natobject.cc

俄罗斯高人Mamaich的Pocket gcc编译器（运行在PocketPC上）的全部源代码。

  address &= ~LOCKED;
  if (!compare_and_swap(&(he -> address), address, (address | LOCKED )))
    {
      wait_unlocked(he);
      goto retry;
    }
  if ((address & ~(HEAVY | REQUEST_CONVERSION)) == 0)
    {
      // Either was_heavy is true, or something changed out from under us,
      // since the initial test for 0 failed.
      assert(!(address & REQUEST_CONVERSION));
	// Can't convert a nonexistent lightweight lock.
      heavy_lock *hl;
      hl = (was_heavy? find_heavy(addr, he) : 0);
      if (0 == hl)
        {
	  // It is OK to use the lighweight lock, since either the
	  // heavyweight lock does not exist, or none of the
	  // heavyweight locks currently exist.  Future threads
	  // trying to acquire the lock will see the lightweight
	  // one first and use that.
	  he -> light_thr_id = self;  // OK, since nobody else can hold
				      // light lock or do this at the same time.
	  assert(he -> light_count == 0);
	  assert(was_heavy == (he -> address & HEAVY));
	  release_set(&(he -> address), (addr | was_heavy));
        }
      else
	{
	  // Must use heavy lock.
	  ++ (he -> heavy_count);
	  assert(0 == (address & ~HEAVY));
          release_set(&(he -> address), HEAVY);
          _Jv_MutexLock(&(hl->si.mutex));
	  keep_live(addr);
        }
      return;
    }
  // Lightweight lock is held, but does not correspond to this object.
  // We hold the lock on the hash entry, and he -> address can't
  // change from under us.  Neither can the chain of heavy locks.
    {
      assert(0 == he -> heavy_count || (address & HEAVY));
      heavy_lock *hl = get_heavy(addr, he);
      ++ (he -> heavy_count);
      release_set(&(he -> address), address | HEAVY);
      _Jv_MutexLock(&(hl->si.mutex));
      keep_live(addr);
    }
}


void
_Jv_MonitorExit (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
  _Jv_ThreadId_t self = _Jv_ThreadSelf();
  unsigned hash = JV_SYNC_HASH(addr);
  hash_entry * he = light_locks + hash;
  _Jv_ThreadId_t light_thr_id;
  unsigned count;
  obj_addr_t address;

retry:
  light_thr_id = he -> light_thr_id;
  // Unfortunately, it turns out we always need to read the address
  // first.  Even if we are going to update it with compare_and_swap,
  // we need to reset light_thr_id, and that's not safe unless we know
  // that we hold the lock.
  address = he -> address;
  // First the (relatively) fast cases:
  if (__builtin_expect(light_thr_id == self, true))
    // Above must fail if addr == 0 .
    {
      count = he -> light_count;
      if (__builtin_expect((address & ~HEAVY) == addr, true))
	{
          if (count != 0)
            {
	      // We held the lightweight lock all along.  Thus the values
	      // we saw for light_thr_id and light_count must have been valid. 
	      he -> light_count = count - 1;
	      return;
            }
	  else
	    {
	      // We hold the lightweight lock once.
	      he -> light_thr_id = INVALID_THREAD_ID;
              if (compare_and_swap_release(&(he -> address), address,
					   address & HEAVY))
	        return;
	      else
		{
	          he -> light_thr_id = light_thr_id; // Undo prior damage.
	          goto retry;
	        }
            }
        }
      // else lock is not for this address, conversion is requested,
      // or the lock bit in the address field is set.
    }
  else
    {
      if (__builtin_expect(!addr, false))
	throw new java::lang::NullPointerException;
      if ((address & ~(HEAVY | REQUEST_CONVERSION)) == addr)
	{
#	  ifdef LOCK_DEBUG
	    fprintf(stderr, "Lightweight lock held by other thread\n\t"
			    "light_thr_id = 0x%lx, self = 0x%lx, "
			    "address = 0x%lx, pid = %d\n",
			    light_thr_id, self, address, getpid());
	    print_he(he);
	    for(;;) {}
#	  endif
	  // Someone holds the lightweight lock for this object, and
	  // it can't be us.
	  throw new java::lang::IllegalMonitorStateException(
			JvNewStringLatin1("current thread not owner"));
        }
      else
	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;
        }
      assert(he -> light_thr_id == self);
      assert(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);
      assert (0 != hl);
		// Requestor created it.
      he -> light_count = 0;
      assert(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);
	  	// 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.
  assert(!(address & LOCKED));
  assert((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
      throw new java::lang::IllegalMonitorStateException(
			JvNewStringLatin1("current thread not owner"));
    }
  assert(address & HEAVY);
  count = he -> heavy_count;
  assert(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));
    }
  keep_live(addr);
}     

// 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 does not have the lock bit set.  We 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.
	if (address & REQUEST_CONVERSION)
	  _Jv_CondNotify (&(hl->si.condition), &(hl->si.mutex));
    }
  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"));
	}
      assert(address & HEAVY);
    }
  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;        
    }
}

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 thee 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;
    }
  result = _Jv_CondNotify(&(hl->si.condition), &(hl->si.mutex));
  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));
  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 */