From 0ed03a153549c75142332cd44641ba0328df350e Mon Sep 17 00:00:00 2001
From: Antonio SJ Musumeci <trapexit@spawn.link>
Date: Mon, 21 Aug 2023 13:33:58 -0500
Subject: [PATCH] Use relaxed memory order for atomic counters

---
 libfuse/lib/bounded_thread_pool.hpp |   7 +-
 libfuse/lib/fuse_msgbuf.cpp         |   8 +-
 libfuse/lib/thread_pool.hpp         | 125 ----------------------------
 src/unbounded_thread_pool.hpp       |   7 +-
 4 files changed, 12 insertions(+), 135 deletions(-)
 delete mode 100644 libfuse/lib/thread_pool.hpp

diff --git a/libfuse/lib/bounded_thread_pool.hpp b/libfuse/lib/bounded_thread_pool.hpp
index 707fa1d87..d0e3bf2da 100644
--- a/libfuse/lib/bounded_thread_pool.hpp
+++ b/libfuse/lib/bounded_thread_pool.hpp
@@ -85,7 +85,7 @@ class BoundedThreadPool
   void
   enqueue_work(F&& f_)
   {
-    auto i = _index++;
+    auto i = _index.fetch_add(1,std::memory_order_relaxed);
 
     for(std::size_t n = 0; n < (_count * K); ++n)
       {
@@ -104,10 +104,11 @@ class BoundedThreadPool
     using TaskReturnType = typename std::result_of<F()>::type;
     using Promise        = std::promise<TaskReturnType>;
 
-    auto i       = _index++;
+    auto i       = _index.fetch_add(1,std::memory_order_relaxed);
     auto promise = std::make_shared<Promise>();
     auto future  = promise->get_future();
-    auto work    = [=]() {
+    auto work    = [=]()
+    {
       auto rv = f_();
       promise->set_value(rv);
     };
diff --git a/libfuse/lib/fuse_msgbuf.cpp b/libfuse/lib/fuse_msgbuf.cpp
index e683874d5..828a4c44f 100644
--- a/libfuse/lib/fuse_msgbuf.cpp
+++ b/libfuse/lib/fuse_msgbuf.cpp
@@ -115,7 +115,7 @@ _msgbuf_alloc(msgbuf_setup_func_t setup_func_)
       if(msgbuf == NULL)
         return NULL;
 
-      g_MSGBUF_ALLOC_COUNT++;
+      g_MSGBUF_ALLOC_COUNT.fetch_add(1,std::memory_order_relaxed);
     }
   else
     {
@@ -160,7 +160,7 @@ msgbuf_free(fuse_msgbuf_t *msgbuf_)
   if(msgbuf_->size != (g_BUFSIZE - g_PAGESIZE))
     {
       msgbuf_destroy(msgbuf_);
-      g_MSGBUF_ALLOC_COUNT--;
+      g_MSGBUF_ALLOC_COUNT.fetch_sub(1,std::memory_order_relaxed);
       return;
     }
 
@@ -206,7 +206,7 @@ msgbuf_gc_10percent()
   for(auto msgbuf : togc)
     {
       msgbuf_destroy(msgbuf);
-      g_MSGBUF_ALLOC_COUNT--;
+      g_MSGBUF_ALLOC_COUNT.fetch_sub(1,std::memory_order_relaxed);
     }
 }
 
@@ -223,6 +223,6 @@ msgbuf_gc()
   for(auto msgbuf: oldstack)
     {
       msgbuf_destroy(msgbuf);
-      g_MSGBUF_ALLOC_COUNT--;
+      g_MSGBUF_ALLOC_COUNT.fetch_sub(1,std::memory_order_relaxed);
     }
 }
diff --git a/libfuse/lib/thread_pool.hpp b/libfuse/lib/thread_pool.hpp
deleted file mode 100644
index 3737a1861..000000000
--- a/libfuse/lib/thread_pool.hpp
+++ /dev/null
@@ -1,125 +0,0 @@
-#pragma once
-
-#include "unbounded_queue.hpp"
-#include "bounded_queue.hpp"
-
-#include <tuple>
-#include <atomic>
-#include <vector>
-#include <thread>
-#include <memory>
-#include <future>
-#include <utility>
-#include <functional>
-#include <type_traits>
-
-
-class ThreadPool
-{
-public:
-  explicit
-  ThreadPool(const std::size_t thread_count_ = std::thread::hardware_concurrency())
-    : _queues(thread_count_),
-      _count(thread_count_)
-  {
-    auto worker = [this](std::size_t i)
-    {
-      while(true)
-        {
-          Proc f;
-
-          for(std::size_t n = 0; n < (_count * K); ++n)
-            {
-              if(_queues[(i + n) % _count].try_pop(f))
-                break;
-            }
-
-          if(!f && !_queues[i].pop(f))
-            break;
-
-          f();
-        }
-    };
-
-    _threads.reserve(thread_count_);
-    for(std::size_t i = 0; i < thread_count_; ++i)
-      _threads.emplace_back(worker, i);
-  }
-
-  ~ThreadPool()
-  {
-    for(auto& queue : _queues)
-      queue.unblock();
-    for(auto& thread : _threads)
-      thread.join();
-  }
-
-  template<typename F>
-  void
-  enqueue_work(F&& f_)
-  {
-    auto i = _index++;
-
-    for(std::size_t n = 0; n < (_count * K); ++n)
-      {
-        if(_queues[(i + n) % _count].try_push(f_))
-          return;
-      }
-
-    _queues[i % _count].push(std::move(f_));
-  }
-
-  template<typename F>
-  [[nodiscard]]
-  std::future<typename std::result_of<F()>::type>
-  enqueue_task(F&& f_)
-  {
-    using TaskReturnType = typename std::result_of<F()>::type;
-    using Promise        = std::promise<TaskReturnType>;
-
-    auto i       = _index++;
-    auto promise = std::make_shared<Promise>();
-    auto future  = promise->get_future();
-    auto work    = [=]() {
-      auto rv = f_();
-      promise->set_value(rv);
-    };
-
-    for(std::size_t n = 0; n < (_count * K); ++n)
-      {
-        if(_queues[(i + n) % _count].try_push(work))
-          return future;
-      }
-
-    _queues[i % _count].push(std::move(work));
-
-    return future;
-  }
-
-public:
-  std::vector<pthread_t>
-  threads()
-  {
-    std::vector<pthread_t> rv;
-
-    for(auto &thread : _threads)
-      rv.push_back(thread.native_handle());
-
-    return rv;
-  }
-
-private:
-  using Proc   = std::function<void(void)>;
-  using Queue  = UnboundedQueue<Proc>;
-  using Queues = std::vector<Queue>;
-  Queues _queues;
-
-private:
-  std::vector<std::thread> _threads;
-
-private:
-  const std::size_t _count;
-  std::atomic_uint _index;
-
-  static const unsigned int K = 2;
-};
diff --git a/src/unbounded_thread_pool.hpp b/src/unbounded_thread_pool.hpp
index 6f02e1b32..1bfa1dcdf 100644
--- a/src/unbounded_thread_pool.hpp
+++ b/src/unbounded_thread_pool.hpp
@@ -72,7 +72,7 @@ class ThreadPool
   void
   enqueue_work(F&& f_)
   {
-    auto i = _index++;
+    auto i = _index.fetch_add(1,std::memory_order_relaxed);
 
     for(std::size_t n = 0; n < (_count * K); ++n)
       {
@@ -91,10 +91,11 @@ class ThreadPool
     using TaskReturnType = typename std::result_of<F()>::type;
     using Promise        = std::promise<TaskReturnType>;
 
-    auto i       = _index++;
+    auto i       = _index.fetch_add(1,std::memory_order_relaxed);
     auto promise = std::make_shared<Promise>();
     auto future  = promise->get_future();
-    auto work    = [=]() {
+    auto work    = [=]()
+    {
       auto rv = f_();
       promise->set_value(rv);
     };