Eliminate threadpool exhaustion (#69)

* Try to eliminating the thread pool exhaustion.

* Fix flattening and more trace.

* More tracing.

* Refactor. Raise internal version.

Author: kavics

src/SenseNet.Security/Messaging/SecurityActivityQueue.cs

@@ -198,9 +198,10 @@ private void ControlActivityQueueThread(CancellationToken cancel)
 
                     // Continue working
                     _workCycle++;
-                    SnTrace.SecurityQueue.Write(() => $"SAQT: works (cycle: {_workCycle}, " +
-                                                      $"_arrivalQueue.Count: {_arrivalQueue.Count}), " +
-                                                      $"_executingList.Count: {_executingList.Count}");
+                    SnTrace.SecurityQueue.Write(() => $"SAQT: works (cycle: {_workCycle}, Queues: " +
+                                                      $"arrival: {_arrivalQueue.Count}), " +
+                                                      $"executing: {_executingList.Count}, " +
+                                                      $"waiting: {_waitingList.Count}");
 
                     RemoveGapsIfRequested();
 
@@ -470,6 +471,8 @@ private IEnumerable<SecurityActivity> GetAllFromChains(List<SecurityActivity> ro
                 flattened.AddRange(flattened[index].WaitingForMe);
                 index++;
             }
+            flattened = flattened.Distinct().ToList();
+            SnTrace.SecurityQueue.Write(() => $"SAQT: GetAllFromChains: found {flattened.Count} activities.");
             foreach (var item in flattened)
                 yield return item;
         }

src/SenseNet.Security/Messaging/SecurityMessages/SecurityActivity.cs

@@ -374,20 +374,20 @@ public void OnDeserialization(object sender)
         private Task _executionTask;
         [field: NonSerialized]
         [JsonIgnore]
-        private Task _finalizationTask;
+        private TaskCompletionSource<bool> _finalizationTcs;
 
         internal Task CreateTaskForWait()
         {
-            _finalizationTask = new Task(() => { /* do nothing */ }, CancellationToken, TaskCreationOptions.LongRunning);
-            return _finalizationTask;
+            _finalizationTcs = new TaskCompletionSource<bool>(TaskCreationOptions.RunContinuationsAsynchronously);
+            return _finalizationTcs.Task;
         }
         internal void StartExecutionTask()
         {
             _executionTask = ExecuteInternalAsync(CancellationToken);
         }
         internal void StartFinalizationTask()
         {
-            _finalizationTask?.Start();
+            _finalizationTcs?.TrySetResult(true);
         }
 
         /// <summary>

src/SenseNet.Security/SenseNet.Security.csproj

@@ -2,7 +2,7 @@
 
 	<PropertyGroup>
 		<TargetFramework>net8.0</TargetFramework>
-		<Version>4.3.1</Version>
+		<Version>4.3.2-alpha.5</Version>
 		<Description>A powerful .Net component for managing permission entries in content repositories.</Description>
 		<Company>Sense/Net Inc.</Company>
 		<Copyright>Copyright © Sense/Net Inc.</Copyright>