docs: Signal::recv is cancel-safe (#4634)

tokio/src/macros/select.rs

@@ -101,6 +101,7 @@
 ///  * [`tokio::sync::watch::Receiver::changed`](crate::sync::watch::Receiver::changed)
 ///  * [`tokio::net::TcpListener::accept`](crate::net::TcpListener::accept)
 ///  * [`tokio::net::UnixListener::accept`](crate::net::UnixListener::accept)
+///  * [`tokio::signal::unix::Signal::recv`](crate::signal::unix::Signal::recv)
 ///  * [`tokio::io::AsyncReadExt::read`](crate::io::AsyncReadExt::read) on any `AsyncRead`
 ///  * [`tokio::io::AsyncReadExt::read_buf`](crate::io::AsyncReadExt::read_buf) on any `AsyncRead`
 ///  * [`tokio::io::AsyncWriteExt::write`](crate::io::AsyncWriteExt::write) on any `AsyncWrite`

tokio/src/signal/unix.rs

@@ -407,6 +407,12 @@ impl Signal {
     ///
     /// `None` is returned if no more events can be received by this stream.
     ///
+    /// # Cancel safety
+    ///
+    /// This method is cancel safe. If you use it as the event in a
+    /// [`tokio::select!`](crate::select) statement and some other branch
+    /// completes first, then it is guaranteed that no signal is lost.
+    ///
     /// # Examples
     ///
     /// Wait for SIGHUP