Fix compare_exchange_weak tests to allow spurious failure

Test: Ran bionic unit tests on angler.

Bug: 36869788
Change-Id: Ic1e0e4e409ac719d5b426391a771b4858a6149ee

1 files changed, 19 insertions, 5 deletions

diff --git a/tests/stdatomic_test.cpp b/tests/stdatomic_test.cpp
index 22e0c5016..389b2511d 100644
--- a/tests/stdatomic_test.cpp
+++ b/tests/stdatomic_test.cpp
@@ -116,20 +116,34 @@ TEST(stdatomic, atomic_compare_exchange) {
 
   atomic_store(&i, 123);
   expected = 123;
-  ASSERT_TRUE(atomic_compare_exchange_strong_explicit(&i, &expected, 456, memory_order_relaxed, memory_order_relaxed));
-  ASSERT_FALSE(atomic_compare_exchange_strong_explicit(&i, &expected, 456, memory_order_relaxed, memory_order_relaxed));
+  ASSERT_TRUE(atomic_compare_exchange_strong_explicit(&i, &expected, 456, memory_order_relaxed,
+          memory_order_relaxed));
+  ASSERT_FALSE(atomic_compare_exchange_strong_explicit(&i, &expected, 456, memory_order_relaxed,
+          memory_order_relaxed));
   ASSERT_EQ(456, expected);
 
   atomic_store(&i, 123);
   expected = 123;
-  ASSERT_TRUE(atomic_compare_exchange_weak(&i, &expected, 456));
+  int iter_count = 0;
+  do {
+    ++iter_count;
+    ASSERT_LT(iter_count, 100);  // Arbitrary limit on spurious compare_exchange failures.
+    ASSERT_EQ(expected, 123);
+  } while(!atomic_compare_exchange_weak(&i, &expected, 456));
   ASSERT_FALSE(atomic_compare_exchange_weak(&i, &expected, 456));
   ASSERT_EQ(456, expected);
 
   atomic_store(&i, 123);
   expected = 123;
-  ASSERT_TRUE(atomic_compare_exchange_weak_explicit(&i, &expected, 456, memory_order_relaxed, memory_order_relaxed));
-  ASSERT_FALSE(atomic_compare_exchange_weak_explicit(&i, &expected, 456, memory_order_relaxed, memory_order_relaxed));
+  iter_count = 0;
+  do {
+    ++iter_count;
+    ASSERT_LT(iter_count, 100);
+    ASSERT_EQ(expected, 123);
+  } while(!atomic_compare_exchange_weak_explicit(&i, &expected, 456, memory_order_relaxed,
+          memory_order_relaxed));
+  ASSERT_FALSE(atomic_compare_exchange_weak_explicit(&i, &expected, 456, memory_order_relaxed,
+          memory_order_relaxed));
   ASSERT_EQ(456, expected);
 }