--- /dev/null	2017-10-10 14:31:03.217645158 +0200
+++ new/src/hotspot/share/runtime/handshake.cpp	2017-10-11 15:25:51.150998552 +0200
@@ -0,0 +1,349 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/resourceArea.hpp"
+#include "runtime/handshake.hpp"
+#include "runtime/interfaceSupport.hpp"
+#include "runtime/osThread.hpp"
+#include "runtime/semaphore.hpp"
+#include "runtime/task.hpp"
+#include "runtime/timerTrace.hpp"
+#include "runtime/thread.hpp"
+#include "runtime/vmThread.hpp"
+#include "utilities/formatBuffer.hpp"
+#include "utilities/preserveException.hpp"
+
+#define ALL_JAVA_THREADS(X) for (JavaThread* X = Threads::first(); X; X = X->next())
+
+class HandshakeOperation: public StackObj {
+public:
+  virtual void do_handshake(JavaThread* thread) = 0;
+  virtual void cancel_handshake(JavaThread* thread) = 0;
+};
+
+class HandshakeThreadsOperation: public HandshakeOperation {
+  Semaphore _done;
+  ThreadClosure* _thread_cl;
+
+public:
+  HandshakeThreadsOperation(ThreadClosure* cl) : _done(0), _thread_cl(cl) {}
+  void do_handshake(JavaThread* thread);
+  void cancel_handshake(JavaThread* thread) { _done.signal(); };
+
+  bool thread_has_completed() { return _done.trywait(); }
+};
+
+class VM_Handshake: public VM_Operation {
+  HandshakeThreadsOperation* const _op;
+  const jlong _handshake_timeout;
+ public:
+  bool evaluate_at_safepoint() const { return false; }
+
+  bool evaluate_concurrently() const { return false; }
+
+ protected:
+
+  VM_Handshake(HandshakeThreadsOperation* op) :
+      _op(op),
+      _handshake_timeout(TimeHelper::millis_to_counter(HandshakeTimeout)) {}
+
+  void set_handshake(JavaThread* target) {
+    target->set_handshake_operation(_op);
+  }
+
+  bool poll_for_completed_thread() { return _op->thread_has_completed(); }
+
+  bool handshake_has_timed_out(jlong start_time);
+  static void handle_timeout();
+};
+
+bool VM_Handshake::handshake_has_timed_out(jlong start_time) {
+  // Check if handshake operation has timed out
+  if (_handshake_timeout > 0) {
+    return os::elapsed_counter() >= (start_time + _handshake_timeout);
+  }
+  return false;
+}
+
+void VM_Handshake::handle_timeout() {
+  LogStreamHandle(Warning, handshake) log_stream;
+  MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+  ALL_JAVA_THREADS(thr) {
+    if (thr->has_handshake()) {
+      log_stream.print("Thread " PTR_FORMAT " has not cleared its handshake op", p2i(thr));
+      thr->print_thread_state_on(&log_stream);
+    }
+  }
+  log_stream.flush();
+  fatal("Handshake operation timed out");
+}
+
+
+class VM_HandshakeOneThread: public VM_Handshake {
+  JavaThread* _target;
+  bool _thread_alive;
+ public:
+  VM_HandshakeOneThread(HandshakeThreadsOperation* op, JavaThread* target) :
+    VM_Handshake(op), _target(target), _thread_alive(false) {}
+
+  void doit() {
+    TraceTime timer("Performing single-target operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
+
+    {
+      MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+      if (Threads::includes(_target)) {
+        set_handshake(_target);
+        _thread_alive = true;
+      }
+    }
+
+    if (!_thread_alive) {
+      return;
+    }
+
+    if (!UseMembar) {
+      os::serialize_thread_states();
+    }
+
+    log_trace(handshake)("Thread signaled, begin processing by VMThtread");
+    jlong start_time = os::elapsed_counter();
+    do {
+      if (handshake_has_timed_out(start_time)) {
+        handle_timeout();
+      }
+
+      MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+      _target->handshake_process_by_vmthread();
+
+    } while (!poll_for_completed_thread());
+  }
+
+  VMOp_Type type() const { return VMOp_HandshakeOneThread; }
+
+  bool thread_alive() const { return _thread_alive; }
+};
+
+class VM_HandshakeAllThreads: public VM_Handshake {
+ public:
+  VM_HandshakeAllThreads(HandshakeThreadsOperation* op) : VM_Handshake(op) {}
+
+  void doit() {
+    TraceTime timer("Performing operation (vmoperation doit)", TRACETIME_LOG(Info, handshake));
+
+    int number_of_threads_issued = -1;
+    int number_of_threads_completed = 0;
+    {
+      MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+      number_of_threads_issued = Threads::number_of_threads();
+
+      ALL_JAVA_THREADS(thr) {
+        set_handshake(thr);
+      }
+    }
+
+    if (!UseMembar) {
+      os::serialize_thread_states();
+    }
+
+    log_debug(handshake)("Threads signaled, begin processing blocked threads by VMThtread");
+    const jlong start_time = os::elapsed_counter();
+    do {
+      // Check if handshake operation has timed out
+      if (handshake_has_timed_out(start_time)) {
+        handle_timeout();
+      }
+
+      // Have VM thread perform the handshake operation for blocked threads.
+      // Observing a blocked state may of course be transient but the processing is guarded
+      // by semaphores and we optimistically begin by working on the blocked threads
+      {
+          MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+          ALL_JAVA_THREADS(thr) {
+            thr->handshake_process_by_vmthread();
+          }
+      }
+
+      while (poll_for_completed_thread()) {
+        number_of_threads_completed++;
+      }
+
+    } while (number_of_threads_issued != number_of_threads_completed);
+  }
+
+  VMOp_Type type() const { return VMOp_HandshakeAllThreads; }
+};
+
+class VM_HandshakeFallbackOperation : public VM_Operation {
+  ThreadClosure* _thread_cl;
+  Thread* _target_thread;
+  bool _all_threads;
+  bool _thread_alive;
+public:
+  VM_HandshakeFallbackOperation(ThreadClosure* cl) :
+      _thread_cl(cl), _target_thread(NULL), _all_threads(true), _thread_alive(true) {}
+  VM_HandshakeFallbackOperation(ThreadClosure* cl, Thread* target) :
+      _thread_cl(cl), _target_thread(target), _all_threads(false), _thread_alive(false) {}
+
+  void doit() {
+    ALL_JAVA_THREADS(t) {
+      if (_all_threads || t == _target_thread) {
+        if (t == _target_thread) {
+          _thread_alive = true;
+        }
+        _thread_cl->do_thread(t);
+      }
+    }
+  }
+
+  VMOp_Type type() const { return VMOp_HandshakeFallback; }
+  bool thread_alive() const { return _thread_alive; }
+};
+
+#undef ALL_JAVA_THREADS
+
+void HandshakeThreadsOperation::do_handshake(JavaThread* thread) {
+  ResourceMark rm;
+  FormatBufferResource message("Operation for thread " PTR_FORMAT ", is_vm_thread: %s",
+                               p2i(thread), BOOL_TO_STR(Thread::current()->is_VM_thread()));
+  TraceTime timer(message, TRACETIME_LOG(Debug, handshake, task));
+  _thread_cl->do_thread(thread);
+
+  // Use the semaphore to inform the VM thread that we have completed the operation
+  _done.signal();
+}
+
+void Handshake::execute(ThreadClosure* thread_cl) {
+  if (ThreadLocalHandshakes) {
+    HandshakeThreadsOperation cto(thread_cl);
+    VM_HandshakeAllThreads handshake(&cto);
+    VMThread::execute(&handshake);
+  } else {
+    VM_HandshakeFallbackOperation op(thread_cl);
+    VMThread::execute(&op);
+  }
+}
+
+bool Handshake::execute(ThreadClosure* thread_cl, JavaThread* target) {
+  if (ThreadLocalHandshakes) {
+    HandshakeThreadsOperation cto(thread_cl);
+    VM_HandshakeOneThread handshake(&cto, target);
+    VMThread::execute(&handshake);
+    return handshake.thread_alive();
+  } else {
+    VM_HandshakeFallbackOperation op(thread_cl, target);
+    VMThread::execute(&op);
+    return op.thread_alive();
+  }
+}
+
+HandshakeState::HandshakeState() : _operation(NULL), _semaphore(1), _vmthread_holds_semaphore(false), _thread_in_process_handshake(false) {}
+
+void HandshakeState::set_operation(JavaThread* target, HandshakeOperation* op) {
+  _operation = op;
+  SafepointMechanism::arm_local_poll(target);
+}
+
+void HandshakeState::clear_handshake(JavaThread* target) {
+  _operation = NULL;
+  SafepointMechanism::disarm_local_poll(target);
+}
+
+void HandshakeState::process_self_inner(JavaThread* thread) {
+  assert(Thread::current() == thread, "should call from thread");
+  CautiouslyPreserveExceptionMark pem(thread);
+  ThreadInVMForHandshake tivm(thread);
+  if (!_semaphore.trywait()) {
+    ThreadBlockInVM tbivm(thread);
+    _semaphore.wait();
+  }
+  if (has_operation()) {
+    HandshakeOperation* op = _operation;
+    clear_handshake(thread);
+    if (op != NULL) {
+      op->do_handshake(thread);
+    }
+  }
+  _semaphore.signal();
+}
+
+void HandshakeState::cancel_inner(JavaThread* thread) {
+  assert(Thread::current() == thread, "should call from thread");
+  assert(thread->thread_state() == _thread_in_vm, "must be in vm state");
+#ifdef DEBUG
+  {
+    MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
+    assert(!Threads::includes(thread), "java thread must not be on threads list");
+  }
+#endif
+  HandshakeOperation* op = _operation;
+  clear_handshake(thread);
+  if (op != NULL) {
+    op->cancel_handshake(thread);
+  }
+}
+
+bool HandshakeState::vmthread_can_process_handshake(JavaThread* target) {
+  return SafepointSynchronize::safepoint_safe(target, target->thread_state());
+}
+
+bool HandshakeState::claim_handshake_for_vmthread() {
+  if (_semaphore.trywait()) {
+    if (has_operation()) {
+      _vmthread_holds_semaphore = true;
+    } else {
+      _semaphore.signal();
+    }
+  }
+  return _vmthread_holds_semaphore;
+}
+
+void HandshakeState::process_by_vmthread(JavaThread* target) {
+  assert(Thread::current()->is_VM_thread(), "should call from vm thread");
+
+  if (!has_operation()) {
+    // JT has already cleared its handshake
+    return;
+  }
+
+  if (!vmthread_can_process_handshake(target)) {
+    // JT is observed in an unsafe state, it must notice the handshake itself
+    return;
+  }
+
+  // If we own the semaphore at this point and while owning the semaphore
+  // can observe a safe state the thread cannot possibly continue without
+  // getting caught by the semaphore.
+  if (claim_handshake_for_vmthread() && vmthread_can_process_handshake(target)) {
+    guarantee(!_semaphore.trywait(), "we should already own the semaphore");
+
+    _operation->do_handshake(target);
+    clear_handshake(target);
+    _vmthread_holds_semaphore = false;
+    // Release the thread
+    _semaphore.signal();
+  }
+}