fcntl(fd, O_NONBLOCK) => os.set_blocking(fd, False)

.github/workflows/tox.yml

@@ -19,7 +19,7 @@ jobs:
          - ubuntu-latest
          # not defaulting to macos-latest: Python <= 3.9 was missing from macos-14 @ arm64
          - macos-13
-         # Not testing Windows, because tests need Unix-only fcntl, grp, pwd, etc.
+         # Not testing Windows, because tests need Unix-only non-blocking pipes, grp, pwd, etc.
         python-version:
          # CPython <= 3.7 is EoL since 2023-06-27
          - "3.7"

appveyor.yml

@@ -13,7 +13,7 @@ environment:
     #- TOXENV: run-entrypoint
     #  PYTHON: "C:\\Python38-x64"
     # Windows is not ready for testing!!!
-    # Python's fcntl, grp, pwd, os.geteuid(), and socket.AF_UNIX are all Unix-only.
+    # Python's non-blocking pipes, grp, pwd, os.geteuid(), and socket.AF_UNIX are all Unix-only.
     #- TOXENV: py35
     #  PYTHON: "C:\\Python35-x64"
     #- TOXENV: py36

gunicorn/util.py

@@ -4,7 +4,6 @@
 import ast
 import email.utils
 import errno
-import fcntl
 import html
 import importlib
 import inspect
@@ -258,8 +257,10 @@ def close_on_exec(fd):
 
 
 def set_non_blocking(fd):
-    flags = fcntl.fcntl(fd, fcntl.F_GETFL) | os.O_NONBLOCK
-    fcntl.fcntl(fd, fcntl.F_SETFL, flags)
+    # available since Python 3.5, equivalent to either:
+    # ioctl(fd, FIONBIO)
+    # fcntl(fd, fcntl.F_SETFL, fcntl(fd, F_GETFL) | O_NONBLOCK)
+    os.set_blocking(fd, False)
 
 
 def close(sock):