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#

#

# Copyright (C) 2009, 2010, 2011 Google Inc.

#

# This program 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.

#

# This program 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 this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA

# 02110-1301, USA.

"""Wrapper around mlockall(2).

"""

import os

import logging

from ganeti import errors

try:

  # pylint: disable=F0401

  import ctypes

except ImportError:

  ctypes = None

# Flags for mlockall(2) (from bits/mman.h)

_MCL_CURRENT = 1

_MCL_FUTURE = 2

class _FuncWrapper:

  def __init__(self, ct):

    """Initializes this class.

    """

    # Make use of a dlopen(3) feature whereby giving a NULL handle returns the

    # main program. Functions from all previously loaded libraries can then be

    # used.

    mainprog = ct.CDLL(None)

    # The ctypes module before Python 2.6 does not have built-in functionality

    # to access the global errno global (which, depending on the libc and build

    # options, is per-thread), where function error codes are stored. Use GNU

    # libc's way to retrieve errno(3) instead.

    try:

      errno_loc = getattr(mainprog, "__errno_location")

    except AttributeError, err:

      logging.debug("Unable to find errno location: %s", err)

      errno_fn = None

    else:

      errno_loc.restype = ct.POINTER(ct.c_int)

      errno_fn = lambda: errno_loc().contents.value

    self.errno_fn = errno_fn

    # Try to get mlockall(2)

    self.mlockall_fn = getattr(mainprog, "mlockall", None)

def Mlockall(_ctypes=ctypes):

  """Lock current process' virtual address space into RAM.

  This is equivalent to the C call C{mlockall(MCL_CURRENT | MCL_FUTURE)}. See

  mlockall(2) for more details. This function requires the C{ctypes} module.

  @raises errors.NoCtypesError: If the C{ctypes} module is not found

  """

  if _ctypes is None:

    raise errors.NoCtypesError()

  funcs = _FuncWrapper(_ctypes)

  if funcs.mlockall_fn is None:

    logging.debug("libc doesn't support mlockall(2)")

  else:

    if funcs.mlockall_fn(_MCL_CURRENT | _MCL_FUTURE) == 0:

      logging.debug("Memory lock set")

      return True

    logging.error("Cannot set memory lock: %s", os.strerror(funcs.errno_fn()))

  return False