gh-128277: remove unnecessary critical section from socket.close (#128305)

Remove unnecessary critical section from `socket.close` as it now uses relaxed atomics for `sock_fd`.

Author: kumaraditya303

Lib/test/test_socket.py

@@ -7075,6 +7075,26 @@ def close_fds(fds):
             self.assertEqual(data,  str(index).encode())
 
 
+class FreeThreadingTests(unittest.TestCase):
+
+    def test_close_detach_race(self):
+        s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+
+        def close():
+            for _ in range(1000):
+                s.close()
+
+        def detach():
+            for _ in range(1000):
+                s.detach()
+
+        t1 = threading.Thread(target=close)
+        t2 = threading.Thread(target=detach)
+
+        with threading_helper.start_threads([t1, t2]):
+            pass
+
+
 def setUpModule():
     thread_info = threading_helper.threading_setup()
     unittest.addModuleCleanup(threading_helper.threading_cleanup, *thread_info)

Modules/clinic/socketmodule.c.h

@@ -3386,7 +3386,6 @@ sockets the address is a tuple (ifname, proto [,pkttype [,hatype [,addr]]])");
    will surely fail. */
 
 /*[clinic input]
-@critical_section
 _socket.socket.close
     self as s: self(type="PySocketSockObject *")
 
@@ -3397,7 +3396,7 @@ Close the socket.  It cannot be used after this call.
 
 static PyObject *
 _socket_socket_close_impl(PySocketSockObject *s)
-/*[clinic end generated code: output=038b2418e07f6f6c input=9839a261e05bcb97]*/
+/*[clinic end generated code: output=038b2418e07f6f6c input=dc487e470e55a83c]*/
 {
     SOCKET_T fd;
     int res;