From 9416a1f11d3b23065f71aad8c1d127ca482253d5 Mon Sep 17 00:00:00 2001
From: Coldwings <coldwings@me.com>
Date: Mon, 12 Aug 2024 10:43:52 +0800
Subject: [PATCH] ObjCache V2 remove reflock

---
 common/objectcachev2.h     | 29 ++---------------------------
 common/test/CMakeLists.txt |  1 -
 2 files changed, 2 insertions(+), 28 deletions(-)

diff --git a/common/objectcachev2.h b/common/objectcachev2.h
index 6c1886ed..c8964c45 100644
--- a/common/objectcachev2.h
+++ b/common/objectcachev2.h
@@ -37,12 +37,6 @@ class ObjectCacheV2 {
     struct Box : public intrusive_list_node<Box> {
         const K key;
         std::shared_ptr<V> ref;
-        // protect ref with mutex
-        // If multiple threads of execution access the same shared_ptr object
-        // without synchronization and any of those accesses uses a non-const
-        // member function of shared_ptr then a data race will occur
-        // DTOR of V may cause photon thread yield.
-        photon::mutex reflock;
         // prevent create multiple time when borrow
         photon::spinlock createlock;
         // create timestamp, for cool-down of borrow
@@ -58,15 +52,14 @@ class ObjectCacheV2 {
             : key(std::forward<KeyType>(key)), ref(nullptr) {}
 
         std::shared_ptr<V> update(std::shared_ptr<V> r, uint64_t ts = 0) {
-            SCOPED_LOCK(reflock);
             lastcreate = ts;
-            std::swap(r, ref);
+            r = std::atomic_exchange(&ref, r);
             return r;
         }
         std::shared_ptr<V> reset(uint64_t ts = 0) {
             return update({nullptr}, ts);
         }
-        std::shared_ptr<V> reader() { return ref; }
+        std::shared_ptr<V> reader() { return std::atomic_load(&ref); }
 
         void acquire() {
             timestamp = photon::now;
@@ -116,11 +109,7 @@ class ObjectCacheV2 {
         return *box;
     }
     uint64_t __expire() {
-#if __cplusplus < 201703L
         std::vector<std::shared_ptr<V>> to_release;
-#else
-        intrusive_list<Box> to_release;
-#endif
         uint64_t now = photon::now;
         uint64_t reclaim_before = photon::sat_sub(now, lifespan);
         {
@@ -136,27 +125,13 @@ class ObjectCacheV2 {
                 if (x->rc == 0) {
                     // make vector holds those shared_ptr
                     // prevent object destroy in critical zone
-#if __cplusplus < 201703L
                     to_release.push_back(x->reset());
                     map.erase(*x);
-#else
-                    // Here is a hacked implementation
-                    auto node = map.extract(*x);
-                    to_release.push_back(&node.value());
-                    /// node_handle should be just key&val pointer
-                    // Force make it empty can prevent destroy object
-                    // when node_handle goes to destroy
-                    memset((void*)&node, 0, sizeof(node));
-#endif
                 }
                 x = lru_list.front();
             }
         }
-#if __cplusplus < 201703L
         to_release.clear();
-#else
-        to_release.delete_all();
-#endif
         return 0;
     }
 
diff --git a/common/test/CMakeLists.txt b/common/test/CMakeLists.txt
index 6fe657bc..1a30526c 100644
--- a/common/test/CMakeLists.txt
+++ b/common/test/CMakeLists.txt
@@ -6,7 +6,6 @@ target_link_libraries(test-objcache PRIVATE photon_shared)
 add_test(NAME test-objcache COMMAND $<TARGET_FILE:test-objcache>)
 
 add_executable(perf-objcache perf_objcache.cpp)
-set_target_properties(perf-objcache PROPERTIES CXX_STANDARD 17)
 target_link_libraries(perf-objcache PRIVATE photon_shared)
 add_test(NAME perf-objcache COMMAND $<TARGET_FILE:test-objcache>)