gh-89977: Keep the GIL for short socket and epoll control calls

Author: methane

Lib/test/test_epoll.py

@@ -238,6 +238,16 @@ def test_unregister_closed(self):
             ep.unregister(fd)
         self.assertEqual(cm.exception.errno, errno.EBADF)
 
+    def test_unregister_twice(self):
+        with select.epoll() as ep:
+            ep.register(self.serverSocket)
+            ep.unregister(self.serverSocket)
+            with self.assertRaises(OSError) as cm:
+                ep.unregister(self.serverSocket)
+            self.assertEqual(cm.exception.errno, errno.ENOENT)
+            ep.register(self.serverSocket)
+            ep.unregister(self.serverSocket)
+
     def test_close(self):
         open_file = open(__file__, "rb")
         self.addCleanup(open_file.close)

Lib/test/test_socket.py

@@ -945,6 +945,18 @@ def requireSocket(*args):
 
 class GeneralModuleTests(unittest.TestCase):
 
+    def test_socket_name_errors(self):
+        with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as sock:
+            sock.bind((socket_helper.HOSTv4, 0))
+            self.assertGreater(sock.getsockname()[1], 0)
+            with self.assertRaises(OSError):
+                sock.getpeername()
+
+        with self.assertRaises(OSError):
+            sock.getsockname()
+        with self.assertRaises(OSError):
+            sock.getpeername()
+
     @unittest.skipUnless(_socket is not None, 'need _socket module')
     def test_socket_type(self):
         self.assertTrue(gc.is_tracked(_socket.socket))

Misc/NEWS.d/next/Library/2026-09-23-09-21-25.gh-issue-89977.fmia18.rst

@@ -0,0 +1,3 @@
+Avoid releasing the GIL for :meth:`socket.socket.setblocking`,
+:meth:`socket.socket.getsockname`, :meth:`socket.socket.getpeername`,
+:func:`socket.gethostname`, and :meth:`select.epoll.unregister`.

Modules/selectmodule.c

@@ -1521,9 +1521,8 @@ pyepoll_internal_ctl(int epfd, int op, int fd, unsigned int events)
         /* In kernel versions before 2.6.9, the EPOLL_CTL_DEL
          * operation required a non-NULL pointer in event, even
          * though this argument is ignored. */
-        Py_BEGIN_ALLOW_THREADS
+        /* Removing a watch is normally quick, so keep the GIL. */
         result = epoll_ctl(epfd, op, fd, &ev);
-        Py_END_ALLOW_THREADS
         break;
     default:
         result = -1;

Modules/socketmodule.c

@@ -828,7 +828,6 @@ internal_setblocking(PySocketSockObject *s, int block)
     int delay_flag, new_delay_flag;
 #endif
 
-    Py_BEGIN_ALLOW_THREADS
 #ifndef MS_WINDOWS
 #if (defined(HAVE_SYS_IOCTL_H) && defined(FIONBIO))
     block = !block;
@@ -855,8 +854,6 @@ internal_setblocking(PySocketSockObject *s, int block)
     result = 0;
 
   done:
-    Py_END_ALLOW_THREADS
-
     if (result) {
 #ifndef MS_WINDOWS
         PyErr_SetFromErrno(PyExc_OSError);
@@ -3915,9 +3912,7 @@ _socket_socket_getsockname_impl(PySocketSockObject *s)
     if (!getsockaddrlen(s, &addrlen))
         return NULL;
     memset(&addrbuf, 0, addrlen);
-    Py_BEGIN_ALLOW_THREADS
     res = getsockname(get_sock_fd(s), SAS2SA(&addrbuf), &addrlen);
-    Py_END_ALLOW_THREADS
     if (res < 0)
         return s->errorhandler();
     return makesockaddr(get_sock_fd(s), SAS2SA(&addrbuf), addrlen,
@@ -3950,9 +3945,7 @@ _socket_socket_getpeername_impl(PySocketSockObject *s)
     if (!getsockaddrlen(s, &addrlen))
         return NULL;
     memset(&addrbuf, 0, addrlen);
-    Py_BEGIN_ALLOW_THREADS
     res = getpeername(get_sock_fd(s), SAS2SA(&addrbuf), &addrlen);
-    Py_END_ALLOW_THREADS
     if (res < 0)
         return s->errorhandler();
     return makesockaddr(get_sock_fd(s), SAS2SA(&addrbuf), addrlen,
@@ -5968,9 +5961,7 @@ _socket_gethostname_impl(PyObject *module)
 #else
     char buf[1024];
     int res;
-    Py_BEGIN_ALLOW_THREADS
     res = gethostname(buf, (int) sizeof buf - 1);
-    Py_END_ALLOW_THREADS
     if (res < 0)
         return set_error();
     buf[sizeof buf - 1] = '\0';