hazptr: Clear hazard pointers in ~hazptr_array() and ~hazptr_local()

Summary:
Clear hazard pointers in ~hazptr_array() and ~hazptr_local().
Added tests to detect uncleared hazard pointers when using hazptr_array and hazptr_local.

Differential Revision: D6995057

fbshipit-source-id: 5b8fa1d197c3959ed670d0a019959bd57f5df3d0

folly/experimental/hazptr/hazptr-impl.h

@@ -721,6 +721,7 @@ FOLLY_ALWAYS_INLINE hazptr_array<M>::~hazptr_array() {
       auto count = tc.count();
       if ((M <= HAZPTR_TC_SIZE) && (count + M <= HAZPTR_TC_SIZE)) {
         for (size_t i = 0; i < M; ++i) {
+          h[i].reset();
           tc[count + i].hprec_ = h[i].hazptr_;
           HAZPTR_DEBUG_PRINT(i << " " << &h[i]);
           new (&h[i]) hazptr_holder(nullptr);
@@ -793,7 +794,7 @@ FOLLY_ALWAYS_INLINE hazptr_local<M>::hazptr_local() {
     }
   }
   // Slow path
-  need_destruct_ = true;
+  slow_path_ = true;
   for (size_t i = 0; i < M; ++i) {
     new (&h[i]) hazptr_holder;
     HAZPTR_DEBUG_PRINT(
@@ -803,7 +804,7 @@ FOLLY_ALWAYS_INLINE hazptr_local<M>::hazptr_local() {
 
 template <size_t M>
 FOLLY_ALWAYS_INLINE hazptr_local<M>::~hazptr_local() {
-  if (LIKELY(!need_destruct_)) {
+  if (LIKELY(!slow_path_)) {
     if (kIsDebug) {
       auto ptc = hazptr_tc_tls();
       DCHECK(ptc != nullptr);
@@ -811,6 +812,10 @@ FOLLY_ALWAYS_INLINE hazptr_local<M>::~hazptr_local() {
       DCHECK(tc.local_);
       tc.local_ = false;
     }
+    auto h = reinterpret_cast<hazptr_holder*>(&raw_);
+    for (size_t i = 0; i < M; ++i) {
+      h[i].reset();
+    }
     return;
   }
   // Slow path

folly/experimental/hazptr/hazptr.h

@@ -328,7 +328,7 @@ class hazptr_local {
 
  private:
   aligned_hazptr_holder raw_[M];
-  bool need_destruct_{false};
+  bool slow_path_{false};
 };
 
 } // namespace hazptr

folly/experimental/hazptr/test/HazptrTest.cpp

@@ -639,4 +639,38 @@ TEST_F(HazptrTest, FreeFunctionCleanup) {
   for (auto& t : threads) {
     t.join();
   }
+  { // Cleanup after using array
+    constructed.store(0);
+    destroyed.store(0);
+    { hazptr_array<2> h; }
+    {
+      hazptr_array<2> h;
+      auto p0 = new Foo(0, nullptr);
+      auto p1 = new Foo(0, nullptr);
+      h[0].reset(p0);
+      h[1].reset(p1);
+      p0->retire();
+      p1->retire();
+    }
+    CHECK_EQ(constructed.load(), 2);
+    hazptr_cleanup();
+    CHECK_EQ(destroyed.load(), 2);
+  }
+  { // Cleanup after using local
+    constructed.store(0);
+    destroyed.store(0);
+    { hazptr_local<2> h; }
+    {
+      hazptr_local<2> h;
+      auto p0 = new Foo(0, nullptr);
+      auto p1 = new Foo(0, nullptr);
+      h[0].reset(p0);
+      h[1].reset(p1);
+      p0->retire();
+      p1->retire();
+    }
+    CHECK_EQ(constructed.load(), 2);
+    hazptr_cleanup();
+    CHECK_EQ(destroyed.load(), 2);
+  }
 }