From 24bfcfde7a2b835ab37c380bf8b5319987e55454 Mon Sep 17 00:00:00 2001
From: Rintaro Ishizaki <rishizaki@apple.com>
Date: Wed, 27 May 2026 10:33:50 -0700
Subject: [PATCH] AsyncQueue: await dependencies concurrently to avoid priority
 inversion

A sequentially-awaited list of dependency tasks only propagates a
priority escalation to the dependency currently being awaited. The
rest stay at their original priority and can starve under load,
producing nondeterministic multi-minute hangs in tests that mix
self-serializing and non-self-serializing metadata (e.g. a serial
task waiting on many concurrent tasks).

Replace the sequential await with concurrentForEach so a priority
escalation on the running task reaches every dependency at once.

Speculative fix for rdar://178006261
---
 Sources/ToolsProtocolsSwiftExtensions/AsyncQueue.swift | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Sources/ToolsProtocolsSwiftExtensions/AsyncQueue.swift b/Sources/ToolsProtocolsSwiftExtensions/AsyncQueue.swift
index 5f72f2d1..242d04d6 100644
--- a/Sources/ToolsProtocolsSwiftExtensions/AsyncQueue.swift
+++ b/Sources/ToolsProtocolsSwiftExtensions/AsyncQueue.swift
@@ -137,7 +137,7 @@ public final class AsyncQueue<TaskMetadata: DependencyTracker>: Sendable {
           }
         }
 
-        for dependency in dependencies {
+        await dependencies.concurrentForEach { dependency in
           await dependency.task.waitForCompletion()
         }