complete_exit(TRAPS);
 206   void      reenter(intptr_t recursions, TRAPS);
 207 
 208  private:
 209   void      AddWaiter (ObjectWaiter * waiter) ;
 210   static    void DeferredInitialize();
 211 
 212   ObjectWaiter * DequeueWaiter () ;
 213   void      DequeueSpecificWaiter (ObjectWaiter * waiter) ;
 214   void      EnterI (TRAPS) ;
 215   void      ReenterI (Thread * Self, ObjectWaiter * SelfNode) ;
 216   void      UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode) ;
 217   int       TryLock (Thread * Self) ;
 218   int       NotRunnable (Thread * Self, Thread * Owner) ;
 219   int       TrySpin_Fixed (Thread * Self) ;
 220   int       TrySpin_VaryFrequency (Thread * Self) ;
 221   int       TrySpin_VaryDuration  (Thread * Self) ;
 222   void      ctAsserts () ;
 223   void      ExitEpilog (Thread * Self, ObjectWaiter * Wakee) ;
 224   bool      ExitSuspendEquivalent (JavaThread * Self) ;
 225   void      post_monitor_wait_event(EventJavaMonitorWait * event,
 226                                                    jlong notifier_tid,
 227                                                    jlong timeout,
 228                                                    bool timedout);
 229 
 230  private:
 231   friend class ObjectSynchronizer;
 232   friend class ObjectWaiter;
 233   friend class VMStructs;
 234 
 235   // WARNING: this must be the very first word of ObjectMonitor
 236   // This means this class can't use any virtual member functions.
 237   // TODO-FIXME: assert that offsetof(_header) is 0 or get rid of the
 238   // implicit 0 offset in emitted code.
 239 
 240   volatile markOop   _header;       // displaced object header word - mark
 241   void*     volatile _object;       // backward object pointer - strong root
 242 
 243   double SharingPad [1] ;           // temp to reduce false sharing
 244 
 245   // All the following fields must be machine word aligned
 246   // The VM assumes write ordering wrt these fields, which can be
 247   // read from other threads.
 248 
 249  protected:                         // protected for jvmtiRawMonitor
 250   void *  volatile _owner;          // pointer to owning thread OR BasicLock
 251   volatile jlong _previous_owner_tid; // thread id of the previous owner of the monitor
 252   volatile intptr_t  _recursions;   // recursion count, 0 for first entry
 253  private:
 254   int OwnerIsThread ;               // _owner is (Thread *) vs SP/BasicLock
 255   ObjectWaiter * volatile _cxq ;    // LL of recently-arrived threads blocked on entry.
 256                                     // The list is actually composed of WaitNodes, acting
 257                                     // as proxies for Threads.
 258  protected:
 259   ObjectWaiter * volatile _EntryList ;     // Threads blocked on entry or reentry.
 260  private:
 261   Thread * volatile _succ ;          // Heir presumptive thread - used for futile wakeup throttling
 262   Thread * volatile _Responsible ;
 263   int _PromptDrain ;                // rqst to drain cxq into EntryList ASAP
 264 
 265   volatile int _Spinner ;           // for exit->spinner handoff optimization
 266   volatile int _SpinFreq ;          // Spin 1-out-of-N attempts: success rate
 267   volatile int _SpinClock ;
 268   volatile int _SpinDuration ;
 269   volatile intptr_t _SpinState ;    // MCS/CLH list of spinners
 270 
 271   // TODO-FIXME: _count, _waiters and _recursions should be of
 272   // type int, or int32_t but not intptr_t.  There's no reason
 273   // to use 64-bit fields for these variables on a 64-bit JVM.
 274 
 275   volatile intptr_t  _count;        // reference count to prevent reclaimation/deflation
 276                                     // at stop-the-world time.  See deflate_idle_monitors().
 277                                     // _count is approximately |_WaitSet| + |_EntryList|
 278  protected:
 279   volatile intptr_t  _waiters;      // number of waiting threads
 280  private:
 281  protected:
 282   ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor
 283  private:
 284   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock
 285 
 286  public:
 287   int _QMix ;                       // Mixed prepend queue discipline
 288   ObjectMonitor * FreeNext ;        // Free list linkage
 289   intptr_t StatA, StatsB ;
 290 
 291  public:
 292   static void Initialize () ;
 293   static PerfCounter * _sync_ContendedLockAttempts ;
 294   static PerfCounter * _sync_FutileWakeups ;
 295   static PerfCounter * _sync_Parks ;
 296   static PerfCounter * _sync_EmptyNotifications ;
 297   static PerfCounter * _sync_Notifications ;
 298   static PerfCounter * _sync_SlowEnter ;
 299   static PerfCounter * _sync_SlowExit ;
 300   static PerfCounter * _sync_SlowNotify ;
 301   static PerfCounter * _sync_SlowNotifyAll ;
 302   static PerfCounter * _sync_FailedSpins ;
 303   static PerfCounter * _sync_SuccessfulSpins ;
 304   static PerfCounter * _sync_PrivateA ;
 305   static PerfCounter * _sync_PrivateB ;
 306   static PerfCounter * _sync_MonInCirculation ;
 307   static PerfCounter * _sync_MonScavenged ;
 308   static PerfCounter * _sync_Inflations ;
 309   static PerfCounter * _sync_Deflations ;
 310   static PerfLongVariable * _sync_MonExtant ;
 311 
 312  public:
 313   static int Knob_Verbose;
 314   static int Knob_SpinLimit;
 315   void* operator new (size_t size) {
 316     return AllocateHeap(size, mtInternal);
 317   }
 318   void* operator new[] (size_t size) {
 319     return operator new (size);
 320   }
 321   void operator delete(void* p) {
 322     FreeHeap(p, mtInternal);
 323   }
 324   void operator delete[] (void *p) {
 325     operator delete(p);
 326   }
 327 };
 328 
 329 #undef TEVENT
 330 #define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); }
 331 
 332 #define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }}
 333 
 334 #undef  TEVENT
 335 #define TEVENT(nom) {;}
 336 
 337 
 338 #endif // SHARE_VM_RUNTIME_OBJECTMONITOR_HPP