Make sure RuntimeEventSource is passed to EventListener.OnEventSourceCreated (#19697)

Author: brianrob

src/mscorlib/shared/System/Diagnostics/Tracing/EventSource.cs

@@ -1649,6 +1649,14 @@ private static uint Rol30(uint input)
 
         private static Guid GenerateGuidFromName(string name)
         {
+            if (namespaceBytes == null)
+            {
+                namespaceBytes = new byte[] {
+                    0x48, 0x2C, 0x2D, 0xB2, 0xC3, 0x90, 0x47, 0xC8,
+                    0x87, 0xF8, 0x1A, 0x15, 0xBF, 0xC1, 0x30, 0xFB,
+                };
+            }
+
             byte[] bytes = Encoding.BigEndianUnicode.GetBytes(name);
             var hash = new Sha1ForNonSecretPurposes();
             hash.Start();
@@ -3734,11 +3742,12 @@ private bool SelfDescribingEvents
         internal const string s_ActivityStartSuffix = "Start";
         internal const string s_ActivityStopSuffix = "Stop";
 
+        // WARNING: Do not depend upon initialized statics during creation of EventSources, as it is possible for creation of an EventSource to trigger
+        // creation of yet another EventSource.  When this happens, these statics may not yet be initialized.
+        // Rather than depending on initialized statics, use lazy initialization to ensure that the statics are initialized exactly when they are needed.
+
         // used for generating GUID from eventsource name
-        private static readonly byte[] namespaceBytes = new byte[] {
-            0x48, 0x2C, 0x2D, 0xB2, 0xC3, 0x90, 0x47, 0xC8,
-            0x87, 0xF8, 0x1A, 0x15, 0xBF, 0xC1, 0x30, 0xFB,
-        };
+        private static byte[] namespaceBytes;
 
 #endregion
     }
@@ -3847,6 +3856,16 @@ public event EventHandler<EventSourceCreatedEventArgs> EventSourceCreated
         /// </summary>
         public event EventHandler<EventWrittenEventArgs> EventWritten;
 
+        static EventListener()
+        {
+#if FEATURE_PERFTRACING
+            // Ensure that RuntimeEventSource is initialized so that EventListeners get an opportunity to subscribe to its events.
+            // This is required because RuntimeEventSource never emit events on its own, and thus will never be initialized
+            // in the normal way that EventSources are initialized.
+            GC.KeepAlive(RuntimeEventSource.Log);
+#endif // FEATURE_PERFTRACING
+        }
+
         /// <summary>
         /// Create a new EventListener in which all events start off turned off (use EnableEvents to turn
         /// them on).  
@@ -4082,9 +4101,24 @@ internal static void AddEventSource(EventSource newEventSource)
                 }
                 newEventSource.m_id = newIndex;
 
-                // Add every existing dispatcher to the new EventSource
-                for (EventListener listener = s_Listeners; listener != null; listener = listener.m_Next)
-                    newEventSource.AddListener(listener);
+#if DEBUG
+                // Disable validation of EventSource/EventListener connections in case a call to EventSource.AddListener
+                // causes a recursive call into this method.
+                bool previousValue = s_ConnectingEventSourcesAndListener;
+                s_ConnectingEventSourcesAndListener = true;
+                try
+                {
+#endif
+                    // Add every existing dispatcher to the new EventSource
+                    for (EventListener listener = s_Listeners; listener != null; listener = listener.m_Next)
+                        newEventSource.AddListener(listener);
+#if DEBUG
+                }
+                finally
+                {
+                    s_ConnectingEventSourcesAndListener = previousValue;
+                }
+#endif
 
                 Validate();
             }
@@ -4165,6 +4199,14 @@ private static void RemoveReferencesToListenerInEventSources(EventListener liste
         [Conditional("DEBUG")]
         internal static void Validate()
         {
+#if DEBUG
+            // Don't run validation code if we're in the middle of modifying the connections between EventSources and EventListeners.
+            if (s_ConnectingEventSourcesAndListener)
+            {
+                return;
+            }
+#endif
+
             lock (EventListenersLock)
             {
                 // Get all listeners 
@@ -4254,18 +4296,30 @@ private void CallBackForExistingEventSources(bool addToListenersList, EventHandl
                     // is created.
                     WeakReference[] eventSourcesSnapshot = s_EventSources.ToArray();
 
-                    for (int i = 0; i < eventSourcesSnapshot.Length; i++)
+#if DEBUG
+                    bool previousValue = s_ConnectingEventSourcesAndListener;
+                    s_ConnectingEventSourcesAndListener = true;
+                    try
                     {
-                        WeakReference eventSourceRef = eventSourcesSnapshot[i];
-                        EventSource eventSource = eventSourceRef.Target as EventSource;
-                        if (eventSource != null)
+#endif
+                        for (int i = 0; i < eventSourcesSnapshot.Length; i++)
                         {
-                            EventSourceCreatedEventArgs args = new EventSourceCreatedEventArgs();
-                            args.EventSource = eventSource;
-                            callback(this, args);
+                            WeakReference eventSourceRef = eventSourcesSnapshot[i];
+                            EventSource eventSource = eventSourceRef.Target as EventSource;
+                            if (eventSource != null)
+                            {
+                                EventSourceCreatedEventArgs args = new EventSourceCreatedEventArgs();
+                                args.EventSource = eventSource;
+                                callback(this, args);
+                            }
                         }
+#if DEBUG
                     }
-
+                    finally
+                    {
+                        s_ConnectingEventSourcesAndListener = previousValue;
+                    }
+#endif
                     Validate();
                 }
                 finally
@@ -4299,6 +4353,16 @@ private void CallBackForExistingEventSources(bool addToListenersList, EventHandl
         /// </summary>
         private static bool s_CreatingListener = false;
 
+#if DEBUG
+        /// <summary>
+        /// Used to disable validation of EventSource and EventListener connectivity.
+        /// This is needed when an EventListener is in the middle of being published to all EventSources
+        /// and another EventSource is created as part of the process.
+        /// </summary>
+        [ThreadStatic]
+        private static bool s_ConnectingEventSourcesAndListener = false;
+#endif
+
         /// <summary>
         /// Used to register AD/Process shutdown callbacks.
         /// </summary>
@@ -4637,7 +4701,7 @@ public DateTime TimeStamp
             internal set;
         }
 
-        #region private
+#region private
         internal EventWrittenEventArgs(EventSource eventSource)
         {
             m_eventSource = eventSource;

tests/src/tracing/common/RuntimeEventSource.cs

@@ -28,7 +28,6 @@
     <Compile Include="Assert.cs" />
     <Compile Include="EtlFile.cs" />
     <Compile Include="NetPerfFile.cs" />
-    <Compile Include="RuntimeEventSource.cs" />
     <Compile Include="TraceControl.cs" />
     <Compile Include="TraceConfiguration.cs" />
   </ItemGroup>

tests/src/tracing/common/common.csproj

@@ -17,23 +17,16 @@ public sealed class RuntimeEventSourceTest
     {
         static int Main(string[] args)
         {
-            // Get the RuntimeEventSource.
-            EventSource eventSource = RuntimeEventSource.Log;
-
+            SimpleEventListener.EnableKeywords = (EventKeywords)0;
             using (SimpleEventListener noEventsListener = new SimpleEventListener("NoEvents"))
             {
-                // Enable the provider, but not any keywords, so we should get no events as long as no rundown occurs.
-                noEventsListener.EnableEvents(eventSource, EventLevel.Critical, (EventKeywords)(0));
-
                 // Create an EventListener.
+                SimpleEventListener.EnableKeywords = (EventKeywords)0x4c14fccbd;
                 using (SimpleEventListener listener = new SimpleEventListener("Simple"))
                 {
                     // Trigger the allocator task.
                     System.Threading.Tasks.Task.Run(new Action(Allocator));
 
-                    // Enable events.
-                    listener.EnableEvents(eventSource, EventLevel.Verbose, (EventKeywords)(0x4c14fccbd));
-
                     // Wait for events.
                     Thread.Sleep(1000);
 
@@ -73,13 +66,37 @@ internal sealed class SimpleEventListener : EventListener
     {
         private string m_name;
 
+        // Keep track of the set of keywords to be enabled.
+        public static EventKeywords EnableKeywords
+        {
+            get;
+            set;
+        }
+
         public SimpleEventListener(string name)
         {
             m_name = name;
         }
 
         public int EventCount { get; private set; } = 0;
 
+        protected override void OnEventSourceCreated(EventSource eventSource)
+        {
+            if (eventSource.Name.Equals("Microsoft-Windows-DotNETRuntime"))
+            {
+                if (EnableKeywords != 0)
+                {
+                    // Enable events.
+                    EnableEvents(eventSource, EventLevel.Verbose, EnableKeywords);
+                }
+                else
+                {
+                    // Enable the provider, but not any keywords, so we should get no events as long as no rundown occurs.
+                    EnableEvents(eventSource, EventLevel.Critical, EnableKeywords);
+                }
+            }
+        }
+
         protected override void OnEventWritten(EventWrittenEventArgs eventData)
         {
             long osThreadId = -1;