8295303: cleanup debug agent's confusing use of EI_GC_FINISH

Reviewed-by: amenkov, sspitsyn

Author: plummercj

src/jdk.jdwp.agent/share/native/libjdwp/error_messages.c

@@ -232,6 +232,7 @@ eventText(int i)
         CASE_RETURN_TEXT(EI_THREAD_START)
         CASE_RETURN_TEXT(EI_THREAD_END)
         CASE_RETURN_TEXT(EI_CLASS_PREPARE)
+        CASE_RETURN_TEXT(EI_CLASS_UNLOAD)
         CASE_RETURN_TEXT(EI_CLASS_LOAD)
         CASE_RETURN_TEXT(EI_FIELD_ACCESS)
         CASE_RETURN_TEXT(EI_FIELD_MODIFICATION)
@@ -240,7 +241,6 @@ eventText(int i)
         CASE_RETURN_TEXT(EI_METHOD_EXIT)
         CASE_RETURN_TEXT(EI_VM_INIT)
         CASE_RETURN_TEXT(EI_VM_DEATH)
-        CASE_RETURN_TEXT(EI_GC_FINISH)
         CASE_RETURN_TEXT(EI_VIRTUAL_THREAD_START)
         CASE_RETURN_TEXT(EI_VIRTUAL_THREAD_END)
         default: return "EVENT_unknown";

src/jdk.jdwp.agent/share/native/libjdwp/eventFilter.c

@@ -397,7 +397,7 @@ eventFilterRestricted_passesFilter(JNIEnv *env,
      * Suppress most events if they happen in debug threads
      */
     if ((evinfo->ei != EI_CLASS_PREPARE) &&
-        (evinfo->ei != EI_GC_FINISH) &&
+        (evinfo->ei != EI_CLASS_UNLOAD) &&
         (evinfo->ei != EI_CLASS_LOAD) &&
         threadControl_isDebugThread(thread)) {
         return JNI_FALSE;
@@ -749,7 +749,7 @@ eventFilter_setThreadOnlyFilter(HandlerNode *node, jint index,
     if (index >= FILTER_COUNT(node)) {
         return AGENT_ERROR_ILLEGAL_ARGUMENT;
     }
-    if (NODE_EI(node) == EI_GC_FINISH) {
+    if (NODE_EI(node) == EI_CLASS_UNLOAD) {
         return AGENT_ERROR_ILLEGAL_ARGUMENT;
     }
 
@@ -821,7 +821,7 @@ eventFilter_setClassOnlyFilter(HandlerNode *node, jint index,
         return AGENT_ERROR_ILLEGAL_ARGUMENT;
     }
     if (
-        (NODE_EI(node) == EI_GC_FINISH) ||
+        (NODE_EI(node) == EI_CLASS_UNLOAD) ||
         (NODE_EI(node) == EI_THREAD_START) ||
         (NODE_EI(node) == EI_THREAD_END)) {
 
@@ -1265,7 +1265,7 @@ enableEvents(HandlerNode *node)
         case EI_THREAD_END:
         case EI_VM_INIT:
         case EI_VM_DEATH:
-        case EI_GC_FINISH:
+        case EI_CLASS_UNLOAD:
         case EI_VIRTUAL_THREAD_START:
         case EI_VIRTUAL_THREAD_END:
             return error;
@@ -1325,7 +1325,7 @@ disableEvents(HandlerNode *node)
         case EI_THREAD_END:
         case EI_VM_INIT:
         case EI_VM_DEATH:
-        case EI_GC_FINISH:
+        case EI_CLASS_UNLOAD:
         case EI_VIRTUAL_THREAD_START:
         case EI_VIRTUAL_THREAD_END:
             return error;

src/jdk.jdwp.agent/share/native/libjdwp/eventHandler.c

@@ -487,7 +487,7 @@ eventHandler_synthesizeUnloadEvent(char *signature, JNIEnv *env)
 
     debugMonitorEnter(handlerLock);
 
-    node = getHandlerChain(EI_GC_FINISH)->first;
+    node = getHandlerChain(EI_CLASS_UNLOAD)->first;
     while (node != NULL) {
         /* save next so handlers can remove themselves */
         HandlerNode *next = NEXT(node);
@@ -1508,8 +1508,13 @@ eventHandler_initialize(jbyte sessionID)
     if (error != JVMTI_ERROR_NONE) {
         EXIT_ERROR(error,"Can't enable thread end events");
     }
-    error = threadControl_setEventMode(JVMTI_ENABLE,
-                                       EI_GC_FINISH, NULL);
+
+    /*
+     * GARBAGE_COLLECTION_FINISH is special since it is not tied to any handlers or an EI,
+     * so it cannot be setup using threadControl_setEventMode(). Use JVMTI API directly.
+     */
+    error = JVMTI_FUNC_PTR(gdata->jvmti,SetEventNotificationMode)
+            (gdata->jvmti, JVMTI_ENABLE, JVMTI_EVENT_GARBAGE_COLLECTION_FINISH, NULL);
     if (error != JVMTI_ERROR_NONE) {
         EXIT_ERROR(error,"Can't enable garbage collection finish events");
     }

src/jdk.jdwp.agent/share/native/libjdwp/standardHandlers.c

@@ -78,11 +78,15 @@ handleClassPrepare(JNIEnv *env, EventInfo *evinfo,
 
 /* HandlerFunction - Invoked from event_callback() */
 static void
-handleGarbageCollectionFinish(JNIEnv *env, EventInfo *evinfo,
+handleClassUnload(JNIEnv *env, EventInfo *evinfo,
                   HandlerNode *node,
                   struct bag *eventBag)
 {
-    JDI_ASSERT_MSG(JNI_FALSE, "Should never call handleGarbageCollectionFinish");
+  /*
+   * CLASS_UNLOAD events are synthesized by the class tracking code, so
+   * we should never have this handler called.
+   */
+    JDI_ASSERT_MSG(JNI_FALSE, "Should never call handleClassUnload");
 }
 
 /* HandlerFunction - Invoked from event_callback() for METHOD_ENTRY and METHOD_EXIT. */
@@ -162,8 +166,8 @@ standardHandlers_defaultHandler(EventIndex ei)
         case EI_CLASS_PREPARE:
             return &handleClassPrepare;
 
-        case EI_GC_FINISH:
-            return &handleGarbageCollectionFinish;
+        case EI_CLASS_UNLOAD:
+            return &handleClassUnload;
 
         case EI_METHOD_ENTRY:
         case EI_METHOD_EXIT:

src/jdk.jdwp.agent/share/native/libjdwp/util.c

@@ -1935,7 +1935,7 @@ eventIndexInit(void)
     index2jvmti[EI_THREAD_START       -EI_min] = JVMTI_EVENT_THREAD_START;
     index2jvmti[EI_THREAD_END         -EI_min] = JVMTI_EVENT_THREAD_END;
     index2jvmti[EI_CLASS_PREPARE      -EI_min] = JVMTI_EVENT_CLASS_PREPARE;
-    index2jvmti[EI_GC_FINISH          -EI_min] = JVMTI_EVENT_GARBAGE_COLLECTION_FINISH;
+    index2jvmti[EI_CLASS_UNLOAD       -EI_min] = 0; // No mapping to JVMTI event
     index2jvmti[EI_CLASS_LOAD         -EI_min] = JVMTI_EVENT_CLASS_LOAD;
     index2jvmti[EI_FIELD_ACCESS       -EI_min] = JVMTI_EVENT_FIELD_ACCESS;
     index2jvmti[EI_FIELD_MODIFICATION -EI_min] = JVMTI_EVENT_FIELD_MODIFICATION;
@@ -1958,7 +1958,7 @@ eventIndexInit(void)
     index2jdwp[EI_THREAD_START        -EI_min] = JDWP_EVENT(THREAD_START);
     index2jdwp[EI_THREAD_END          -EI_min] = JDWP_EVENT(THREAD_END);
     index2jdwp[EI_CLASS_PREPARE       -EI_min] = JDWP_EVENT(CLASS_PREPARE);
-    index2jdwp[EI_GC_FINISH           -EI_min] = JDWP_EVENT(CLASS_UNLOAD);
+    index2jdwp[EI_CLASS_UNLOAD        -EI_min] = JDWP_EVENT(CLASS_UNLOAD);
     index2jdwp[EI_CLASS_LOAD          -EI_min] = JDWP_EVENT(CLASS_LOAD);
     index2jdwp[EI_FIELD_ACCESS        -EI_min] = JDWP_EVENT(FIELD_ACCESS);
     index2jdwp[EI_FIELD_MODIFICATION  -EI_min] = JDWP_EVENT(FIELD_MODIFICATION);
@@ -1977,21 +1977,29 @@ eventIndexInit(void)
 }
 
 jdwpEvent
-eventIndex2jdwp(EventIndex i)
+eventIndex2jdwp(EventIndex ei)
 {
-    if ( i < EI_min || i > EI_max ) {
-        EXIT_ERROR(AGENT_ERROR_INVALID_INDEX,"bad EventIndex");
+    jdwpEvent event = 0;
+    if (ei >= EI_min && ei <= EI_max) {
+        event = index2jdwp[ei - EI_min];
     }
-    return index2jdwp[i-EI_min];
+    if (event == 0) {
+        EXIT_ERROR(AGENT_ERROR_INVALID_INDEX, "bad EventIndex");
+    }
+    return event;
 }
 
 jvmtiEvent
-eventIndex2jvmti(EventIndex i)
+eventIndex2jvmti(EventIndex ei)
 {
-    if ( i < EI_min || i > EI_max ) {
-        EXIT_ERROR(AGENT_ERROR_INVALID_INDEX,"bad EventIndex");
+    jvmtiEvent event = 0;
+    if (ei >= EI_min && ei <= EI_max) {
+        event = index2jvmti[ei - EI_min];
+    }
+    if (event == 0) {
+        EXIT_ERROR(AGENT_ERROR_INVALID_INDEX, "bad EventIndex");
     }
-    return index2jvmti[i-EI_min];
+    return event;
 }
 
 #ifdef DEBUG
@@ -2014,8 +2022,8 @@ eventIndex2EventName(EventIndex ei)
             return "EI_THREAD_END";
         case EI_CLASS_PREPARE:
             return "EI_CLASS_PREPARE";
-        case EI_GC_FINISH:
-            return "EI_GC_FINISH";
+        case EI_CLASS_UNLOAD:
+            return "EI_CLASS_UNLOAD";
         case EI_CLASS_LOAD:
             return "EI_CLASS_LOAD";
         case EI_FIELD_ACCESS:
@@ -2071,7 +2079,7 @@ jdwp2EventIndex(jdwpEvent eventType)
         case JDWP_EVENT(CLASS_PREPARE):
             return EI_CLASS_PREPARE;
         case JDWP_EVENT(CLASS_UNLOAD):
-            return EI_GC_FINISH;
+            return EI_CLASS_UNLOAD;
         case JDWP_EVENT(CLASS_LOAD):
             return EI_CLASS_LOAD;
         case JDWP_EVENT(FIELD_ACCESS):
@@ -2127,8 +2135,6 @@ jvmti2EventIndex(jvmtiEvent kind)
             return EI_THREAD_END;
         case JVMTI_EVENT_CLASS_PREPARE:
             return EI_CLASS_PREPARE;
-        case JVMTI_EVENT_GARBAGE_COLLECTION_FINISH:
-            return EI_GC_FINISH;
         case JVMTI_EVENT_CLASS_LOAD:
             return EI_CLASS_LOAD;
         case JVMTI_EVENT_FIELD_ACCESS:

src/jdk.jdwp.agent/share/native/libjdwp/util.h

@@ -161,7 +161,7 @@ typedef enum {
         EI_THREAD_START         =  5,
         EI_THREAD_END           =  6,
         EI_CLASS_PREPARE        =  7,
-        EI_GC_FINISH            =  8,
+        EI_CLASS_UNLOAD         =  8,
         EI_CLASS_LOAD           =  9,
         EI_FIELD_ACCESS         = 10,
         EI_FIELD_MODIFICATION   = 11,