Source Code for Module ganeti.utils.mlock

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29   
30  """Wrapper around mlockall(2). 
31   
32  """ 
33   
34  import os 
35  import logging 
36   
37  from ganeti import errors 
38   
39  try: 
40    # pylint: disable=F0401 
41    import ctypes 
42  except ImportError: 
43    ctypes = None 
44   
45   
46  # Flags for mlockall(2) (from bits/mman.h) 
47  _MCL_CURRENT = 1 
48  _MCL_FUTURE = 2 
49   
50   
51 -def Mlockall(_ctypes=ctypes): 
52    """Lock current process' virtual address space into RAM. 
53   
54    This is equivalent to the C call C{mlockall(MCL_CURRENT | MCL_FUTURE)}. See 
55    mlockall(2) for more details. This function requires the C{ctypes} module. 
56   
57    @raises errors.NoCtypesError: If the C{ctypes} module is not found 
58   
59    """ 
60    if _ctypes is None: 
61      raise errors.NoCtypesError() 
62   
63    try: 
64      libc = _ctypes.cdll.LoadLibrary("libc.so.6") 
65    except EnvironmentError, err: 
66      logging.error("Failure trying to load libc: %s", err) 
67      libc = None 
68    if libc is None: 
69      logging.error("Cannot set memory lock, ctypes cannot load libc") 
70      return 
71   
72    # The ctypes module before Python 2.6 does not have built-in functionality to 
73    # access the global errno global (which, depending on the libc and build 
74    # options, is per thread), where function error codes are stored. Use GNU 
75    # libc's way to retrieve errno(3) instead, which is to use the pointer named 
76    # "__errno_location" (see errno.h and bits/errno.h). 
77    # pylint: disable=W0212 
78    libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int) 
79   
80    if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE): 
81      # pylint: disable=W0212 
82      logging.error("Cannot set memory lock: %s", 
83                    os.strerror(libc.__errno_location().contents.value)) 
84      return 
85   
86    logging.debug("Memory lock set") 
87