From 5b887b8c85dda3ea2e685e4a5a3ec676fbfb99c7 Mon Sep 17 00:00:00 2001
From: Richard Reingruber <richard.reingruber@sap.com>
Date: Wed, 5 Jul 2023 16:56:30 +0200
Subject: [PATCH] SapMachine #1438: Vitals: ClassLoaderDataGraph by
 SamplerThread is unsynchronized

---
 .../share/classfile/classLoaderData.cpp       |  5 +++
 .../share/classfile/classLoaderDataGraph.cpp  |  4 ++
 src/hotspot/share/vitals/vitals.cpp           | 42 ++++++++-----------
 src/hotspot/share/vitals/vitals.hpp           |  2 +
 4 files changed, 29 insertions(+), 24 deletions(-)

diff --git a/src/hotspot/share/classfile/classLoaderData.cpp b/src/hotspot/share/classfile/classLoaderData.cpp
index d164c5f1555..7a39e299280 100644
--- a/src/hotspot/share/classfile/classLoaderData.cpp
+++ b/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() {
diff --git a/src/hotspot/share/classfile/classLoaderDataGraph.cpp b/src/hotspot/share/classfile/classLoaderDataGraph.cpp
index 72a1e78838f..f4578667ce0 100644
--- a/src/hotspot/share/classfile/classLoaderDataGraph.cpp
+++ b/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();
diff --git a/src/hotspot/share/vitals/vitals.cpp b/src/hotspot/share/vitals/vitals.cpp
index d3a12a46611..4926d351835 100644
--- a/src/hotspot/share/vitals/vitals.cpp
+++ b/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,
diff --git a/src/hotspot/share/vitals/vitals.hpp b/src/hotspot/share/vitals/vitals.hpp
index 55b8b0d1539..8f2bb99827e 100644
--- a/src/hotspot/share/vitals/vitals.hpp
+++ b/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);