EventSource startup initialization (#106014)

* EventSource startup initialization

Fixes #105845

Previously MetricsEventSource wasn't being created for apps that didn't ever create a Meter. This caused a chicken-and-egg problem for RuntimeMetrics which weren't created until MetricsEventSource started a tracing session. This change ensures that MetricsEventSource will be created on demand if ETW, EventPipe, or EventListener based tooling starts a tracing session. I took some extra effort to create the EventSource in a deferred fashion to avoid eager loading System.Diagnostics.DiagnosticSource.dll when it might never be needed.

Aside from the fix there were some small improvements:
- Moved NativeRuntimeEventSource to initialize in the same place as other startup EventSources
- Removed a useless lock(EventListener.EventListenersLock) around EventPipe eventProvider registration

src/coreclr/vm/corelib.h

@@ -775,8 +775,8 @@ DEFINE_FIELD_U(rgiColumnNumber,            StackFrameHelper,   rgiColumnNumber)
 DEFINE_FIELD_U(rgiLastFrameFromForeignExceptionStackTrace,            StackFrameHelper,   rgiLastFrameFromForeignExceptionStackTrace)
 DEFINE_FIELD_U(iFrameCount,                StackFrameHelper,   iFrameCount)
 
-DEFINE_CLASS(RUNTIME_EVENT_SOURCE,  Tracing,                RuntimeEventSource)
-DEFINE_METHOD(RUNTIME_EVENT_SOURCE, INITIALIZE, Initialize, SM_RetVoid)
+DEFINE_CLASS(EVENT_SOURCE,           Tracing,            EventSource)
+DEFINE_METHOD(EVENT_SOURCE,          INITIALIZE_DEFAULT_EVENT_SOURCES, InitializeDefaultEventSources, SM_RetVoid)
 
 DEFINE_CLASS(STARTUP_HOOK_PROVIDER,  System,                StartupHookProvider)
 DEFINE_METHOD(STARTUP_HOOK_PROVIDER, MANAGED_STARTUP, ManagedStartup, SM_PtrChar_RetVoid)

src/coreclr/vm/corhost.cpp

@@ -665,11 +665,11 @@ HRESULT CorHost2::CreateAppDomainWithManager(
     m_fAppDomainCreated = TRUE;
 
 #ifdef FEATURE_PERFTRACING
-    // Initialize RuntimeEventSource
+    // Initialize default event sources
     {
         GCX_COOP();
-        MethodDescCallSite initRuntimeEventSource(METHOD__RUNTIME_EVENT_SOURCE__INITIALIZE);
-        initRuntimeEventSource.Call(NULL);
+        MethodDescCallSite initEventSources(METHOD__EVENT_SOURCE__INITIALIZE_DEFAULT_EVENT_SOURCES);
+        initEventSources.Call(NULL);
     }
 #endif // FEATURE_PERFTRACING
 

src/libraries/System.Diagnostics.DiagnosticSource/src/ILLink/ILLink.Descriptors.LibraryBuild.xml

@@ -0,0 +1,8 @@
+<linker>
+  <assembly fullname="System.Diagnostics.DiagnosticSource">
+    <type fullname="System.Diagnostics.Metrics.MetricsEventSource">
+      <!-- Used by System.Private.CoreLib via reflection to init the EventSource -->
+      <method name="GetInstance" />
+    </type>
+  </assembly>
+</linker>

src/libraries/System.Diagnostics.DiagnosticSource/src/System.Diagnostics.DiagnosticSource.csproj

@@ -25,6 +25,7 @@ System.Diagnostics.DiagnosticSource</PackageDescription>
 
   <ItemGroup>
     <ILLinkSubstitutionsXmls Include="ILLink/ILLink.Substitutions.Shared.xml" />
+    <Content Include="ILLink\ILLink.Descriptors.LibraryBuild.xml" />
   </ItemGroup>
 
   <ItemGroup>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Metrics/MetricsEventSource.cs

@@ -46,6 +46,11 @@ internal sealed class MetricsEventSource : EventSource
     {
         public static readonly MetricsEventSource Log = new();
 
+        // Although this API isn't public, it is invoked via reflection from System.Private.CoreLib and needs the same back-compat
+        // consideration as a public API. See EventSource.InitializeDefaultEventSources() in System.Private.CoreLib source for more
+        // details. We have a unit test GetInstanceMethodIsReflectable that verifies this method isn't accidentally removed or renamed.
+        public static MetricsEventSource GetInstance() { return Log; }
+
         private const string SharedSessionId = "SHARED";
         private const string ClientIdKey = "ClientId";
         private const string MaxHistogramsKey = "MaxHistograms";

src/libraries/System.Diagnostics.DiagnosticSource/tests/MetricEventSourceTests.cs

@@ -5,6 +5,7 @@
 using System.Diagnostics.Tracing;
 using System.Globalization;
 using System.Linq;
+using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Text;
 using System.Threading;
@@ -26,6 +27,23 @@ public MetricEventSourceTests(ITestOutputHelper output)
             _output = output;
         }
 
+        [Fact]
+        public void GetInstanceMethodIsReflectable()
+        {
+            // The startup code in System.Private.CoreLib needs to be able to get the MetricsEventSource instance via reflection. See EventSource.InitializeDefaultEventSources() in
+            // the System.Private.CoreLib source.
+            // Even though the the type isn't public this test ensures the GetInstance() API isn't removed or renamed.
+            Type? metricsEventSourceType = Type.GetType("System.Diagnostics.Metrics.MetricsEventSource, System.Diagnostics.DiagnosticSource", throwOnError: false);
+            Assert.True(metricsEventSourceType != null, "Unable to get MetricsEventSource type via reflection");
+
+            MethodInfo? getInstanceMethod = metricsEventSourceType.GetMethod("GetInstance", BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static, null, Type.EmptyTypes, null);
+            Assert.True(getInstanceMethod != null, "Unable to get MetricsEventSource.GetInstance method via reflection");
+
+            object? o = getInstanceMethod.Invoke(null, null);
+            Assert.True(o != null, "Expected non-null result invoking MetricsEventSource.GetInstance() via reflection");
+            Assert.True(o is EventSource, "Expected object returned from MetricsEventSource.GetInstance() to be assignable to EventSource");
+        }
+
         [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotBrowser))]
         [OuterLoop("Slow and has lots of console spew")]
         public void MultipleListeners_DifferentCounters()

src/libraries/System.Diagnostics.Tracing/tests/BasicEventSourceTest/TestUtilities.cs

@@ -31,6 +31,7 @@ public static void CheckNoEventSourcesRunning(string message = "")
                     eventSource.Name != "System.Reflection.Runtime.Tracing" &&
                     eventSource.Name != "Microsoft-Windows-DotNETRuntime" &&
                     eventSource.Name != "System.Runtime" &&
+                    eventSource.Name != "System.Diagnostics.Metrics" &&
 
                     // event source from xunit runner
                     eventSource.Name != "xUnit.TestEventSource" &&

src/libraries/System.Private.CoreLib/src/ILLink/ILLink.Descriptors.EventSource.xml

@@ -1,7 +1,7 @@
 <linker>
   <assembly fullname="System.Private.CoreLib" feature="System.Diagnostics.Tracing.EventSource.IsSupported" featurevalue="true" featuredefault="true">
-    <type fullname="System.Diagnostics.Tracing.RuntimeEventSource">
-      <method signature="System.Void Initialize()" />
+    <type fullname="System.Diagnostics.Tracing.EventSource">
+      <method signature="System.Void InitializeDefaultEventSources()" />
     </type>
   </assembly>
 </linker>

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventPipeEventProvider.cs

@@ -70,12 +70,12 @@ private static unsafe void Callback(byte* sourceId, int isEnabled, byte level,
         }
 
         // Register an event provider.
-        internal override unsafe void Register(EventSource eventSource)
+        internal override unsafe void Register(Guid id, string name)
         {
             Debug.Assert(!_gcHandle.IsAllocated);
             _gcHandle = GCHandle.Alloc(this);
 
-            _provHandle = EventPipeInternal.CreateProvider(eventSource.Name, &Callback, (void*)GCHandle.ToIntPtr(_gcHandle));
+            _provHandle = EventPipeInternal.CreateProvider(name, &Callback, (void*)GCHandle.ToIntPtr(_gcHandle));
             if (_provHandle == 0)
             {
                 // Unable to create the provider.

src/libraries/System.Private.CoreLib/src/System/Diagnostics/Tracing/EventProvider.cs

@@ -103,14 +103,14 @@ internal EventProvider(EventProviderType providerType)
         }
 
         /// <summary>
-        /// This method registers the controlGuid of this class with ETW.
+        /// This method registers the provider with the backing tracing mechanism, either ETW or EventPipe.
         /// </summary>
-        internal unsafe void Register(EventSource eventSource)
+        internal unsafe void Register(Guid id, string name)
         {
-            _providerName = eventSource.Name;
-            _providerId = eventSource.Guid;
+            _providerName = name;
+            _providerId = id;
 
-            _eventProvider.Register(eventSource);
+            _eventProvider.Register(id, name);
         }
 
         //
@@ -827,13 +827,13 @@ private static unsafe void Callback(Guid* sourceId, int isEnabled, byte level,
 
 
         // Register an event provider.
-        internal override unsafe void Register(EventSource eventSource)
+        internal override unsafe void Register(Guid id, string name)
         {
             Debug.Assert(!_gcHandle.IsAllocated);
             _gcHandle = GCHandle.Alloc(this);
 
             long registrationHandle = 0;
-            _providerId = eventSource.Guid;
+            _providerId = id;
             Guid providerId = _providerId;
             uint status = Interop.Advapi32.EventRegister(
                 &providerId,
@@ -1235,7 +1235,7 @@ internal virtual void Disable()
             _allKeywordMask = 0;
         }
 
-        internal virtual void Register(EventSource eventSource)
+        internal virtual void Register(Guid id, string name)
         {
         }