From 68d6c44e06c47271baf543d9edbc14a15b86777a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Piotr=20Wo=CC=81jcik?=
 <3044353+pwojcikdev@users.noreply.github.com>
Date: Mon, 4 Nov 2024 16:32:57 +0100
Subject: [PATCH] Track writer request id

---
 nano/store/write_queue.cpp | 24 ++++++++++++++----------
 nano/store/write_queue.hpp |  4 +++-
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/nano/store/write_queue.cpp b/nano/store/write_queue.cpp
index 41b687ce7..9791a0645 100644
--- a/nano/store/write_queue.cpp
+++ b/nano/store/write_queue.cpp
@@ -66,7 +66,9 @@ nano::store::write_guard nano::store::write_queue::wait (writer writer)
 bool nano::store::write_queue::contains (writer writer) const
 {
 	nano::lock_guard<nano::mutex> guard{ mutex };
-	return std::find (queue.cbegin (), queue.cend (), writer) != queue.cend ();
+	return std::any_of (queue.cbegin (), queue.cend (), [writer] (auto const & item) {
+		return item.first == writer;
+	});
 }
 
 void nano::store::write_queue::pop ()
@@ -83,17 +85,19 @@ void nano::store::write_queue::acquire (writer writer)
 {
 	nano::unique_lock<nano::mutex> lock{ mutex };
 
-	// There should be no duplicates in the queue
-	debug_assert (std::none_of (queue.cbegin (), queue.cend (), [writer] (auto const & item) { return item == writer; }));
+	// There should be no duplicates in the queue (exception is testing)
+	debug_assert (std::none_of (queue.cbegin (), queue.cend (), [writer] (auto const & item) {
+		return item.first == writer;
+	})
+	|| writer == writer::testing);
+
+	auto const id = next++;
 
 	// Add writer to the end of the queue if it's not already waiting
-	auto exists = std::find (queue.cbegin (), queue.cend (), writer) != queue.cend ();
-	if (!exists)
-	{
-		queue.push_back (writer);
-	}
+	queue.push_back ({ writer, id });
 
-	condition.wait (lock, [&] () { return queue.front () == writer; });
+	// Wait until we are at the front of the queue
+	condition.wait (lock, [&] () { return queue.front ().second == id; });
 }
 
 void nano::store::write_queue::release (writer writer)
@@ -101,7 +105,7 @@ void nano::store::write_queue::release (writer writer)
 	{
 		nano::lock_guard<nano::mutex> guard{ mutex };
 		release_assert (!queue.empty ());
-		release_assert (queue.front () == writer);
+		release_assert (queue.front ().first == writer);
 		queue.pop_front ();
 	}
 	condition.notify_all ();
diff --git a/nano/store/write_queue.hpp b/nano/store/write_queue.hpp
index 6b4688618..0171685b8 100644
--- a/nano/store/write_queue.hpp
+++ b/nano/store/write_queue.hpp
@@ -70,7 +70,9 @@ private:
 	void release (writer writer);
 
 private:
-	std::deque<writer> queue;
+	uint64_t next{ 0 };
+	using entry = std::pair<writer, uint64_t>; // uint64_t is a unique id for each write_guard
+	std::deque<entry> queue;
 	mutable nano::mutex mutex;
 	nano::condition_variable condition;