From ff051629044833667e3ebc65655d39f3921bb49a Mon Sep 17 00:00:00 2001
From: Konstantin Morozov <morozov-kst@yandex.ru>
Date: Sun, 5 Feb 2023 19:25:09 +0300
Subject: [PATCH] change mutex to lock-free

---
 src/Common/MultiVersion.h | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/src/Common/MultiVersion.h b/src/Common/MultiVersion.h
index 8a6eac0abad..4b138dc1a35 100644
--- a/src/Common/MultiVersion.h
+++ b/src/Common/MultiVersion.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <atomic>
 #include <mutex>
 #include <memory>
 #include <base/defines.h>
@@ -39,19 +40,15 @@ public:
     /// Obtain current version for read-only usage. Returns shared_ptr, that manages lifetime of version.
     Version get() const
     {
-        /// NOTE: is it possible to lock-free replace of shared_ptr?
-        std::lock_guard lock(mutex);
-        return current_version;
+        return std::atomic_load(&current_version);
     }
 
     /// Update an object with new version.
     void set(std::unique_ptr<const T> && value)
     {
-        std::lock_guard lock(mutex);
-        current_version = std::move(value);
+        std::atomic_store(&current_version, Version{std::move(value)});
     }
 
 private:
-    Version current_version TSA_GUARDED_BY(mutex);
-    mutable std::mutex mutex;
+    Version current_version;
 };