From 18ff54204fa3d60f6cf2493f3358c25aca5ed2de Mon Sep 17 00:00:00 2001
From: Hyunsik Parker <246881935+HyunsikParker@users.noreply.github.com>
Date: Tue, 1 Sep 2026 05:01:20 +0900
Subject: [PATCH] Preserve file descriptor blocking mode for poll handles

---
 tests/test_sockets.py      | 23 +++++++++++++++++++++++
 uvloop/handles/poll.pyx    | 11 ++++++++++-
 uvloop/includes/stdlib.pxi |  2 ++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/tests/test_sockets.py b/tests/test_sockets.py
index e7c335e11..3d2d627ea 100644
--- a/tests/test_sockets.py
+++ b/tests/test_sockets.py
@@ -1,4 +1,5 @@
 import asyncio
+import os
 import pickle
 import select
 import socket
@@ -14,6 +15,28 @@
 
 class _TestSockets:
 
+    def test_add_reader_writer_preserves_blocking_mode(self):
+        read_fd, write_fd = os.pipe()
+        try:
+            self.assertTrue(os.get_blocking(read_fd))
+            self.loop.add_reader(read_fd, lambda: None)
+            try:
+                self.assertTrue(os.get_blocking(read_fd))
+            finally:
+                self.loop.remove_reader(read_fd)
+            self.assertTrue(os.get_blocking(read_fd))
+
+            self.assertTrue(os.get_blocking(write_fd))
+            self.loop.add_writer(write_fd, lambda: None)
+            try:
+                self.assertTrue(os.get_blocking(write_fd))
+            finally:
+                self.loop.remove_writer(write_fd)
+            self.assertTrue(os.get_blocking(write_fd))
+        finally:
+            os.close(read_fd)
+            os.close(write_fd)
+
     async def recv_all(self, sock, nbytes):
         buf = b''
         while len(buf) < nbytes:
diff --git a/uvloop/handles/poll.pyx b/uvloop/handles/poll.pyx
index c905e9b0b..1a7e7cbda 100644
--- a/uvloop/handles/poll.pyx
+++ b/uvloop/handles/poll.pyx
@@ -1,7 +1,9 @@
 @cython.no_gc_clear
 cdef class UVPoll(UVHandle):
     cdef _init(self, Loop loop, int fd):
-        cdef int err
+        cdef:
+            int err
+            bint was_blocking = os_get_blocking(fd)
 
         self._start_init(loop)
 
@@ -18,6 +20,13 @@ cdef class UVPoll(UVHandle):
 
         self._finish_init()
 
+        if was_blocking:
+            try:
+                os_set_blocking(fd, True)
+            except BaseException:
+                self._close()
+                raise
+
         self.fd = fd
         self.reading_handle = None
         self.writing_handle = None
diff --git a/uvloop/includes/stdlib.pxi b/uvloop/includes/stdlib.pxi
index 5fff4ad8e..d9aa13e70 100644
--- a/uvloop/includes/stdlib.pxi
+++ b/uvloop/includes/stdlib.pxi
@@ -104,6 +104,8 @@ cdef os_environ = os.environ
 cdef os_dup = os.dup
 cdef os_set_inheritable = os.set_inheritable
 cdef os_get_inheritable = os.get_inheritable
+cdef os_get_blocking = os.get_blocking
+cdef os_set_blocking = os.set_blocking
 cdef os_close = os.close
 cdef os_open = os.open
 cdef os_devnull = os.devnull