text: # Copyright 2012 James McCauley
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at:
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """
  This is an extremely primitive start at some debugging.
  At the moment, it is really just for recoco (maybe it belongs in there?).
  """
  
  from pox.core import core
  log = core.getLogger()
  import time
  import traceback
  import pox.lib.recoco
  
  _frames = []
  
  def _tf (frame, event, arg):
    if _frames is None: return _tf
    #print " " * len(_frames) + event
    if event == 'call':
      _frames.append(frame)
      return _tf
    elif event == 'line':
      return _tf
    elif event == 'exception':
      #_frames.pop()
      return _tf
    elif event == 'return':
      _frames.pop()
    elif event == 'c_call':
      print("c_call")
      _frames.append((frame,arg))
    elif event == 'c_exception':
      _frames.pop()
    elif event == 'c_return':
      _frames.pop()
  
  
  def _trace_thread_proc ():
    last = None
    last_time = None
    warned = None
    while True:
      try:
        time.sleep(1)
        c = len(_frames)
        if c == 0: continue
        f = _frames[-1]
        stopAt = None
        count = 0
        sf = f
        while sf is not None:
          if sf.f_code == pox.lib.recoco.Scheduler.cycle.__func__.__code__:
            stopAt = sf
            break
          count += 1
          sf = sf.f_back
        #if stopAt == None: continue
  
        f = "\n".join([s.strip() for s in
                        traceback.format_stack(f,count)])
        #f = " / ".join([s.strip() for s in
        #                traceback.format_stack(f,1)[0].strip().split("\n")])
        #f = "\n".join([s.strip() for s in
        #                traceback.format_stack(f)])
  
        if f != last:
          if warned:
            log.warning("Running again")
          warned = None
          last = f
          last_time = time.time()
        elif f != warned:
          if time.time() - last_time > 3:
            if stopAt is not None:
              warned = f
              log.warning("Stuck at:\n" + f)
  
        #from pox.core import core
        #core.f = f
  
      except:
        traceback.print_exc()
        pass
  
  
  
  def launch ():
    def f ():
      import sys
      sys.settrace(_tf)
    core.callLater(f)
  
    import threading
    _trace_thread = threading.Thread(target=_trace_thread_proc)
    _trace_thread.daemon = True
    _trace_thread.start()
  