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#
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#
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# Copyright (C) 2009, 2010, 2011 Google Inc.
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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# 02110-1301, USA.
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"""Wrapper around mlockall(2).
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"""
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import os
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import logging
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from ganeti import errors
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try:
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  # pylint: disable=F0401
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  import ctypes
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except ImportError:
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  ctypes = None
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# Flags for mlockall() (from bits/mman.h)
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_MCL_CURRENT = 1
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_MCL_FUTURE = 2
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def Mlockall(_ctypes=ctypes):
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  """Lock current process' virtual address space into RAM.
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  This is equivalent to the C call mlockall(MCL_CURRENT|MCL_FUTURE),
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  see mlock(2) for more details. This function requires ctypes module.
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  @raises errors.NoCtypesError: if ctypes module is not found
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  """
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  if _ctypes is None:
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    raise errors.NoCtypesError()
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  try:
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    libc = _ctypes.cdll.LoadLibrary("libc.so.6")
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  except EnvironmentError, err:
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    logging.error("Failure trying to load libc: %s", err)
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    libc = None
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  if libc is None:
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    logging.error("Cannot set memory lock, ctypes cannot load libc")
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    return
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  # Some older version of the ctypes module don't have built-in functionality
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  # to access the errno global variable, where function error codes are stored.
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  # By declaring this variable as a pointer to an integer we can then access
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  # its value correctly, should the mlockall call fail, in order to see what
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  # the actual error code was.
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  # pylint: disable=W0212
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  libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int)
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  if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE):
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    # pylint: disable=W0212
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    logging.error("Cannot set memory lock: %s",
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                  os.strerror(libc.__errno_location().contents.value))
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    return
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  logging.debug("Memory lock set")