src: consolidate environment cleanup queue

Each Realm tracks its own cleanup hooks and drains the hooks when it is
going to be destroyed.

Moves the implementations of the cleanup queue to its own class so that
it can be used in `node::Realm` too.

node.gyp

@@ -466,6 +466,7 @@
         'src/api/utils.cc',
         'src/async_wrap.cc',
         'src/cares_wrap.cc',
+        'src/cleanup_queue.cc',
         'src/connect_wrap.cc',
         'src/connection_wrap.cc',
         'src/debug_utils.cc',
@@ -567,6 +568,8 @@
         'src/base64-inl.h',
         'src/callback_queue.h',
         'src/callback_queue-inl.h',
+        'src/cleanup_queue.h',
+        'src/cleanup_queue-inl.h',
         'src/connect_wrap.h',
         'src/connection_wrap.h',
         'src/debug_utils.h',

src/base_object.h

@@ -178,7 +178,7 @@ class BaseObject : public MemoryRetainer {
   // position of members in memory are predictable. For more information please
   // refer to `doc/contributing/node-postmortem-support.md`
   friend int GenDebugSymbols();
-  friend class CleanupHookCallback;
+  friend class CleanupQueue;
   template <typename T, bool kIsWeak>
   friend class BaseObjectPtrImpl;
 

src/cleanup_queue-inl.h

@@ -0,0 +1,60 @@
+#ifndef SRC_CLEANUP_QUEUE_INL_H_
+#define SRC_CLEANUP_QUEUE_INL_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include "base_object.h"
+#include "cleanup_queue.h"
+#include "memory_tracker-inl.h"
+#include "util.h"
+
+namespace node {
+
+inline void CleanupQueue::MemoryInfo(MemoryTracker* tracker) const {
+  ForEachBaseObject([&](BaseObject* obj) {
+    if (obj->IsDoneInitializing()) tracker->Track(obj);
+  });
+}
+
+inline size_t CleanupQueue::SelfSize() const {
+  return sizeof(CleanupQueue) +
+         cleanup_hooks_.size() * sizeof(CleanupHookCallback);
+}
+
+bool CleanupQueue::empty() const {
+  return cleanup_hooks_.empty();
+}
+
+void CleanupQueue::Add(Callback cb, void* arg) {
+  auto insertion_info = cleanup_hooks_.emplace(
+      CleanupHookCallback{cb, arg, cleanup_hook_counter_++});
+  // Make sure there was no existing element with these values.
+  CHECK_EQ(insertion_info.second, true);
+}
+
+void CleanupQueue::Remove(Callback cb, void* arg) {
+  CleanupHookCallback search{cb, arg, 0};
+  cleanup_hooks_.erase(search);
+}
+
+template <typename T>
+void CleanupQueue::ForEachBaseObject(T&& iterator) const {
+  for (const auto& hook : cleanup_hooks_) {
+    BaseObject* obj = GetBaseObject(hook);
+    if (obj != nullptr) iterator(obj);
+  }
+}
+
+BaseObject* CleanupQueue::GetBaseObject(
+    const CleanupHookCallback& callback) const {
+  if (callback.fn_ == BaseObject::DeleteMe)
+    return static_cast<BaseObject*>(callback.arg_);
+  else
+    return nullptr;
+}
+
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_CLEANUP_QUEUE_INL_H_

src/cleanup_queue.cc

@@ -0,0 +1,44 @@
+#include "cleanup_queue.h"  // NOLINT(build/include_inline)
+#include <vector>
+#include "cleanup_queue-inl.h"
+
+namespace node {
+
+void CleanupQueue::Drain() {
+  // Copy into a vector, since we can't sort an unordered_set in-place.
+  std::vector<CleanupHookCallback> callbacks(cleanup_hooks_.begin(),
+                                             cleanup_hooks_.end());
+  // We can't erase the copied elements from `cleanup_hooks_` yet, because we
+  // need to be able to check whether they were un-scheduled by another hook.
+
+  std::sort(callbacks.begin(),
+            callbacks.end(),
+            [](const CleanupHookCallback& a, const CleanupHookCallback& b) {
+              // Sort in descending order so that the most recently inserted
+              // callbacks are run first.
+              return a.insertion_order_counter_ > b.insertion_order_counter_;
+            });
+
+  for (const CleanupHookCallback& cb : callbacks) {
+    if (cleanup_hooks_.count(cb) == 0) {
+      // This hook was removed from the `cleanup_hooks_` set during another
+      // hook that was run earlier. Nothing to do here.
+      continue;
+    }
+
+    cb.fn_(cb.arg_);
+    cleanup_hooks_.erase(cb);
+  }
+}
+
+size_t CleanupQueue::CleanupHookCallback::Hash::operator()(
+    const CleanupHookCallback& cb) const {
+  return std::hash<void*>()(cb.arg_);
+}
+
+bool CleanupQueue::CleanupHookCallback::Equal::operator()(
+    const CleanupHookCallback& a, const CleanupHookCallback& b) const {
+  return a.fn_ == b.fn_ && a.arg_ == b.arg_;
+}
+
+}  // namespace node

src/cleanup_queue.h

@@ -0,0 +1,83 @@
+#ifndef SRC_CLEANUP_QUEUE_H_
+#define SRC_CLEANUP_QUEUE_H_
+
+#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#include <cstddef>
+#include <cstdint>
+#include <unordered_set>
+
+#include "memory_tracker.h"
+
+namespace node {
+
+class BaseObject;
+
+class CleanupQueue : public MemoryRetainer {
+ public:
+  typedef void (*Callback)(void*);
+
+  CleanupQueue() {}
+
+  // Not copyable.
+  CleanupQueue(const CleanupQueue&) = delete;
+
+  SET_MEMORY_INFO_NAME(CleanupQueue)
+  inline void MemoryInfo(node::MemoryTracker* tracker) const override;
+  inline size_t SelfSize() const override;
+
+  inline bool empty() const;
+
+  inline void Add(Callback cb, void* arg);
+  inline void Remove(Callback cb, void* arg);
+  void Drain();
+
+  template <typename T>
+  inline void ForEachBaseObject(T&& iterator) const;
+
+ private:
+  class CleanupHookCallback {
+   public:
+    CleanupHookCallback(Callback fn,
+                        void* arg,
+                        uint64_t insertion_order_counter)
+        : fn_(fn),
+          arg_(arg),
+          insertion_order_counter_(insertion_order_counter) {}
+
+    // Only hashes `arg_`, since that is usually enough to identify the hook.
+    struct Hash {
+      size_t operator()(const CleanupHookCallback& cb) const;
+    };
+
+    // Compares by `fn_` and `arg_` being equal.
+    struct Equal {
+      bool operator()(const CleanupHookCallback& a,
+                      const CleanupHookCallback& b) const;
+    };
+
+   private:
+    friend class CleanupQueue;
+    Callback fn_;
+    void* arg_;
+
+    // We keep track of the insertion order for these objects, so that we can
+    // call the callbacks in reverse order when we are cleaning up.
+    uint64_t insertion_order_counter_;
+  };
+
+  inline BaseObject* GetBaseObject(const CleanupHookCallback& callback) const;
+
+  // Use an unordered_set, so that we have efficient insertion and removal.
+  std::unordered_set<CleanupHookCallback,
+                     CleanupHookCallback::Hash,
+                     CleanupHookCallback::Equal>
+      cleanup_hooks_;
+  uint64_t cleanup_hook_counter_ = 0;
+};
+
+}  // namespace node
+
+#endif  // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
+
+#endif  // SRC_CLEANUP_QUEUE_H_

src/env-inl.h

@@ -780,43 +780,17 @@ inline void Environment::ThrowUVException(int errorno,
       UVException(isolate(), errorno, syscall, message, path, dest));
 }
 
-void Environment::AddCleanupHook(CleanupCallback fn, void* arg) {
-  auto insertion_info = cleanup_hooks_.emplace(CleanupHookCallback {
-    fn, arg, cleanup_hook_counter_++
-  });
-  // Make sure there was no existing element with these values.
-  CHECK_EQ(insertion_info.second, true);
-}
-
-void Environment::RemoveCleanupHook(CleanupCallback fn, void* arg) {
-  CleanupHookCallback search { fn, arg, 0 };
-  cleanup_hooks_.erase(search);
-}
-
-size_t CleanupHookCallback::Hash::operator()(
-    const CleanupHookCallback& cb) const {
-  return std::hash<void*>()(cb.arg_);
+void Environment::AddCleanupHook(CleanupQueue::Callback fn, void* arg) {
+  cleanup_queue_.Add(fn, arg);
 }
 
-bool CleanupHookCallback::Equal::operator()(
-    const CleanupHookCallback& a, const CleanupHookCallback& b) const {
-  return a.fn_ == b.fn_ && a.arg_ == b.arg_;
-}
-
-BaseObject* CleanupHookCallback::GetBaseObject() const {
-  if (fn_ == BaseObject::DeleteMe)
-    return static_cast<BaseObject*>(arg_);
-  else
-    return nullptr;
+void Environment::RemoveCleanupHook(CleanupQueue::Callback fn, void* arg) {
+  cleanup_queue_.Remove(fn, arg);
 }
 
 template <typename T>
 void Environment::ForEachBaseObject(T&& iterator) {
-  for (const auto& hook : cleanup_hooks_) {
-    BaseObject* obj = hook.GetBaseObject();
-    if (obj != nullptr)
-      iterator(obj);
-  }
+  cleanup_queue_.ForEachBaseObject(std::forward<T>(iterator));
 }
 
 void Environment::modify_base_object_count(int64_t delta) {

src/env.cc

@@ -1000,33 +1000,10 @@ void Environment::RunCleanup() {
   bindings_.clear();
   CleanupHandles();
 
-  while (!cleanup_hooks_.empty() ||
-         native_immediates_.size() > 0 ||
+  while (!cleanup_queue_.empty() || native_immediates_.size() > 0 ||
          native_immediates_threadsafe_.size() > 0 ||
          native_immediates_interrupts_.size() > 0) {
-    // Copy into a vector, since we can't sort an unordered_set in-place.
-    std::vector<CleanupHookCallback> callbacks(
-        cleanup_hooks_.begin(), cleanup_hooks_.end());
-    // We can't erase the copied elements from `cleanup_hooks_` yet, because we
-    // need to be able to check whether they were un-scheduled by another hook.
-
-    std::sort(callbacks.begin(), callbacks.end(),
-              [](const CleanupHookCallback& a, const CleanupHookCallback& b) {
-      // Sort in descending order so that the most recently inserted callbacks
-      // are run first.
-      return a.insertion_order_counter_ > b.insertion_order_counter_;
-    });
-
-    for (const CleanupHookCallback& cb : callbacks) {
-      if (cleanup_hooks_.count(cb) == 0) {
-        // This hook was removed from the `cleanup_hooks_` set during another
-        // hook that was run earlier. Nothing to do here.
-        continue;
-      }
-
-      cb.fn_(cb.arg_);
-      cleanup_hooks_.erase(cb);
-    }
+    cleanup_queue_.Drain();
     CleanupHandles();
   }
 
@@ -1730,10 +1707,6 @@ void Environment::BuildEmbedderGraph(Isolate* isolate,
   MemoryTracker tracker(isolate, graph);
   Environment* env = static_cast<Environment*>(data);
   tracker.Track(env);
-  env->ForEachBaseObject([&](BaseObject* obj) {
-    if (obj->IsDoneInitializing())
-      tracker.Track(obj);
-  });
 }
 
 size_t Environment::NearHeapLimitCallback(void* data,
@@ -1868,6 +1841,7 @@ inline size_t Environment::SelfSize() const {
   // this can be done for common types within the Track* calls automatically
   // if a certain scope is entered.
   size -= sizeof(async_hooks_);
+  size -= sizeof(cleanup_queue_);
   size -= sizeof(tick_info_);
   size -= sizeof(immediate_info_);
   return size;
@@ -1885,8 +1859,7 @@ void Environment::MemoryInfo(MemoryTracker* tracker) const {
   tracker->TrackField("should_abort_on_uncaught_toggle",
                       should_abort_on_uncaught_toggle_);
   tracker->TrackField("stream_base_state", stream_base_state_);
-  tracker->TrackFieldWithSize(
-      "cleanup_hooks", cleanup_hooks_.size() * sizeof(CleanupHookCallback));
+  tracker->TrackField("cleanup_queue", cleanup_queue_);
   tracker->TrackField("async_hooks", async_hooks_);
   tracker->TrackField("immediate_info", immediate_info_);
   tracker->TrackField("tick_info", tick_info_);