From e5b26815138ece649747f094962c18c232855f8a Mon Sep 17 00:00:00 2001
From: Stjepan Glavina <stjepang@gmail.com>
Date: Tue, 31 Jul 2018 05:46:46 +0200
Subject: [PATCH] Fix a race in thread wakeup (#507)

---
 tokio-executor/src/park.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/tokio-executor/src/park.rs b/tokio-executor/src/park.rs
index 13713261c..4f278fdd3 100644
--- a/tokio-executor/src/park.rs
+++ b/tokio-executor/src/park.rs
@@ -288,10 +288,12 @@ impl Inner {
         // The other half is sleeping, this requires a lock
         let _m = self.mutex.lock().unwrap();
 
-        // Transition from SLEEP -> NOTIFY
-        match self.state.compare_and_swap(SLEEP, NOTIFY, Ordering::SeqCst) {
+        // Transition to NOTIFY
+        match self.state.swap(NOTIFY, Ordering::SeqCst) {
             SLEEP => {}
-            _ => return,
+            NOTIFY => return,
+            IDLE => return,
+            _ => unreachable!(),
         }
 
         // Wakeup the sleeper