ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) {

   // Inflate mutates the heap ...

   // Relaxing assertion for bug 6320749.

   assert (Universe::verify_in_progress() ||

           !SafepointSynchronize::is_at_safepoint(), "invariant") ;

   for (;;) {//自旋

       const markOop mark = object->mark() ;

       assert (!mark->has_bias_pattern(), "invariant") ;

       // The mark can be in one of the following states:

       // *  Inflated     - just return

       // *  Stack-locked - coerce it to inflated

       // *  INFLATING    - busy wait for conversion to complete

       // *  Neutral      - aggressively inflate the object.

       // *  BIASED       - Illegal.  We should never see this

       // CASE: inflated已膨胀，即重量级锁

       if (mark->has_monitor()) {//判断当前是否为重量级锁

           ObjectMonitor * inf = mark->monitor() ;//获取指向ObjectMonitor的指针

           assert (inf->header()->is_neutral(), "invariant");

           assert (inf->object() == object, "invariant") ;

           assert (ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid");

           return inf ;

       }

       // CASE: inflation in progress - inflating over a stack-lock.膨胀等待（其他线程正在从轻量级锁转为膨胀锁）

       // Some other thread is converting from stack-locked to inflated.

       // Only that thread can complete inflation -- other threads must wait.

       // The INFLATING value is transient.

       // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish.

       // We could always eliminate polling by parking the thread on some auxiliary list.

       if (mark == markOopDesc::INFLATING()) {

          TEVENT (Inflate: spin while INFLATING) ;

          ReadStableMark(object) ;

          continue ;

       }

       // CASE: stack-locked栈锁（轻量级锁）

       // Could be stack-locked either by this thread or by some other thread.

       //

       // Note that we allocate the objectmonitor speculatively, _before_ attempting

       // to install INFLATING into the mark word.  We originally installed INFLATING,

       // allocated the objectmonitor, and then finally STed the address of the

       // objectmonitor into the mark.  This was correct, but artificially lengthened

       // the interval in which INFLATED appeared in the mark, thus increasing

       // the odds of inflation contention.

       //

       // We now use per-thread private objectmonitor free lists.

       // These list are reprovisioned from the global free list outside the

       // critical INFLATING...ST interval.  A thread can transfer

       // multiple objectmonitors en-mass from the global free list to its local free list.

       // This reduces coherency traffic and lock contention on the global free list.

       // Using such local free lists, it doesn't matter if the omAlloc() call appears

       // before or after the CAS(INFLATING) operation.

       // See the comments in omAlloc().

       if (mark->has_locker()) {

           ObjectMonitor * m = omAlloc (Self) ;//获取一个可用的ObjectMonitor

           // Optimistically prepare the objectmonitor - anticipate successful CAS

           // We do this before the CAS in order to minimize the length of time

           // in which INFLATING appears in the mark.

           m->Recycle();

           m->_Responsible  = NULL ;

           m->OwnerIsThread =  ;

           m->_recursions   =  ;

           m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ;   // Consider: maintain by type/class

           markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ;

           if (cmp != mark) {//CAS失败//CAS失败，说明冲突了，自旋等待//CAS失败，说明冲突了，自旋等待//CAS失败，说明冲突了，自旋等待

              omRelease (Self, m, true) ;//释放监视器锁

              continue ;       // Interference -- just retry

           }

           // We've successfully installed INFLATING (0) into the mark-word.

           // This is the only case where 0 will appear in a mark-work.

           // Only the singular thread that successfully swings the mark-word

           // to 0 can perform (or more precisely, complete) inflation.

           //

           // Why do we CAS a 0 into the mark-word instead of just CASing the

           // mark-word from the stack-locked value directly to the new inflated state?

           // Consider what happens when a thread unlocks a stack-locked object.

           // It attempts to use CAS to swing the displaced header value from the

           // on-stack basiclock back into the object header.  Recall also that the

           // header value (hashcode, etc) can reside in (a) the object header, or

           // (b) a displaced header associated with the stack-lock, or (c) a displaced

           // header in an objectMonitor.  The inflate() routine must copy the header

           // value from the basiclock on the owner's stack to the objectMonitor, all

           // the while preserving the hashCode stability invariants.  If the owner

           // decides to release the lock while the value is 0, the unlock will fail

           // and control will eventually pass from slow_exit() to inflate.  The owner

           // will then spin, waiting for the 0 value to disappear.   Put another way,

           // the 0 causes the owner to stall if the owner happens to try to

           // drop the lock (restoring the header from the basiclock to the object)

           // while inflation is in-progress.  This protocol avoids races that might

           // would otherwise permit hashCode values to change or "flicker" for an object.

           // Critically, while object->mark is 0 mark->displaced_mark_helper() is stable.

           // 0 serves as a "BUSY" inflate-in-progress indicator.

           // fetch the displaced mark from the owner's stack.

           // The owner can't die or unwind past the lock while our INFLATING

           // object is in the mark.  Furthermore the owner can't complete

           // an unlock on the object, either.

           markOop dmw = mark->displaced_mark_helper() ;

           assert (dmw->is_neutral(), "invariant") ;

           //CAS成功，设置ObjectMonitor的_header、_owner和_object等

           // Setup monitor fields to proper values -- prepare the monitor

           m->set_header(dmw) ;

           // Optimization: if the mark->locker stack address is associated

           // with this thread we could simply set m->_owner = Self and

           // m->OwnerIsThread = 1. Note that a thread can inflate an object

           // that it has stack-locked -- as might happen in wait() -- directly

           // with CAS.  That is, we can avoid the xchg-NULL .... ST idiom.

           m->set_owner(mark->locker());

           m->set_object(object);

           // TODO-FIXME: assert BasicLock->dhw != 0.

           // Must preserve store ordering. The monitor state must

           // be stable at the time of publishing the monitor address.

           guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ;

           object->release_set_mark(markOopDesc::encode(m));

           // Hopefully the performance counters are allocated on distinct cache lines

           // to avoid false sharing on MP systems ...

           if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ;

           TEVENT(Inflate: overwrite stacklock) ;

           if (TraceMonitorInflation) {

             if (object->is_instance()) {

               ResourceMark rm;

               tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",

                 (void *) object, (intptr_t) object->mark(),

                 object->klass()->external_name());

             }

           }

           return m ;

       }

       // CASE: neutral 无锁

       // TODO-FIXME: for entry we currently inflate and then try to CAS _owner.

       // If we know we're inflating for entry it's better to inflate by swinging a

       // pre-locked objectMonitor pointer into the object header.   A successful

       // CAS inflates the object *and* confers ownership to the inflating thread.

       // In the current implementation we use a 2-step mechanism where we CAS()

       // to inflate and then CAS() again to try to swing _owner from NULL to Self.

       // An inflateTry() method that we could call from fast_enter() and slow_enter()

       // would be useful.

       assert (mark->is_neutral(), "invariant");

       ObjectMonitor * m = omAlloc (Self) ;

       // prepare m for installation - set monitor to initial state

       m->Recycle();

       m->set_header(mark);

       m->set_owner(NULL);

       m->set_object(object);

       m->OwnerIsThread =  ;

       m->_recursions   =  ;

       m->_Responsible  = NULL ;

       m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ;       // consider: keep metastats by type/class

       if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) {

           m->set_object (NULL) ;

           m->set_owner  (NULL) ;

           m->OwnerIsThread =  ;

           m->Recycle() ;

           omRelease (Self, m, true) ;

           m = NULL ;

           continue ;

           // interference - the markword changed - just retry.

           // The state-transitions are one-way, so there's no chance of

           // live-lock -- "Inflated" is an absorbing state.

       }

       // Hopefully the performance counters are allocated on distinct

       // cache lines to avoid false sharing on MP systems ...

       if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ;

       TEVENT(Inflate: overwrite neutral) ;

       if (TraceMonitorInflation) {

         if (object->is_instance()) {

           ResourceMark rm;

           tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",

             (void *) object, (intptr_t) object->mark(),

             object->klass()->external_name());

         }

       }

       return m ;

   }

 }

膨胀过程的实现比较复杂，大概实现过程如下：
1、整个膨胀过程在自旋下完成；
2、mark->has_monitor()方法判断当前是否为重量级锁（上图18-25行），即Mark Word的锁标识位为 10，如果当前状态为重量级锁，执行步骤（3），否则执行步骤（4）；
3、mark->monitor()方法获取指向ObjectMonitor的指针，并返回，说明膨胀过程已经完成；
4、如果当前锁处于膨胀中（上图33-37行），说明该锁正在被其它线程执行膨胀操作，则当前线程就进行自旋等待锁膨胀完成，这里需要注意一点，虽然是自旋操作，但不会一直占用cpu资源，每隔一段时间会通过os::NakedYield方法放弃cpu资源，或通过park方法挂起；如果其他线程完成锁的膨胀操作，则退出自旋并返回；
5、如果当前是轻量级锁状态（上图58-138行），即锁标识位为 00，膨胀过程如下：

1、通过CAS尝试把monitor的_owner字段设置为当前线程；
2、如果设置之前的_owner指向当前线程，说明当前线程再次进入monitor，即重入锁，执行_recursions ++ ，记录重入的次数；
3、如果之前的_owner指向的地址在当前线程中，这种描述有点拗口，换一种说法：之前_owner指向的BasicLock在当前线程栈上，说明当前线程是第一次进入该monitor，设置_recursions为1，_owner为当前线程，该线程成功获得锁并返回；
4、如果获取锁失败，则等待锁的释放；

1、当前线程被封装成ObjectWaiter对象node，状态设置成ObjectWaiter::TS_CXQ；
2、在for循环中，通过CAS把node节点push到_cxq列表中，同一时刻可能有多个线程把自己的node节点push到_cxq列表中；
3、node节点push到_cxq列表之后，通过自旋尝试获取锁，如果还是没有获取到锁，则通过park将当前线程挂起，等待被唤醒，实现如下：

 int ObjectMonitor::TryLock (Thread * Self) {

    for (;;) {

       void * own = _owner ;

       if (own != NULL) return  ;

       if (Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) {//CAS成功，获取锁

          // Either guarantee _recursions == 0 or set _recursions = 0.

          assert (_recursions == , "invariant") ;

          assert (_owner == Self, "invariant") ;

          // CONSIDER: set or assert that OwnerIsThread == 1

          return  ;

       }

       // The lock had been free momentarily, but we lost the race to the lock.

       // Interference -- the CAS failed.

       // We can either return -1 or retry.

       // Retry doesn't make as much sense because the lock was just acquired.

       if (true) return - ;

    }

 }