From 7e06aa2077be2875045e0e15262c05335565eeca Mon Sep 17 00:00:00 2001
From: Misha Shneerson <mshneer@fb.com>
Date: Mon, 16 Nov 2020 17:52:26 -0800
Subject: [PATCH] small refactor of AtomicNotificationQueue, move Node out of
 Queue

Reviewed By: andriigrynenko

Differential Revision: D24880761

fbshipit-source-id: 643da2b0fd461955ea33b4ba48f377c30720d442
---
 folly/io/async/AtomicNotificationQueue-inl.h |  7 +++---
 folly/io/async/AtomicNotificationQueue.h     | 26 +++++++++-----------
 2 files changed, 15 insertions(+), 18 deletions(-)

diff --git a/folly/io/async/AtomicNotificationQueue-inl.h b/folly/io/async/AtomicNotificationQueue-inl.h
index d127fa5b804..603f019240b 100644
--- a/folly/io/async/AtomicNotificationQueue-inl.h
+++ b/folly/io/async/AtomicNotificationQueue-inl.h
@@ -54,7 +54,7 @@ ssize_t AtomicNotificationQueue<Task, Consumer>::Queue::size() const {
 }
 
 template <typename Task, typename Consumer>
-typename AtomicNotificationQueue<Task, Consumer>::Queue::Node&
+typename AtomicNotificationQueue<Task, Consumer>::Node&
 AtomicNotificationQueue<Task, Consumer>::Queue::front() {
   return *head_;
 }
@@ -104,8 +104,7 @@ AtomicNotificationQueue<Task, Consumer>::AtomicQueue::~AtomicQueue() {
 template <typename Task, typename Consumer>
 template <typename T>
 bool AtomicNotificationQueue<Task, Consumer>::AtomicQueue::push(T&& value) {
-  std::unique_ptr<typename Queue::Node> node(
-      new typename Queue::Node(std::forward<T>(value)));
+  std::unique_ptr<Node> node(new Node(std::forward<T>(value)));
   auto head = head_.load(std::memory_order_relaxed);
   while (true) {
     node->next =
@@ -147,7 +146,7 @@ AtomicNotificationQueue<Task, Consumer>::AtomicQueue::arm() {
   if (!head &&
       head_.compare_exchange_strong(
           head,
-          reinterpret_cast<typename Queue::Node*>(kQueueArmedTag),
+          reinterpret_cast<Node*>(kQueueArmedTag),
           std::memory_order_relaxed,
           std::memory_order_relaxed)) {
     ++successfulArmCount_;
diff --git a/folly/io/async/AtomicNotificationQueue.h b/folly/io/async/AtomicNotificationQueue.h
index 72411b992eb..45656a0af58 100644
--- a/folly/io/async/AtomicNotificationQueue.h
+++ b/folly/io/async/AtomicNotificationQueue.h
@@ -44,22 +44,21 @@ class AtomicNotificationQueue : private EventBase::LoopCallback,
       noexcept(std::declval<Consumer>()(std::declval<Task&&>())),
       "Consumer::operator()(Task&&) should be noexcept.");
   class AtomicQueue;
-  class Queue {
-   public:
-    struct Node {
-      Task task;
-      std::shared_ptr<RequestContext> rctx{RequestContext::saveContext()};
+  struct Node {
+    Task task;
+    std::shared_ptr<RequestContext> rctx{RequestContext::saveContext()};
 
-     private:
-      friend class AtomicNotificationQueue::AtomicQueue;
-      friend class Queue;
+   private:
+    friend class AtomicNotificationQueue;
 
-      template <typename T>
-      explicit Node(T&& t) : task(std::forward<T>(t)) {}
+    template <typename T>
+    explicit Node(T&& t) : task(std::forward<T>(t)) {}
 
-      Node* next{};
-    };
+    Node* next{};
+  };
 
+  class Queue {
+   public:
     Queue() {}
     Queue(Queue&& other) noexcept;
     Queue& operator=(Queue&& other) noexcept;
@@ -174,8 +173,7 @@ class AtomicNotificationQueue : private EventBase::LoopCallback,
     }
 
    private:
-    alignas(
-        folly::cacheline_align_v) std::atomic<typename Queue::Node*> head_{};
+    alignas(folly::cacheline_align_v) std::atomic<Node*> head_{};
     alignas(folly::cacheline_align_v) ssize_t successfulArmCount_{0};
     ssize_t consumerDisarmCount_{0};
     static constexpr intptr_t kQueueArmedTag = 1;