From 30d3d50e1d78db4092464930dd5d476ccd19bf34 Mon Sep 17 00:00:00 2001
From: Alice Ryhl <aliceryhl@google.com>
Date: Fri, 17 Sep 2021 23:32:26 +0200
Subject: [PATCH] mpsc: use spin_loop_hint instead of yield_now

---
 tokio/src/loom/std/mod.rs    | 15 ++++++++++++++-
 tokio/src/sync/mpsc/block.rs |  6 ------
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/tokio/src/loom/std/mod.rs b/tokio/src/loom/std/mod.rs
index b29cbeeb89c..8b6e8bc19d7 100644
--- a/tokio/src/loom/std/mod.rs
+++ b/tokio/src/loom/std/mod.rs
@@ -93,4 +93,17 @@ pub(crate) mod sys {
     }
 }
 
-pub(crate) use std::thread;
+pub(crate) mod thread {
+    #[inline]
+    pub(crate) fn yield_now() {
+        // TODO: once we bump MSRV to 1.49+, use `hint::spin_loop` instead.
+        #[allow(deprecated)]
+        std::sync::atomic::spin_loop_hint();
+    }
+
+    #[allow(unused_imports)]
+    pub(crate) use std::thread::{
+        current, panicking, park, park_timeout, sleep, spawn, Builder, JoinHandle, LocalKey,
+        Result, Thread, ThreadId,
+    };
+}
diff --git a/tokio/src/sync/mpsc/block.rs b/tokio/src/sync/mpsc/block.rs
index 7a0873bc4ac..6e7b70058c9 100644
--- a/tokio/src/sync/mpsc/block.rs
+++ b/tokio/src/sync/mpsc/block.rs
@@ -343,13 +343,7 @@ impl<T> Block<T> {
                 Err(curr) => curr,
             };
 
-            #[cfg(all(test, loom))]
             crate::loom::thread::yield_now();
-
-            // TODO: once we bump MSRV to 1.49+, use `hint::spin_loop` instead.
-            #[cfg(not(all(test, loom)))]
-            #[allow(deprecated)]
-            std::sync::atomic::spin_loop_hint();
         }
     }
 }