From fddd9865f7c4616a5c9573175815a87cc972d85f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Gr=C3=A9goire?= <loic@gregoire.dev>
Date: Sat, 18 Jul 2026 16:08:34 -0400
Subject: [PATCH] ke/mutex: do TTAS spin

This is better to do than `pause`-ing in a CAS loop.
---
 src/kern/mutex.zig | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/kern/mutex.zig b/src/kern/mutex.zig
index cbea8a3..8d82d99 100644
--- a/src/kern/mutex.zig
+++ b/src/kern/mutex.zig
@@ -31,11 +31,15 @@ pub const Mutex = struct {
 
         // Fast path: Try to acquire without a turnstile by spinning a bit.
         for (0..optimistic_spins) |_| {
-            if (m.owner.cmpxchgWeak(null, curtd, .acquire, .monotonic) != null) {
+            if (m.owner.load(.monotonic) != null) {
                 std.atomic.spinLoopHint();
                 continue;
             }
 
+            if (m.owner.cmpxchgWeak(null, curtd, .acquire, .monotonic) != null) {
+                continue;
+            }
+
             ke.ipl.lower(ipl);
             return;
         }