From 1d980145cb51c3a352fe6947b7758f8d9125117d Mon Sep 17 00:00:00 2001
From: "Oliver E. Anderson" <50836158+olivereanderson@users.noreply.github.com>
Date: Sun, 8 Jun 2025 20:57:36 +0200
Subject: [PATCH] io: document cancellation safety of `AsyncWriteExt::flush`
 (#7364)

---
 tokio/src/io/util/async_write_ext.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/tokio/src/io/util/async_write_ext.rs b/tokio/src/io/util/async_write_ext.rs
index 2760e9129..cd42d4f0f 100644
--- a/tokio/src/io/util/async_write_ext.rs
+++ b/tokio/src/io/util/async_write_ext.rs
@@ -1231,6 +1231,16 @@ cfg_io_util! {
         /// It is considered an error if not all bytes could be written due to
         /// I/O errors or EOF being reached.
         ///
+        /// # Cancel safety
+        ///
+        /// This method is cancel safe.
+        ///
+        /// If `flush` is used as the event in a [`tokio::select!`](crate::select)
+        /// statement and some other branch completes first, then the data in the
+        /// buffered data in this `AsyncWrite` may have been partially flushed.
+        /// However, it is guaranteed that the buffer is advanced by the amount of
+        /// bytes that have been partially flushed.
+        ///
         /// # Examples
         ///
         /// ```no_run