Method test_stress_delivery_dependent

Lib/test/test_signal.py:1270–1312

This test uses dependent signal handlers.

(self)

    @unittest.skipUnless(hasattr(signal, "setitimer"),
                         "test needs setitimer()")
    def test_stress_delivery_dependent(self):
        """
        This test uses dependent signal handlers.
        """
        N = self.decide_itimer_count()
        sigs = []

        def first_handler(signum, frame):
            # 1e-6 is the minimum non-zero value for `setitimer()`.
            # Choose a random delay so as to improve chances of
            # triggering a race condition.  Ideally the signal is received
            # when inside critical signal-handling routines such as
            # Py_MakePendingCalls().
            signal.setitimer(signal.ITIMER_REAL, 1e-6 + random.random() * 1e-5)

        def second_handler(signum=None, frame=None):
            sigs.append(signum)

        # Here on Linux, SIGPROF > SIGALRM > SIGUSR1.  By using both
        # ascending and descending sequences (SIGUSR1 then SIGALRM,
        # SIGPROF then SIGALRM), we maximize chances of hitting a bug.
        self.setsig(signal.SIGPROF, first_handler)
        self.setsig(signal.SIGUSR1, first_handler)
        self.setsig(signal.SIGALRM, second_handler)  # for ITIMER_REAL

        expected_sigs = 0
        deadline = time.monotonic() + support.SHORT_TIMEOUT

        while expected_sigs < N:
            os.kill(os.getpid(), signal.SIGPROF)
            expected_sigs += 1
            # Wait for handlers to run to avoid signal coalescing
            while len(sigs) < expected_sigs and time.monotonic() < deadline:
                time.sleep(1e-5)

            os.kill(os.getpid(), signal.SIGUSR1)
            expected_sigs += 1
            while len(sigs) < expected_sigs and time.monotonic() < deadline:
                time.sleep(1e-5)

        # All ITIMER_REAL signals should have been delivered to the
        # Python handler
        self.assertEqual(len(sigs), N, "Some signals were lost")

    @unittest.skipUnless(hasattr(signal, "setitimer"),
                         "test needs setitimer()")