From 60ac4e78ebb6de925b7bd1dc8571af55d096f964 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sun, 1 Feb 2026 18:44:08 -0800
Subject: [PATCH] std.Io.Mutex: fix tryLock

`@cmpxchgWeak` can return the expected value sometimes.
---
 lib/std/Io.zig | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/lib/std/Io.zig b/lib/std/Io.zig
index d2b9648245d822660b871aaabe1d29f496edd573..bb9610c0904b670b1eff8933efac16bd3138eca2 100644
--- a/lib/std/Io.zig
+++ b/lib/std/Io.zig
@@ -1236,15 +1236,7 @@ pub const Mutex = extern struct {
     };
 
     pub fn tryLock(m: *Mutex) bool {
-        switch (m.state.cmpxchgWeak(
-            .unlocked,
-            .locked_once,
-            .acquire,
-            .monotonic,
-        ) orelse return true) {
-            .unlocked => unreachable,
-            .locked_once, .contended => return false,
-        }
+        return m.state.cmpxchgWeak(.unlocked, .locked_once, .acquire, .monotonic) == null;
     }
 
     pub fn lock(m: *Mutex, io: Io) Cancelable!void {
-- 
2.54.0