[llvm] [CAS][Tests] Fix unit tests that hangs on two cores (PR #154151)

[Steven Wu via llvm-commits]

https://github.com/cachemeifyoucan created https://github.com/llvm/llvm-project/pull/154151

Reorder the task in the CAS concurrency test so that on low core count,
producer is called before consumer so it won't hang. This can still test
the concurrent behavior on higher core counts.


>From 4bf31d17c04c4aeeca116bd7207410c17e1dcf42 Mon Sep 17 00:00:00 2001
From: Steven Wu <stevenwu at apple.com>
Date: Mon, 18 Aug 2025 09:29:55 -0700
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.6
---
 llvm/unittests/CAS/ObjectStoreTest.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/llvm/unittests/CAS/ObjectStoreTest.cpp b/llvm/unittests/CAS/ObjectStoreTest.cpp
index e84e30374c9aa..54083fdb408f6 100644
--- a/llvm/unittests/CAS/ObjectStoreTest.cpp
+++ b/llvm/unittests/CAS/ObjectStoreTest.cpp
@@ -269,8 +269,7 @@ TEST_P(CASTest, NodesBig) {
     ASSERT_THAT_ERROR(CAS->validate(CAS->getID(ID)), Succeeded());
 }
 
-// FIXME: Re-enable the test.
-#if 0
+#if LLVM_ENABLE_THREADS
 /// Common test functionality for creating blobs in parallel. You can vary which
 /// cas instances are the same or different, and the size of the created blobs.
 static void testBlobsParallel(ObjectStore &Read1, ObjectStore &Read2,
@@ -318,10 +317,10 @@ static void testBlobsParallel(ObjectStore &Read1, ObjectStore &Read2,
 
   DefaultThreadPool Threads;
   for (unsigned I = 0; I < BlobCount; ++I) {
-    Threads.async(Consumer, I, &Read1);
-    Threads.async(Consumer, I, &Read2);
     Threads.async(Producer, I, &Write1);
     Threads.async(Producer, I, &Write2);
+    Threads.async(Consumer, I, &Read1);
+    Threads.async(Consumer, I, &Read2);
   }
 
   Threads.wait();