natobject.cc

gcc的组建

	count = he -> light_count;
    }
  if (address & LOCKED)
    {
      wait_unlocked(he);
      goto retry;
    }
  // Now the unlikely cases.
  // We do know that:
  // - Address is set, and doesn't contain the LOCKED bit.
  // - If address refers to the same object as addr, then he -> light_thr_id
  //   refers to this thread, and count is valid.
  // - The case in which we held the lightweight lock has been
  //   completely handled, except for the REQUEST_CONVERSION case.
  //   
  if ((address & ~FLAGS) == addr)
    {
      // The lightweight lock is assigned to this object.
      // Thus we must be in the REQUEST_CONVERSION case.
      if (0 != count)
        {
	  // Defer conversion until we exit completely.
	  he -> light_count = count - 1;
	  return;
        }
      JvAssert(he -> light_thr_id == self);
      JvAssert(address & REQUEST_CONVERSION);
      // Conversion requested
      // Convert now.
      if (!compare_and_swap(&(he -> address), address, address | LOCKED))
	goto retry;
      heavy_lock *hl = find_heavy(addr, he);
      JvAssert (0 != hl);
		// Requestor created it.
      he -> light_count = 0;
      JvAssert(he -> heavy_count > 0);
	  	// was incremented by requestor.
      _Jv_MutexLock(&(hl->si.mutex));
	// Release the he lock after acquiring the mutex.
	// Otherwise we can accidentally
	// notify a thread that has already seen a heavyweight
	// lock.
      he -> light_thr_id = INVALID_THREAD_ID;
      release_set(&(he -> address), HEAVY);
      LOG(PROMOTE, address, self);
	  	// lightweight lock now unused.
      _Jv_CondNotifyAll(&(hl->si.condition), &(hl->si.mutex));
      _Jv_MutexUnlock(&(hl->si.mutex));
      // heavy_count was already incremented by original requestor.
      keep_live(addr);
      return;
    }
  // lightweight lock not for this object.
  JvAssert(!(address & LOCKED));
  JvAssert((address & ~FLAGS) != addr);
  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
	goto retry;
  heavy_lock *hl = find_heavy(addr, he);
  if (NULL == hl)
    {
#     ifdef LOCK_DEBUG
	fprintf(stderr, "Failed to find heavyweight lock for addr 0x%lx"
			" pid = %d\n", addr, getpid());
	print_he(he);
	for(;;) {}
#     endif
      release_set(&(he -> address), address);
      throw new java::lang::IllegalMonitorStateException(
			JvNewStringLatin1("current thread not owner"));
    }
  JvAssert(address & HEAVY);
  count = he -> heavy_count;
  JvAssert(count > 0);
  --count;
  he -> heavy_count = count;
  if (0 == count)
    {
      const unsigned test_freq = 16;  // Power of 2
      static volatile unsigned counter = 0;
      unsigned my_counter = counter;

      counter = my_counter + 1;
      if (my_counter%test_freq == 0)
	{
	  // Randomize the interval length a bit.
	    counter = my_counter + (my_counter >> 4) % (test_freq/2);
	  // Unlock mutex first, to avoid self-deadlock, or worse.
          _Jv_MutexUnlock(&(hl->si.mutex));
	  maybe_remove_all_heavy(he, address &~HEAVY);
    				// release lock bit, preserving
				// REQUEST_CONVERSION
    				// and object address.
	}
      else
        {
          release_set(&(he -> address), address &~HEAVY);
          _Jv_MutexUnlock(&(hl->si.mutex));
  			// Unlock after releasing the lock bit, so that
  			// we don't switch to another thread prematurely.
	}
    } 
  else
    {
      release_set(&(he -> address), address);
      _Jv_MutexUnlock(&(hl->si.mutex));
    }
  LOG(REL_HEAVY, addr, self);
  keep_live(addr);
}     

// Return false if obj's monitor is held by the current thread
bool
_Jv_ObjectCheckMonitor (jobject obj)
{
#ifdef JV_LINKER_CANNOT_8BYTE_ALIGN_STATICS
  obj_addr_t addr = (obj_addr_t)obj & ~((obj_addr_t)FLAGS);
#else
  obj_addr_t addr = (obj_addr_t)obj;
#endif
  obj_addr_t address;
  unsigned hash = JV_SYNC_HASH(addr);
  hash_entry * he = light_locks + hash;

  JvAssert(!(addr & FLAGS));
  address = he -> address;
  // Try it the easy way first:
    if (address == 0) return true;
    _Jv_ThreadId_t self = _Jv_ThreadSelf();
    if ((address & ~(HEAVY | REQUEST_CONVERSION)) == addr)
	// Fails if entry is LOCKED.
	// I can't asynchronously become or stop being the holder.
	return he -> light_thr_id != self;
retry:
  // Acquire the hash table entry lock
  address &= ~LOCKED;
  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
    {
      wait_unlocked(he);
      goto retry;
    }

  bool not_mine;

  if ((address & ~FLAGS) == addr)
    not_mine = (he -> light_thr_id != self);
  else
    {
      heavy_lock* hl = find_heavy(addr, he);
      not_mine = hl ? _Jv_MutexCheckMonitor(&hl->si.mutex) : true;
    }

  release_set(&(he -> address), address);	// unlock hash entry
  return not_mine;
}

// The rest of these are moderately thin veneers on _Jv_Cond ops.
// The current version of Notify might be able to make the pthread
// call AFTER releasing the lock, thus saving some context switches??

void
java::lang::Object::wait (jlong timeout, jint nanos)
{
#ifdef JV_LINKER_CANNOT_8BYTE_ALIGN_STATICS
  obj_addr_t addr = (obj_addr_t)this & ~((obj_addr_t)FLAGS);
#else
  obj_addr_t addr = (obj_addr_t)this;
#endif
  _Jv_ThreadId_t self = _Jv_ThreadSelf();
  unsigned hash = JV_SYNC_HASH(addr);
  hash_entry * he = light_locks + hash;
  unsigned count;
  obj_addr_t address;
  heavy_lock *hl;
    
  if (__builtin_expect (timeout < 0 || nanos < 0 || nanos > 999999, false))
    throw new IllegalArgumentException;
retry:
  address = he -> address;
  address &= ~LOCKED;
  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
    {
      wait_unlocked(he);
      goto retry;
    }
  // address did not have the lock bit set.  We now hold the lock on he.
  if ((address & ~FLAGS) == addr)
    {
      // Convert to heavyweight.
	if (he -> light_thr_id != self)
	  {
#	    ifdef LOCK_DEBUG
	      fprintf(stderr, "Found wrong lightweight lock owner in wait "
			      "address = 0x%lx pid = %d\n", address, getpid());
	      print_he(he);
	      for(;;) {}
#	    endif
	    release_set(&(he -> address), address);
	    throw new IllegalMonitorStateException (JvNewStringLatin1 
                          ("current thread not owner"));
	  }
	count = he -> light_count;
	hl = get_heavy(addr, he);
	he -> light_count = 0;
	he -> heavy_count += count + 1;
	for (unsigned i = 0; i <= count; ++i)
	  _Jv_MutexLock(&(hl->si.mutex));
	// Again release the he lock after acquiring the mutex.
        he -> light_thr_id = INVALID_THREAD_ID;
	release_set(&(he -> address), HEAVY);  // lightweight lock now unused.
	LOG(PROMOTE2, addr, self);
	if (address & REQUEST_CONVERSION)
	  _Jv_CondNotifyAll (&(hl->si.condition), &(hl->si.mutex));
	  // Since we do this before we do a CondWait, we guarantee that
	  // threads waiting on requested conversion are awoken before
	  // a real wait on the same condition variable.
	  // No other notification can occur in the interim, since
	  // we hold the heavy lock, and notifications are made
	  // without acquiring it.
    }
  else /* We should hold the heavyweight lock. */
    {
      hl = find_heavy(addr, he);
      release_set(&(he -> address), address);
      if (0 == hl)
	{
#	  ifdef LOCK_DEBUG
	    fprintf(stderr, "Couldn't find heavy lock in wait "
		 	    "addr = 0x%lx pid = %d\n", addr, getpid());
	    print_he(he);
	    for(;;) {}
#	  endif
	  throw new IllegalMonitorStateException (JvNewStringLatin1 
                          ("current thread not owner"));
	}
      JvAssert(address & HEAVY);
    }
  LOG(WAIT_START, addr, self);
  switch (_Jv_CondWait (&(hl->si.condition), &(hl->si.mutex), timeout, nanos))
    {
      case _JV_NOT_OWNER:
	throw new IllegalMonitorStateException (JvNewStringLatin1 
                          ("current thread not owner"));        
      case _JV_INTERRUPTED:
	if (Thread::interrupted ())
	  throw new InterruptedException;        
    }
  LOG(WAIT_END, addr, self);
}

void
java::lang::Object::notify (void)
{
#ifdef JV_LINKER_CANNOT_8BYTE_ALIGN_STATICS
  obj_addr_t addr = (obj_addr_t)this & ~((obj_addr_t)FLAGS);
#else
  obj_addr_t addr = (obj_addr_t)this;
#endif
  _Jv_ThreadId_t self = _Jv_ThreadSelf();
  unsigned hash = JV_SYNC_HASH(addr);
  hash_entry * he = light_locks + hash;
  heavy_lock *hl;
  obj_addr_t address;
  int result;

retry:
  address = ((he -> address) & ~LOCKED);
  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
    {
      wait_unlocked(he);
      goto retry;
    }
  if ((address & ~FLAGS) == addr && he -> light_thr_id == self)
    {
      // We hold lightweight lock.  Since it has not
      // been inflated, there are no waiters.
      release_set(&(he -> address), address);	// unlock
      return;
    }
  hl = find_heavy(addr, he);
  // Hl can't disappear since we point to the underlying object.
  // It's important that we release the lock bit before the notify, since
  // otherwise we will try to wake up the target while we still hold the
  // bit.  This results in lock bit contention, which we don't handle
  // terribly well.
  release_set(&(he -> address), address); // unlock
  if (0 == hl)
    {
      throw new IllegalMonitorStateException(JvNewStringLatin1 
                                              ("current thread not owner"));
      return;
    }
  // We know that we hold the heavyweight lock at this point,
  // and the lightweight lock is not in use.
  result = _Jv_CondNotify(&(hl->si.condition), &(hl->si.mutex));
  LOG(NOTIFY, addr, self);
  keep_live(addr);
  if (__builtin_expect (result, 0))
    throw new IllegalMonitorStateException(JvNewStringLatin1 
                                              ("current thread not owner"));
}

void
java::lang::Object::notifyAll (void)
{
#ifdef JV_LINKER_CANNOT_8BYTE_ALIGN_STATICS
  obj_addr_t addr = (obj_addr_t)this & ~((obj_addr_t)FLAGS);
#else
  obj_addr_t addr = (obj_addr_t)this;
#endif
  _Jv_ThreadId_t self = _Jv_ThreadSelf();
  unsigned hash = JV_SYNC_HASH(addr);
  hash_entry * he = light_locks + hash;
  heavy_lock *hl;
  obj_addr_t address;
  int result;

retry:
  address = (he -> address) & ~LOCKED;
  if (!compare_and_swap(&(he -> address), address, address | LOCKED))
    {
      wait_unlocked(he);
      goto retry;
    }
  hl = find_heavy(addr, he);
  if ((address & ~FLAGS) == addr && he -> light_thr_id == self)
    {
      // We hold lightweight lock.  Since it has not
      // been inflated, there are no waiters.
      release_set(&(he -> address), address);	// unlock
      return;
    }
  release_set(&(he -> address), address); // unlock
  if (0 == hl)
    {
      throw new IllegalMonitorStateException(JvNewStringLatin1 
                                              ("current thread not owner"));
    }
  result = _Jv_CondNotifyAll(&(hl->si.condition), &(hl->si.mutex));
  LOG(NOTIFY_ALL, addr, self);
  if (__builtin_expect (result, 0))
    throw new IllegalMonitorStateException(JvNewStringLatin1 
                                              ("current thread not owner"));
}

// This is declared in Java code and in Object.h.
// It should never be called with JV_HASH_SYNCHRONIZATION
void
java::lang::Object::sync_init (void)
{
  throw new IllegalMonitorStateException(JvNewStringLatin1 
                                              ("internal error: sync_init"));
}

// This is called on startup and declared in Object.h.
// For now we just make it a no-op.
void
_Jv_InitializeSyncMutex (void)
{
}

#endif /* JV_HASH_SYNCHRONIZATION */