From 1d00e4746b89b3971cef74ea0f29fead502029ab Mon Sep 17 00:00:00 2001
From: Cursor Agent <cursoragent@cursor.com>
Date: Fri, 12 Dec 2025 08:45:13 +0000
Subject: [PATCH] Refactor: Lazily start ml-service extension message thread

Co-authored-by: myungjoo.ham <myungjoo.ham@samsung.com>
---
 c/src/ml-api-service-extension.c | 79 +++++++++++++++++++++++++++-----
 1 file changed, 68 insertions(+), 11 deletions(-)

diff --git a/c/src/ml-api-service-extension.c b/c/src/ml-api-service-extension.c
index e8cecc20..fd3247e4 100644
--- a/c/src/ml-api-service-extension.c
+++ b/c/src/ml-api-service-extension.c
@@ -174,7 +174,6 @@ _ml_extension_msg_thread (gpointer data)
   int status;
 
   g_mutex_lock (&mls->lock);
-  ext->running = TRUE;
   g_cond_signal (&mls->cond);
   g_mutex_unlock (&mls->lock);
 
@@ -233,6 +232,66 @@ _ml_extension_msg_thread (gpointer data)
   return NULL;
 }
 
+/**
+ * @brief Internal function to lazily start the message thread.
+ * @note This avoids creating/joining threads for applications that only create/destroy handles.
+ */
+static int
+_ml_extension_ensure_msg_thread (ml_service_s * mls)
+{
+  ml_extension_s *ext;
+  g_autofree gchar *thread_name = NULL;
+  g_autoptr (GError) err = NULL;
+
+  if (!mls || !mls->priv)
+    return ML_ERROR_INVALID_PARAMETER;
+
+  ext = (ml_extension_s *) mls->priv;
+
+  /* Fast path: already created. */
+  if (ext->msg_thread && ext->msg_queue)
+    return ML_ERROR_NONE;
+
+  g_mutex_lock (&mls->lock);
+
+  /* Double-check under lock. */
+  if (ext->msg_thread && ext->msg_queue) {
+    g_mutex_unlock (&mls->lock);
+    return ML_ERROR_NONE;
+  }
+
+  if (!ext->msg_queue) {
+    ext->msg_queue = g_async_queue_new_full (_ml_extension_msg_free);
+    if (!ext->msg_queue) {
+      g_mutex_unlock (&mls->lock);
+      return ML_ERROR_OUT_OF_MEMORY;
+    }
+  }
+
+  if (!ext->msg_thread) {
+    ext->running = TRUE;
+
+    thread_name = g_strdup_printf ("ml-ext-msg-%d", getpid ());
+    ext->msg_thread = g_thread_try_new (thread_name, _ml_extension_msg_thread,
+        mls, &err);
+    if (!ext->msg_thread) {
+      ext->running = FALSE;
+      _ml_error_report ("Failed to create ml-service extension message thread: %s",
+          err ? err->message : "unknown error");
+
+      /* Keep msg_queue for a later retry, but stop the thread control flag. */
+      g_mutex_unlock (&mls->lock);
+      return ML_ERROR_OUT_OF_MEMORY;
+    }
+
+    /* Wait until the message thread has been initialized. */
+    g_cond_wait (&mls->cond, &mls->lock);
+  }
+
+  g_mutex_unlock (&mls->lock);
+  return ML_ERROR_NONE;
+}
+
 /**
  * @brief Wrapper to release tensors-info handle.
  */
@@ -586,7 +645,6 @@ int
 _ml_service_extension_create (ml_service_s * mls, JsonObject * object)
 {
   ml_extension_s *ext;
-  g_autofree gchar *thread_name = g_strdup_printf ("ml-ext-msg-%d", getpid ());
   int status;
 
   mls->priv = ext = g_try_new0 (ml_extension_s, 1);
@@ -601,6 +659,8 @@ _ml_service_extension_create (ml_service_s * mls, JsonObject * object)
   ext->max_input = DEFAULT_MAX_INPUT;
   ext->node_table = g_hash_table_new_full (g_str_hash, g_str_equal, g_free,
       _ml_extension_node_info_free);
+  ext->msg_thread = NULL;
+  ext->msg_queue = NULL;
 
   status = _ml_extension_conf_parse_json (mls, object);
   if (status != ML_ERROR_NONE) {
@@ -608,15 +668,6 @@ _ml_service_extension_create (ml_service_s * mls, JsonObject * object)
         "Failed to parse the ml-service extension configuration.");
   }
 
-  g_mutex_lock (&mls->lock);
-
-  ext->msg_queue = g_async_queue_new_full (_ml_extension_msg_free);
-  ext->msg_thread = g_thread_new (thread_name, _ml_extension_msg_thread, mls);
-
-  /* Wait until the message thread has been initialized. */
-  g_cond_wait (&mls->cond, &mls->lock);
-  g_mutex_unlock (&mls->lock);
-
   return ML_ERROR_NONE;
 }
 
@@ -826,6 +877,12 @@ _ml_service_extension_request (ml_service_s * mls, const char *name,
   ml_extension_msg_s *msg;
   int status, len;
 
+  status = _ml_extension_ensure_msg_thread (mls);
+  if (status != ML_ERROR_NONE) {
+    _ml_error_report_return (status,
+        "Failed to start ml-service extension internal message thread.");
+  }
+
   if (ext->type == ML_EXTENSION_TYPE_PIPELINE) {
     ml_service_node_info_s *node_info;