--- old/src/hotspot/share/runtime/thread.cpp	Tue Nov 21 14:38:36 2017
+++ new/src/hotspot/share/runtime/thread.cpp	Tue Nov 21 14:38:35 2017
@@ -3429,10 +3429,15 @@
 // ======= Threads ========
 
 // The Threads class links together all active threads, and provides
-// operations over all threads.  It is protected by its own Mutex
-// lock, which is also used in other contexts to protect thread
-// operations from having the thread being operated on from exiting
-// and going away unexpectedly (e.g., safepoint synchronization)
+// operations over all threads. It is protected by the Threads_lock,
+// which is also used in other global contexts like safepointing.
+// ThreadsListHandles are used to safely perform operations on one
+// or more threads without the risk of the thread exiting during the
+// operation.
+//
+// Note: The Threads_lock is currently more widely used than we
+// would like. We are actively migrating Threads_lock uses to other
+// mechanisms in order to reduce Threads_lock contention.
 
 JavaThread*           Threads::_thread_list = NULL;
 int                   Threads::_number_of_threads = 0;
@@ -4891,8 +4896,8 @@
     // Retry the whole scenario.
   }
 
-  // If someone set a handshake on us just as we entered exit path, we simple cancel it.
   if (ThreadLocalHandshakes) {
+    // The thread is about to be deleted so cancel any handshake.
     thread->cancel_handshake();
   }