From 0c654b649fd5797da992398d9ba56435fae3f123 Mon Sep 17 00:00:00 2001
From: Tor Egge <Tor.Egge@online.no>
Date: Mon, 10 Jul 2023 10:27:08 +0200
Subject: Avoid livelock when running rcu vector unit test with valgrind.

---
 vespalib/src/tests/util/rcuvector/rcuvector_test.cpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

(limited to 'vespalib/src/tests/util/rcuvector/rcuvector_test.cpp')

diff --git a/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp b/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
index b842d009ce8..2c5af5c02ec 100644
--- a/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
+++ b/vespalib/src/tests/util/rcuvector/rcuvector_test.cpp
@@ -10,6 +10,7 @@
 #include <vespa/vespalib/util/size_literals.h>
 #include <vespa/vespalib/util/threadstackexecutor.h>
 #include <random>
+#include <thread>
 
 using namespace vespalib;
 
@@ -20,6 +21,18 @@ using vespalib::makeLambdaTask;
 using MyMemoryAllocator = vespalib::alloc::test::MemoryAllocatorObserver;
 using AllocStats = MyMemoryAllocator::Stats;
 
+namespace {
+
+void consider_yield(uint32_t i)
+{
+    if ((i % 1111) == 0) {
+        // Need to yield sometimes to avoid livelock when running unit test with valgrind
+        std::this_thread::yield();
+    }
+}
+
+}
+
 bool
 assertUsage(const MemoryUsage & exp, const MemoryUsage & act)
 {
@@ -452,12 +465,15 @@ StressFixture::read_work()
     std::mt19937 gen(rd());
     std::uniform_int_distribution<uint32_t> distrib(0, read_area - 1);
     std::vector<int> old(read_area);
+    uint32_t i = 0;
     while (!stop_read.load(std::memory_order_relaxed)) {
         uint32_t idx = distrib(gen);
         auto guard = generation_handler.takeGuard();
         int value = arr.acquire_elem_ref(idx).load_acquire();
         EXPECT_LE(old[idx], value);
         old[idx] = value;
+        consider_yield(i);
+        ++i;
     }
 }
 
@@ -478,6 +494,7 @@ StressFixture::write_work(uint32_t cnt)
         uint32_t idx = distrib(gen);
         arr[idx].store_release(arr[idx].load_relaxed() + 1);
         commit();
+        consider_yield(i);
     }
 }
 
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