From 52188192b99ee4f3e7848ac1690bc1ccae338c56 Mon Sep 17 00:00:00 2001
From: wwuoneway <wwuoneway@gmail.com>
Date: Fri, 16 Oct 2026 13:30:57 -0500
Subject: [PATCH 1/2] Enable ROOT thread safety during FORM initialization

---
 form/root_storage/CMakeLists.txt         |  1 +
 form/root_storage/root_thread_safety.cpp | 17 +++++++++++++++++
 form/root_storage/root_thread_safety.hpp | 13 +++++++++++++
 form/storage/factories.cpp               |  8 ++++++++
 form/storage/factories.hpp               |  2 ++
 form/storage/storage_reader.cpp          |  1 +
 form/storage/storage_writer.cpp          |  1 +
 7 files changed, 43 insertions(+)
 create mode 100644 form/root_storage/root_thread_safety.cpp
 create mode 100644 form/root_storage/root_thread_safety.hpp

diff --git a/form/root_storage/CMakeLists.txt b/form/root_storage/CMakeLists.txt
index 4cc5e46f9..b1473e51c 100644
--- a/form/root_storage/CMakeLists.txt
+++ b/form/root_storage/CMakeLists.txt
@@ -7,6 +7,7 @@ set(FORM_ROOT_STORAGE_SOURCES)
 list(
   APPEND FORM_ROOT_STORAGE_SOURCES
   root_tfile.cpp
+  root_thread_safety.cpp
   root_ttree_write_container.cpp
   root_tbranch_read_container.cpp
   root_tbranch_write_container.cpp
diff --git a/form/root_storage/root_thread_safety.cpp b/form/root_storage/root_thread_safety.cpp
new file mode 100644
index 000000000..f0decc803
--- /dev/null
+++ b/form/root_storage/root_thread_safety.cpp
@@ -0,0 +1,17 @@
+// Copyright (C) 2025 ...
+
+#include "root_thread_safety.hpp"
+
+#include <TROOT.h>
+
+#include <mutex>
+
+namespace form::detail::experimental {
+
+  void ensure_root_thread_safety()
+  {
+    static std::once_flag enabled;
+    std::call_once(enabled, [] { ROOT::EnableThreadSafety(); });
+  }
+
+} // namespace form::detail::experimental
diff --git a/form/root_storage/root_thread_safety.hpp b/form/root_storage/root_thread_safety.hpp
new file mode 100644
index 000000000..b092c918b
--- /dev/null
+++ b/form/root_storage/root_thread_safety.hpp
@@ -0,0 +1,13 @@
+// Copyright (C) 2025 ...
+
+#ifndef FORM_ROOT_STORAGE_ROOT_THREAD_SAFETY_HPP
+#define FORM_ROOT_STORAGE_ROOT_THREAD_SAFETY_HPP
+
+namespace form::detail::experimental {
+
+  /// Enable ROOT thread safety.
+  void ensure_root_thread_safety();
+
+} // namespace form::detail::experimental
+
+#endif // FORM_ROOT_STORAGE_ROOT_THREAD_SAFETY_HPP
diff --git a/form/storage/factories.cpp b/form/storage/factories.cpp
index 8276567c1..33a223974 100644
--- a/form/storage/factories.cpp
+++ b/form/storage/factories.cpp
@@ -16,6 +16,7 @@
 #include "root_storage/root_tbranch_read_container.hpp"
 #include "root_storage/root_tbranch_write_container.hpp"
 #include "root_storage/root_tfile.hpp"
+#include "root_storage/root_thread_safety.hpp"
 #include "root_storage/root_ttree_write_container.hpp"
 #endif
 
@@ -31,6 +32,13 @@ namespace form::detail::experimental {
 
   using major = form::technology::major;
 
+  void ensure_backend_thread_safety()
+  {
+#ifdef USE_ROOT_STORAGE
+    ensure_root_thread_safety();
+#endif
+  }
+
   std::shared_ptr<i_storage_file> create_file(form::technology::id tech,
                                               std::string const& name,
                                               char mode)
diff --git a/form/storage/factories.hpp b/form/storage/factories.hpp
index 2a4bcda38..9eacc270e 100644
--- a/form/storage/factories.hpp
+++ b/form/storage/factories.hpp
@@ -11,6 +11,8 @@
 
 namespace form::detail::experimental {
 
+  void ensure_backend_thread_safety();
+
   std::shared_ptr<i_storage_file> create_file(form::technology::id tech,
                                               std::string const& name,
                                               char mode);
diff --git a/form/storage/storage_reader.cpp b/form/storage/storage_reader.cpp
index 43f02bfdb..5d22b4ad1 100644
--- a/form/storage/storage_reader.cpp
+++ b/form/storage/storage_reader.cpp
@@ -190,6 +190,7 @@ namespace {
 namespace form::detail::experimental {
   std::unique_ptr<i_storage_reader> create_storage_reader()
   {
+    ensure_backend_thread_safety();
     return std::unique_ptr<i_storage_reader>(new storage_reader());
   }
 }
diff --git a/form/storage/storage_writer.cpp b/form/storage/storage_writer.cpp
index 1d6076bd7..d10aab24e 100644
--- a/form/storage/storage_writer.cpp
+++ b/form/storage/storage_writer.cpp
@@ -58,6 +58,7 @@ namespace {
 namespace form::detail::experimental {
   std::unique_ptr<i_storage_writer> create_storage_writer()
   {
+    ensure_backend_thread_safety();
     return std::unique_ptr<i_storage_writer>(new storage_writer());
   }
 }

From 12795e05ae734bcc2acd0c07978793f6c2809395 Mon Sep 17 00:00:00 2001
From: wwuoneway <wwuoneway@gmail.com>
Date: Fri, 23 Oct 2026 13:38:35 -0500
Subject: [PATCH 2/2] Remove call_once from ROOT thread safety initialization;
 Rely on ROOT::EnableThreadSafety() to handle repeated calls instead of
 enforcing one-time initialization in FORM.

---
 form/root_storage/root_thread_safety.cpp | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/form/root_storage/root_thread_safety.cpp b/form/root_storage/root_thread_safety.cpp
index f0decc803..8eccf96d0 100644
--- a/form/root_storage/root_thread_safety.cpp
+++ b/form/root_storage/root_thread_safety.cpp
@@ -4,14 +4,8 @@
 
 #include <TROOT.h>
 
-#include <mutex>
-
 namespace form::detail::experimental {
 
-  void ensure_root_thread_safety()
-  {
-    static std::once_flag enabled;
-    std::call_once(enabled, [] { ROOT::EnableThreadSafety(); });
-  }
+  void ensure_root_thread_safety() { ROOT::EnableThreadSafety(); }
 
 } // namespace form::detail::experimental