diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/utilities/events.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/utilities/events.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,304 @@
+/*
+ * Copyright (c) 1997, 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.
+ *
+ */
+
+#ifndef SHARE_VM_UTILITIES_EVENTS_HPP
+#define SHARE_VM_UTILITIES_EVENTS_HPP
+
+#include "memory/allocation.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "runtime/thread.hpp"
+#include "utilities/formatBuffer.hpp"
+#include "utilities/vmError.hpp"
+
+// Events and EventMark provide interfaces to log events taking place in the vm.
+// This facility is extremly useful for post-mortem debugging. The eventlog
+// often provides crucial information about events leading up to the crash.
+//
+// Abstractly the logs can record whatever they way but normally they
+// would record at least a timestamp and the current Thread, along
+// with whatever data they need in a ring buffer.  Commonly fixed
+// length text messages are recorded for simplicity but other
+// strategies could be used.  Several logs are provided by default but
+// new instances can be created as needed.
+
+// The base event log dumping class that is registered for dumping at
+// crash time.  This is a very generic interface that is mainly here
+// for completeness.  Normally the templated EventLogBase would be
+// subclassed to provide different log types.
+class EventLog : public CHeapObj<mtInternal> {
+  friend class Events;
+
+ private:
+  EventLog* _next;
+
+  EventLog* next() const { return _next; }
+
+ public:
+  // Automatically registers the log so that it will be printed during
+  // crashes.
+  EventLog();
+
+  virtual void print_log_on(outputStream* out) = 0;
+};
+
+
+// A templated subclass of EventLog that provides basic ring buffer
+// functionality.  Most event loggers should subclass this, possibly
+// providing a more featureful log function if the existing copy
+// semantics aren't appropriate.  The name is used as the label of the
+// log when it is dumped during a crash.
+template <class T> class EventLogBase : public EventLog {
+  template <class X> class EventRecord : public CHeapObj<mtInternal> {
+   public:
+    double  timestamp;
+    Thread* thread;
+    X       data;
+  };
+
+ protected:
+  Mutex           _mutex;
+  const char*     _name;
+  int             _length;
+  int             _index;
+  int             _count;
+  EventRecord<T>* _records;
+
+ public:
+  EventLogBase<T>(const char* name, int length = LogEventsBufferEntries):
+    _name(name),
+    _length(length),
+    _count(0),
+    _index(0),
+    _mutex(Mutex::event, name, false, Monitor::_safepoint_check_never) {
+    _records = new EventRecord<T>[length];
+  }
+
+  double fetch_timestamp() {
+    return os::elapsedTime();
+  }
+
+  // move the ring buffer to next open slot and return the index of
+  // the slot to use for the current message.  Should only be called
+  // while mutex is held.
+  int compute_log_index() {
+    int index = _index;
+    if (_count < _length) _count++;
+    _index++;
+    if (_index >= _length) _index = 0;
+    return index;
+  }
+
+  bool should_log() {
+    // Don't bother adding new entries when we're crashing.  This also
+    // avoids mutating the ring buffer when printing the log.
+    return !VMError::fatal_error_in_progress();
+  }
+
+  // Print the contents of the log
+  void print_log_on(outputStream* out);
+
+ private:
+  void print_log_impl(outputStream* out);
+
+  // Print a single element.  A templated implementation might need to
+  // be declared by subclasses.
+  void print(outputStream* out, T& e);
+
+  void print(outputStream* out, EventRecord<T>& e) {
+    out->print("Event: %.3f ", e.timestamp);
+    if (e.thread != NULL) {
+      out->print("Thread " INTPTR_FORMAT " ", p2i(e.thread));
+    }
+    print(out, e.data);
+  }
+};
+
+// A simple wrapper class for fixed size text messages.
+class StringLogMessage : public FormatBuffer<256> {
+ public:
+  // Wrap this buffer in a stringStream.
+  stringStream stream() {
+    return stringStream(_buf, size());
+  }
+};
+
+// A simple ring buffer of fixed size text messages.
+class StringEventLog : public EventLogBase<StringLogMessage> {
+ public:
+  StringEventLog(const char* name, int count = LogEventsBufferEntries) : EventLogBase<StringLogMessage>(name, count) {}
+
+  void logv(Thread* thread, const char* format, va_list ap) ATTRIBUTE_PRINTF(3, 0) {
+    if (!should_log()) return;
+
+    double timestamp = fetch_timestamp();
+    MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
+    int index = compute_log_index();
+    _records[index].thread = thread;
+    _records[index].timestamp = timestamp;
+    _records[index].data.printv(format, ap);
+  }
+
+  void log(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(3, 4) {
+    va_list ap;
+    va_start(ap, format);
+    logv(thread, format, ap);
+    va_end(ap);
+  }
+
+};
+
+
+
+class Events : AllStatic {
+  friend class EventLog;
+
+ private:
+  static EventLog* _logs;
+
+  // A log for generic messages that aren't well categorized.
+  static StringEventLog* _messages;
+
+  // A log for internal exception related messages, like internal
+  // throws and implicit exceptions.
+  static StringEventLog* _exceptions;
+
+  // Deoptization related messages
+  static StringEventLog* _deopt_messages;
+
+  // Redefinition related messages
+  static StringEventLog* _redefinitions;
+
+ public:
+  static void print_all(outputStream* out);
+
+  // Dump all events to the tty
+  static void print();
+
+  // Logs a generic message with timestamp and format as printf.
+  static void log(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
+
+  // Log exception related message
+  static void log_exception(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
+
+  static void log_redefinition(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
+
+  static void log_deopt_message(Thread* thread, const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
+
+  // Register default loggers
+  static void init();
+};
+
+inline void Events::log(Thread* thread, const char* format, ...) {
+  if (LogEvents) {
+    va_list ap;
+    va_start(ap, format);
+    _messages->logv(thread, format, ap);
+    va_end(ap);
+  }
+}
+
+inline void Events::log_exception(Thread* thread, const char* format, ...) {
+  if (LogEvents) {
+    va_list ap;
+    va_start(ap, format);
+    _exceptions->logv(thread, format, ap);
+    va_end(ap);
+  }
+}
+
+inline void Events::log_redefinition(Thread* thread, const char* format, ...) {
+  if (LogEvents) {
+    va_list ap;
+    va_start(ap, format);
+    _redefinitions->logv(thread, format, ap);
+    va_end(ap);
+  }
+}
+
+inline void Events::log_deopt_message(Thread* thread, const char* format, ...) {
+  if (LogEvents) {
+    va_list ap;
+    va_start(ap, format);
+    _deopt_messages->logv(thread, format, ap);
+    va_end(ap);
+  }
+}
+
+
+template <class T>
+inline void EventLogBase<T>::print_log_on(outputStream* out) {
+  if (Thread::current_or_null() == NULL) {
+    // Not yet attached? Don't try to use locking
+    print_log_impl(out);
+  } else {
+    MutexLockerEx ml(&_mutex, Mutex::_no_safepoint_check_flag);
+    print_log_impl(out);
+  }
+}
+
+// Dump the ring buffer entries that current have entries.
+template <class T>
+inline void EventLogBase<T>::print_log_impl(outputStream* out) {
+  out->print_cr("%s (%d events):", _name, _count);
+  if (_count == 0) {
+    out->print_cr("No events");
+    out->cr();
+    return;
+  }
+
+  if (_count < _length) {
+    for (int i = 0; i < _count; i++) {
+      print(out, _records[i]);
+    }
+  } else {
+    for (int i = _index; i < _length; i++) {
+      print(out, _records[i]);
+    }
+    for (int i = 0; i < _index; i++) {
+      print(out, _records[i]);
+    }
+  }
+  out->cr();
+}
+
+// Implement a printing routine for the StringLogMessage
+template <>
+inline void EventLogBase<StringLogMessage>::print(outputStream* out, StringLogMessage& lm) {
+  out->print_raw(lm);
+  out->cr();
+}
+
+// Place markers for the beginning and end up of a set of events.
+// These end up in the default log.
+class EventMark : public StackObj {
+  StringLogMessage _buffer;
+
+ public:
+  // log a begin event, format as printf
+  EventMark(const char* format, ...) ATTRIBUTE_PRINTF(2, 3);
+  // log an end event
+  ~EventMark();
+};
+
+#endif // SHARE_VM_UTILITIES_EVENTS_HPP