From 889ea1bda97227dfd096b44755925b5e1ebf6bd3 Mon Sep 17 00:00:00 2001
From: KRM7 <70973547+KRM7@users.noreply.github.com>
Date: Thu, 28 Mar 2024 23:09:54 +0100
Subject: [PATCH] minor improvements to shared_spinlock

---
 src/utility/shared_spinlock.hpp | 16 ++++++----------
 src/utility/spinlock.hpp        |  4 +---
 src/utility/utility.hpp         | 19 +++++++++++++++++++
 3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/src/utility/shared_spinlock.hpp b/src/utility/shared_spinlock.hpp
index e14722d6..4142cf91 100644
--- a/src/utility/shared_spinlock.hpp
+++ b/src/utility/shared_spinlock.hpp
@@ -4,10 +4,7 @@
 #define GA_UTILITY_SHARED_SPINLOCK_HPP
 
 #include "utility.hpp"
-#include "spinlock.hpp"
 #include <atomic>
-#include <thread>
-#include <tuple>
 #include <limits>
 #include <cstdint>
 
@@ -20,16 +17,15 @@ namespace gapp::detail
         {
             while (true)
             {
-                while (cntr_.load(std::memory_order_relaxed)) GAPP_PAUSE();
                 if (try_lock()) break;
-                std::this_thread::yield();
+                while (cntr_.load(std::memory_order_relaxed)) GAPP_PAUSE();
             }
         }
 
         bool try_lock() noexcept
         {
             std::uint32_t expected = 0;
-            return cntr_.compare_exchange_strong(expected, WRITER, std::memory_order_acq_rel, std::memory_order_relaxed);
+            return cntr_.compare_exchange_strong(expected, WRITER, std::memory_order_acquire, std::memory_order_relaxed);
         }
 
         void unlock() noexcept
@@ -39,15 +35,15 @@ namespace gapp::detail
 
         void lock_shared() noexcept
         {
-            cntr_.fetch_add(1, std::memory_order_release);
+            cntr_.fetch_add(1, std::memory_order_relaxed);
             while (cntr_.load(std::memory_order_relaxed) >= WRITER) GAPP_PAUSE();
-            std::ignore = cntr_.load(std::memory_order_acquire);
+            std::atomic_thread_fence(std::memory_order_acquire);
+            GAPP_ANNOTATE_TSAN_ACQUIRE(&cntr_);
         }
 
         bool try_lock_shared() noexcept
         {
-            cntr_.fetch_add(1, std::memory_order_release);
-            if (cntr_.load(std::memory_order_acquire) < WRITER) return true;
+            if (cntr_.fetch_add(1, std::memory_order_acquire) < WRITER) return true;
             cntr_.fetch_sub(1, std::memory_order_relaxed);
             return false;
         }
diff --git a/src/utility/spinlock.hpp b/src/utility/spinlock.hpp
index 3a6efdcc..4c7e58dd 100644
--- a/src/utility/spinlock.hpp
+++ b/src/utility/spinlock.hpp
@@ -5,7 +5,6 @@
 
 #include "utility.hpp"
 #include <atomic>
-#include <thread>
 
 namespace gapp::detail
 {
@@ -16,9 +15,8 @@ namespace gapp::detail
         {
             while (true)
             {
-                while (locked_.test(std::memory_order_relaxed)) GAPP_PAUSE();
                 if (!locked_.test_and_set(std::memory_order_acquire)) break;
-                std::this_thread::yield();
+                while (locked_.test(std::memory_order_relaxed)) GAPP_PAUSE();
             }
         }
 
diff --git a/src/utility/utility.hpp b/src/utility/utility.hpp
index 6a3cf4c6..f247937a 100644
--- a/src/utility/utility.hpp
+++ b/src/utility/utility.hpp
@@ -86,6 +86,25 @@
 #endif
 
 
+#if defined(__has_feature)
+#   if __has_feature(thread_sanitizer) && __has_include(<sanitizer/tsan_interface.h>)
+#       include <sanitizer/tsan_interface.h>
+#       define GAPP_ANNOTATE_TSAN_ACQUIRE(p) __tsan_acquire(p)
+#       define GAPP_ANNOTATE_TSAN_RELEASE(p) __tsan_release(p)
+#   else
+#       define GAPP_ANNOTATE_TSAN_ACQUIRE(p)
+#       define GAPP_ANNOTATE_TSAN_RELEASE(p)
+#   endif
+#elif defined(__SANITIZE_THREAD__) && __has_include(<sanitizer/tsan_interface.h>)
+#   include <sanitizer/tsan_interface.h>
+#   define GAPP_ANNOTATE_TSAN_ACQUIRE(p) __tsan_acquire(p)
+#   define GAPP_ANNOTATE_TSAN_RELEASE(p) __tsan_release(p)
+#else
+#   define GAPP_ANNOTATE_TSAN_ACQUIRE(p)
+#   define GAPP_ANNOTATE_TSAN_RELEASE(p)
+#endif
+
+
 #if defined(_WIN32) && !defined(GAPP_BUILD_STATIC)
 #   if defined(gapp_EXPORTS)
 #       define GAPP_API __declspec(dllexport)