fixes gh-96078: os.sched_yield release the GIL while calling sched_yield(2). (gh-97965)

(cherry picked from commit b9d2e81716)

Co-authored-by: Dong-hee Na <donghee.na@python.org>

Misc/NEWS.d/next/Core and Builtins/2022-10-06-15-45-57.gh-issue-96078.fS-6mU.rst

@@ -0,0 +1,2 @@
+:func:`os.sched_yield` now release the GIL while calling sched_yield(2).
+Patch by Dong-hee Na.

Modules/posixmodule.c

@@ -7096,8 +7096,13 @@ static PyObject *
 os_sched_yield_impl(PyObject *module)
 /*[clinic end generated code: output=902323500f222cac input=e54d6f98189391d4]*/
 {
-    if (sched_yield())
+    int result;
+    Py_BEGIN_ALLOW_THREADS
+    result = sched_yield();
+    Py_END_ALLOW_THREADS
+    if (result < 0) {
         return posix_error();
+    }
     Py_RETURN_NONE;
 }