perf: fix NVIM_CONN deadlock and unoptimized lock across await point

nvim-core/src/lib.rs

@@ -113,7 +113,7 @@ async fn get_socket_path() -> Result<String, String> {
 }
 use std::sync::LazyLock;
 use std::sync::Arc;
-use tokio::sync::{Mutex, mpsc, oneshot};
+use tokio::sync::{mpsc, oneshot};
 use std::collections::HashMap;
 
 
@@ -123,13 +123,15 @@ pub struct NvimRequest {
     pub reply: oneshot::Sender<Result<rmpv::Value, String>>,
 }
 
-static NVIM_CONN: LazyLock<Arc<Mutex<Option<mpsc::Sender<NvimRequest>>>>> = LazyLock::new(|| Arc::new(Mutex::new(None)));
+static NVIM_CONN: LazyLock<Arc<std::sync::Mutex<Option<mpsc::Sender<NvimRequest>>>>> = LazyLock::new(|| Arc::new(std::sync::Mutex::new(None)));
 
 async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
-    let mut conn_lock = NVIM_CONN.lock().await;
-    if let Some(sender) = conn_lock.as_ref() {
-        if !sender.is_closed() {
-            return Ok(sender.clone());
+    {
+        let conn_lock = NVIM_CONN.lock().unwrap();
+        if let Some(sender) = conn_lock.as_ref() {
+            if !sender.is_closed() {
+                return Ok(sender.clone());
+            }
         }
     }
 
@@ -244,6 +246,13 @@ async fn get_nvim_connection() -> Result<mpsc::Sender<NvimRequest>, String> {
         }
     });
 
+    let mut conn_lock = NVIM_CONN.lock().unwrap();
+    if let Some(existing_sender) = conn_lock.as_ref() {
+        if !existing_sender.is_closed() {
+            // Another task established the connection while we were waiting
+            return Ok(existing_sender.clone());
+        }
+    }
     *conn_lock = Some(tx.clone());
     Ok(tx)
 }