Pure Python solution to locking the GIL

lockgil.py

# Use libc in ctypes "PyDLL" mode, which prevents CPython from
# releasing the GIL during procedure calls.
_libc_name = ctypes.util.find_library("c")
if _libc_name is None:
    raise RuntimeError("Cannot find libc")
libc_py = ctypes.PyDLL(_libc_name)
...
libc_py.usleep(...)


# --- Optional, for using with pickle ---

class PickleableCtypesFuncPtr:
    """A version of a ctypes._FuncPtr that can be pickled. The shared library
    must be available in the depickling environment.
    """

    def __init__(self, dll_type, lib, name):
        self.__setstate__((dll_type, lib, name))

    def __setstate__(self, state):
        self.state = state
        dll_type, lib, func = self.state
        dll_loader = getattr(ctypes, dll_type)
        self.funcptr = dll_loader(lib)[func]

    def __getstate__(self):
        return self.state

    def __call__(self, *args):
        return self.funcptr(*args)

usleep = PickleableCtypesFuncPtr("PyDLL", _libc_name, "usleep")