--- old/src/hotspot/share/runtime/biasedLocking.cpp	Tue Nov 21 14:38:30 2017
+++ new/src/hotspot/share/runtime/biasedLocking.cpp	Tue Nov 21 14:38:29 2017
@@ -215,12 +215,8 @@
   if (requesting_thread == biased_thread) {
     thread_is_alive = true;
   } else {
-    for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
-      if (cur_thread == biased_thread) {
-        thread_is_alive = true;
-        break;
-      }
-    }
+    ThreadsListHandle tlh;
+    thread_is_alive = tlh.includes(biased_thread);
   }
   if (!thread_is_alive) {
     if (allow_rebias) {
--- old/src/hotspot/share/runtime/memprofiler.cpp	Tue Nov 21 14:38:33 2017
+++ new/src/hotspot/share/runtime/memprofiler.cpp	Tue Nov 21 14:38:32 2017
@@ -52,8 +52,6 @@
 
 
 void MemProfilerTask::task() {
-  // Get thread lock to provide mutual exclusion, and so we can iterate safely over the thread list.
-  MutexLocker mu(Threads_lock);
   MemProfiler::do_trace();
 }
 
--- 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();
   }
 
--- old/src/hotspot/share/runtime/thread.hpp	Tue Nov 21 14:38:39 2017
+++ new/src/hotspot/share/runtime/thread.hpp	Tue Nov 21 14:38:38 2017
@@ -1176,7 +1176,7 @@
 
   // JavaThread termination and lifecycle support:
   void smr_delete();
-  bool on_thread_list() { return _on_thread_list; }
+  bool on_thread_list() const { return _on_thread_list; }
   void set_on_thread_list() { _on_thread_list = true; }
 
   // thread has called JavaThread::exit() or is terminated
@@ -1187,7 +1187,7 @@
   bool check_is_terminated(TerminatedTypes l_terminated) const {
     return l_terminated != _not_terminated && l_terminated != _thread_exiting;
   }
-  bool is_terminated();
+  bool is_terminated() const;
   void set_terminated(TerminatedTypes t);
   // special for Threads::remove() which is static:
   void set_terminated_value();
--- old/src/hotspot/share/runtime/thread.inline.hpp	Tue Nov 21 14:38:42 2017
+++ new/src/hotspot/share/runtime/thread.inline.hpp	Tue Nov 21 14:38:41 2017
@@ -192,12 +192,12 @@
   return l_terminated == _thread_exiting || check_is_terminated(l_terminated);
 }
 
-inline bool JavaThread::is_terminated() {
+inline bool JavaThread::is_terminated() const {
   // Use load-acquire so that setting of _terminated by
   // JavaThread::exit() is seen more quickly.
   TerminatedTypes l_terminated = (TerminatedTypes)
       OrderAccess::load_acquire((volatile jint *) &_terminated);
-  return check_is_terminated(_terminated);
+  return check_is_terminated(l_terminated);
 }
 
 inline void JavaThread::set_terminated(TerminatedTypes t) {
--- old/src/hotspot/share/runtime/vm_operations.hpp	Tue Nov 21 14:38:45 2017
+++ new/src/hotspot/share/runtime/vm_operations.hpp	Tue Nov 21 14:38:44 2017
@@ -403,8 +403,8 @@
   VM_FindDeadlocks(outputStream* st) : _concurrent_locks(true), _out(st), _deadlocks(NULL) {};
   ~VM_FindDeadlocks();
 
-  DeadlockCycle* result()               { return _deadlocks; };
-  VMOp_Type type() const                { return VMOp_FindDeadlocks; }
+  DeadlockCycle* result()      { return _deadlocks; };
+  VMOp_Type type() const       { return VMOp_FindDeadlocks; }
   void doit();
   bool doit_prologue();
 };