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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

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()

  try:

    libc = _ctypes.cdll.LoadLibrary("libc.so.6")

  except EnvironmentError, err:

    logging.error("Failure trying to load libc: %s", err)

    libc = None

  if libc is None:

    logging.error("Cannot set memory lock, ctypes cannot load libc")

    return

  # 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, which is to use the pointer named

  # "__errno_location" (see errno.h and bits/errno.h).

  # pylint: disable=W0212

  libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int)

  if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE):

    # pylint: disable=W0212

    logging.error("Cannot set memory lock: %s",

                  os.strerror(libc.__errno_location().contents.value))

    return

  logging.debug("Memory lock set")