From cafd0b629bbcdbc454a372d643fd9b719fbb10ed Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Fri, 5 Apr 2024 08:41:03 -0500
Subject: [PATCH] GH-2102 Add a large_atomic wrapper around mutex

---
 .../include/eosio/chain/thread_utils.hpp      | 38 +++++++++++++++++++
 plugins/net_plugin/net_plugin.cpp             | 10 -----
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/libraries/chain/include/eosio/chain/thread_utils.hpp b/libraries/chain/include/eosio/chain/thread_utils.hpp
index d3e9e8a261..f687096aaa 100644
--- a/libraries/chain/include/eosio/chain/thread_utils.hpp
+++ b/libraries/chain/include/eosio/chain/thread_utils.hpp
@@ -12,6 +12,44 @@
 
 namespace eosio { namespace chain {
 
+   // should be defined for c++17, but clang++16 still has not implemented it
+#ifdef __cpp_lib_hardware_interference_size
+   using std::hardware_constructive_interference_size;
+   using std::hardware_destructive_interference_size;
+#else
+   // 64 bytes on x86-64 │ L1_CACHE_BYTES │ L1_CACHE_SHIFT │ __cacheline_aligned │ ...
+   [[maybe_unused]] constexpr std::size_t hardware_constructive_interference_size = 64;
+   [[maybe_unused]] constexpr std::size_t hardware_destructive_interference_size  = 64;
+#endif
+
+   // Use instead of std::atomic when std::atomic does not support type
+   template <typename T>
+   class large_atomic {
+      alignas(hardware_destructive_interference_size)
+      mutable std::mutex mtx;
+      T value{};
+   public:
+      T load() const {
+         std::lock_guard g(mtx);
+         return value;
+      }
+      void store(const T& v) {
+         std::lock_guard g(mtx);
+         value = v;
+      }
+
+      class accessor {
+         std::lock_guard<std::mutex> g;
+         T& v;
+      public:
+         accessor(std::mutex& m, T& v)
+            : g(m), v(v) {}
+         T& value() { return v; }
+      };
+
+      auto make_accessor() { return accessor{mtx, value}; }
+   };
+
    /**
     * Wrapper class for thread pool of boost asio io_context run.
     * Also names threads so that tools like htop can see thread name.
diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 8da4b26a70..a3ab7201fe 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -33,16 +33,6 @@
 #include <new>
 #include <regex>
 
-// should be defined for c++17, but clang++16 still has not implemented it
-#ifdef __cpp_lib_hardware_interference_size
-   using std::hardware_constructive_interference_size;
-   using std::hardware_destructive_interference_size;
-#else
-   // 64 bytes on x86-64 │ L1_CACHE_BYTES │ L1_CACHE_SHIFT │ __cacheline_aligned │ ...
-   [[maybe_unused]] constexpr std::size_t hardware_constructive_interference_size = 64;
-   [[maybe_unused]] constexpr std::size_t hardware_destructive_interference_size = 64;
-#endif
-
 using namespace eosio::chain::plugin_interface;
 
 using namespace std::chrono_literals;