sgpemv2/plugins/pyloader/python_policy.cc

// src/backend/pyloader/python_policy.cc - Copyright 2005, 2006, University
//               of Padova, dept. of Pure and Applied
//               Mathematics
//
// This file is part of SGPEMv2.
//
// This is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// SGPEMv2 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 for more details.
//
// You should have received a copy of the GNU General Public License
// along with SGPEMv2; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA

#include "python_policy.hh"
#include <limits>
#include <unistd.h>
#include <iostream>
using namespace sgpem;
using namespace std;

#define WAIT_FOR (250000)

// WARNING :  this class needs extensive and above all
// *strong* exception checking / handling!

PythonPolicy::PythonPolicy(const char* name)
  : _upolicy_dict(NULL), _adapter(NULL), _name(name)
{
  PyObject* pLoadmeStr = PyString_FromString(name);
  PyObject* pUserPolicyModule = PyImport_Import(pLoadmeStr);
  Py_DECREF(pLoadmeStr);
  
  if( !pUserPolicyModule ) 
  {
    PyErr_Print(); // Error in import
    // FIXME : don't exit abruptly, but fall back gracefully
    exit(-1);
  }
  
  // Dictionary with defined ``symbols'' for .pyc file
  _upolicy_dict = PyModule_GetDict(pUserPolicyModule);
  assert(_upolicy_dict);

  // Loads ScriptAdapter module and get its dictionary
  pLoadmeStr = PyString_FromString("ScriptAdapter");
  PyObject* pScriptAdapterModule = PyImport_Import(pLoadmeStr);
  Py_DECREF(pLoadmeStr);
  assert(pScriptAdapterModule);
  PyObject* pAdapterDict = PyModule_GetDict(pScriptAdapterModule);
  assert(pAdapterDict);
  
  // Now takes the user-defined policy class from pUserPolicyDict
  PyObject* pPolicyClass = PyDict_GetItemString(_upolicy_dict, name);
  assert(pPolicyClass); // FIXME needs stricter checking and exception throwing
    
  // Creates a new object of type ScriptAdapter :
  // takes init function from ScriptAdapter class
  PyObject* pAdapterClass = PyDict_GetItemString(pAdapterDict, "ScriptAdapter");
  PyObject* pAdapterCtorParam = PyTuple_New(1);
  Py_INCREF(pPolicyClass); // PyTuple_SetItem steals a reference
  PyTuple_SetItem(pAdapterCtorParam, 0, pPolicyClass);
  _adapter = PyInstance_New(pAdapterClass, pAdapterCtorParam, NULL);
  Py_DECREF(pAdapterCtorParam);
  assert(_adapter);

  Py_DECREF(pScriptAdapterModule);

  // And now, who's your daddy, huh?
}


PythonPolicy::~PythonPolicy()
{
  if(_adapter)      Py_DECREF(_adapter);

	// We keep this alive until dtor time, because
	// the user may have defined some static global-space
	// variables and they make use of them.
	if(_upolicy_dict) Py_DECREF(_upolicy_dict);
}


void
PythonPolicy::configure() throw(UserInterruptException)
{
  PyObject* retval = PyObject_CallMethod(_adapter, "async_configure", NULL);
  Py_DECREF(retval);

  wait_unlock();
}


void
PythonPolicy::sort_queue(Scheduler::event event) const throw(UserInterruptException)
{
  PyObject* pEvent = PyInt_FromLong(event);
  PyObject* pMethodName = PyString_FromString("async_sort_queue");
  PyObject* retval = PyObject_CallMethodObjArgs(_adapter, pMethodName, pEvent, NULL);
  
  // Do minimal debugging
  if(!retval) PyErr_Print();
  else Py_DECREF(retval);
  
  Py_DECREF(pMethodName);
  Py_DECREF(pEvent);

  wait_unlock();
}


Glib::ustring
PythonPolicy::get_description() const 
{
  return _name;
}


bool
PythonPolicy::is_pre_emptive() const throw(UserInterruptException) 
{
  PyObject* retval = PyObject_CallMethod(_adapter, "async_is_preemptive", NULL);
  Py_DECREF(retval);
  
  wait_unlock();
  
  // Parse return value stored in global Python object
  retval = PyObject_CallMethod(_adapter, "get_return_value", NULL);
  assert(retval);
  bool ret = PyObject_IsTrue(retval);
  Py_DECREF(retval);
  return ret;
}


int
PythonPolicy::get_time_slice() const throw(UserInterruptException) {
  PyObject* retval = PyObject_CallMethod(_adapter, "async_get_time_slice", NULL);
  Py_DECREF(retval);
  
  wait_unlock();
  
  // Parse return value stored in global Python object
  retval = PyObject_CallMethod(_adapter, "get_return_value", NULL);
  assert(retval);
  long tmp = PyInt_AsLong(retval);
  Py_DECREF(retval);

  return tmp < 0 ? numeric_limits<int>::max() : static_cast<int>(tmp);
}

    
void
PythonPolicy::wait_unlock() const throw(UserInterruptException)
{
  PyThreadState* _save;
  int i = 0; // We give the sort_queue() three seconds max time, then...
             // we shot it stone dead! Bang.

  bool still_locked;
  do 
    {
      Py_UNBLOCK_THREADS;
      usleep(WAIT_FOR); // hack'a'ton! magggggiccc nummmbeeerrrrrs!!
      Py_BLOCK_THREADS;
      
      PyObject* retval = PyObject_CallMethod(_adapter, "mutex_test_lock", NULL);
      assert(retval);
      still_locked = PyObject_IsTrue(retval);
      Py_DECREF(retval);

      if(i++ > 12) /* waits for WAIT_FOR * 12 microseconds == 3 secs */
      {
	PyThreadState_Clear(_save);
	// As the API documentation says, the caller of PyEval_RestoreThread
	// should NOT possess the interpreter lock
	Py_UNBLOCK_THREADS;
	PyEval_RestoreThread(_save);
	

	throw UserInterruptException("User-defined policy is " 
				     "taking too long to terminate.");
	}
    } 
  while(still_locked);

  // What we should really do here:
  /* do {
     enable python threads
     wait for some time...
     disable python threads
     ...check if user asked for interruption, reading a
        syncronized variable...
     ...if he has, break
     ...else:
           if the global lock is set:
	      stay in this loop
	   else:
	      all's went okay, can exit loop
  } */

}