From 5a27030ff8494c5552a7a23884d96a7628941d60 Mon Sep 17 00:00:00 2001
From: Jason Rhinelander <jason@imaginary.ca>
Date: Sun, 21 Jun 2020 22:51:32 -0300
Subject: [PATCH] Replace thread "pool" with a single thread

When you have a comment just before your thread pool initialization that
reads:

    // we only need 1

that is a pretty good indicator that you don't need a thread *pool* for
the thing you are doing.

Replace it with a single std::thread.
---
 src/cryptonote_core/blockchain.cpp | 5 ++---
 src/cryptonote_core/blockchain.h   | 3 +--
 2 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index f0cf6d550..53a884eee 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -508,8 +508,7 @@ bool Blockchain::init(BlockchainDB* db, sqlite3 *lns_db, const network_type nett
   // create general purpose async service queue
 
   m_async_work_idle = std::unique_ptr < boost::asio::io_service::work > (new boost::asio::io_service::work(m_async_service));
-  // we only need 1
-  m_async_pool.create_thread([this] { m_async_service.run(); });
+  m_async_thread = std::thread{[this] { m_async_service.run(); }};
 
 #if defined(PER_BLOCK_CHECKPOINT)
   if (m_nettype != FAKECHAIN)
@@ -647,7 +646,7 @@ bool Blockchain::deinit()
 
  // stop async service
   m_async_work_idle.reset();
-  m_async_pool.join_all();
+  m_async_thread.join();
   m_async_service.stop();
 
   // as this should be called if handling a SIGSEGV, need to check
diff --git a/src/cryptonote_core/blockchain.h b/src/cryptonote_core/blockchain.h
index 50d914ece..06d07ee20 100644
--- a/src/cryptonote_core/blockchain.h
+++ b/src/cryptonote_core/blockchain.h
@@ -37,7 +37,6 @@
 #include <boost/multi_index/global_fun.hpp>
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/member.hpp>
-#include <boost/thread/thread.hpp>
 #include <atomic>
 #include <functional>
 #include <unordered_map>
@@ -1118,7 +1117,7 @@ namespace cryptonote
     difficulty_type m_difficulty_for_next_block;
 
     boost::asio::io_service m_async_service;
-    boost::thread_group m_async_pool;
+    std::thread m_async_thread;
     std::unique_ptr<boost::asio::io_service::work> m_async_work_idle;
 
     // some invalid blocks