Refactor reload logic with semaphore for concurrency

https://github.com/2dust/v2rayN/issues/8276

v2rayN/ServiceLib/ViewModels/MainWindowViewModel.cs

@@ -64,8 +64,6 @@ public class MainWindowViewModel : MyReactiveObject
 
     #endregion Menu
 
-    private bool _hasNextReloadJob = false;
-
     #region Init
 
     public MainWindowViewModel(Func<EViewAction, object?, Task<bool>>? updateView)
@@ -268,7 +266,6 @@ public class MainWindowViewModel : MyReactiveObject
         }
         await RefreshServers();
 
-        SetReloadEnabled(true);
         await Reload();
     }
 
@@ -525,15 +522,20 @@ public class MainWindowViewModel : MyReactiveObject
 
     #region core job
 
+    private bool _hasNextReloadJob = false;
+    private readonly SemaphoreSlim _reloadSemaphore = new(1, 1);
+
     public async Task Reload()
     {
         //If there are unfinished reload job, marked with next job.
-        if (!BlReloadEnabled)
+        if (!await _reloadSemaphore.WaitAsync(0))
         {
             _hasNextReloadJob = true;
             return;
         }
 
+        try
+        {
             SetReloadEnabled(false);
 
             var msgs = await ActionPrecheckManager.Instance.Check(_config.IndexId);
@@ -544,7 +546,6 @@ public class MainWindowViewModel : MyReactiveObject
                     NoticeManager.Instance.SendMessage(msg);
                 }
                 NoticeManager.Instance.Enqueue(Utils.List2String(msgs.Take(10).ToList(), true));
-            SetReloadEnabled(true);
                 return;
             }
 
@@ -563,13 +564,19 @@ public class MainWindowViewModel : MyReactiveObject
             }
 
             ReloadResult(showClashUI);
+        }
+        finally
+        {
             SetReloadEnabled(true);
+            _reloadSemaphore.Release();
+            //If there is a next reload job, execute it.
             if (_hasNextReloadJob)
             {
                 _hasNextReloadJob = false;
                 await Reload();
             }
         }
+    }
 
     private void ReloadResult(bool showClashUI)
     {