Issue #23285: PEP 475 -- Retry system calls failing with EINTR.

Doc/whatsnew/3.5.rst

@@ -111,6 +111,16 @@ Please read on for a comprehensive list of user-facing changes.
        PEP written by Carl Meyer
 
 
+PEP 475: Retry system calls failing with EINTR
+----------------------------------------------
+
+:pep:`475` adds support for automatic retry of system calls failing with EINTR:
+this means that user code doesn't have to deal with EINTR or InterruptedError
+manually, and should make it more robust against asynchronous signal reception.
+
+.. seealso::
+
+   :pep:`475` -- Retry system calls failing with EINTR
 
 
 Other Language Changes

Lib/_pyio.py

@@ -1012,10 +1012,7 @@ class BufferedReader(_BufferedIOMixin):
             current_size = 0
             while True:
                 # Read until EOF or until read() would block.
-                try:
                 chunk = self.raw.read()
-                except InterruptedError:
-                    continue
                 if chunk in empty_values:
                     nodata_val = chunk
                     break
@@ -1034,10 +1031,7 @@ class BufferedReader(_BufferedIOMixin):
         chunks = [buf[pos:]]
         wanted = max(self.buffer_size, n)
         while avail < n:
-            try:
             chunk = self.raw.read(wanted)
-            except InterruptedError:
-                continue
             if chunk in empty_values:
                 nodata_val = chunk
                 break
@@ -1066,12 +1060,7 @@ class BufferedReader(_BufferedIOMixin):
         have = len(self._read_buf) - self._read_pos
         if have < want or have <= 0:
             to_read = self.buffer_size - have
-            while True:
-                try:
             current = self.raw.read(to_read)
-                except InterruptedError:
-                    continue
-                break
             if current:
                 self._read_buf = self._read_buf[self._read_pos:] + current
                 self._read_pos = 0
@@ -1220,8 +1209,6 @@ class BufferedWriter(_BufferedIOMixin):
         while self._write_buf:
             try:
                 n = self.raw.write(self._write_buf)
-            except InterruptedError:
-                continue
             except BlockingIOError:
                 raise RuntimeError("self.raw should implement RawIOBase: it "
                                    "should not raise BlockingIOError")

Lib/distutils/spawn.py

@@ -137,9 +137,6 @@ def _spawn_posix(cmd, search_path=1, verbose=0, dry_run=0):
             try:
                 pid, status = os.waitpid(pid, 0)
             except OSError as exc:
-                import errno
-                if exc.errno == errno.EINTR:
-                    continue
                 if not DEBUG:
                     cmd = executable
                 raise DistutilsExecError(

Lib/multiprocessing/connection.py

@@ -365,10 +365,7 @@ class Connection(_ConnectionBase):
     def _send(self, buf, write=_write):
         remaining = len(buf)
         while True:
-            try:
             n = write(self._handle, buf)
-            except InterruptedError:
-                continue
             remaining -= n
             if remaining == 0:
                 break
@@ -379,10 +376,7 @@ class Connection(_ConnectionBase):
         handle = self._handle
         remaining = size
         while remaining > 0:
-            try:
             chunk = read(handle, remaining)
-            except InterruptedError:
-                continue
             n = len(chunk)
             if n == 0:
                 if remaining == size:
@@ -595,13 +589,7 @@ class SocketListener(object):
             self._unlink = None
 
     def accept(self):
-        while True:
-            try:
         s, self._last_accepted = self._socket.accept()
-            except InterruptedError:
-                pass
-            else:
-                break
         s.setblocking(True)
         return Connection(s.detach())
 

Lib/multiprocessing/forkserver.py

@@ -188,8 +188,6 @@ def main(listener_fd, alive_r, preload, main_path=None, sys_path=None):
                         finally:
                             os._exit(code)
 
-            except InterruptedError:
-                pass
             except OSError as e:
                 if e.errno != errno.ECONNABORTED:
                     raise
@@ -230,13 +228,7 @@ def read_unsigned(fd):
     data = b''
     length = UNSIGNED_STRUCT.size
     while len(data) < length:
-        while True:
-            try:
         s = os.read(fd, length - len(data))
-            except InterruptedError:
-                pass
-            else:
-                break
         if not s:
             raise EOFError('unexpected EOF')
         data += s
@@ -245,13 +237,7 @@ def read_unsigned(fd):
 def write_unsigned(fd, n):
     msg = UNSIGNED_STRUCT.pack(n)
     while msg:
-        while True:
-            try:
         nbytes = os.write(fd, msg)
-            except InterruptedError:
-                pass
-            else:
-                break
         if nbytes == 0:
             raise RuntimeError('should not get here')
         msg = msg[nbytes:]

Lib/multiprocessing/popen_fork.py

 import os
 import sys
 import signal
-import errno
 
 from . import util
 
@@ -29,8 +28,6 @@ class Popen(object):
                 try:
                     pid, sts = os.waitpid(self.pid, flag)
                 except OSError as e:
-                    if e.errno == errno.EINTR:
-                        continue
                     # Child process not yet created. See #1731717
                     # e.errno == errno.ECHILD == 10
                     return None

Lib/socket.py

@@ -572,8 +572,6 @@ class SocketIO(io.RawIOBase):
             except timeout:
                 self._timeout_occurred = True
                 raise
-            except InterruptedError:
-                continue
             except error as e:
                 if e.args[0] in _blocking_errnos:
                     return None

Lib/socketserver.py

@@ -553,8 +553,6 @@ class ForkingMixIn:
             try:
                 pid, _ = os.waitpid(-1, 0)
                 self.active_children.discard(pid)
-            except InterruptedError:
-                pass
             except ChildProcessError:
                 # we don't have any children, we're done
                 self.active_children.clear()

Lib/subprocess.py

@@ -489,14 +489,6 @@ STDOUT = -2
 DEVNULL = -3
 
 
-def _eintr_retry_call(func, *args):
-    while True:
-        try:
-            return func(*args)
-        except InterruptedError:
-            continue
-
-
 # XXX This function is only used by multiprocessing and the test suite,
 # but it's here so that it can be imported when Python is compiled without
 # threads.
@@ -963,10 +955,10 @@ class Popen(object):
             if self.stdin:
                 self._stdin_write(input)
             elif self.stdout:
-                stdout = _eintr_retry_call(self.stdout.read)
+                stdout = self.stdout.read()
                 self.stdout.close()
             elif self.stderr:
-                stderr = _eintr_retry_call(self.stderr.read)
+                stderr = self.stderr.read()
                 self.stderr.close()
             self.wait()
         else:
@@ -1410,7 +1402,7 @@ class Popen(object):
                 # exception (limited in size)
                 errpipe_data = bytearray()
                 while True:
-                    part = _eintr_retry_call(os.read, errpipe_read, 50000)
+                    part = os.read(errpipe_read, 50000)
                     errpipe_data += part
                     if not part or len(errpipe_data) > 50000:
                         break
@@ -1420,7 +1412,7 @@ class Popen(object):
 
             if errpipe_data:
                 try:
-                    _eintr_retry_call(os.waitpid, self.pid, 0)
+                    os.waitpid(self.pid, 0)
                 except ChildProcessError:
                     pass
                 try:
@@ -1505,7 +1497,7 @@ class Popen(object):
         def _try_wait(self, wait_flags):
             """All callers to this function MUST hold self._waitpid_lock."""
             try:
-                (pid, sts) = _eintr_retry_call(os.waitpid, self.pid, wait_flags)
+                (pid, sts) = os.waitpid(self.pid, wait_flags)
             except ChildProcessError:
                 # This happens if SIGCLD is set to be ignored or waiting
                 # for child processes has otherwise been disabled for our

Lib/test/eintrdata/eintr_tester.py

+"""
+This test suite exercises some system calls subject to interruption with EINTR,
+to check that it is actually handled transparently.
+It is intended to be run by the main test suite within a child process, to
+ensure there is no background thread running (so that signals are delivered to
+the correct thread).
+Signals are generated in-process using setitimer(ITIMER_REAL), which allows
+sub-second periodicity (contrarily to signal()).
+"""
+
+import io
+import os
+import signal
+import socket
+import time
+import unittest
+
+from test import support
+
+
+@unittest.skipUnless(hasattr(signal, "setitimer"), "requires setitimer()")
+class EINTRBaseTest(unittest.TestCase):
+    """ Base class for EINTR tests. """
+
+    # delay for initial signal delivery
+    signal_delay = 0.1
+    # signal delivery periodicity
+    signal_period = 0.1
+    # default sleep time for tests - should obviously have:
+    # sleep_time > signal_period
+    sleep_time = 0.2
+
+    @classmethod
+    def setUpClass(cls):
+        cls.orig_handler = signal.signal(signal.SIGALRM, lambda *args: None)
+        signal.setitimer(signal.ITIMER_REAL, cls.signal_delay,
+                         cls.signal_period)
+
+    @classmethod
+    def tearDownClass(cls):
+        signal.setitimer(signal.ITIMER_REAL, 0, 0)
+        signal.signal(signal.SIGALRM, cls.orig_handler)
+
+    @classmethod
+    def _sleep(cls):
+        # default sleep time
+        time.sleep(cls.sleep_time)
+
+
+@unittest.skipUnless(hasattr(signal, "setitimer"), "requires setitimer()")
+class OSEINTRTest(EINTRBaseTest):
+    """ EINTR tests for the os module. """
+
+    def _test_wait_multiple(self, wait_func):
+        num = 3
+        for _ in range(num):
+            pid = os.fork()
+            if pid == 0:
+                self._sleep()
+                os._exit(0)
+        for _ in range(num):
+            wait_func()
+
+    def test_wait(self):
+        self._test_wait_multiple(os.wait)
+
+    @unittest.skipUnless(hasattr(os, 'wait3'), 'requires wait3()')
+    def test_wait3(self):
+        self._test_wait_multiple(lambda: os.wait3(0))
+
+    def _test_wait_single(self, wait_func):
+        pid = os.fork()
+        if pid == 0:
+            self._sleep()
+            os._exit(0)
+        else:
+            wait_func(pid)
+
+    def test_waitpid(self):
+        self._test_wait_single(lambda pid: os.waitpid(pid, 0))
+
+    @unittest.skipUnless(hasattr(os, 'wait4'), 'requires wait4()')
+    def test_wait4(self):
+        self._test_wait_single(lambda pid: os.wait4(pid, 0))
+
+    def test_read(self):
+        rd, wr = os.pipe()
+        self.addCleanup(os.close, rd)
+        # wr closed explicitly by parent
+
+        # the payload below are smaller than PIPE_BUF, hence the writes will be
+        # atomic
+        datas = [b"hello", b"world", b"spam"]
+
+        pid = os.fork()
+        if pid == 0:
+            os.close(rd)
+            for data in datas:
+                # let the parent block on read()
+                self._sleep()
+                os.write(wr, data)
+            os._exit(0)
+        else:
+            self.addCleanup(os.waitpid, pid, 0)
+            os.close(wr)
+            for data in datas:
+                self.assertEqual(data, os.read(rd, len(data)))
+
+    def test_write(self):
+        rd, wr = os.pipe()
+        self.addCleanup(os.close, wr)
+        # rd closed explicitly by parent
+
+        # we must write enough data for the write() to block
+        data = b"xyz" * support.PIPE_MAX_SIZE
+
+        pid = os.fork()
+        if pid == 0:
+            os.close(wr)
+            read_data = io.BytesIO()
+            # let the parent block on write()
+            self._sleep()
+            while len(read_data.getvalue()) < len(data):
+                chunk = os.read(rd, 2 * len(data))
+                read_data.write(chunk)
+            self.assertEqual(read_data.getvalue(), data)
+            os._exit(0)
+        else:
+            os.close(rd)
+            written = 0
+            while written < len(data):
+                written += os.write(wr, memoryview(data)[written:])
+            self.assertEqual(0, os.waitpid(pid, 0)[1])
+
+
+@unittest.skipUnless(hasattr(signal, "setitimer"), "requires setitimer()")
+class SocketEINTRTest(EINTRBaseTest):
+    """ EINTR tests for the socket module. """
+
+    @unittest.skipUnless(hasattr(socket, 'socketpair'), 'needs socketpair()')
+    def _test_recv(self, recv_func):
+        rd, wr = socket.socketpair()
+        self.addCleanup(rd.close)
+        # wr closed explicitly by parent
+
+        # single-byte payload guard us against partial recv
+        datas = [b"x", b"y", b"z"]
+
+        pid = os.fork()
+        if pid == 0:
+            rd.close()
+            for data in datas:
+                # let the parent block on recv()
+                self._sleep()
+                wr.sendall(data)
+            os._exit(0)
+        else:
+            self.addCleanup(os.waitpid, pid, 0)
+            wr.close()
+            for data in datas:
+                self.assertEqual(data, recv_func(rd, len(data)))
+
+    def test_recv(self):
+        self._test_recv(socket.socket.recv)
+
+    @unittest.skipUnless(hasattr(socket.socket, 'recvmsg'), 'needs recvmsg()')
+    def test_recvmsg(self):
+        self._test_recv(lambda sock, data: sock.recvmsg(data)[0])
+
+    def _test_send(self, send_func):
+        rd, wr = socket.socketpair()
+        self.addCleanup(wr.close)
+        # rd closed explicitly by parent
+
+        # we must send enough data for the send() to block
+        data = b"xyz" * (support.SOCK_MAX_SIZE // 3)
+
+        pid = os.fork()
+        if pid == 0:
+            wr.close()
+            # let the parent block on send()
+            self._sleep()
+            received_data = bytearray(len(data))
+            n = 0
+            while n < len(data):
+                n += rd.recv_into(memoryview(received_data)[n:])
+            self.assertEqual(received_data, data)
+            os._exit(0)
+        else:
+            rd.close()
+            written = 0
+            while written < len(data):
+                sent = send_func(wr, memoryview(data)[written:])
+                # sendall() returns None
+                written += len(data) if sent is None else sent
+            self.assertEqual(0, os.waitpid(pid, 0)[1])
+
+    def test_send(self):
+        self._test_send(socket.socket.send)
+
+    def test_sendall(self):
+        self._test_send(socket.socket.sendall)
+
+    @unittest.skipUnless(hasattr(socket.socket, 'sendmsg'), 'needs sendmsg()')
+    def test_sendmsg(self):
+        self._test_send(lambda sock, data: sock.sendmsg([data]))
+
+    def test_accept(self):
+        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self.addCleanup(sock.close)
+
+        sock.bind((support.HOST, 0))
+        _, port = sock.getsockname()
+        sock.listen()
+
+        pid = os.fork()
+        if pid == 0:
+            # let parent block on accept()
+            self._sleep()
+            with socket.create_connection((support.HOST, port)):
+                self._sleep()
+            os._exit(0)
+        else:
+            self.addCleanup(os.waitpid, pid, 0)
+            client_sock, _ = sock.accept()
+            client_sock.close()
+
+    @unittest.skipUnless(hasattr(os, 'mkfifo'), 'needs mkfifo()')
+    def _test_open(self, do_open_close_reader, do_open_close_writer):
+        # Use a fifo: until the child opens it for reading, the parent will
+        # block when trying to open it for writing.
+        support.unlink(support.TESTFN)
+        os.mkfifo(support.TESTFN)
+        self.addCleanup(support.unlink, support.TESTFN)
+
+        pid = os.fork()
+        if pid == 0:
+            # let the parent block
+            self._sleep()
+            do_open_close_reader(support.TESTFN)
+            os._exit(0)
+        else:
+            self.addCleanup(os.waitpid, pid, 0)
+            do_open_close_writer(support.TESTFN)
+
+    def test_open(self):
+        self._test_open(lambda path: open(path, 'r').close(),
+                        lambda path: open(path, 'w').close())
+
+    def test_os_open(self):
+        self._test_open(lambda path: os.close(os.open(path, os.O_RDONLY)),
+                        lambda path: os.close(os.open(path, os.O_WRONLY)))
+
+
+def test_main():
+    support.run_unittest(OSEINTRTest, SocketEINTRTest)
+
+
+if __name__ == "__main__":
+    test_main()

Lib/test/test_eintr.py

+import os
+import signal
+import unittest
+
+from test import script_helper, support
+
+
+@unittest.skipUnless(os.name == "posix", "only supported on Unix")
+class EINTRTests(unittest.TestCase):
+
+    @unittest.skipUnless(hasattr(signal, "setitimer"), "requires setitimer()")
+    def test_all(self):
+        # Run the tester in a sub-process, to make sure there is only one
+        # thread (for reliable signal delivery).
+        tester = support.findfile("eintr_tester.py", subdir="eintrdata")
+        script_helper.assert_python_ok(tester)
+
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_signal.py

@@ -587,7 +587,7 @@ class SiginterruptTest(unittest.TestCase):
             r, w = os.pipe()
 
             def handler(signum, frame):
-                pass
+                1 / 0
 
             signal.signal(signal.SIGALRM, handler)
             if interrupt is not None:
@@ -604,9 +604,8 @@ class SiginterruptTest(unittest.TestCase):
                     try:
                         # blocking call: read from a pipe without data
                         os.read(r, 1)
-                    except OSError as err:
-                        if err.errno != errno.EINTR:
-                            raise
+                    except ZeroDivisionError:
+                        pass
                     else:
                         sys.exit(2)
                 sys.exit(3)

Lib/test/test_socket.py

@@ -3590,7 +3590,7 @@ class InterruptedTimeoutBase(unittest.TestCase):
     def setUp(self):
         super().setUp()
         orig_alrm_handler = signal.signal(signal.SIGALRM,
-                                          lambda signum, frame: None)
+                                          lambda signum, frame: 1 / 0)
         self.addCleanup(signal.signal, signal.SIGALRM, orig_alrm_handler)
         self.addCleanup(self.setAlarm, 0)
 
@@ -3627,13 +3627,11 @@ class InterruptedRecvTimeoutTest(InterruptedTimeoutBase, UDPTestBase):
         self.serv.settimeout(self.timeout)
 
     def checkInterruptedRecv(self, func, *args, **kwargs):
-        # Check that func(*args, **kwargs) raises OSError with an
+        # Check that func(*args, **kwargs) raises 
         # errno of EINTR when interrupted by a signal.
         self.setAlarm(self.alarm_time)
-        with self.assertRaises(OSError) as cm:
+        with self.assertRaises(ZeroDivisionError) as cm:
             func(*args, **kwargs)
-        self.assertNotIsInstance(cm.exception, socket.timeout)
-        self.assertEqual(cm.exception.errno, errno.EINTR)
 
     def testInterruptedRecvTimeout(self):
         self.checkInterruptedRecv(self.serv.recv, 1024)
@@ -3689,12 +3687,10 @@ class InterruptedSendTimeoutTest(InterruptedTimeoutBase,
         # Check that func(*args, **kwargs), run in a loop, raises
         # OSError with an errno of EINTR when interrupted by a
         # signal.
-        with self.assertRaises(OSError) as cm:
+        with self.assertRaises(ZeroDivisionError) as cm:
             while True:
                 self.setAlarm(self.alarm_time)
                 func(*args, **kwargs)
-        self.assertNotIsInstance(cm.exception, socket.timeout)
-        self.assertEqual(cm.exception.errno, errno.EINTR)
 
     # Issue #12958: The following tests have problems on OS X prior to 10.7
     @support.requires_mac_ver(10, 7)
@@ -4062,117 +4058,6 @@ class FileObjectClassTestCase(SocketConnectedTest):
         pass
 
 
-class FileObjectInterruptedTestCase(unittest.TestCase):
-    """Test that the file object correctly handles EINTR internally."""
-
-    class MockSocket(object):
-        def __init__(self, recv_funcs=()):
-            # A generator that returns callables that we'll call for each
-            # call to recv().
-            self._recv_step = iter(recv_funcs)
-
-        def recv_into(self, buffer):
-            data = next(self._recv_step)()
-            assert len(buffer) >= len(data)
-            buffer[:len(data)] = data
-            return len(data)
-
-        def _decref_socketios(self):
-            pass
-
-        def _textiowrap_for_test(self, buffering=-1):
-            raw = socket.SocketIO(self, "r")
-            if buffering < 0:
-                buffering = io.DEFAULT_BUFFER_SIZE
-            if buffering == 0:
-                return raw
-            buffer = io.BufferedReader(raw, buffering)
-            text = io.TextIOWrapper(buffer, None, None)
-            text.mode = "rb"
-            return text
-
-    @staticmethod
-    def _raise_eintr():
-        raise OSError(errno.EINTR, "interrupted")
-
-    def _textiowrap_mock_socket(self, mock, buffering=-1):
-        raw = socket.SocketIO(mock, "r")
-        if buffering < 0:
-            buffering = io.DEFAULT_BUFFER_SIZE
-        if buffering == 0:
-            return raw
-        buffer = io.BufferedReader(raw, buffering)
-        text = io.TextIOWrapper(buffer, None, None)
-        text.mode = "rb"
-        return text
-
-    def _test_readline(self, size=-1, buffering=-1):
-        mock_sock = self.MockSocket(recv_funcs=[
-                lambda : b"This is the first line\nAnd the sec",
-                self._raise_eintr,
-                lambda : b"ond line is here\n",
-                lambda : b"",
-                lambda : b"",  # XXX(gps): io library does an extra EOF read
-            ])
-        fo = mock_sock._textiowrap_for_test(buffering=buffering)
-        self.assertEqual(fo.readline(size), "This is the first line\n")
-        self.assertEqual(fo.readline(size), "And the second line is here\n")
-
-    def _test_read(self, size=-1, buffering=-1):
-        mock_sock = self.MockSocket(recv_funcs=[
-                lambda : b"This is the first line\nAnd the sec",
-                self._raise_eintr,
-                lambda : b"ond line is here\n",
-                lambda : b"",
-                lambda : b"",  # XXX(gps): io library does an extra EOF read
-            ])
-        expecting = (b"This is the first line\n"
-                     b"And the second line is here\n")
-        fo = mock_sock._textiowrap_for_test(buffering=buffering)
-        if buffering == 0:
-            data = b''
-        else:
-            data = ''
-            expecting = expecting.decode('utf-8')
-        while len(data) != len(expecting):
-            part = fo.read(size)
-            if not part:
-                break
-            data += part
-        self.assertEqual(data, expecting)
-
-    def test_default(self):
-        self._test_readline()
-        self._test_readline(size=100)
-        self._test_read()
-        self._test_read(size=100)
-
-    def test_with_1k_buffer(self):
-        self._test_readline(buffering=1024)
-        self._test_readline(size=100, buffering=1024)
-        self._test_read(buffering=1024)
-        self._test_read(size=100, buffering=1024)
-
-    def _test_readline_no_buffer(self, size=-1):
-        mock_sock = self.MockSocket(recv_funcs=[
-                lambda : b"a",
-                lambda : b"\n",
-                lambda : b"B",
-                self._raise_eintr,
-                lambda : b"b",
-                lambda : b"",
-            ])
-        fo = mock_sock._textiowrap_for_test(buffering=0)
-        self.assertEqual(fo.readline(size), b"a\n")
-        self.assertEqual(fo.readline(size), b"Bb")
-
-    def test_no_buffer(self):
-        self._test_readline_no_buffer()
-        self._test_readline_no_buffer(size=4)
-        self._test_read(buffering=0)
-        self._test_read(size=100, buffering=0)
-
-
 class UnbufferedFileObjectClassTestCase(FileObjectClassTestCase):
 
     """Repeat the tests from FileObjectClassTestCase with bufsize==0.
@@ -5388,7 +5273,6 @@ def test_main():
     tests.extend([
         NonBlockingTCPTests,
         FileObjectClassTestCase,
-        FileObjectInterruptedTestCase,
         UnbufferedFileObjectClassTestCase,
         LineBufferedFileObjectClassTestCase,
         SmallBufferedFileObjectClassTestCase,

Lib/test/test_subprocess.py

@@ -2421,25 +2421,6 @@ class ProcessTestCaseNoPoll(ProcessTestCase):
         ProcessTestCase.tearDown(self)
 
 
-class HelperFunctionTests(unittest.TestCase):
-    @unittest.skipIf(mswindows, "errno and EINTR make no sense on windows")
-    def test_eintr_retry_call(self):
-        record_calls = []
-        def fake_os_func(*args):
-            record_calls.append(args)
-            if len(record_calls) == 2:
-                raise OSError(errno.EINTR, "fake interrupted system call")
-            return tuple(reversed(args))
-
-        self.assertEqual((999, 256),
-                         subprocess._eintr_retry_call(fake_os_func, 256, 999))
-        self.assertEqual([(256, 999)], record_calls)
-        # This time there will be an EINTR so it will loop once.
-        self.assertEqual((666,),
-                         subprocess._eintr_retry_call(fake_os_func, 666))
-        self.assertEqual([(256, 999), (666,), (666,)], record_calls)
-
-
 @unittest.skipUnless(mswindows, "Windows-specific tests")
 class CommandsWithSpaces (BaseTestCase):
 
@@ -2528,7 +2509,6 @@ def test_main():
                   Win32ProcessTestCase,
                   CommandTests,
                   ProcessTestCaseNoPoll,
-                  HelperFunctionTests,
                   CommandsWithSpaces,
                   ContextManagerTests,
                   )

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: TBA
 Core and Builtins
 -----------------
 
+- Issue #23285: PEP 475 - EINTR handling.
+
 - Issue #22735: Fix many edge cases (including crashes) involving custom mro()
   implementations.
 

Modules/_io/fileio.c

@@ -218,6 +218,7 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 #ifdef HAVE_FSTAT
     struct stat fdfstat;
 #endif
+    int async_err = 0;
 
     assert(PyFileIO_Check(oself));
     if (self->fd >= 0) {
@@ -360,6 +361,7 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 
         errno = 0;
         if (opener == Py_None) {
+            do {
                 Py_BEGIN_ALLOW_THREADS
 #ifdef MS_WINDOWS
                 if (widename != NULL)
@@ -369,6 +371,8 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
                     self->fd = open(name, flags, 0666);
 
                 Py_END_ALLOW_THREADS
+            } while (self->fd < 0 && errno == EINTR &&
+                     !(async_err = PyErr_CheckSignals()));
         }
         else {
             PyObject *fdobj;
@@ -397,6 +401,7 @@ fileio_init(PyObject *oself, PyObject *args, PyObject *kwds)
 
         fd_is_own = 1;
         if (self->fd < 0) {
+            if (!async_err)
                 PyErr_SetFromErrnoWithFilenameObject(PyExc_OSError, nameobj);
             goto error;
         }
@@ -550,7 +555,7 @@ fileio_readinto(fileio *self, PyObject *args)
 {
     Py_buffer pbuf;
     Py_ssize_t n, len;
-    int err;
+    int err, async_err = 0;
 
     if (self->fd < 0)
         return err_closed();
@@ -562,6 +567,7 @@ fileio_readinto(fileio *self, PyObject *args)
 
     if (_PyVerify_fd(self->fd)) {
         len = pbuf.len;
+        do {
             Py_BEGIN_ALLOW_THREADS
             errno = 0;
 #ifdef MS_WINDOWS
@@ -572,6 +578,8 @@ fileio_readinto(fileio *self, PyObject *args)
             n = read(self->fd, pbuf.buf, len);
 #endif
             Py_END_ALLOW_THREADS
+        } while (n < 0 && errno == EINTR &&
+                 !(async_err = PyErr_CheckSignals()));
     } else
         n = -1;
     err = errno;
@@ -580,6 +588,7 @@ fileio_readinto(fileio *self, PyObject *args)
         if (err == EAGAIN)
             Py_RETURN_NONE;
         errno = err;
+        if (!async_err)
             PyErr_SetFromErrno(PyExc_IOError);
         return NULL;
     }
@@ -627,6 +636,7 @@ fileio_readall(fileio *self)
     Py_ssize_t bytes_read = 0;
     Py_ssize_t n;
     size_t bufsize;
+    int async_err = 0;
 
     if (self->fd < 0)
         return err_closed();
@@ -673,6 +683,7 @@ fileio_readall(fileio *self)
                     return NULL;
             }
         }
+        do {
             Py_BEGIN_ALLOW_THREADS
             errno = 0;
             n = bufsize - bytes_read;
@@ -684,16 +695,11 @@ fileio_readall(fileio *self)
             n = read(self->fd, PyBytes_AS_STRING(result) + bytes_read, n);
 #endif
             Py_END_ALLOW_THREADS
+        } while (n < 0 && errno == EINTR &&
+                 !(async_err = PyErr_CheckSignals()));
         if (n == 0)
             break;
         if (n < 0) {
-            if (errno == EINTR) {
-                if (PyErr_CheckSignals()) {
-                    Py_DECREF(result);
-                    return NULL;
-                }
-                continue;
-            }
             if (errno == EAGAIN) {
                 if (bytes_read > 0)
                     break;
@@ -701,6 +707,7 @@ fileio_readall(fileio *self)
                 Py_RETURN_NONE;
             }
             Py_DECREF(result);
+            if (!async_err)
                 PyErr_SetFromErrno(PyExc_IOError);
             return NULL;
         }
@@ -723,6 +730,7 @@ fileio_read(fileio *self, PyObject *args)
     char *ptr;
     Py_ssize_t n;
     Py_ssize_t size = -1;
+    int async_err = 0;
     PyObject *bytes;
 
     if (self->fd < 0)
@@ -747,6 +755,7 @@ fileio_read(fileio *self, PyObject *args)
     ptr = PyBytes_AS_STRING(bytes);
 
     if (_PyVerify_fd(self->fd)) {
+        do {
             Py_BEGIN_ALLOW_THREADS
             errno = 0;
 #ifdef MS_WINDOWS
@@ -755,6 +764,8 @@ fileio_read(fileio *self, PyObject *args)
             n = read(self->fd, ptr, size);
 #endif
             Py_END_ALLOW_THREADS
+        } while (n < 0 && errno == EINTR &&
+                 !(async_err = PyErr_CheckSignals()));
     } else
         n = -1;
 
@@ -764,6 +775,7 @@ fileio_read(fileio *self, PyObject *args)
         if (err == EAGAIN)
             Py_RETURN_NONE;
         errno = err;
+        if (!async_err)
             PyErr_SetFromErrno(PyExc_IOError);
         return NULL;
     }
@@ -783,7 +795,7 @@ fileio_write(fileio *self, PyObject *args)
 {
     Py_buffer pbuf;
     Py_ssize_t n, len;
-    int err;
+    int err, async_err = 0;
 
     if (self->fd < 0)
         return err_closed();
@@ -794,6 +806,7 @@ fileio_write(fileio *self, PyObject *args)
         return NULL;
 
     if (_PyVerify_fd(self->fd)) {
+        do {
             Py_BEGIN_ALLOW_THREADS
             errno = 0;
             len = pbuf.len;
@@ -804,14 +817,15 @@ fileio_write(fileio *self, PyObject *args)
                    binary and the length is greater than 66,000 bytes (or less,
                    depending on heap usage). */
                 len = 32767;
-        }
-        else if (len > INT_MAX)
+            } else if (len > INT_MAX)
                 len = INT_MAX;
             n = write(self->fd, pbuf.buf, (int)len);
 #else
             n = write(self->fd, pbuf.buf, len);
 #endif
             Py_END_ALLOW_THREADS
+        } while (n < 0 && errno == EINTR &&
+                 !(async_err = PyErr_CheckSignals()));
     } else
         n = -1;
     err = errno;
@@ -822,6 +836,7 @@ fileio_write(fileio *self, PyObject *args)
         if (err == EAGAIN)
             Py_RETURN_NONE;
         errno = err;
+        if (!async_err)
             PyErr_SetFromErrno(PyExc_IOError);
         return NULL;
     }

Modules/socketmodule.c

@@ -2037,6 +2037,7 @@ sock_accept(PySocketSockObject *s)
     PyObject *addr = NULL;
     PyObject *res = NULL;
     int timeout;
+    int async_err = 0;
 #if defined(HAVE_ACCEPT4) && defined(SOCK_CLOEXEC)
     /* accept4() is available on Linux 2.6.28+ and glibc 2.10 */
     static int accept4_works = -1;
@@ -2050,7 +2051,7 @@ sock_accept(PySocketSockObject *s)
         return select_error();
 
     BEGIN_SELECT_LOOP(s)
-
+    do {
         Py_BEGIN_ALLOW_THREADS
         timeout = internal_select_ex(s, 0, interval);
         if (!timeout) {
@@ -2070,7 +2071,7 @@ sock_accept(PySocketSockObject *s)
 #endif
         }
         Py_END_ALLOW_THREADS
-
+    } while (newfd < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
     if (timeout == 1) {
         PyErr_SetString(socket_timeout, "timed out");
         return NULL;
@@ -2078,7 +2079,7 @@ sock_accept(PySocketSockObject *s)
     END_SELECT_LOOP(s)
 
     if (newfd == INVALID_SOCKET)
-        return s->errorhandler();
+        return (!async_err) ? s->errorhandler() : NULL;
 
 #ifdef MS_WINDOWS
     if (!SetHandleInformation((HANDLE)newfd, HANDLE_FLAG_INHERIT, 0)) {
@@ -2341,6 +2342,10 @@ sock_close(PySocketSockObject *s)
 {
     SOCKET_T fd;
 
+    /* We do not want to retry upon EINTR: see http://lwn.net/Articles/576478/
+     * and http://linux.derkeiler.com/Mailing-Lists/Kernel/2005-09/3000.html
+     * for more details.
+     */
     if ((fd = s->sock_fd) != -1) {
         s->sock_fd = -1;
         Py_BEGIN_ALLOW_THREADS
@@ -2513,10 +2518,8 @@ sock_connect_ex(PySocketSockObject *s, PyObject *addro)
 
     /* Signals are not errors (though they may raise exceptions).  Adapted
        from PyErr_SetFromErrnoWithFilenameObject(). */
-#ifdef EINTR
     if (res == EINTR && PyErr_CheckSignals())
         return NULL;
-#endif
 
     return PyLong_FromLong((long) res);
 }
@@ -2650,6 +2653,7 @@ sock_recv_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags)
 {
     Py_ssize_t outlen = -1;
     int timeout;
+    int async_err = 0;
 
     if (!IS_SELECTABLE(s)) {
         select_error();
@@ -2661,6 +2665,7 @@ sock_recv_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags)
     }
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS
         timeout = internal_select_ex(s, 0, interval);
         if (!timeout) {
@@ -2673,6 +2678,7 @@ sock_recv_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags)
 #endif
         }
         Py_END_ALLOW_THREADS
+    } while (outlen < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
     if (timeout == 1) {
         PyErr_SetString(socket_timeout, "timed out");
@@ -2682,6 +2688,7 @@ sock_recv_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags)
     if (outlen < 0) {
         /* Note: the call to errorhandler() ALWAYS indirectly returned
            NULL, so ignore its return value */
+        if (!async_err)
             s->errorhandler();
         return -1;
     }
@@ -2819,6 +2826,7 @@ sock_recvfrom_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags,
     int timeout;
     Py_ssize_t n = -1;
     socklen_t addrlen;
+    int async_err = 0;
 
     *addr = NULL;
 
@@ -2831,6 +2839,7 @@ sock_recvfrom_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags,
     }
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS
         memset(&addrbuf, 0, addrlen);
         timeout = internal_select_ex(s, 0, interval);
@@ -2846,6 +2855,7 @@ sock_recvfrom_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags,
 #endif
         }
         Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
     if (timeout == 1) {
         PyErr_SetString(socket_timeout, "timed out");
@@ -2853,6 +2863,7 @@ sock_recvfrom_guts(PySocketSockObject *s, char* cbuf, Py_ssize_t len, int flags,
     }
     END_SELECT_LOOP(s)
     if (n < 0) {
+        if (!async_err)
             s->errorhandler();
         return -1;
     }
@@ -2993,6 +3004,7 @@ sock_recvmsg_guts(PySocketSockObject *s, struct iovec *iov, int iovlen,
 {
     ssize_t bytes_received = -1;
     int timeout;
+    int async_err = 0;
     sock_addr_t addrbuf;
     socklen_t addrbuflen;
     struct msghdr msg = {0};
@@ -3028,6 +3040,7 @@ sock_recvmsg_guts(PySocketSockObject *s, struct iovec *iov, int iovlen,
     }
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS;
         msg.msg_name = SAS2SA(&addrbuf);
         msg.msg_namelen = addrbuflen;
@@ -3043,9 +3056,12 @@ sock_recvmsg_guts(PySocketSockObject *s, struct iovec *iov, int iovlen,
             PyErr_SetString(socket_timeout, "timed out");
             goto finally;
         }
+    } while (bytes_received < 0 && errno == EINTR &&
+             !(async_err = PyErr_CheckSignals()));
     END_SELECT_LOOP(s)
 
     if (bytes_received < 0) {
+        if (!async_err)
             s->errorhandler();
         goto finally;
     }
@@ -3305,6 +3321,7 @@ sock_send(PySocketSockObject *s, PyObject *args)
 {
     char *buf;
     Py_ssize_t len, n = -1;
+    int async_err = 0;
     int flags = 0, timeout;
     Py_buffer pbuf;
 
@@ -3319,6 +3336,7 @@ sock_send(PySocketSockObject *s, PyObject *args)
     len = pbuf.len;
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS
         timeout = internal_select_ex(s, 1, interval);
         if (!timeout) {
@@ -3331,6 +3349,7 @@ sock_send(PySocketSockObject *s, PyObject *args)
 #endif
         }
         Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
     if (timeout == 1) {
         PyBuffer_Release(&pbuf);
         PyErr_SetString(socket_timeout, "timed out");
@@ -3340,7 +3359,7 @@ sock_send(PySocketSockObject *s, PyObject *args)
 
     PyBuffer_Release(&pbuf);
     if (n < 0)
-        return s->errorhandler();
+        return (!async_err) ? s->errorhandler() : NULL;
     return PyLong_FromSsize_t(n);
 }
 
@@ -3359,7 +3378,8 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
 {
     char *buf;
     Py_ssize_t len, n = -1;
-    int flags = 0, timeout, saved_errno;
+    int async_err = 0;
+    int flags = 0, timeout;
     Py_buffer pbuf;
 
     if (!PyArg_ParseTuple(args, "y*|i:sendall", &pbuf, &flags))
@@ -3391,29 +3411,16 @@ sock_sendall(PySocketSockObject *s, PyObject *args)
             PyErr_SetString(socket_timeout, "timed out");
             return NULL;
         }
-        /* PyErr_CheckSignals() might change errno */
-        saved_errno = errno;
-        /* We must run our signal handlers before looping again.
-           send() can return a successful partial write when it is
-           interrupted, so we can't restrict ourselves to EINTR. */
-        if (PyErr_CheckSignals()) {
-            PyBuffer_Release(&pbuf);
-            return NULL;
-        }
-        if (n < 0) {
-            /* If interrupted, try again */
-            if (saved_errno == EINTR)
-                continue;
-            else
-                break;
-        }
+        if (n >= 0) {
             buf += n;
             len -= n;
-    } while (len > 0);
+        }
+    } while (len > 0 && (n >= 0 || errno == EINTR) &&
+             !(async_err = PyErr_CheckSignals()));
     PyBuffer_Release(&pbuf);
 
-    if (n < 0)
-        return s->errorhandler();
+    if (n < 0 || async_err)
+        return (!async_err) ? s->errorhandler() : NULL;
 
     Py_INCREF(Py_None);
     return Py_None;
@@ -3439,6 +3446,7 @@ sock_sendto(PySocketSockObject *s, PyObject *args)
     Py_ssize_t len, arglen;
     sock_addr_t addrbuf;
     int addrlen, n = -1, flags, timeout;
+    int async_err = 0;
 
     flags = 0;
     arglen = PyTuple_Size(args);
@@ -3473,6 +3481,7 @@ sock_sendto(PySocketSockObject *s, PyObject *args)
     }
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS
         timeout = internal_select_ex(s, 1, interval);
         if (!timeout) {
@@ -3487,6 +3496,7 @@ sock_sendto(PySocketSockObject *s, PyObject *args)
 #endif
         }
         Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 
     if (timeout == 1) {
         PyBuffer_Release(&pbuf);
@@ -3496,7 +3506,7 @@ sock_sendto(PySocketSockObject *s, PyObject *args)
     END_SELECT_LOOP(s)
     PyBuffer_Release(&pbuf);
     if (n < 0)
-        return s->errorhandler();
+        return (!async_err) ? s->errorhandler() : NULL;
     return PyLong_FromSsize_t(n);
 }
 
@@ -3528,6 +3538,7 @@ sock_sendmsg(PySocketSockObject *s, PyObject *args)
     void *controlbuf = NULL;
     size_t controllen, controllen_last;
     ssize_t bytes_sent = -1;
+    int async_err = 0;
     int addrlen, timeout, flags = 0;
     PyObject *data_arg, *cmsg_arg = NULL, *addr_arg = NULL, *data_fast = NULL,
         *cmsg_fast = NULL, *retval = NULL;
@@ -3685,6 +3696,7 @@ sock_sendmsg(PySocketSockObject *s, PyObject *args)
     }
 
     BEGIN_SELECT_LOOP(s)
+    do {
         Py_BEGIN_ALLOW_THREADS;
         timeout = internal_select_ex(s, 1, interval);
         if (!timeout)
@@ -3694,9 +3706,12 @@ sock_sendmsg(PySocketSockObject *s, PyObject *args)
             PyErr_SetString(socket_timeout, "timed out");
             goto finally;
         }
+    } while (bytes_sent < 0 && errno == EINTR &&
+             !(async_err = PyErr_CheckSignals()));
     END_SELECT_LOOP(s)
 
     if (bytes_sent < 0) {
+        if (!async_err)
             s->errorhandler();
         goto finally;
     }