Merge #19197: init: use std::thread for ThreadImport()

83fd3a6d73 init: use std::thread for ThreadImport() (fanquake)

Pull request description:

  [Mentioned](https://github.com/bitcoin/bitcoin/pull/19142#issuecomment-638090759) in #19142, which removed the `boost::interruption_point()`
  in `ThreadImport()`.

ACKs for top commit:
  hebasto:
    ACK 83fd3a6d73, I have reviewed the code and it looks OK, I agree it can be merged.
  donaloconnor:
    ACK 83fd3a6
  laanwj:
    Code review ACK 83fd3a6d73
  MarcoFalke:
    ACK 83fd3a6d73

Tree-SHA512: 0644947d669feb61eed3a944012dad1bd3dd75cf994aa2630013043c213a335b162b63e20aa37e0997740d8e3a3ec367b660b5196007a09e13f0ac455b36c821

src/init.cpp

@@ -152,6 +152,8 @@ NODISCARD static bool CreatePidFile()
 
 static std::unique_ptr<ECCVerifyHandle> globalVerifyHandle;
 
+static std::thread g_load_block;
+
 static boost::thread_group threadGroup;
 
 void Interrupt(NodeContext& node)
@@ -214,8 +216,9 @@ void Shutdown(NodeContext& node)
     StopTorControl();
 
     // After everything has been shut down, but before things get flushed, stop the
-    // CScheduler/checkqueue threadGroup
+    // CScheduler/checkqueue, threadGroup and load block thread.
     if (node.scheduler) node.scheduler->stop();
+    if (g_load_block.joinable()) g_load_block.join();
     threadGroup.interrupt_all();
     threadGroup.join_all();
 
@@ -680,7 +683,6 @@ static void CleanupBlockRevFiles()
 static void ThreadImport(ChainstateManager& chainman, std::vector<fs::path> vImportFiles)
 {
     const CChainParams& chainparams = Params();
-    util::ThreadRename("loadblk");
     ScheduleBatchPriority();
 
     {
@@ -1842,7 +1844,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node)
         vImportFiles.push_back(strFile);
     }
 
-    threadGroup.create_thread([=, &chainman] { ThreadImport(chainman, vImportFiles); });
+    g_load_block = std::thread(&TraceThread<std::function<void()>>, "loadblk", [=, &chainman]{ ThreadImport(chainman, vImportFiles); });
 
     // Wait for genesis block to be processed
     {