bpo-46398: posixshmem module shm_rename freebsd support.

Doc/library/multiprocessing.shared_memory.rst

@@ -112,6 +112,15 @@ copying of data.
       This method has no effect on Windows, where the only way to delete a
       shared memory block is to close all handles.
 
+   .. method:: rename(newname, flags)
+
+      Renames the underlying shared memory block to ``newname``. By
+      default, if ``newname`` already exists, it will be unlinked
+      beforehand. Passing the ``os.SHM_RENAME_EXCHANGE`` as ``flags``,
+      an exchange with ``newname``  will be proceeded instead. Passing
+      the ``os.SHM_RENAME_NOREPLACE`` as ``flags``, an error
+      will be triggered if ``newname`` already exists.
+
    .. attribute:: buf
 
       A memoryview of contents of the shared memory block.

Lib/multiprocessing/shared_memory.py

@@ -11,6 +11,7 @@
 from functools import partial
 import mmap
 import os
+import platform
 import errno
 import struct
 import secrets
@@ -253,6 +254,27 @@ def unlink(self):
             if self._track:
                 resource_tracker.unregister(self._name, "shared_memory")
 
+    def rename(self, newname, flags = 0):
+        """Renames a shared memory block.
+
+        The policy how the operation is handled depends on the flag passed.
+        The default behavior is if the newname already exists, it will
+        be unlinked beforehand.
+        With the SHM_RENAME_EXCHANGE flag, the old and new name will
+        be exchanged.
+        With the SHM_RENAME_NOREPLACE flag, an error will be returned
+        if the new name exists.
+        """
+        if !platform.hasattr("shm_rename"):
+            raise OSError("Unsupported operation on this platform")
+
+        if newname:
+            newname = "/" + newname if self._prepend_leading_slash else newname
+            self._fd = _posixshmem.shm_rename(self._name, newname, flags)
+            self._name = newname
+            return True
+        return False
+
 
 _encoding = "utf8"
 

Misc/NEWS.d/next/Library/2022-01-17-20-03-56.bpo-46398.FATeqM.rst

@@ -0,0 +1 @@
+Add :method:`rename` to the `multiprocessing.shared_memory` library for FreeBSD.

Modules/_multiprocessing/posixshmem.c

@@ -68,6 +68,53 @@ _posixshmem_shm_open_impl(PyObject *module, PyObject *path, int flags,
 }
 #endif /* HAVE_SHM_OPEN */
 
+#ifdef HAVE_SHM_RENAME
+/*[clinic input]
+_posixshmem.shm_rename
+    path_from: unicode
+    path_to: unicode
+    flags: int
+    /
+
+Rename a shared memory object.
+
+Remove a shared memory object and relink to another path.
+By default, if the destination path already exist, it will be unlinked.
+With the SHM_RENAME_EXCHANGE flag, source and destination paths
+will be exchanged.
+With the SHM_RENAME_NOREPLACE flag, an error will be triggered
+if the destination alredady exists.
+
+[clinic start generated code]*/
+
+static int
+_posixshmem_shm_rename_impl(PyObject *module, PyObject *path_from,
+                            PyObject *path_to, int flags)
+/*[clinic end generated code: output=a9101f606826ad30 input=0373bfc9c491e123]*/
+{
+    int rv;
+    int async_err = 0;
+    const char *from = PyUnicode_AsUTF8AndSize(path_from, NULL);
+    const char *to = PyUnicode_AsUTF8AndSize(path_to, NULL);
+    if (from == NULL || to == NULL) {
+        return -1;
+    }
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        rv = shm_rename(from, to, flags);
+        Py_END_ALLOW_THREADS
+    } while (rv < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+
+    if (rv < 0) {
+        if (!async_err)
+            PyErr_SetFromErrnoWithFilenameObjects(PyExc_OSError, path_from, path_to);
+        return -1;
+    }
+
+    return rv;
+}
+#endif /* HAVE_SHM_RENAME */
+
 #ifdef HAVE_SHM_UNLINK
 /*[clinic input]
 _posixshmem.shm_unlink
@@ -111,6 +158,9 @@ _posixshmem_shm_unlink_impl(PyObject *module, PyObject *path)
 
 static PyMethodDef module_methods[ ] = {
     _POSIXSHMEM_SHM_OPEN_METHODDEF
+#if defined(HAVE_SHM_RENAME)
+    _POSIXSHMEM_SHM_RENAME_METHODDEF
+#endif
     _POSIXSHMEM_SHM_UNLINK_METHODDEF
     {NULL} /* Sentinel */
 };

Modules/posixmodule.c

@@ -17288,6 +17288,15 @@ all_ins(PyObject *m)
 #endif
 #endif /* HAVE_MEMFD_CREATE */
 
+#ifdef HAVE_SHM_RENAME
+#ifdef SHM_RENAME_EXCHANGE
+    if (PyModule_AddIntMacro(m, SHM_RENAME_EXCHANGE)) return -1;
+#endif
+#ifdef SHM_RENAME_NOREPLACE
+    if (PyModule_AddIntMacro(m, SHM_RENAME_NOREPLACE)) return -1;
+#endif
+#endif /* HAVE_SHM_RENAME */
+
 #if defined(HAVE_EVENTFD) && defined(EFD_CLOEXEC)
     if (PyModule_AddIntMacro(m, EFD_CLOEXEC)) return -1;
 #ifdef EFD_NONBLOCK

configure.ac

@@ -6873,7 +6873,7 @@ WITH_SAVE_ENV([
   #  endif
   #endif
   "
-  AC_CHECK_FUNCS([shm_open shm_unlink], [have_posix_shmem=yes], [have_posix_shmem=no])
+  AC_CHECK_FUNCS([shm_open shm_rename shm_unlink], [have_posix_shmem=yes], [have_posix_shmem=no])
   _RESTORE_VAR([ac_includes_default])
 ])
 

pyconfig.h.in

@@ -1138,6 +1138,9 @@
 /* Define to 1 if you have the `shm_open' function. */
 #undef HAVE_SHM_OPEN
 
+/* Define to 1 if you have the `shm_rename' function. */
+#undef HAVE_SHM_RENAME
+
 /* Define to 1 if you have the `shm_unlink' function. */
 #undef HAVE_SHM_UNLINK