gh-95672 skip fcntl when pipesize is smaller than pagesize

Lib/test/test_fcntl.py

@@ -201,7 +201,8 @@ def test_fcntl_f_pipesize(self):
             # Get the default pipesize with F_GETPIPE_SZ
             pipesize_default = fcntl.fcntl(test_pipe_w, fcntl.F_GETPIPE_SZ)
             pipesize = pipesize_default // 2  # A new value to detect change.
-            if pipesize < 512:  # the POSIX minimum
+            minimum_pipe_size = os.sysconf('SC_PAGESIZE')   # There's a check that attempts to skip the tests if the pipe capacity is 512 bytes, but that's less than the smallest page size on x86.
+            if pipesize < minimum_pipe_size:  # the POSIX minimum
                 raise unittest.SkipTest(
                     'default pipesize too small to perform test.')
             fcntl.fcntl(test_pipe_w, fcntl.F_SETPIPE_SZ, pipesize)

Lib/test/test_subprocess.py

@@ -717,7 +717,8 @@ def test_pipesizes(self):
             os.close(test_pipe_r)
             os.close(test_pipe_w)
         pipesize = pipesize_default // 2
-        if pipesize < 512:  # the POSIX minimum
+        minimum_pipe_size = os.sysconf('SC_PAGESIZE')   # There's a check that attempts to skip the tests if the pipe capacity is 512 bytes, but that's less than the smallest page size on x86.
+        if pipesize < minimum_pipe_size:  # the POSIX minimum
             raise unittest.SkipTest(
                 'default pipesize too small to perform test.')
         p = subprocess.Popen(