Use TBB arena index for profiler recording

src/ipc/utils/profiler.cpp

@@ -2,12 +2,20 @@
 
 #ifdef IPC_TOOLKIT_WITH_PROFILER
 
+#include <tbb/task_arena.h>
+
 #include <fstream>
 #include <queue>
 
 namespace ipc {
 
-Profiler::Profiler() : m_main_thread_id(std::this_thread::get_id()) { }
+Profiler::Profiler() = default;
+
+bool Profiler::is_recording_thread() const
+{
+    const int idx = tbb::this_task_arena::current_thread_index();
+    return idx == tbb::task_arena::not_initialized || idx == 0;
+}
 
 Profiler& profiler()
 {
@@ -23,7 +31,7 @@ void Profiler::clear()
 
 void Profiler::start(const std::string& name)
 {
-    if (std::this_thread::get_id() != m_main_thread_id) {
+    if (!is_recording_thread()) {
         return;
     }
 
@@ -39,7 +47,7 @@ void Profiler::start(const std::string& name)
 
 void Profiler::stop(const double time_ms)
 {
-    if (std::this_thread::get_id() != m_main_thread_id) {
+    if (!is_recording_thread()) {
         return;
     }
 
@@ -63,9 +71,7 @@ void Profiler::stop(const double time_ms)
 
 void Profiler::reset()
 {
-    m_main_thread_id = std::this_thread::get_id();
     m_data.clear();
-    // reset the calling thread's scope
     m_current_scope = nlohmann::json::json_pointer(); // root
 }
 

src/ipc/utils/profiler.hpp

@@ -22,7 +22,6 @@
 
 #include <chrono>
 #include <iostream>
-#include <thread>
 
 // Helper macro to stringify/paste after expansion
 #define IPC_TOOLKIT_PROFILE_BLOCK_CONCAT_IMPL(a, b) a##b
@@ -74,21 +73,19 @@ class Profiler {
     /// @brief Access the profiling data as a JSON object.
     nlohmann::json& data() { return m_data; }
 
-    bool is_recording_thread() const
-    {
-        return std::this_thread::get_id() == m_main_thread_id;
-    }
+    /// @brief Returns true if the current thread should record profiling data.
+    ///        When the current thread is not in a TBB arena, this returns
+    ///        true. Inside a TBB arena, only the external/coordinator thread
+    ///        (slot 0) records, giving a single-thread estimate of parallel
+    ///        block costs.
+    bool is_recording_thread() const;
 
 protected:
     /// @brief The profiling data stored as a JSON object.
     nlohmann::json m_data;
 
     /// @brief The global scope pointer into the JSON data.
     nlohmann::json::json_pointer m_current_scope;
-
-    /// @brief The thread that records data; calls from all other threads are
-    ///        silently ignored, giving a single-thread estimate of block costs.
-    std::thread::id m_main_thread_id;
 };
 
 Profiler& profiler();

tests/src/tests/utils/test_profiler.cpp

@@ -17,10 +17,14 @@
 #include <tbb/parallel_for.h>
 #include <tbb/task_arena.h>
 
+#include <thread>
+
 using namespace ipc;
 
 TEST_CASE("Profiler", "[profiler]")
 {
+    profiler().reset();
+
     constexpr int sleep_time_ms = 100;
     constexpr int num_threads = 10;