Source Code for Module ganeti.utils.mlock

 1  # 
 2  # 
 3   
 4  # Copyright (C) 2009, 2010, 2011 Google Inc. 
 5  # 
 6  # This program is free software; you can redistribute it and/or modify 
 7  # it under the terms of the GNU General Public License as published by 
 8  # the Free Software Foundation; either version 2 of the License, or 
 9  # (at your option) any later version. 
10  # 
11  # This program is distributed in the hope that it will be useful, but 
12  # WITHOUT ANY WARRANTY; without even the implied warranty of 
13  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU 
14  # General Public License for more details. 
15  # 
16  # You should have received a copy of the GNU General Public License 
17  # along with this program; if not, write to the Free Software 
18  # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 
19  # 02110-1301, USA. 
20   
21  """Wrapper around mlockall(2). 
22   
23  """ 
24   
25  import os 
26  import logging 
27   
28  from ganeti import errors 
29   
30  try: 
31    # pylint: disable=F0401 
32    import ctypes 
33  except ImportError: 
34    ctypes = None 
35   
36   
37  # Flags for mlockall(2) (from bits/mman.h) 
38  _MCL_CURRENT = 1 
39  _MCL_FUTURE = 2 
40   
41   
42 -def Mlockall(_ctypes=ctypes): 
43    """Lock current process' virtual address space into RAM. 
44   
45    This is equivalent to the C call C{mlockall(MCL_CURRENT | MCL_FUTURE)}. See 
46    mlockall(2) for more details. This function requires the C{ctypes} module. 
47   
48    @raises errors.NoCtypesError: If the C{ctypes} module is not found 
49   
50    """ 
51    if _ctypes is None: 
52      raise errors.NoCtypesError() 
53   
54    try: 
55      libc = _ctypes.cdll.LoadLibrary("libc.so.6") 
56    except EnvironmentError, err: 
57      logging.error("Failure trying to load libc: %s", err) 
58      libc = None 
59    if libc is None: 
60      logging.error("Cannot set memory lock, ctypes cannot load libc") 
61      return 
62   
63    # The ctypes module before Python 2.6 does not have built-in functionality to 
64    # access the global errno global (which, depending on the libc and build 
65    # options, is per thread), where function error codes are stored. Use GNU 
66    # libc's way to retrieve errno(3) instead, which is to use the pointer named 
67    # "__errno_location" (see errno.h and bits/errno.h). 
68    # pylint: disable=W0212 
69    libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int) 
70   
71    if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE): 
72      # pylint: disable=W0212 
73      logging.error("Cannot set memory lock: %s", 
74                    os.strerror(libc.__errno_location().contents.value)) 
75      return 
76   
77    logging.debug("Memory lock set") 
78