--- /dev/null	2017-11-09 09:38:01.297999907 +0100
+++ new/src/hotspot/share/jfr/writers/jfrJavaEventWriter.cpp	2018-04-09 15:27:51.492654348 +0200
@@ -0,0 +1,242 @@
+/*
+ * Copyright (c) 2016, 2018, 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 "jni.h"
+#include "classfile/symbolTable.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "classfile/vmSymbols.hpp"
+#include "jfr/jni/jfrJavaSupport.hpp"
+#include "jfr/recorder/storage/jfrStorage.hpp"
+#include "jfr/utilities/jfrTypes.hpp"
+#include "jfr/writers/jfrJavaEventWriter.hpp"
+#include "oops/instanceKlass.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/fieldDescriptor.hpp"
+#include "runtime/handles.hpp"
+#include "runtime/jniHandles.inline.hpp"
+#include "runtime/thread.inline.hpp"
+#include "trace/traceMacros.hpp"
+
+static int start_pos_offset = invalid_offset;
+static int start_pos_address_offset = invalid_offset;
+static int current_pos_offset = invalid_offset;
+static int max_pos_offset = invalid_offset;
+static int max_event_size_offset = invalid_offset;
+static int notified_offset = invalid_offset;
+static int thread_id_offset = invalid_offset;
+static int valid_offset = invalid_offset;
+
+static bool find_field(InstanceKlass* ik,
+                       Symbol* name_symbol,
+                       Symbol* signature_symbol,
+                       fieldDescriptor* fd,
+                       bool is_static = false,
+                       bool allow_super = false) {
+  if (allow_super || is_static) {
+    return ik->find_field(name_symbol, signature_symbol, is_static, fd) != NULL;
+  } else {
+    return ik->find_local_field(name_symbol, signature_symbol, fd);
+  }
+}
+
+static void compute_offset(int &dest_offset,
+                           Klass* klass,
+                           Symbol* name_symbol,
+                           Symbol* signature_symbol,
+                           bool is_static = false, bool allow_super = false) {
+  fieldDescriptor fd;
+  InstanceKlass* ik = InstanceKlass::cast(klass);
+  if (!find_field(ik, name_symbol, signature_symbol, &fd, is_static, allow_super)) {
+    assert(false, "invariant");
+  }
+  dest_offset = fd.offset();
+}
+
+static bool setup_event_writer_offsets(TRAPS) {
+  const char class_name[] = "jdk/jfr/internal/EventWriter";
+  Symbol* const k_sym = SymbolTable::lookup(class_name, sizeof class_name - 1, CHECK_false);
+  assert(k_sym != NULL, "invariant");
+  Klass* klass = SystemDictionary::resolve_or_fail(k_sym, true, CHECK_false);
+  assert(klass != NULL, "invariant");
+
+  const char start_pos_name[] = "startPosition";
+  Symbol* const start_pos_sym = SymbolTable::lookup(start_pos_name, sizeof start_pos_name - 1, CHECK_false);
+  assert(start_pos_sym != NULL, "invariant");
+  assert(invalid_offset == start_pos_offset, "invariant");
+  compute_offset(start_pos_offset, klass, start_pos_sym, vmSymbols::long_signature());
+  assert(start_pos_offset != invalid_offset, "invariant");
+
+  const char start_pos_address_name[] = "startPositionAddress";
+  Symbol* const start_pos_address_sym = SymbolTable::lookup(start_pos_address_name, sizeof start_pos_address_name - 1, CHECK_false);
+  assert(start_pos_address_sym != NULL, "invariant");
+  assert(invalid_offset == start_pos_address_offset, "invariant");
+  compute_offset(start_pos_address_offset, klass, start_pos_address_sym, vmSymbols::long_signature());
+  assert(start_pos_address_offset != invalid_offset, "invariant");
+
+  const char event_pos_name[] = "currentPosition";
+  Symbol* const event_pos_sym = SymbolTable::lookup(event_pos_name, sizeof event_pos_name - 1, CHECK_false);
+  assert(event_pos_sym != NULL, "invariant");
+  assert(invalid_offset == current_pos_offset, "invariant");
+  compute_offset(current_pos_offset, klass, event_pos_sym,vmSymbols::long_signature());
+  assert(current_pos_offset != invalid_offset, "invariant");
+
+  const char max_pos_name[] = "maxPosition";
+  Symbol* const max_pos_sym = SymbolTable::lookup(max_pos_name, sizeof max_pos_name - 1, CHECK_false);
+  assert(max_pos_sym != NULL, "invariant");
+  assert(invalid_offset == max_pos_offset, "invariant");
+  compute_offset(max_pos_offset, klass, max_pos_sym, vmSymbols::long_signature());
+  assert(max_pos_offset != invalid_offset, "invariant");
+
+  const char max_event_size_name[] = "maxEventSize";
+  Symbol* const max_event_size_sym = SymbolTable::lookup(max_event_size_name, sizeof max_event_size_name - 1, CHECK_false);
+  assert (max_event_size_sym != NULL, "invariant");
+  assert(invalid_offset == max_event_size_offset, "invariant");
+  compute_offset(max_event_size_offset, klass, max_event_size_sym, vmSymbols::int_signature());
+  assert(max_event_size_offset != invalid_offset, "invariant");
+
+  const char notified_name[] = "notified";
+  Symbol* const notified_sym = SymbolTable::lookup(notified_name, sizeof notified_name - 1, CHECK_false);
+  assert (notified_sym != NULL, "invariant");
+  assert(invalid_offset == notified_offset, "invariant");
+  compute_offset(notified_offset, klass, notified_sym, vmSymbols::bool_signature());
+  assert(notified_offset != invalid_offset, "invariant");
+
+  const char valid_name[] = "valid";
+  Symbol* const valid_sym = SymbolTable::lookup(valid_name, sizeof valid_name - 1, CHECK_false);
+  assert (valid_sym != NULL, "invariant");
+  assert(invalid_offset == valid_offset, "invariant");
+  compute_offset(valid_offset, klass, valid_sym, vmSymbols::bool_signature());
+  assert(valid_offset != invalid_offset, "invariant");
+  return true;
+}
+
+bool JfrJavaEventWriter::initialize() {
+  static bool initialized = false;
+  if (!initialized) {
+    Thread* thread = Thread::current();
+    initialized = setup_event_writer_offsets(thread);
+  }
+  return initialized;
+}
+
+jboolean JfrJavaEventWriter::flush(jobject writer, jint used, jint requested, JavaThread* jt) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(jt));
+  assert(writer != NULL, "invariant");
+  oop const w = JNIHandles::resolve_non_null(writer);
+  assert(w != NULL, "invariant");
+  JfrBuffer* const current = jt->trace_data()->java_buffer();
+  assert(current != NULL, "invariant");
+  JfrBuffer* const buffer = JfrStorage::flush(current, used, requested, false, jt);
+  assert(buffer != NULL, "invariant");
+  // "validity" is contextually defined here to mean
+  // that some memory location was provided that is
+  // large enough to accommodate the "requested size".
+  const bool is_valid = buffer->free_size() >= (size_t)(used + requested);
+  u1* const new_current_position = is_valid ? buffer->pos() + used : buffer->pos();
+  w->long_field_put(start_pos_offset, (jlong)buffer->pos());
+  w->long_field_put(current_pos_offset, (jlong)new_current_position);
+  // only update java writer if underlying memory changed
+  if (buffer != current) {
+    w->long_field_put(start_pos_address_offset, (jlong)buffer->pos_address());
+    w->long_field_put(max_pos_offset, (jlong)buffer->end());
+  }
+  if (!is_valid) {
+    // mark writer as invalid for this write attempt
+    w->release_bool_field_put(valid_offset, JNI_FALSE);
+    return JNI_FALSE;
+  }
+  // An exclusive use of a leased buffer is treated equivalent to
+  // holding a system resource. As such, it should be released as soon as possible.
+  // Returning true here signals that the thread will need to call flush again
+  // on EventWriter.endEvent() and that flush will return the lease.
+  return buffer->lease() ? JNI_TRUE : JNI_FALSE;
+}
+
+class JfrJavaEventWriterNotificationClosure : public ThreadClosure {
+ public:
+   void do_thread(Thread* t) {
+     if (t->is_Java_thread()) {
+       JfrJavaEventWriter::notify((JavaThread*)t);
+     }
+   }
+};
+
+void JfrJavaEventWriter::notify() {
+  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
+  JfrJavaEventWriterNotificationClosure closure;
+  Threads::threads_do(&closure);
+}
+
+void JfrJavaEventWriter::notify(JavaThread* jt) {
+  assert(jt != NULL, "invariant");
+  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
+  if (jt->trace_data()->has_java_event_writer()) {
+    oop buffer_writer = JNIHandles::resolve_non_null(jt->trace_data()->java_event_writer());
+    assert(buffer_writer != NULL, "invariant");
+    buffer_writer->release_bool_field_put(notified_offset, JNI_TRUE);
+  }
+}
+
+static jobject create_new_event_writer(JfrBuffer* buffer, TRAPS) {
+  assert(buffer != NULL, "invariant");
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(THREAD));
+  HandleMark hm(THREAD);
+  static const char klass[] = "jdk/jfr/internal/EventWriter";
+  static const char method[] = "<init>";
+  static const char signature[] = "(JJJJZ)V";
+  JavaValue result(T_OBJECT);
+  JfrJavaArguments args(&result, klass, method, signature, CHECK_NULL);
+  // parameters
+  args.push_long((jlong)buffer->pos());
+  args.push_long((jlong)buffer->end());
+  args.push_long((jlong)buffer->pos_address());
+  args.push_long((jlong)THREAD_TRACE_ID(THREAD));
+  args.push_int((int)JNI_TRUE);
+  JfrJavaSupport::new_object_global_ref(&args, CHECK_NULL);
+  return result.get_jobject();
+}
+
+jobject JfrJavaEventWriter::event_writer(Thread* t) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(t));
+  JfrThreadData* const trace_data = t->trace_data();
+  assert(trace_data->shelved_buffer() == NULL, "invariant");
+  return trace_data->java_event_writer();
+}
+
+jobject JfrJavaEventWriter::new_event_writer(TRAPS) {
+  DEBUG_ONLY(JfrJavaSupport::check_java_thread_in_vm(THREAD));
+  assert(event_writer(THREAD) == NULL, "invariant");
+  JfrThreadData* const trace_data = THREAD->trace_data();
+  assert(!trace_data->has_java_buffer(), "invariant");
+  JfrBuffer* const buffer = trace_data->java_buffer();
+  if (buffer == NULL) {
+    JfrJavaSupport::throw_out_of_memory_error("OOME for thread local buffer", THREAD);
+    return NULL;
+  }
+  jobject java_event_writer = create_new_event_writer(buffer, CHECK_NULL);
+  trace_data->set_java_event_writer(java_event_writer);
+  assert(trace_data->has_java_event_writer(), "invariant");
+  return java_event_writer;
+}