--- old/src/hotspot/share/runtime/globals.hpp	2017-10-23 17:10:24.540123033 +0200
+++ new/src/hotspot/share/runtime/globals.hpp	2017-10-23 17:10:24.090108244 +0200
@@ -605,7 +605,7 @@
           "Clean the chunk pool asynchronously")                            \
                                                                             \
   product(bool, ThreadLocalHandshakes, false,                               \
-          "Enable use of thread local handshake operations")                \
+          "Use thread-local polls instead of global poll for safepoints.")  \
           constraint(ThreadLocalHandshakesConstraintFunc,AfterErgo)         \
                                                                             \
   diagnostic(uint, HandshakeTimeout, 0,                                     \
--- old/src/hotspot/share/runtime/handshake.cpp	2017-10-23 17:10:26.644192178 +0200
+++ new/src/hotspot/share/runtime/handshake.cpp	2017-10-23 17:10:26.220178244 +0200
@@ -75,6 +75,9 @@
     target->set_handshake_operation(_op);
   }
 
+  // This method returns true for threads completed their operation
+  // and true for threads canceled their operation.
+  // A cancellation can happen if the thread is exiting.
   bool poll_for_completed_thread() { return _op->thread_has_completed(); }
 
   bool handshake_has_timed_out(jlong start_time);
--- old/src/hotspot/share/runtime/safepointMechanism.inline.hpp	2017-10-23 17:10:28.406250084 +0200
+++ new/src/hotspot/share/runtime/safepointMechanism.inline.hpp	2017-10-23 17:10:27.996236610 +0200
@@ -39,11 +39,10 @@
 }
 
 bool SafepointMechanism::local_poll(Thread* thread) {
-  // Mutexes can be taken but none JavaThread. These cannot have handshakes
-  // operation but they must stop for safepoints.
   if (thread->is_Java_thread()) {
     return local_poll_armed((JavaThread*)thread);
   } else {
+    // If the poll is on a non-java thread we can only check the global state.
     return global_poll();
   }
 }