Vitals: ClassLoaderDataGraph by SamplerThread is unsynchronized

src/hotspot/share/classfile/classLoaderData.cpp

@@ -177,6 +177,11 @@ ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_ho
  NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
 
  JFR_ONLY(INIT_ID(this);)
+
+ // SapMachine 2023-07-04 : vitals
+ if (EnableVitals) {
+ sapmachine_vitals::counters::inc_cld_count(has_class_mirror_holder);
+ }
 }
 
 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {

src/hotspot/share/classfile/classLoaderDataGraph.cpp

@@ -515,6 +515,10 @@ bool ClassLoaderDataGraph::do_unloading() {
  }
  seen_dead_loader = true;
  loaders_removed++;
+ // SapMachine 2023-07-04 : vitals
+ if (EnableVitals) {
+ sapmachine_vitals::counters::dec_cld_count(data->has_class_mirror_holder());
+ }
  ClassLoaderData* dead = data;
  dead->unload();
  data = data->next();

src/hotspot/share/vitals/vitals.cpp

@@ -66,10 +66,26 @@ static Lock g_vitals_lock("VitalsLock");
 
 namespace counters {
 
+static volatile size_t g_number_of_clds = 0;
+static volatile size_t g_number_of_anon_clds = 0;
 static volatile size_t g_classes_loaded = 0;
 static volatile size_t g_classes_unloaded = 0;
 static volatile size_t g_threads_created = 0;
 
+void inc_cld_count(bool is_anon_cld) {
+ Atomic::inc(&g_number_of_clds);
+ if (is_anon_cld) {
+ Atomic::inc(&g_number_of_anon_clds);
+ }
+}
+
+void dec_cld_count(bool is_anon_cld) {
+ Atomic::dec(&g_number_of_clds);
+ if (is_anon_cld) {
+ Atomic::dec(&g_number_of_anon_clds);
+ }
+}
+
 void inc_classes_loaded(size_t count) {
  Atomic::add(&g_classes_loaded, count);
 }
@@ -1104,21 +1120,6 @@ static void set_value_in_sample(const Column* col, Sample* sample, T t) {
  }
 }
 
-// Count CLDs
-class CLDCounterClosure: public CLDClosure {
-public:
- int _cnt;
- int _anon_cnt;
- CLDCounterClosure() : _cnt(0), _anon_cnt(0) {}
- void do_cld(ClassLoaderData* cld) {
- _cnt ++;
- if (cld->has_class_mirror_holder()) {
- _anon_cnt ++;
- }
- }
-};
-
-
 struct nmt_values_t {
  // How much memory, in total, was committed via mmap
  value_t mapped_total;
@@ -1234,15 +1235,8 @@ void sample_jvm_values(Sample* sample, bool avoid_locking) {
  }
 
  // CLDG
- if (!avoid_locking) {
- CLDCounterClosure cl;
- {
- MutexLocker lck(ClassLoaderDataGraph_lock);
- ClassLoaderDataGraph::cld_do(&cl);
- }
- set_value_in_sample(g_col_number_of_clds, sample, cl._cnt);
- set_value_in_sample(g_col_number_of_anon_clds, sample, cl._anon_cnt);
- }
+ set_value_in_sample(g_col_number_of_clds, sample, counters::g_number_of_clds);
+ set_value_in_sample(g_col_number_of_anon_clds, sample, counters::g_number_of_anon_clds);
 
  // Classes
  set_value_in_sample(g_col_number_of_classes, sample,

src/hotspot/share/vitals/vitals.hpp

@@ -73,6 +73,8 @@ namespace sapmachine_vitals {
  const Thread* samplerthread();
 
  namespace counters {
+ void inc_cld_count(bool is_anon_cld);
+ void dec_cld_count(bool is_anon_cld);
  void inc_classes_loaded(size_t count);
  void inc_classes_unloaded(size_t count);
  void inc_threads_created(size_t count);