From a5f2758bcfdd2be7d24e6d9c40eacb50e6c93a3e Mon Sep 17 00:00:00 2001
From: shaun0927 <70629228+shaun0927@users.noreply.github.com>
Date: Thu, 14 May 2026 11:29:22 +0900
Subject: [PATCH] Stop spinning while waiting for zombie cleanup locks

Constraint: Preserve synchronous registry APIs and existing lock timeout/retry semantics.
Rejected: Keep a JavaScript busy-spin loop | it wastes CPU during simulator cleanup contention.
Confidence: high
Scope-risk: narrow
Directive: Any future async lock migration should preserve active-simulator protection semantics first.
Tested: npm test -- --runTestsByPath tests/unit/zombie-cleanup-lock.test.ts tests/unit/zombie-cleanup-cross-session.test.ts; npm run lint -- --quiet src/reliability/zombie-cleanup.ts tests/unit/zombie-cleanup-lock.test.ts; npm run build
Not-tested: Live multi-process lock contention CPU profile.
---
 src/reliability/zombie-cleanup.ts      | 11 +++++++++--
 tests/unit/zombie-cleanup-lock.test.ts | 16 ++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 tests/unit/zombie-cleanup-lock.test.ts

diff --git a/src/reliability/zombie-cleanup.ts b/src/reliability/zombie-cleanup.ts
index 0d62b144..43b38312 100644
--- a/src/reliability/zombie-cleanup.ts
+++ b/src/reliability/zombie-cleanup.ts
@@ -12,6 +12,14 @@ const LOCK_STALE_MS = 10000;
 const LOCK_RETRY_MS = 50;
 const LOCK_TIMEOUT_MS = 5000;
 
+export function sleepWithoutBusySpin(ms: number): void {
+  const duration = Math.max(0, Math.floor(ms));
+  if (duration === 0) return;
+  const buffer = new SharedArrayBuffer(4);
+  const view = new Int32Array(buffer);
+  Atomics.wait(view, 0, 0, duration);
+}
+
 function acquireLock(): boolean {
   const deadline = Date.now() + LOCK_TIMEOUT_MS;
   while (Date.now() < deadline) {
@@ -34,8 +42,7 @@ function acquireLock(): boolean {
           releaseLock();
           continue;
         }
-        const waitUntil = Date.now() + LOCK_RETRY_MS;
-        while (Date.now() < waitUntil) { /* spin */ }
+        sleepWithoutBusySpin(LOCK_RETRY_MS);
         continue;
       }
       return false;
diff --git a/tests/unit/zombie-cleanup-lock.test.ts b/tests/unit/zombie-cleanup-lock.test.ts
new file mode 100644
index 00000000..7ce1b3fa
--- /dev/null
+++ b/tests/unit/zombie-cleanup-lock.test.ts
@@ -0,0 +1,16 @@
+import { sleepWithoutBusySpin } from '../../src/reliability/zombie-cleanup';
+
+describe('zombie cleanup registry lock wait helper', () => {
+  it('returns immediately for non-positive durations', () => {
+    const start = Date.now();
+    sleepWithoutBusySpin(0);
+    sleepWithoutBusySpin(-10);
+    expect(Date.now() - start).toBeLessThan(25);
+  });
+
+  it('waits for approximately the requested duration without a JavaScript spin loop', () => {
+    const start = Date.now();
+    sleepWithoutBusySpin(15);
+    expect(Date.now() - start).toBeGreaterThanOrEqual(10);
+  });
+});