events.hpp

/*
 * Copyright (c) 1997, 2014, 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/top.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) {
    _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;

 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_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_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 (ThreadLocalStorage::get_thread_slow() == NULL) {
    // Not a regular Java thread so don't bother 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