ObjCache V2 remove reflock

Coldwings · Aug 12, 2024 · 5e85637 · 5e85637
1 parent e1502a4
commit 5e85637
Show file tree

Hide file tree

Showing 2 changed files with 2 additions and 28 deletions.
diff --git 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
@@ -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>)