From c4ed79a85927054836ee6cb6f8cdb62649c6a2b8 Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Wed, 3 Jan 2024 13:37:55 -0600
Subject: [PATCH] GH-2021 Simplify pause implementation.

---
 libraries/chain/controller.cpp    | 15 ++++++---------
 plugins/net_plugin/net_plugin.cpp | 26 +++-----------------------
 2 files changed, 9 insertions(+), 32 deletions(-)

diff --git a/libraries/chain/controller.cpp b/libraries/chain/controller.cpp
index decbce140c..d61c23737e 100644
--- a/libraries/chain/controller.cpp
+++ b/libraries/chain/controller.cpp
@@ -3247,18 +3247,15 @@ fc::sha256 controller::calculate_integrity_hash() { try {
 
 void controller::write_snapshot( const snapshot_writer_ptr& snapshot ) {
    EOS_ASSERT( !my->pending, block_validate_exception, "cannot take a consistent snapshot with a pending block" );
-   my->writing_snapshot = true;
-   try {
-      my->add_to_snapshot(snapshot);
-      my->writing_snapshot = false;
-   } catch(...) {
-      my->writing_snapshot = false;
-      throw;
-   }
+   my->writing_snapshot.store(true, std::memory_order_release);
+   fc::scoped_exit<std::function<void()>> e = [&] {
+      my->writing_snapshot.store(false, std::memory_order_release);
+   };
+   my->add_to_snapshot(snapshot);
 }
 
 bool controller::is_writing_snapshot() const {
-   return my->writing_snapshot;
+   return my->writing_snapshot.load(std::memory_order_acquire);
 }
 
 int64_t controller::set_proposed_producers( vector<producer_authority> producers ) {
diff --git a/plugins/net_plugin/net_plugin.cpp b/plugins/net_plugin/net_plugin.cpp
index 02d6ec0bf4..ce34dceafd 100644
--- a/plugins/net_plugin/net_plugin.cpp
+++ b/plugins/net_plugin/net_plugin.cpp
@@ -522,11 +522,6 @@ namespace eosio {
       mutable fc::mutex             chain_info_mtx; // protects chain_info_t
       chain_info_t                  chain_info GUARDED_BY(chain_info_mtx);
 
-      alignas(hardware_destructive_interference_size)
-      std::mutex                            pause_mtx;
-      std::condition_variable               pause_cv;
-      bool                                  paused = false;
-
    public:
       void update_chain_info();
       chain_info_t get_chain_info() const;
@@ -542,25 +537,11 @@ namespace eosio {
       void start_expire_timer();
       void start_monitors();
 
+      // we currently pause on snapshot generation
       void wait_if_paused() {
          controller& cc = chain_plug->chain();
-         if (!cc.is_writing_snapshot())
-            return;
-
-         std::unique_lock l(pause_mtx);
-         paused = true;
-         while (!pause_cv.wait_for(l, std::chrono::milliseconds(10), [&]{ return !paused; } )) {
-            if (!cc.is_writing_snapshot()) {
-               paused = false;
-            }
-         }
-      }
-
-      void unpause() {
-         std::lock_guard g(pause_mtx);
-         if (paused) {
-            paused = false;
-            pause_cv.notify_all();
+         while (cc.is_writing_snapshot()) {
+            std::this_thread::sleep_for(std::chrono::milliseconds(10));
          }
       }
 
@@ -3919,7 +3900,6 @@ namespace eosio {
 
    // called from application thread
    void net_plugin_impl::on_accepted_block_header(const block_state_ptr& bs) {
-      unpause();
       update_chain_info();
 
       dispatcher->strand.post([bs]() {