hazptr: Add test to detect no reclamation, without calling cleanup.

Summary: Add test to detect no reclamation (without calling hazptr_cleanup). The test retires a number of objects that would trigger bulk reclamation. One or more objects are expected be reclaimed. The number of retired objects must be greater than or equal to hazptr_domain::kThreshold to expect reclamation to happen.

Reviewed By: yfeldblum

Differential Revision: D8849957

fbshipit-source-id: ef590af21a55348ed0ed72be3637853eceb21cbc

folly/synchronization/HazptrDomain.h

@@ -33,6 +33,14 @@
 
 namespace folly {
 
+namespace detail {
+
+constexpr int hazptr_domain_rcount_threshold() {
+  return 1000;
+}
+
+} // namespace detail
+
 /**
  *  hazptr_domain
  *
@@ -42,7 +50,7 @@ namespace folly {
  */
 template <template <typename> class Atom>
 class hazptr_domain {
-  static constexpr int kThreshold = 1000;
+  static constexpr int kThreshold = detail::hazptr_domain_rcount_threshold();
   static constexpr int kMultiplier = 2;
   static constexpr uint64_t kSyncTimePeriod{2000000000}; // nanoseconds
 

folly/synchronization/test/HazptrTest.cpp

@@ -1078,6 +1078,25 @@ TEST(HazptrTest, dsched_wide_cas) {
   wide_cas_test<DeterministicAtomic>();
 }
 
+TEST(HazptrTest, reclamation_without_calling_cleanup) {
+  c_.clear();
+  int nthr = 5;
+  int objs = folly::detail::hazptr_domain_rcount_threshold();
+  std::vector<std::thread> thr(nthr);
+  for (int tid = 0; tid < nthr; ++tid) {
+    thr[tid] = std::thread([&, tid] {
+      for (int i = tid; i < objs; i += nthr) {
+        auto p = new Node<>;
+        p->retire();
+      }
+    });
+  }
+  for (auto& t : thr) {
+    t.join();
+  }
+  ASSERT_GT(c_.dtors(), 0);
+}
+
 // Benchmark drivers
 
 template <typename InitFunc, typename Func, typename EndFunc>