Revision 6915fe26 lib/utils/cfunc.py
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ctypes = None |
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# Flags for mlockall() (from bits/mman.h) |
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# Flags for mlockall(2) (from bits/mman.h)
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_MCL_CURRENT = 1 |
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_MCL_FUTURE = 2 |
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class _FuncWrapper: |
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def __init__(self, ct): |
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"""Initializes this class. |
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""" |
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# Make use of a dlopen(3) feature whereby giving a NULL handle returns the |
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# main program. Functions from all previously loaded libraries can then be |
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# used. |
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mainprog = ct.CDLL(None) |
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# The ctypes module before Python 2.6 does not have built-in functionality |
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# to access the global errno global (which, depending on the libc and build |
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# options, is per-thread), where function error codes are stored. Use GNU |
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# libc's way to retrieve errno(3) instead. |
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try: |
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errno_loc = getattr(mainprog, "__errno_location") |
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except AttributeError, err: |
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logging.debug("Unable to find errno location: %s", err)
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errno_fn = None |
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else: |
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errno_loc.restype = ct.POINTER(ct.c_int) |
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errno_fn = lambda: errno_loc().contents.value |
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self.errno_fn = errno_fn |
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# Try to get mlockall(2) |
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self.mlockall_fn = getattr(mainprog, "mlockall", None) |
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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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This is equivalent to the C call C{mlockall(MCL_CURRENT | MCL_FUTURE)}. See
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mlockall(2) for more details. This function requires the C{ctypes} module.
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@raises errors.NoCtypesError: if ctypes module is not found
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@raises errors.NoCtypesError: If the C{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")
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funcs = _FuncWrapper(_ctypes) |
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if funcs.mlockall_fn is None: |
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logging.debug("libc doesn't support mlockall(2)")
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else: |
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if funcs.mlockall_fn(_MCL_CURRENT | _MCL_FUTURE) == 0: |
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logging.debug("Memory lock set")
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return True |
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logging.error("Cannot set memory lock: %s", os.strerror(funcs.errno_fn()))
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return False |
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