Index: Doc/library/signal.rst
===================================================================
--- Doc/library/signal.rst	(revision 59557)
+++ Doc/library/signal.rst	(working copy)
@@ -110,6 +110,20 @@
    :manpage:`signal(2)`.)
 
 
+.. function:: set_wakeup_fd(fd)
+
+   Set the wakeup fd to *fd*.  When a signal is received, a ``'\0'`` byte is
+   written to the fd.  This can be used by a library to wakeup a poll or select
+   call, allowing the signal to be fully processed.
+
+   The old wakeup fd is returned.  *fd* must be non-blocking.  It is up to the
+   library to remove any bytes before calling poll or select again.
+
+   When threads are enabled, this function can only be called from the main thread;
+   attempting to call it from other threads will cause a :exc:`ValueError`
+   exception to be raised.
+
+
 .. function:: signal(signalnum, handler)
 
    Set the handler for signal *signalnum* to the function *handler*.  *handler* can
Index: Lib/test/test_signal.py
===================================================================
--- Lib/test/test_signal.py	(revision 59557)
+++ Lib/test/test_signal.py	(working copy)
@@ -165,12 +165,59 @@
         self.assertRaises(TypeError, signal.signal,
                           signal.SIGUSR1, None)
 
+class WakeupSignalTests(unittest.TestCase):
+    TIMEOUT_FULL = 10
+    TIMEOUT_HALF = 5
+
+    def test_wakeup_fd_early(self):
+        import select
+
+        signal.alarm(1)
+        before_time = time.time()
+        # We attempt to get a signal during the sleep,
+        # before select is called
+        time.sleep(self.TIMEOUT_FULL)
+        mid_time = time.time()
+        self.assert_(mid_time - before_time < self.TIMEOUT_HALF)
+        select.select([self.read], [], [], self.TIMEOUT_FULL)
+        after_time = time.time()
+        self.assert_(after_time - mid_time < self.TIMEOUT_HALF)
+
+    def test_wakeup_fd_during(self):
+        import select
+
+        signal.alarm(1)
+        before_time = time.time()
+        # We attempt to get a signal during the select call
+        self.assertRaises(select.error, select.select,
+            [self.read], [], [], self.TIMEOUT_FULL)
+        after_time = time.time()
+        self.assert_(after_time - before_time < self.TIMEOUT_HALF)
+
+    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 test_main():
     if sys.platform[:3] in ('win', 'os2') or sys.platform == 'riscos':
         raise test_support.TestSkipped("Can't test signal on %s" % \
                                        sys.platform)
 
-    test_support.run_unittest(BasicSignalTests, InterProcessSignalTests)
+    test_support.run_unittest(BasicSignalTests, InterProcessSignalTests,
+        WakeupSignalTests)
 
 
 if __name__ == "__main__":
Index: Modules/signalmodule.c
===================================================================
--- Modules/signalmodule.c	(revision 59557)
+++ Modules/signalmodule.c	(working copy)
@@ -12,6 +12,8 @@
 
 #include <signal.h>
 
+#include <sys/stat.h>
+
 #ifndef SIG_ERR
 #define SIG_ERR ((PyOS_sighandler_t)(-1))
 #endif
@@ -75,6 +77,8 @@
         PyObject *func;
 } Handlers[NSIG];
 
+static sig_atomic_t wakeup_fd = -1;
+
 /* Speed up sigcheck() when none tripped */
 static volatile sig_atomic_t is_tripped = 0;
 
@@ -113,6 +117,7 @@
 static void
 signal_handler(int sig_num)
 {
+	const char dummy_byte = '\0';
 #ifdef WITH_THREAD
 #ifdef WITH_PTH
 	if (PyThread_get_thread_ident() != main_thread) {
@@ -128,6 +133,8 @@
                    cleared in PyErr_CheckSignals() before .tripped. */
 		is_tripped = 1;
 		Py_AddPendingCall(checksignals_witharg, NULL);
+		if (wakeup_fd != -1)
+			write(wakeup_fd, &dummy_byte, 1);
 #ifdef WITH_THREAD
 	}
 #endif
@@ -267,6 +274,39 @@
 anything else -- the callable Python object used as a handler");
 
 
+static PyObject *
+signal_set_wakeup_fd(PyObject *self, PyObject *args)
+{
+	struct stat buf;
+	int fd, old_fd;
+	if (!PyArg_ParseTuple(args, "i:set_wakeup_fd", &fd))
+		return NULL;
+#ifdef WITH_THREAD
+	if (PyThread_get_thread_ident() != main_thread) {
+		PyErr_SetString(PyExc_ValueError,
+				"set_wakeup_fd only works in main thread");
+		return NULL;
+	}
+#endif
+	if (fd != -1 && fstat(fd, &buf) != 0) {
+		PyErr_SetString(PyExc_ValueError, "invalid fd");
+		return NULL;
+	}
+	old_fd = wakeup_fd;
+	wakeup_fd = fd;
+	return PyLong_FromLong(old_fd);
+}
+
+PyDoc_STRVAR(set_wakeup_fd_doc,
+"set_wakeup_fd(fd) -> fd\n\
+\n\
+Sets the fd to be written to (with '\\0') when a signal\n\
+comes in.  A library can use this to wakeup select or poll.\n\
+The previous fd is returned.\n\
+\n\
+The fd must be non-blocking.");
+
+
 /* List of functions defined in the module */
 static PyMethodDef signal_methods[] = {
 #ifdef HAVE_ALARM
@@ -274,6 +314,7 @@
 #endif
 	{"signal",	        signal_signal, METH_VARARGS, signal_doc},
 	{"getsignal",	        signal_getsignal, METH_VARARGS, getsignal_doc},
+	{"set_wakeup_fd",	signal_set_wakeup_fd, METH_VARARGS, set_wakeup_fd_doc},
 #ifdef HAVE_PAUSE
 	{"pause",	        (PyCFunction)signal_pause,
 	 METH_NOARGS,pause_doc},