Python signal.set_wakeup_fd() Examples

def __init__(self, app, QAbstractSocket):
        self._app = app
        self.old_fd = None
        # Create a socket pair
        self.wsock, self.rsock = socketpair(type=SOCK_DGRAM)
        self.socket = QAbstractSocket(QAbstractSocket.UdpSocket, app)
        # Let Qt listen on the one end
        self.socket.setSocketDescriptor(self.rsock.fileno())
        # And let Python write on the other end
        self.wsock.setblocking(False)
        self.old_fd = signal.set_wakeup_fd(self.wsock.fileno())
        # First Python code executed gets any exception from
        # the signal handler, so add a dummy handler first
        self.socket.readyRead.connect(lambda : None)
        # Second handler does the real handling
        self.socket.readyRead.connect(self._readSignal) 

def __init__(self):
        # Setup signal fd, this allows signal to behave correctly
        if os.name == 'posix':
            self.signal_pipe_r, self.signal_pipe_w = os.pipe()
            self._set_nonblock(self.signal_pipe_r)
            self._set_nonblock(self.signal_pipe_w)
            signal.set_wakeup_fd(self.signal_pipe_w)

        self._signals_received = collections.deque()

        signal.signal(signal.SIGINT, signal.SIG_DFL)
        if os.name == 'posix':
            signal.signal(signal.SIGCHLD, signal.SIG_DFL)
            signal.signal(signal.SIGTERM, self._signal_catcher)
            signal.signal(signal.SIGALRM, self._signal_catcher)
            signal.signal(signal.SIGHUP, self._signal_catcher)
        else:
            # currently a noop on window...
            signal.signal(signal.SIGTERM, self._signal_catcher)
            # FIXME(sileht): should allow to catch signal CTRL_BREAK_EVENT,
            # but we to create the child process with CREATE_NEW_PROCESS_GROUP
            # to make this work, so current this is a noop for later fix
            signal.signal(signal.SIGBREAK, self._signal_catcher) 

def installHandler(fd):
    """
    Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.

    This is implemented by installing a SIGCHLD handler that does nothing,
    setting the I{SIGCHLD} handler as not allowed to interrupt system calls,
    and using L{signal.set_wakeup_fd} to do the actual writing.

    @param fd: The file descriptor to which to write when I{SIGCHLD} is
        received.
    @type fd: C{int}
    """
    if fd == -1:
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        def noopSignalHandler(*args):
            pass
        signal.signal(signal.SIGCHLD, noopSignalHandler)
        signal.siginterrupt(signal.SIGCHLD, False)
    return signal.set_wakeup_fd(fd) 

def test_set_wakeup_fd_result(self):
        r1, w1 = os.pipe()
        self.addCleanup(os.close, r1)
        self.addCleanup(os.close, w1)
        r2, w2 = os.pipe()
        self.addCleanup(os.close, r2)
        self.addCleanup(os.close, w2)

        if hasattr(os, 'set_blocking'):
            os.set_blocking(w1, False)
            os.set_blocking(w2, False)

        signal.set_wakeup_fd(w1)
        self.assertEqual(signal.set_wakeup_fd(w2), w1)
        self.assertEqual(signal.set_wakeup_fd(-1), w2)
        self.assertEqual(signal.set_wakeup_fd(-1), -1) 

def handle_unix_signals(self):
        if iswindows:
            # TODO: test this on windows
            self.signal_read_socket, self.signal_write_socket = socket.socketpair()
            self.signal_read_socket.setblocking(False)
            self.signal_write_socket.setblocking(False)
            read_fd, write_fd = self.signal_read_socket.fileno(), self.signal_write_socket.fileno()
        else:
            read_fd, write_fd = pipe2()
        for sig in (signal.SIGINT, signal.SIGTERM):
            signal.signal(sig, lambda x, y: None)
            signal.siginterrupt(sig, False)
        signal.set_wakeup_fd(write_fd)
        self.signal_notifier = QSocketNotifier(read_fd, QSocketNotifier.Read, self)
        self.signal_notifier.setEnabled(True)
        self.signal_notifier.activated.connect(self.signal_received, type=Qt.QueuedConnection) 

def test_set_wakeup_fd_blocking(self):
        rfd, wfd = os.pipe()
        self.addCleanup(os.close, rfd)
        self.addCleanup(os.close, wfd)

        # fd must be non-blocking
        os.set_blocking(wfd, True)
        with self.assertRaises(ValueError) as cm:
            signal.set_wakeup_fd(wfd)
        self.assertEqual(str(cm.exception),
                         "the fd %s must be in non-blocking mode" % wfd)

        # non-blocking is ok
        os.set_blocking(wfd, False)
        signal.set_wakeup_fd(wfd)
        signal.set_wakeup_fd(-1) 

def test_set_wakeup_fd_blocking(self):
        rfd, wfd = os.pipe()
        self.addCleanup(os.close, rfd)
        self.addCleanup(os.close, wfd)

        # fd must be non-blocking
        os.set_blocking(wfd, True)
        with self.assertRaises(ValueError) as cm:
            signal.set_wakeup_fd(wfd)
        self.assertEqual(str(cm.exception),
                         "the fd %s must be in non-blocking mode" % wfd)

        # non-blocking is ok
        os.set_blocking(wfd, False)
        signal.set_wakeup_fd(wfd)
        signal.set_wakeup_fd(-1) 

def installHandler(fd):
    """
    Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.

    This is implemented by installing a SIGCHLD handler that does nothing,
    setting the I{SIGCHLD} handler as not allowed to interrupt system calls,
    and using L{signal.set_wakeup_fd} to do the actual writing.

    @param fd: The file descriptor to which to write when I{SIGCHLD} is
        received.
    @type fd: C{int}
    """
    if fd == -1:
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        def noopSignalHandler(*args):
            pass
        signal.signal(signal.SIGCHLD, noopSignalHandler)
        signal.siginterrupt(signal.SIGCHLD, False)
    return signal.set_wakeup_fd(fd) 

def test_set_wakeup_fd_result(self):
        r1, w1 = os.pipe()
        self.addCleanup(os.close, r1)
        self.addCleanup(os.close, w1)
        r2, w2 = os.pipe()
        self.addCleanup(os.close, r2)
        self.addCleanup(os.close, w2)

        if hasattr(os, 'set_blocking'):
            os.set_blocking(w1, False)
            os.set_blocking(w2, False)

        signal.set_wakeup_fd(w1)
        self.assertEqual(signal.set_wakeup_fd(w2), w1)
        self.assertEqual(signal.set_wakeup_fd(-1), w2)
        self.assertEqual(signal.set_wakeup_fd(-1), -1) 

def _serve_one(child_r, fds, unused_fds, handlers):
    # close unnecessary stuff and reset signal handlers
    signal.set_wakeup_fd(-1)
    for sig, val in handlers.items():
        signal.signal(sig, val)
    for fd in unused_fds:
        os.close(fd)

    (_forkserver._forkserver_alive_fd,
     semaphore_tracker._semaphore_tracker._fd,
     *_forkserver._inherited_fds) = fds

    # Run process object received over pipe
    code = spawn._main(child_r)

    return code


#
# Read and write signed numbers
# 

def test_set_wakeup_fd_socket_result(self):
        sock1 = socket.socket()
        self.addCleanup(sock1.close)
        sock1.setblocking(False)
        fd1 = sock1.fileno()

        sock2 = socket.socket()
        self.addCleanup(sock2.close)
        sock2.setblocking(False)
        fd2 = sock2.fileno()

        signal.set_wakeup_fd(fd1)
        self.assertEqual(signal.set_wakeup_fd(fd2), fd1)
        self.assertEqual(signal.set_wakeup_fd(-1), fd2)
        self.assertEqual(signal.set_wakeup_fd(-1), -1)

    # On Windows, files are always blocking and Windows does not provide a
    # function to test if a socket is in non-blocking mode. 

def test_set_wakeup_fd_blocking(self):
        rfd, wfd = os.pipe()
        self.addCleanup(os.close, rfd)
        self.addCleanup(os.close, wfd)

        # fd must be non-blocking
        os.set_blocking(wfd, True)
        with self.assertRaises(ValueError) as cm:
            signal.set_wakeup_fd(wfd)
        self.assertEqual(str(cm.exception),
                         "the fd %s must be in non-blocking mode" % wfd)

        # non-blocking is ok
        os.set_blocking(wfd, False)
        signal.set_wakeup_fd(wfd)
        signal.set_wakeup_fd(-1) 

def _installHandlerUsingSetWakeup(fd):
    """
    Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.

    This is implemented by installing an instance of L{_Handler} wrapped
    around C{None}, setting the I{SIGCHLD} handler as not allowed to
    interrupt system calls, and using L{signal.set_wakeup_fd} to do the
    actual writing.

    @param fd: The file descriptor to which to write when I{SIGCHLD} is
        received.
    @type fd: C{int}
    """
    if fd == -1:
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        signal.signal(signal.SIGCHLD, _Handler(None))
        siginterrupt(signal.SIGCHLD, False)
    return set_wakeup_fd(fd) 

def remove_signal_handler(self, sig):
        """Remove a handler for a signal.  UNIX only.

        Return True if a signal handler was removed, False if not.
        """
        self._check_signal(sig)
        try:
            del self._signal_handlers[sig]
        except KeyError:
            return False

        if sig == signal.SIGINT:
            handler = signal.default_int_handler
        else:
            handler = signal.SIG_DFL

        try:
            signal.signal(sig, handler)
        except OSError as exc:
            if exc.errno == errno.EINVAL:
                raise RuntimeError(f'sig {sig} cannot be caught')
            else:
                raise

        if not self._signal_handlers:
            try:
                signal.set_wakeup_fd(-1)
            except (ValueError, OSError) as exc:
                logger.info('set_wakeup_fd(-1) failed: %s', exc)

        return True 

def test_invalid_call(self):
        # First parameter is positional-only
        with self.assertRaises(TypeError):
            signal.set_wakeup_fd(signum=signal.SIGINT)

        # warn_on_full_buffer is a keyword-only parameter
        with self.assertRaises(TypeError):
            signal.set_wakeup_fd(signal.SIGINT, False) 

def test_invalid_fd(self):
        fd = support.make_bad_fd()
        self.assertRaises((ValueError, OSError),
                          signal.set_wakeup_fd, fd) 

def test_invalid_socket(self):
        sock = socket.socket()
        fd = sock.fileno()
        sock.close()
        self.assertRaises((ValueError, OSError),
                          signal.set_wakeup_fd, fd) 

def check_wakeup(self, test_body, *signals, ordered=True):
        # use a subprocess to have only one thread
        code = """if 1:
        import _testcapi
        import os
        import signal
        import struct

        signals = {!r}

        def handler(signum, frame):
            pass

        def check_signum(signals):
            data = os.read(read, len(signals)+1)
            raised = struct.unpack('%uB' % len(data), data)
            if not {!r}:
                raised = set(raised)
                signals = set(signals)
            if raised != signals:
                raise Exception("%r != %r" % (raised, signals))

        {}

        signal.signal(signal.SIGALRM, handler)
        read, write = os.pipe()
        os.set_blocking(write, False)
        signal.set_wakeup_fd(write)

        test()
        check_signum(signals)

        os.close(read)
        os.close(write)
        """.format(tuple(map(int, signals)), ordered, test_body)

        assert_python_ok('-c', code) 

def setUp(self):
        import fcntl

        self.alrm = signal.signal(signal.SIGALRM, lambda x,y:None)
        self.read, self.write = os.pipe()
        flags = fcntl.fcntl(self.write, fcntl.F_GETFL, 0)
        flags = flags | os.O_NONBLOCK
        fcntl.fcntl(self.write, fcntl.F_SETFL, flags)
        self.old_wakeup = signal.set_wakeup_fd(self.write) 

def tearDown(self):
        signal.set_wakeup_fd(self.old_wakeup)
        os.close(self.read)
        os.close(self.write)
        signal.signal(signal.SIGALRM, self.alrm) 

def activate(self):
        """Set up signal handlers.

        On Windows this uses a QTimer to periodically hand control over to
        Python so it can handle signals.

        On Unix, it uses a QSocketNotifier with os.set_wakeup_fd to get
        notified.
        """
        self._orig_handlers[signal.SIGINT] = signal.signal(
            signal.SIGINT, self.interrupt)
        self._orig_handlers[signal.SIGTERM] = signal.signal(
            signal.SIGTERM, self.interrupt)

        if utils.is_posix and hasattr(signal, 'set_wakeup_fd'):
            # pylint: disable=import-error,no-member,useless-suppression
            import fcntl
            read_fd, write_fd = os.pipe()
            for fd in [read_fd, write_fd]:
                flags = fcntl.fcntl(fd, fcntl.F_GETFL)
                fcntl.fcntl(fd, fcntl.F_SETFL, flags | os.O_NONBLOCK)
            self._notifier = QSocketNotifier(typing.cast(sip.voidptr, read_fd),
                                             QSocketNotifier.Read,
                                             self)
            self._notifier.activated.connect(  # type: ignore[attr-defined]
                self.handle_signal_wakeup)
            self._orig_wakeup_fd = signal.set_wakeup_fd(write_fd)
            # pylint: enable=import-error,no-member,useless-suppression
        else:
            self._timer.start(1000)
            self._timer.timeout.connect(lambda: None)
        self._activated = True 

def test_send_error(self):
        # Use a subprocess to have only one thread.
        if os.name == 'nt':
            action = 'send'
        else:
            action = 'write'
        code = """if 1:
        import errno
        import signal
        import socket
        import sys
        import time
        import _testcapi
        from test.support import captured_stderr

        signum = signal.SIGINT

        def handler(signum, frame):
            pass

        signal.signal(signum, handler)

        read, write = socket.socketpair()
        read.setblocking(False)
        write.setblocking(False)

        signal.set_wakeup_fd(write.fileno())

        # Close sockets: send() will fail
        read.close()
        write.close()

        with captured_stderr() as err:
            _testcapi.raise_signal(signum)

        err = err.getvalue()
        if ('Exception ignored when trying to {action} to the signal wakeup fd'
            not in err):
            raise AssertionError(err)
        """.format(action=action)
        assert_python_ok('-c', code) 

def test_socket(self):
        # use a subprocess to have only one thread
        code = """if 1:
        import signal
        import socket
        import struct
        import _testcapi

        signum = signal.SIGINT
        signals = (signum,)

        def handler(signum, frame):
            pass

        signal.signal(signum, handler)

        read, write = socket.socketpair()
        read.setblocking(False)
        write.setblocking(False)
        signal.set_wakeup_fd(write.fileno())

        _testcapi.raise_signal(signum)

        data = read.recv(1)
        if not data:
            raise Exception("no signum written")
        raised = struct.unpack('B', data)
        if raised != signals:
            raise Exception("%r != %r" % (raised, signals))

        read.close()
        write.close()
        """

        assert_python_ok('-c', code) 

def check_wakeup(self, test_body, *signals, ordered=True):
        # use a subprocess to have only one thread
        code = """if 1:
        import _testcapi
        import os
        import signal
        import struct

        signals = {!r}

        def handler(signum, frame):
            pass

        def check_signum(signals):
            data = os.read(read, len(signals)+1)
            raised = struct.unpack('%uB' % len(data), data)
            if not {!r}:
                raised = set(raised)
                signals = set(signals)
            if raised != signals:
                raise Exception("%r != %r" % (raised, signals))

        {}

        signal.signal(signal.SIGALRM, handler)
        read, write = os.pipe()
        os.set_blocking(write, False)
        signal.set_wakeup_fd(write)

        test()
        check_signum(signals)

        os.close(read)
        os.close(write)
        """.format(tuple(map(int, signals)), ordered, test_body)

        assert_python_ok('-c', code) 

def test_invalid_socket(self):
        sock = socket.socket()
        fd = sock.fileno()
        sock.close()
        self.assertRaises((ValueError, OSError),
                          signal.set_wakeup_fd, fd) 

def test_invalid_fd(self):
        fd = support.make_bad_fd()
        self.assertRaises((ValueError, OSError),
                          signal.set_wakeup_fd, fd) 

def remove_signal_handler(self, sig):
        """Remove a handler for a signal.  UNIX only.

        Return True if a signal handler was removed, False if not.
        """
        self._check_signal(sig)
        try:
            del self._signal_handlers[sig]
        except KeyError:
            return False

        if sig == signal.SIGINT:
            handler = signal.default_int_handler
        else:
            handler = signal.SIG_DFL

        try:
            signal.signal(sig, handler)
        except OSError as exc:
            if exc.errno == errno.EINVAL:
                raise RuntimeError('sig {} cannot be caught'.format(sig))
            else:
                raise

        if not self._signal_handlers:
            try:
                signal.set_wakeup_fd(-1)
            except (ValueError, OSError) as exc:
                logger.info('set_wakeup_fd(-1) failed: %s', exc)

        return True 

def remove_signal_handler(self, sig):
        """Remove a handler for a signal.  UNIX only.

        Return True if a signal handler was removed, False if not.
        """
        self._check_signal(sig)
        try:
            del self._signal_handlers[sig]
        except KeyError:
            return False

        if sig == signal.SIGINT:
            handler = signal.default_int_handler
        else:
            handler = signal.SIG_DFL

        try:
            signal.signal(sig, handler)
        except OSError as exc:
            if exc.errno == errno.EINVAL:
                raise RuntimeError('sig {} cannot be caught'.format(sig))
            else:
                raise

        if not self._signal_handlers:
            try:
                signal.set_wakeup_fd(-1)
            except (ValueError, OSError) as exc:
                logger.info('set_wakeup_fd(-1) failed: %s', exc)

        return True 

def tearDown(self):
        signal.set_wakeup_fd(self.old_wakeup)
        os.close(self.read)
        os.close(self.write)
        signal.signal(signal.SIGALRM, self.alrm) 

def setUp(self):
        import fcntl

        self.alrm = signal.signal(signal.SIGALRM, lambda x,y:None)
        self.read, self.write = os.pipe()
        flags = fcntl.fcntl(self.write, fcntl.F_GETFL, 0)
        flags = flags | os.O_NONBLOCK
        fcntl.fcntl(self.write, fcntl.F_SETFL, flags)
        self.old_wakeup = signal.set_wakeup_fd(self.write)