Python sys.getswitchinterval() Examples

def acquire(self, blocking: bool = True, timeout: float = -1) -> bool:
            tident = threading.get_ident()
            if blocking == 0:
                blocking = False
            start_time = Scalene.gettime()
            if blocking:
                if timeout < 0:
                    interval = sys.getswitchinterval()
                else:
                    interval = min(timeout, sys.getswitchinterval())
            else:
                interval = -1
            while True:
                Scalene.set_thread_sleeping(tident)
                acquired_lock = self.__lock.acquire(blocking, interval)
                Scalene.reset_thread_sleeping(tident)
                if acquired_lock:
                    return True
                if not blocking:
                    return False
                # If a timeout was specified, check to see if it's expired.
                if timeout != -1:
                    end_time = Scalene.gettime()
                    if end_time - start_time >= timeout:
                        return False 

def thread_join_replacement(
        self: threading.Thread, timeout: Optional[float] = None
    ) -> None:
        """We replace threading.Thread.join with this method which always
periodically yields."""
        start_time = Scalene.gettime()
        interval = sys.getswitchinterval()
        while self.is_alive():
            Scalene.__is_thread_sleeping[threading.get_ident()] = True
            Scalene.__original_thread_join(self, interval)
            Scalene.__is_thread_sleeping[threading.get_ident()] = False
            # If a timeout was specified, check to see if it's expired.
            if timeout:
                end_time = Scalene.gettime()
                if end_time - start_time >= timeout:
                    return None
        return None 

def test_enumerate_after_join(self):
        # Try hard to trigger #1703448: a thread is still returned in
        # threading.enumerate() after it has been join()ed.
        enum = threading.enumerate
        old_interval = sys.getswitchinterval()
        try:
            for i in range(1, 100):
                sys.setswitchinterval(i * 0.0002)
                t = threading.Thread(target=lambda: None)
                t.start()
                t.join()
                l = enum()
                self.assertNotIn(t, l,
                    "#1703448 triggered after %d trials: %s" % (i, l))
        finally:
            sys.setswitchinterval(old_interval) 

def test_is_alive_after_fork(self):
        # Try hard to trigger #18418: is_alive() could sometimes be True on
        # threads that vanished after a fork.
        old_interval = sys.getswitchinterval()
        self.addCleanup(sys.setswitchinterval, old_interval)

        # Make the bug more likely to manifest.
        sys.setswitchinterval(1e-6)

        for i in range(20):
            t = threading.Thread(target=lambda: None)
            t.start()
            self.addCleanup(t.join)
            pid = os.fork()
            if pid == 0:
                os._exit(1 if t.is_alive() else 0)
            else:
                pid, status = os.waitpid(pid, 0)
                self.assertEqual(0, status) 

def test_is_alive_after_fork(self):
        # Try hard to trigger #18418: is_alive() could sometimes be True on
        # threads that vanished after a fork.
        old_interval = sys.getswitchinterval()
        self.addCleanup(sys.setswitchinterval, old_interval)

        # Make the bug more likely to manifest.
        test.support.setswitchinterval(1e-6)

        for i in range(20):
            t = threading.Thread(target=lambda: None)
            t.start()
            pid = os.fork()
            if pid == 0:
                os._exit(11 if t.is_alive() else 10)
            else:
                t.join()

                pid, status = os.waitpid(pid, 0)
                self.assertTrue(os.WIFEXITED(status))
                self.assertEqual(10, os.WEXITSTATUS(status)) 

def test_enumerate_after_join(self):
        # Try hard to trigger #1703448: a thread is still returned in
        # threading.enumerate() after it has been join()ed.
        enum = threading.enumerate
        old_interval = sys.getswitchinterval()
        try:
            for i in range(1, 100):
                sys.setswitchinterval(i * 0.0002)
                t = threading.Thread(target=lambda: None)
                t.start()
                t.join()
                l = enum()
                self.assertNotIn(t, l,
                    "#1703448 triggered after %d trials: %s" % (i, l))
        finally:
            sys.setswitchinterval(old_interval) 

def test_enumerate_after_join(self):
        # Try hard to trigger #1703448: a thread is still returned in
        # threading.enumerate() after it has been join()ed.
        enum = threading.enumerate
        old_interval = sys.getswitchinterval()
        try:
            for i in range(1, 100):
                sys.setswitchinterval(i * 0.0002)
                t = threading.Thread(target=lambda: None)
                t.start()
                t.join()
                l = enum()
                self.assertNotIn(t, l,
                    "#1703448 triggered after %d trials: %s" % (i, l))
        finally:
            sys.setswitchinterval(old_interval) 

def test_is_alive_after_fork(self):
        # Try hard to trigger #18418: is_alive() could sometimes be True on
        # threads that vanished after a fork.
        old_interval = sys.getswitchinterval()
        self.addCleanup(sys.setswitchinterval, old_interval)

        # Make the bug more likely to manifest.
        sys.setswitchinterval(1e-6)

        for i in range(20):
            t = threading.Thread(target=lambda: None)
            t.start()
            self.addCleanup(t.join)
            pid = os.fork()
            if pid == 0:
                os._exit(1 if t.is_alive() else 0)
            else:
                pid, status = os.waitpid(pid, 0)
                self.assertEqual(0, status) 

def test_is_alive_after_fork(self):
        # Try hard to trigger #18418: is_alive() could sometimes be True on
        # threads that vanished after a fork.
        old_interval = sys.getswitchinterval()
        self.addCleanup(sys.setswitchinterval, old_interval)

        # Make the bug more likely to manifest.
        sys.setswitchinterval(1e-6)

        for i in range(20):
            t = threading.Thread(target=lambda: None)
            t.start()
            pid = os.fork()
            if pid == 0:
                os._exit(11 if t.is_alive() else 10)
            else:
                t.join()

                pid, status = os.waitpid(pid, 0)
                self.assertTrue(os.WIFEXITED(status))
                self.assertEqual(10, os.WEXITSTATUS(status)) 

def test_enumerate_after_join(self):
        # Try hard to trigger #1703448: a thread is still returned in
        # threading.enumerate() after it has been join()ed.
        enum = threading.enumerate
        old_interval = sys.getswitchinterval()
        try:
            for i in range(1, 100):
                sys.setswitchinterval(i * 0.0002)
                t = threading.Thread(target=lambda: None)
                t.start()
                t.join()
                l = enum()
                self.assertNotIn(t, l,
                    "#1703448 triggered after %d trials: %s" % (i, l))
        finally:
            sys.setswitchinterval(old_interval) 

def test_main():
    old_switchinterval = None
    try:
        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
    except AttributeError:
        pass
    try:
        run_unittest(ThreadedImportTests)
    finally:
        if old_switchinterval is not None:
            sys.setswitchinterval(old_switchinterval) 

def test_pending_calls_race(self):
        # Issue #14406: multi-threaded race condition when waiting on all
        # futures.
        event = threading.Event()
        def future_func():
            event.wait()
        oldswitchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            fs = {self.executor.submit(future_func) for i in range(100)}
            event.set()
            futures.wait(fs, return_when=futures.ALL_COMPLETED)
        finally:
            sys.setswitchinterval(oldswitchinterval) 

def test_main():
    old_switchinterval = None
    try:
        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
    except AttributeError:
        pass
    try:
        run_unittest(ThreadedImportTests)
    finally:
        if old_switchinterval is not None:
            sys.setswitchinterval(old_switchinterval) 

def setUp(self):
            try:
                self.old_switchinterval = sys.getswitchinterval()
                sys.setswitchinterval(0.000001)
            except AttributeError:
                self.old_switchinterval = None 

def test_pending_calls_race(self):
        # Issue #14406: multi-threaded race condition when waiting on all
        # futures.
        event = threading.Event()
        def future_func():
            event.wait()
        oldswitchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            fs = {self.executor.submit(future_func) for i in range(100)}
            event.set()
            futures.wait(fs, return_when=futures.ALL_COMPLETED)
        finally:
            sys.setswitchinterval(oldswitchinterval) 

def setUp(self):
        """
        Reduce the CPython check interval so that thread switches happen much
        more often, hopefully exercising more possible race conditions.  Also,
        delay actual test startup until the reactor has been started.
        """
        if _PY3:
            if getattr(sys, 'getswitchinterval', None) is not None:
                self.addCleanup(sys.setswitchinterval, sys.getswitchinterval())
                sys.setswitchinterval(0.0000001)
        else:
            if getattr(sys, 'getcheckinterval', None) is not None:
                self.addCleanup(sys.setcheckinterval, sys.getcheckinterval())
                sys.setcheckinterval(7) 

def setUp(self):
        try:
            self.old_switchinterval = sys.getswitchinterval()
            sys.setswitchinterval(0.000001)
        except AttributeError:
            self.old_switchinterval = None 

def test_switchinterval(self):
        self.assertRaises(TypeError, sys.setswitchinterval)
        self.assertRaises(TypeError, sys.setswitchinterval, "a")
        self.assertRaises(ValueError, sys.setswitchinterval, -1.0)
        self.assertRaises(ValueError, sys.setswitchinterval, 0.0)
        orig = sys.getswitchinterval()
        # sanity check
        self.assertTrue(orig < 0.5, orig)
        try:
            for n in 0.00001, 0.05, 3.0, orig:
                sys.setswitchinterval(n)
                self.assertAlmostEqual(sys.getswitchinterval(), n)
        finally:
            sys.setswitchinterval(orig) 

def test_pending_calls_race(self):
        # Issue #14406: multi-threaded race condition when waiting on all
        # futures.
        event = threading.Event()
        def future_func():
            event.wait()
        oldswitchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            fs = {self.executor.submit(future_func) for i in range(100)}
            event.set()
            futures.wait(fs, return_when=futures.ALL_COMPLETED)
        finally:
            sys.setswitchinterval(oldswitchinterval) 

def test_main():
    old_switchinterval = None
    try:
        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
    except AttributeError:
        pass
    try:
        run_unittest(ThreadedImportTests)
    finally:
        if old_switchinterval is not None:
            sys.setswitchinterval(old_switchinterval) 

def setUp(self):
        """
        Reduce the CPython check interval so that thread switches happen much
        more often, hopefully exercising more possible race conditions.  Also,
        delay actual test startup until the reactor has been started.
        """
        if _PY3:
            if getattr(sys, 'getswitchinterval', None) is not None:
                self.addCleanup(sys.setswitchinterval, sys.getswitchinterval())
                sys.setswitchinterval(0.0000001)
        else:
            if getattr(sys, 'getcheckinterval', None) is not None:
                self.addCleanup(sys.setcheckinterval, sys.getcheckinterval())
                sys.setcheckinterval(7) 

def setUp(self):
            try:
                self.old_switchinterval = sys.getswitchinterval()
                sys.setswitchinterval(0.000001)
            except AttributeError:
                self.old_switchinterval = None 

def test_pending_calls_race(self):
        # Issue #14406: multi-threaded race condition when waiting on all
        # futures.
        event = threading.Event()
        def future_func():
            event.wait()
        oldswitchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            fs = {self.executor.submit(future_func) for i in range(100)}
            event.set()
            futures.wait(fs, return_when=futures.ALL_COMPLETED)
        finally:
            sys.setswitchinterval(oldswitchinterval) 

def test_main():
    old_switchinterval = None
    try:
        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
    except AttributeError:
        pass
    try:
        run_unittest(ThreadedImportTests)
    finally:
        if old_switchinterval is not None:
            sys.setswitchinterval(old_switchinterval) 

def test_lru_cache_threaded(self):
        n, m = 5, 11
        def orig(x, y):
            return 3 * x + y
        f = self.module.lru_cache(maxsize=n*m)(orig)
        hits, misses, maxsize, currsize = f.cache_info()
        self.assertEqual(currsize, 0)

        start = threading.Event()
        def full(k):
            start.wait(10)
            for _ in range(m):
                self.assertEqual(f(k, 0), orig(k, 0))

        def clear():
            start.wait(10)
            for _ in range(2*m):
                f.cache_clear()

        orig_si = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            # create n threads in order to fill cache
            threads = [threading.Thread(target=full, args=[k])
                       for k in range(n)]
            with support.start_threads(threads):
                start.set()

            hits, misses, maxsize, currsize = f.cache_info()
            if self.module is py_functools:
                # XXX: Why can be not equal?
                self.assertLessEqual(misses, n)
                self.assertLessEqual(hits, m*n - misses)
            else:
                self.assertEqual(misses, n)
                self.assertEqual(hits, m*n - misses)
            self.assertEqual(currsize, n)

            # create n threads in order to fill cache and 1 to clear it
            threads = [threading.Thread(target=clear)]
            threads += [threading.Thread(target=full, args=[k])
                        for k in range(n)]
            start.clear()
            with support.start_threads(threads):
                start.set()
        finally:
            sys.setswitchinterval(orig_si) 

def test_trashcan_threads(self):
        # Issue #13992: trashcan mechanism should be thread-safe
        NESTING = 60
        N_THREADS = 2

        def sleeper_gen():
            """A generator that releases the GIL when closed or dealloc'ed."""
            try:
                yield
            finally:
                time.sleep(0.000001)

        class C(list):
            # Appending to a list is atomic, which avoids the use of a lock.
            inits = []
            dels = []
            def __init__(self, alist):
                self[:] = alist
                C.inits.append(None)
            def __del__(self):
                # This __del__ is called by subtype_dealloc().
                C.dels.append(None)
                # `g` will release the GIL when garbage-collected.  This
                # helps assert subtype_dealloc's behaviour when threads
                # switch in the middle of it.
                g = sleeper_gen()
                next(g)
                # Now that __del__ is finished, subtype_dealloc will proceed
                # to call list_dealloc, which also uses the trashcan mechanism.

        def make_nested():
            """Create a sufficiently nested container object so that the
            trashcan mechanism is invoked when deallocating it."""
            x = C([])
            for i in range(NESTING):
                x = [C([x])]
            del x

        def run_thread():
            """Exercise make_nested() in a loop."""
            while not exit:
                make_nested()

        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
        try:
            exit = []
            threads = []
            for i in range(N_THREADS):
                t = threading.Thread(target=run_thread)
                threads.append(t)
            with start_threads(threads, lambda: exit.append(1)):
                time.sleep(1.0)
        finally:
            sys.setswitchinterval(old_switchinterval)
        gc.collect()
        self.assertEqual(len(C.inits), len(C.dels)) 

def test_thread_safety(self):
        # bpo-24484: _run_finalizers() should be thread-safe
        def cb():
            pass

        class Foo(object):
            def __init__(self):
                self.ref = self  # create reference cycle
                # insert finalizer at random key
                util.Finalize(self, cb, exitpriority=random.randint(1, 100))

        finish = False
        exc = None

        def run_finalizers():
            nonlocal exc
            while not finish:
                time.sleep(random.random() * 1e-1)
                try:
                    # A GC run will eventually happen during this,
                    # collecting stale Foo's and mutating the registry
                    util._run_finalizers()
                except Exception as e:
                    exc = e

        def make_finalizers():
            nonlocal exc
            d = {}
            while not finish:
                try:
                    # Old Foo's get gradually replaced and later
                    # collected by the GC (because of the cyclic ref)
                    d[random.getrandbits(5)] = {Foo() for i in range(10)}
                except Exception as e:
                    exc = e
                    d.clear()

        old_interval = sys.getswitchinterval()
        old_threshold = gc.get_threshold()
        try:
            sys.setswitchinterval(1e-6)
            gc.set_threshold(5, 5, 5)
            threads = [threading.Thread(target=run_finalizers),
                       threading.Thread(target=make_finalizers)]
            with test.support.start_threads(threads):
                time.sleep(4.0)  # Wait a bit to trigger race condition
                finish = True
            if exc is not None:
                raise exc
        finally:
            sys.setswitchinterval(old_interval)
            gc.set_threshold(*old_threshold)
            gc.collect()  # Collect remaining Foo's


#
# Test that from ... import * works for each module
# 

def test_lru_cache_threaded(self):
        n, m = 5, 11
        def orig(x, y):
            return 3 * x + y
        f = self.module.lru_cache(maxsize=n*m)(orig)
        hits, misses, maxsize, currsize = f.cache_info()
        self.assertEqual(currsize, 0)

        start = threading.Event()
        def full(k):
            start.wait(10)
            for _ in range(m):
                self.assertEqual(f(k, 0), orig(k, 0))

        def clear():
            start.wait(10)
            for _ in range(2*m):
                f.cache_clear()

        orig_si = sys.getswitchinterval()
        support.setswitchinterval(1e-6)
        try:
            # create n threads in order to fill cache
            threads = [threading.Thread(target=full, args=[k])
                       for k in range(n)]
            with support.start_threads(threads):
                start.set()

            hits, misses, maxsize, currsize = f.cache_info()
            if self.module is py_functools:
                # XXX: Why can be not equal?
                self.assertLessEqual(misses, n)
                self.assertLessEqual(hits, m*n - misses)
            else:
                self.assertEqual(misses, n)
                self.assertEqual(hits, m*n - misses)
            self.assertEqual(currsize, n)

            # create n threads in order to fill cache and 1 to clear it
            threads = [threading.Thread(target=clear)]
            threads += [threading.Thread(target=full, args=[k])
                        for k in range(n)]
            start.clear()
            with support.start_threads(threads):
                start.set()
        finally:
            sys.setswitchinterval(orig_si) 

def test_trashcan_threads(self):
        # Issue #13992: trashcan mechanism should be thread-safe
        NESTING = 60
        N_THREADS = 2

        def sleeper_gen():
            """A generator that releases the GIL when closed or dealloc'ed."""
            try:
                yield
            finally:
                time.sleep(0.000001)

        class C(list):
            # Appending to a list is atomic, which avoids the use of a lock.
            inits = []
            dels = []
            def __init__(self, alist):
                self[:] = alist
                C.inits.append(None)
            def __del__(self):
                # This __del__ is called by subtype_dealloc().
                C.dels.append(None)
                # `g` will release the GIL when garbage-collected.  This
                # helps assert subtype_dealloc's behaviour when threads
                # switch in the middle of it.
                g = sleeper_gen()
                next(g)
                # Now that __del__ is finished, subtype_dealloc will proceed
                # to call list_dealloc, which also uses the trashcan mechanism.

        def make_nested():
            """Create a sufficiently nested container object so that the
            trashcan mechanism is invoked when deallocating it."""
            x = C([])
            for i in range(NESTING):
                x = [C([x])]
            del x

        def run_thread():
            """Exercise make_nested() in a loop."""
            while not exit:
                make_nested()

        old_switchinterval = sys.getswitchinterval()
        sys.setswitchinterval(1e-5)
        try:
            exit = []
            threads = []
            for i in range(N_THREADS):
                t = threading.Thread(target=run_thread)
                threads.append(t)
            with start_threads(threads, lambda: exit.append(1)):
                time.sleep(1.0)
        finally:
            sys.setswitchinterval(old_switchinterval)
        gc.collect()
        self.assertEqual(len(C.inits), len(C.dels)) 

def test_lru_cache_threaded(self):
        n, m = 5, 11
        def orig(x, y):
            return 3 * x + y
        f = self.module.lru_cache(maxsize=n*m)(orig)
        hits, misses, maxsize, currsize = f.cache_info()
        self.assertEqual(currsize, 0)

        start = threading.Event()
        def full(k):
            start.wait(10)
            for _ in range(m):
                self.assertEqual(f(k, 0), orig(k, 0))

        def clear():
            start.wait(10)
            for _ in range(2*m):
                f.cache_clear()

        orig_si = sys.getswitchinterval()
        sys.setswitchinterval(1e-6)
        try:
            # create n threads in order to fill cache
            threads = [threading.Thread(target=full, args=[k])
                       for k in range(n)]
            with support.start_threads(threads):
                start.set()

            hits, misses, maxsize, currsize = f.cache_info()
            if self.module is py_functools:
                # XXX: Why can be not equal?
                self.assertLessEqual(misses, n)
                self.assertLessEqual(hits, m*n - misses)
            else:
                self.assertEqual(misses, n)
                self.assertEqual(hits, m*n - misses)
            self.assertEqual(currsize, n)

            # create n threads in order to fill cache and 1 to clear it
            threads = [threading.Thread(target=clear)]
            threads += [threading.Thread(target=full, args=[k])
                        for k in range(n)]
            start.clear()
            with support.start_threads(threads):
                start.set()
        finally:
            sys.setswitchinterval(orig_si)