8332488: Add JVMTI DataDumpRequest to the debug agent

Reviewed-by: sspitsyn, lmesnik

Author: plummercj

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1998, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1998, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -995,6 +995,8 @@ parseOptions(char *options)
     gdata->includeVThreads = JNI_FALSE;
     gdata->rememberVThreadsWhenDisconnected = JNI_FALSE;
 
+    gdata->jvmti_data_dump = JNI_FALSE;
+
     /* Options being NULL will end up being an error. */
     if (options == NULL) {
         options = "";
@@ -1159,6 +1161,13 @@ parseOptions(char *options)
             if ( dopause ) {
                 do_pause();
             }
+        } else if (strcmp(buf, "datadump") == 0) {
+          // Enable JVMTI DATA_DUMP_REQUEST support.
+          // This is not a documented flag. This feature is experimental and is only intended
+          // to be used by debug agent developers. See comment for cbDataDump() for more details.
+          if ( !get_boolean(&str, &(gdata->jvmti_data_dump)) ) {
+                goto syntax_error;
+            }
         } else if (strcmp(buf, "coredump") == 0) {
             if ( !get_boolean(&str, &docoredump) ) {
                 goto syntax_error;

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -1387,9 +1387,7 @@ eventFilterRestricted_deinstall(HandlerNode *node)
     return error1 != JVMTI_ERROR_NONE? error1 : error2;
 }
 
-/***** debugging *****/
-
-#ifdef DEBUG
+/***** APIs for debugging the debug agent *****/
 
 void
 eventFilter_dumpHandlerFilters(HandlerNode *node)
@@ -1476,5 +1474,3 @@ eventFilter_dumpHandlerFilters(HandlerNode *node)
         }
     }
 }
-
-#endif /* DEBUG */

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -76,10 +76,8 @@ jvmtiError eventFilter_setPlatformThreadsOnlyFilter(HandlerNode *node, jint inde
 jboolean eventFilter_predictFiltering(HandlerNode *node, jclass clazz, char *classname);
 jboolean isBreakpointSet(jclass clazz, jmethodID method, jlocation location);
 
-/***** debugging *****/
+/***** APIs for debugging the debug agent *****/
 
-#ifdef DEBUG
 void eventFilter_dumpHandlerFilters(HandlerNode *node);
-#endif
 
 #endif /* _EVENT_FILTER_H */

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

@@ -1330,6 +1330,44 @@ cbVMDeath(jvmtiEnv *jvmti_env, JNIEnv *env)
     LOG_MISC(("END cbVMDeath"));
 }
 
+/**
+ * Event callback for JVMTI_EVENT_DATA_DUMP_REQUEST
+ *
+ * This callback is made when a JVMTI data dump is requested. The common way of doing
+ * this is with "jcmd <pid> JVMTI.data_dump".
+ *
+ * Debug agent data dumps are experimental and only intended to be used by debug agent
+ * developers. Data dumps are disabled by default.
+ *
+ * This callback is enabled by launching the debug agent with datadump=y. The easiest
+ * way to enabled data dumps with debugger tests or when using jdb is to use the
+ * _JAVA_JDWP_OPTIONS export. The following works well when running tests:
+ *
+ *  make test TEST=<test> \
+ *    JTREG='JAVA_OPTIONS=-XX:+StartAttachListener;OPTIONS=-e:_JAVA_JDWP_OPTIONS=datadump=y'
+ *
+ * Data dumps may fail to happen due to the debug agent suspending all threads.
+ * This causes the Signal Dispatcher and Attach Listener threads to be suspended,
+ * which can cause issues with jcmd attaching. Running with -XX:+StartAttachListener can
+ * help, but in general it is best not to try a datadump when all threads are suspended.
+ *
+ * Data dumps are also risky when the debug agent is handling events or commands from
+ * the debugger, due to dumping data that is not lock protected. This can cause a
+ * crash.
+ *
+ * Data dumps are meant to aid with post mortem debugging (debugging after a
+ * problem has been detected), not for ongoing periodic data gathering.
+ */
+static void JNICALL
+cbDataDump(jvmtiEnv *jvmti_env)
+{
+    tty_message("Debug Agent Data Dump");
+    tty_message("=== START DUMP ===");
+    threadControl_dumpAllThreads();
+    eventHandler_dumpAllHandlers(JNI_TRUE);
+    tty_message("=== END DUMP ===");
+}
+
 /**
  * Delete this handler (do not delete permanent handlers):
  * Deinsert handler from active list,
@@ -1518,6 +1556,19 @@ eventHandler_initialize(jbyte sessionID)
     if (error != JVMTI_ERROR_NONE) {
         EXIT_ERROR(error,"Can't enable garbage collection finish events");
     }
+
+    /*
+     * DATA_DUMP_REQUEST 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.
+     */
+    if (gdata->jvmti_data_dump) {
+        error = JVMTI_FUNC_PTR(gdata->jvmti,SetEventNotificationMode)
+                (gdata->jvmti, JVMTI_ENABLE, JVMTI_EVENT_DATA_DUMP_REQUEST, NULL);
+        if (error != JVMTI_ERROR_NONE) {
+            EXIT_ERROR(error,"Can't enable data dump request events");
+        }
+    }
+
     /*
      * Only enable vthread START and END events if we want to remember
      * vthreads when no debugger is connected.
@@ -1580,6 +1631,8 @@ eventHandler_initialize(jbyte sessionID)
     gdata->callbacks.VirtualThreadStart         = &cbVThreadStart;
     /* Event callback for JVMTI_EVENT_VIRTUAL_THREAD_END */
     gdata->callbacks.VirtualThreadEnd           = &cbVThreadEnd;
+    /* Event callback for JVMTI_EVENT_DATA_DUMP_REQUEST */
+    gdata->callbacks.DataDumpRequest = &cbDataDump;
 
     error = JVMTI_FUNC_PTR(gdata->jvmti,SetEventCallbacks)
                 (gdata->jvmti, &(gdata->callbacks), sizeof(gdata->callbacks));
@@ -1851,9 +1904,7 @@ eventHandler_installExternal(HandlerNode *node)
                           JNI_TRUE);
 }
 
-/***** debugging *****/
-
-#ifdef DEBUG
+/***** APIs for debugging the debug agent *****/
 
 void
 eventHandler_dumpAllHandlers(jboolean dumpPermanent)
@@ -1892,5 +1943,3 @@ eventHandler_dumpHandler(HandlerNode *node)
     tty_message("Handler for %s(%d)\n", eventIndex2EventName(node->ei), node->ei);
     eventFilter_dumpHandlerFilters(node);
 }
-
-#endif /* DEBUG */

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

@@ -85,12 +85,10 @@ jboolean eventHandler_synthesizeUnloadEvent(char *signature, JNIEnv *env);
 
 jclass getMethodClass(jvmtiEnv *jvmti_env, jmethodID method);
 
-/***** debugging *****/
+/***** APIs for debugging the debug agent *****/
 
-#ifdef DEBUG
 void eventHandler_dumpAllHandlers(jboolean dumpPermanent);
 void eventHandler_dumpHandlers(EventIndex ei, jboolean dumpPermanent);
 void eventHandler_dumpHandler(HandlerNode *node);
-#endif
 
 #endif /* _EVENTHANDLER_H */

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

@@ -137,11 +137,6 @@ typedef struct {
 
 static DeferredEventModeList deferredEventModes;
 
-#ifdef DEBUG
-static void dumpThreadList(ThreadList *list);
-static void dumpThread(ThreadNode *node);
-#endif
-
 /* Get the state of the thread direct from JVMTI */
 static jvmtiError
 threadState(jthread thread, jint *pstate)
@@ -2561,13 +2556,15 @@ threadControl_allVThreads(jint *numVThreads)
     return vthreads;
 }
 
-/***** debugging *****/
+/***** APIs for debugging the debug agent *****/
 
-#ifdef DEBUG
+static void dumpThreadList(ThreadList *list);
+static void dumpThread(ThreadNode *node);
 
 void
 threadControl_dumpAllThreads()
 {
+    tty_message("suspendAllCount: %d", suspendAllCount);
     tty_message("Dumping runningThreads:");
     dumpThreadList(&runningThreads);
     tty_message("\nDumping runningVThreads:");
@@ -2652,5 +2649,3 @@ dumpThread(ThreadNode *node) {
     tty_message("\tobjID: %d", commonRef_refToID(getEnv(), node->thread));
 #endif
 }
-
-#endif /* DEBUG */

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

@@ -76,11 +76,9 @@ jlong threadControl_getFrameGeneration(jthread thread);
 
 jthread *threadControl_allVThreads(jint *numVThreads);
 
-/***** debugging *****/
+/***** APIs for debugging the debug agent *****/
 
-#ifdef DEBUG
 void threadControl_dumpAllThreads();
 void threadControl_dumpThread(jthread thread);
-#endif
 
 #endif

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

@@ -1984,8 +1984,6 @@ eventIndex2jvmti(EventIndex ei)
     return event;
 }
 
-#ifdef DEBUG
-
 char*
 eventIndex2EventName(EventIndex ei)
 {
@@ -2040,8 +2038,6 @@ eventIndex2EventName(EventIndex ei)
     }
 }
 
-#endif
-
 EventIndex
 jdwp2EventIndex(jdwpEvent eventType)
 {

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

@@ -90,6 +90,7 @@ typedef struct {
     jboolean doerrorexit;
     jboolean modifiedUtf8;
     jboolean quiet;
+    jboolean jvmti_data_dump; /* If true, then support JVMTI DATA_DUMP_REQUEST events. */
 
     /* Debug flags (bit mask) */
     int      debugflags;
@@ -389,9 +390,7 @@ void *jvmtiAllocate(jint numBytes);
 void jvmtiDeallocate(void *buffer);
 
 void             eventIndexInit(void);
-#ifdef DEBUG
 char*            eventIndex2EventName(EventIndex ei);
-#endif
 jdwpEvent        eventIndex2jdwp(EventIndex i);
 jvmtiEvent       eventIndex2jvmti(EventIndex i);
 EventIndex       jdwp2EventIndex(jdwpEvent eventType);