From e039c44a534713ef49173e723695caa6eb767c97 Mon Sep 17 00:00:00 2001
From: Taiki Endo <te316e89@gmail.com>
Date: Thu, 24 Dec 2020 21:20:33 +0900
Subject: [PATCH] Replace deprecated compare_and_swap with compare_exchange

---
 src/lib.rs | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 17f87f4..53c1e8b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@
 use std::cell::UnsafeCell;
 use std::fmt;
 use std::sync::atomic::AtomicUsize;
-use std::sync::atomic::Ordering::{Acquire, Release, AcqRel};
+use std::sync::atomic::Ordering::{AcqRel, Acquire, Release};
 use std::task::Waker;
 
 /// A synchronization primitive for task wakeup.
@@ -261,7 +261,11 @@ impl AtomicWaker {
     /// }
     /// ```
     pub fn register(&self, waker: &Waker) {
-        match self.state.compare_and_swap(WAITING, REGISTERING, Acquire) {
+        match self
+            .state
+            .compare_exchange(WAITING, REGISTERING, Acquire, Acquire)
+            .unwrap_or_else(|x| x)
+        {
             WAITING => {
                 unsafe {
                     // Locked acquired, update the waker cell
@@ -277,8 +281,9 @@ impl AtomicWaker {
                     // nothing to acquire, only release. In case of concurrent
                     // wakers, we need to acquire their releases, so success needs
                     // to do both.
-                    let res = self.state.compare_exchange(
-                        REGISTERING, WAITING, AcqRel, Acquire);
+                    let res = self
+                        .state
+                        .compare_exchange(REGISTERING, WAITING, AcqRel, Acquire);
 
                     match res {
                         Ok(_) => {
@@ -342,9 +347,7 @@ impl AtomicWaker {
                 //
                 // We just want to maintain memory safety. It is ok to drop the
                 // call to `register`.
-                debug_assert!(
-                    state == REGISTERING ||
-                    state == REGISTERING | WAKING);
+                debug_assert!(state == REGISTERING || state == REGISTERING | WAKING);
             }
         }
     }
@@ -389,9 +392,8 @@ impl AtomicWaker {
                 // not.
                 //
                 debug_assert!(
-                    state == REGISTERING ||
-                    state == REGISTERING | WAKING ||
-                    state == WAKING);
+                    state == REGISTERING || state == REGISTERING | WAKING || state == WAKING
+                );
                 None
             }
         }