[Local GC] FEATURE_EVENT_TRACE 1/n: Tracking Event State (#15873)

* [Local GC] FEATURE_EVENT_TRACE 1/n: Add infrastructure for keeping event state within the GC and plumbing to communicate event state changes

* Code review feedback: use a load without a barrier in IsEnabled and put debug-only code under TRACE_GC_EVENT_STATE

* Address code review feedback: add EventPipe callback and comments

* Fix the non-FEATURE_PAL build

* Fix an issue where the GC fails to react to ETW callbacks to occur before the GC is initialized (e.g. on startup when an ETW session is already active)

* Simplify callback locking scheme

* Add a separate callback for each EventPipe provider and funnel them all through a common handler

* Fix non-FEATURE_PAL build

13 files changed, 283 insertions, 0 deletions

diff --git a/src/gc/CMakeLists.txt b/src/gc/CMakeLists.txt
index 3240074b9b..e7aacdb831 100644
--- a/src/gc/CMakeLists.txt
+++ b/src/gc/CMakeLists.txt
@@ -18,6 +18,7 @@ remove_definitions(-DWRITE_BARRIER_CHECK)
 add_definitions(-DFEATURE_REDHAWK)
 
 set( GC_SOURCES
+  gceventstatus.cpp
   gcconfig.cpp
   gccommon.cpp
   gcscan.cpp
diff --git a/src/gc/env/gcenv.h b/src/gc/env/gcenv.h
index 3de756021d..a3071a1397 100644
--- a/src/gc/env/gcenv.h
+++ b/src/gc/env/gcenv.h
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
+#ifndef __GCENV_H__
+#define __GCENV_H__
 
 #if defined(_DEBUG)
 #ifndef _DEBUG_IMPL
@@ -71,3 +73,5 @@
 
 #include "etmdummy.h"
 #define ETW_EVENT_ENABLED(e,f) false
+
+#endif // __GCENV_H__
diff --git a/src/gc/env/gcenv.object.h b/src/gc/env/gcenv.object.h
index 4d611e562d..dd152f2f3c 100644
--- a/src/gc/env/gcenv.object.h
+++ b/src/gc/env/gcenv.object.h
@@ -2,6 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#ifndef __GCENV_OBJECT_H__
+#define __GCENV_OBJECT_H__
+
 //-------------------------------------------------------------------------------------------------
 //
 // Low-level types describing GC object layouts.
@@ -168,3 +171,5 @@ public:
         return offsetof(ArrayBase, m_dwLength);
     }
 };
+
+#endif // __GCENV_OBJECT_H__
diff --git a/src/gc/env/gcenv.sync.h b/src/gc/env/gcenv.sync.h
index d6bee05a19..5b7b77ddd4 100644
--- a/src/gc/env/gcenv.sync.h
+++ b/src/gc/env/gcenv.sync.h
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
+#ifndef __GCENV_SYNC_H__
+#define __GCENV_SYNC_H__
 
 // -----------------------------------------------------------------------------------------------------------
 //
@@ -143,3 +145,5 @@ private:
     HANDLE  m_hEvent;
     bool    m_fInitialized;
 };
+
+#endif // __GCENV_SYNC_H__
diff --git a/src/gc/gcee.cpp b/src/gc/gcee.cpp
index 90939b3d97..c5cc88b373 100644
--- a/src/gc/gcee.cpp
+++ b/src/gc/gcee.cpp
@@ -687,6 +687,15 @@ bool GCHeap::RuntimeStructuresValid()
     return GCScan::GetGcRuntimeStructuresValid();
 }
 
+void GCHeap::ControlEvents(GCEventKeyword keyword, GCEventLevel level)
+{
+    GCEventStatus::Set(GCEventProvider_Default, keyword, level);
+}
+
+void GCHeap::ControlPrivateEvents(GCEventKeyword keyword, GCEventLevel level)
+{
+    GCEventStatus::Set(GCEventProvider_Private, keyword, level);
+}
 
 #endif // !DACCESS_COMPILE
 
diff --git a/src/gc/gceesvr.cpp b/src/gc/gceesvr.cpp
index e216834f8e..cfcbe5869a 100644
--- a/src/gc/gceesvr.cpp
+++ b/src/gc/gceesvr.cpp
@@ -13,6 +13,7 @@
 #include "gc.h"
 #include "gcscan.h"
 #include "gchandletableimpl.h"
+#include "gceventstatus.h"
 
 #define SERVER_GC 1
 
diff --git a/src/gc/gceewks.cpp b/src/gc/gceewks.cpp
index f23038f012..9a4038cdd9 100644
--- a/src/gc/gceewks.cpp
+++ b/src/gc/gceewks.cpp
@@ -11,6 +11,7 @@
 #include "gc.h"
 #include "gcscan.h"
 #include "gchandletableimpl.h"
+#include "gceventstatus.h"
 
 #ifdef SERVER_GC
 #undef SERVER_GC
diff --git a/src/gc/gceventstatus.cpp b/src/gc/gceventstatus.cpp
new file mode 100644
index 0000000000..9c4f35bfde
--- /dev/null
+++ b/src/gc/gceventstatus.cpp
@@ -0,0 +1,9 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#include "common.h"
+#include "gceventstatus.h"
+
+Volatile<GCEventLevel> GCEventStatus::enabledLevels[2] = {GCEventLevel_None, GCEventLevel_None};
+Volatile<GCEventKeyword> GCEventStatus::enabledKeywords[2] = {GCEventKeyword_None, GCEventKeyword_None};
diff --git a/src/gc/gceventstatus.h b/src/gc/gceventstatus.h
new file mode 100644
index 0000000000..4b7310b8a7
--- /dev/null
+++ b/src/gc/gceventstatus.h
@@ -0,0 +1,190 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#ifndef __GCEVENTSTATUS_H__
+#define __GCEVENTSTATUS_H__
+
+
+/*
+ * gceventstatus.h - Eventing status for a standalone GC
+ *
+ * In order for a local GC to determine what events are enabled
+ * in an efficient manner, the GC maintains some local state about
+ * keywords and levels that are enabled for each eventing provider.
+ *
+ * The GC fires events from two providers: the "main" provider
+ * and the "private" provider. This file tracks keyword and level
+ * information for each provider separately.
+ *
+ * It is the responsibility of the EE to inform the GC of changes
+ * to eventing state. This is accomplished by invoking the
+ * `IGCHeap::ControlEvents` and `IGCHeap::ControlPrivateEvents` callbacks
+ * on the EE's heap instance, which ultimately will enable and disable keywords
+ * and levels within this file.
+ */
+
+#include "common.h"
+#include "gcenv.h"
+#include "gc.h"
+
+// Uncomment this define to print out event state changes to standard error.
+// #define TRACE_GC_EVENT_STATE 1
+
+/*
+ * GCEventProvider represents one of the two providers that the GC can
+ * fire events from: the default and private providers.
+ */
+enum GCEventProvider
+{
+    GCEventProvider_Default = 0,
+    GCEventProvider_Private = 1
+};
+
+/*
+ * GCEventStatus maintains all eventing state for the GC. It consists
+ * of a keyword bitmask and level for each provider that the GC can use
+ * to fire events.
+ *
+ * A level and event pair are considered to be "enabled" on a given provider
+ * if the given level is less than or equal to the current enabled level
+ * and if the keyword is present in the enabled keyword bitmask for that
+ * provider.
+ */
+class GCEventStatus
+{
+private:
+    /*
+     * The enabled level for each provider.
+     */
+    static Volatile<GCEventLevel> enabledLevels[2];
+
+    /*
+     * The bitmap of enabled keywords for each provider.
+     */
+    static Volatile<GCEventKeyword> enabledKeywords[2];
+
+public:
+    /*
+     * IsEnabled queries whether or not the given level and keyword are
+     * enabled on the given provider, returning true if they are.
+     */
+    __forceinline static bool IsEnabled(GCEventProvider provider, GCEventKeyword keyword, GCEventLevel level)
+    {
+        assert(level >= GCEventLevel_None && level < GCEventLevel_Max);
+
+        size_t index = static_cast<size_t>(provider);
+        return (enabledLevels[index].LoadWithoutBarrier() >= level)
+          && (enabledKeywords[index].LoadWithoutBarrier() & keyword);
+    }
+
+    /*
+     * Set sets the eventing state (level and keyword bitmap) for a given
+     * provider to the provided values.
+     */
+    static void Set(GCEventProvider provider, GCEventKeyword keywords, GCEventLevel level)
+    {
+        assert(level >= GCEventLevel_None && level < GCEventLevel_Max);
+
+        size_t index = static_cast<size_t>(provider);
+
+        enabledLevels[index] = level;
+        enabledKeywords[index] = keywords;
+
+#if TRACE_GC_EVENT_STATE
+        fprintf(stderr, "event state change:\n");
+        DebugDumpState(provider);
+#endif // TRACE_GC_EVENT_STATE
+    }
+
+#if TRACE_GC_EVENT_STATE
+private:
+    static void DebugDumpState(GCEventProvider provider)
+    {
+        size_t index = static_cast<size_t>(provider);
+        GCEventLevel level = enabledLevels[index];
+        GCEventKeyword keyword = enabledKeywords[index];
+        if (provider == GCEventProvider_Default)
+        {
+            fprintf(stderr, "provider: default\n");
+        }
+        else
+        {
+            fprintf(stderr, "provider: private\n");
+        }
+
+        switch (level)
+        {
+        case GCEventLevel_None:
+            fprintf(stderr, "  level: None\n");
+            break;
+        case GCEventLevel_Fatal:
+            fprintf(stderr, "  level: Fatal\n");
+            break;
+        case GCEventLevel_Error:
+            fprintf(stderr, "  level: Error\n");
+            break;
+        case GCEventLevel_Warning:
+            fprintf(stderr, "  level: Warning\n");
+            break;
+        case GCEventLevel_Information:
+            fprintf(stderr, "  level: Information\n");
+            break;
+        case GCEventLevel_Verbose:
+            fprintf(stderr, "  level: Verbose\n");
+            break;
+        default:
+            fprintf(stderr, "  level: %d?\n", level);
+            break;
+        }
+
+        fprintf(stderr, "  keywords: ");
+        if (keyword & GCEventKeyword_GC)
+        {
+            fprintf(stderr, "GC ");
+        }
+
+        if (keyword & GCEventKeyword_GCHandle)
+        {
+            fprintf(stderr, "GCHandle ");
+        }
+
+        if (keyword & GCEventKeyword_GCHeapDump)
+        {
+            fprintf(stderr, "GCHeapDump ");
+        }
+
+        if (keyword & GCEventKeyword_GCSampledObjectAllocationHigh)
+        {
+            fprintf(stderr, "GCSampledObjectAllocationHigh ");
+        }
+
+        if (keyword & GCEventKeyword_GCHeapSurvivalAndMovement)
+        {
+            fprintf(stderr, "GCHeapSurvivalAndMovement ");
+        }
+
+        if (keyword & GCEventKeyword_GCHeapCollect)
+        {
+            fprintf(stderr, "GCHeapCollect ");
+        }
+
+        if (keyword & GCEventKeyword_GCHeapAndTypeNames)
+        {
+            fprintf(stderr, "GCHeapAndTypeNames ");
+        }
+
+        if (keyword & GCEventKeyword_GCSampledObjectAllocationLow)
+        {
+            fprintf(stderr, "GCSampledObjectAllocationLow ");
+        }
+
+        fprintf(stderr, "\n");
+    }
+#endif // TRACE_GC_EVENT_STATUS
+
+    // This class is a singleton and can't be instantiated.
+    GCEventStatus() = delete;
+};
+
+#endif // __GCEVENTSTATUS_H__
diff --git a/src/gc/gcimpl.h b/src/gc/gcimpl.h
index c0efa69531..7210b9bcf0 100644
--- a/src/gc/gcimpl.h
+++ b/src/gc/gcimpl.h
@@ -230,6 +230,10 @@ public:	// FIX
     virtual segment_handle RegisterFrozenSegment(segment_info *pseginfo);
     virtual void UnregisterFrozenSegment(segment_handle seg);
 
+    // Event control functions
+    void ControlEvents(GCEventKeyword keyword, GCEventLevel level);
+    void ControlPrivateEvents(GCEventKeyword keyword, GCEventLevel level);
+
     void    WaitUntilConcurrentGCComplete ();                               // Use in managd threads
 #ifndef DACCESS_COMPILE    
     HRESULT WaitUntilConcurrentGCCompleteAsync(int millisecondsTimeout);    // Use in native threads. TRUE if succeed. FALSE if failed or timeout
diff --git a/src/gc/gcinterface.h b/src/gc/gcinterface.h
index afd3db3fe4..26e7c096d2 100644
--- a/src/gc/gcinterface.h
+++ b/src/gc/gcinterface.h
@@ -205,6 +205,44 @@ extern uint8_t* g_shadow_lowest_address;
 // For low memory notification from host
 extern int32_t g_bLowMemoryFromHost;
 
+// Event levels corresponding to events that can be fired by the GC.
+enum GCEventLevel
+{
+    GCEventLevel_None = 0,
+    GCEventLevel_Fatal = 1,
+    GCEventLevel_Error = 2,
+    GCEventLevel_Warning = 3,
+    GCEventLevel_Information = 4,
+    GCEventLevel_Verbose = 5,
+    GCEventLevel_Max = 6
+};
+
+// Event keywords corresponding to events that can be fired by the GC. These
+// numbers come from the ETW manifest itself - please make changes to this enum
+// if you add, remove, or change keyword sets that are used by the GC!
+enum GCEventKeyword
+{
+    GCEventKeyword_None                          =       0x0,
+    GCEventKeyword_GC                            =       0x1,
+    GCEventKeyword_GCHandle                      =       0x2,
+    GCEventKeyword_GCHeapDump                    =  0x100000,
+    GCEventKeyword_GCSampledObjectAllocationHigh =  0x200000,
+    GCEventKeyword_GCHeapSurvivalAndMovement     =  0x400000,
+    GCEventKeyword_GCHeapCollect                 =  0x800000,
+    GCEventKeyword_GCHeapAndTypeNames            = 0x1000000,
+    GCEventKeyword_GCSampledObjectAllocationLow  = 0x2000000,
+    GCEventKeyword_All = GCEventKeyword_GC
+      | GCEventKeyword_GCHandle
+      | GCEventKeyword_GCHeapDump
+      | GCEventKeyword_GCSampledObjectAllocationHigh
+      | GCEventKeyword_GCHeapDump
+      | GCEventKeyword_GCSampledObjectAllocationHigh
+      | GCEventKeyword_GCHeapSurvivalAndMovement
+      | GCEventKeyword_GCHeapCollect
+      | GCEventKeyword_GCHeapAndTypeNames
+      | GCEventKeyword_GCSampledObjectAllocationLow
+};
+
 // !!!!!!!!!!!!!!!!!!!!!!!
 // make sure you change the def in bcl\system\gc.cs 
 // if you change this!
@@ -809,6 +847,18 @@ public:
     // Unregisters a frozen segment.
     virtual void UnregisterFrozenSegment(segment_handle seg) = 0;
 
+    /*
+    ===========================================================================
+    Routines for informing the GC about which events are enabled.
+    ===========================================================================
+    */
+
+    // Enables or disables the given keyword or level on the default event provider.
+    virtual void ControlEvents(GCEventKeyword keyword, GCEventLevel level) = 0;
+
+    // Enables or disables the given keyword or level on the private event provider.
+    virtual void ControlPrivateEvents(GCEventKeyword keyword, GCEventLevel level) = 0;
+
     IGCHeap() {}
     virtual ~IGCHeap() {}
 };
diff --git a/src/gc/sample/CMakeLists.txt b/src/gc/sample/CMakeLists.txt
index 6f8aa615d7..953d0498e0 100644
--- a/src/gc/sample/CMakeLists.txt
+++ b/src/gc/sample/CMakeLists.txt
@@ -10,6 +10,7 @@ add_definitions(-DFEATURE_REDHAWK)
 set(SOURCES
     GCSample.cpp
     gcenv.ee.cpp
+    ../gceventstatus.cpp
     ../gcconfig.cpp
     ../gccommon.cpp
     ../gceewks.cpp
diff --git a/src/gc/sample/gcenv.h b/src/gc/sample/gcenv.h
index a86cf535d5..54b596e141 100644
--- a/src/gc/sample/gcenv.h
+++ b/src/gc/sample/gcenv.h
@@ -1,6 +1,8 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
+#ifndef __GCENV_H__
+#define __GCENV_H__
 
 // The sample is to be kept simple, so building the sample
 // in tandem with a standalone GC is currently not supported.
@@ -200,3 +202,5 @@ extern EEConfig * g_pConfig;
 
 #include "etmdummy.h"
 #define ETW_EVENT_ENABLED(e,f) false
+
+#endif // __GCENV_H__