jdk/src/share/back/threadControl.c
changeset 2 90ce3da70b43
child 5506 202f599c92aa
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/back/threadControl.c	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,2501 @@
+/*
+ * Copyright 1998-2007 Sun Microsystems, Inc.  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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+#include "util.h"
+#include "eventHandler.h"
+#include "threadControl.h"
+#include "commonRef.h"
+#include "eventHelper.h"
+#include "stepControl.h"
+#include "invoker.h"
+#include "bag.h"
+
+#define HANDLING_EVENT(node) ((node)->current_ei != 0)
+
+/*
+ * Collection of info for properly handling co-located events.
+ * If the ei field is non-zero, then one of the possible
+ * co-located events has been posted and the other fields describe
+ * the event's location.
+ */
+typedef struct CoLocatedEventInfo_ {
+    EventIndex ei;
+    jclass    clazz;
+    jmethodID method;
+    jlocation location;
+} CoLocatedEventInfo;
+
+/**
+ * The main data structure in threadControl is the ThreadNode.
+ * This is a per-thread structure that is allocated on the
+ * first event that occurs in a thread. It is freed after the
+ * thread's thread end event has completed processing. The
+ * structure contains state information on its thread including
+ * suspend counts. It also acts as a repository for other
+ * per-thread state such as the current method invocation or
+ * current step.
+ *
+ * suspendCount is the number of outstanding suspends
+ * from the debugger. suspends from the app itself are
+ * not included in this count.
+ */
+typedef struct ThreadNode {
+    jthread thread;
+    unsigned int toBeResumed : 1;
+    unsigned int pendingInterrupt : 1;
+    unsigned int isDebugThread : 1;
+    unsigned int suspendOnStart : 1;
+    unsigned int isStarted : 1;
+    unsigned int popFrameEvent : 1;
+    unsigned int popFrameProceed : 1;
+    unsigned int popFrameThread : 1;
+    EventIndex current_ei;
+    jobject pendingStop;
+    jint suspendCount;
+    jint resumeFrameDepth; /* !=0 => This thread is in a call to Thread.resume() */
+    jvmtiEventMode instructionStepMode;
+    StepRequest currentStep;
+    InvokeRequest currentInvoke;
+    struct bag *eventBag;
+    CoLocatedEventInfo cleInfo;
+    struct ThreadNode *next;
+    struct ThreadNode *prev;
+    jlong frameGeneration;
+    struct ThreadList *list;  /* Tells us what list this thread is in */
+} ThreadNode;
+
+static jint suspendAllCount;
+
+typedef struct ThreadList {
+    ThreadNode *first;
+} ThreadList;
+
+/*
+ * popFrameEventLock is used to notify that the event has been received
+ */
+static jrawMonitorID popFrameEventLock = NULL;
+
+/*
+ * popFrameProceedLock is used to assure that the event thread is
+ * re-suspended immediately after the event is acknowledged.
+ */
+static jrawMonitorID popFrameProceedLock = NULL;
+
+static jrawMonitorID threadLock;
+static jlocation resumeLocation;
+static HandlerNode *breakpointHandlerNode;
+static HandlerNode *framePopHandlerNode;
+static HandlerNode *catchHandlerNode;
+
+static jvmtiError threadControl_removeDebugThread(jthread thread);
+
+/*
+ * Threads which have issued thread start events and not yet issued thread
+ * end events are maintained in the "runningThreads" list. All other threads known
+ * to this module are kept in the "otherThreads" list.
+ */
+static ThreadList runningThreads;
+static ThreadList otherThreads;
+
+#define MAX_DEBUG_THREADS 10
+static int debugThreadCount;
+static jthread debugThreads[MAX_DEBUG_THREADS];
+
+typedef struct DeferredEventMode {
+    EventIndex ei;
+    jvmtiEventMode mode;
+    jthread thread;
+    struct DeferredEventMode *next;
+} DeferredEventMode;
+
+typedef struct {
+    DeferredEventMode *first;
+    DeferredEventMode *last;
+} DeferredEventModeList;
+
+static DeferredEventModeList deferredEventModes;
+
+static jint
+getStackDepth(jthread thread)
+{
+    jint count = 0;
+    jvmtiError error;
+
+    error = JVMTI_FUNC_PTR(gdata->jvmti,GetFrameCount)
+                        (gdata->jvmti, thread, &count);
+    if (error != JVMTI_ERROR_NONE) {
+        EXIT_ERROR(error, "getting frame count");
+    }
+    return count;
+}
+
+/* Get the state of the thread direct from JVMTI */
+static jvmtiError
+threadState(jthread thread, jint *pstate)
+{
+    *pstate = 0;
+    return JVMTI_FUNC_PTR(gdata->jvmti,GetThreadState)
+                        (gdata->jvmti, thread, pstate);
+}
+
+/* Set TLS on a specific jthread to the ThreadNode* */
+static void
+setThreadLocalStorage(jthread thread, ThreadNode *node)
+{
+    jvmtiError  error;
+
+    error = JVMTI_FUNC_PTR(gdata->jvmti,SetThreadLocalStorage)
+            (gdata->jvmti, thread, (void*)node);
+    if ( error == JVMTI_ERROR_THREAD_NOT_ALIVE ) {
+        /* Just return, thread hasn't started yet */
+        return;
+    } else if ( error != JVMTI_ERROR_NONE ) {
+        /* The jthread object must be valid, so this must be a fatal error */
+        EXIT_ERROR(error, "cannot set thread local storage");
+    }
+}
+
+/* Get TLS on a specific jthread, which is the ThreadNode* */
+static ThreadNode *
+getThreadLocalStorage(jthread thread)
+{
+    jvmtiError  error;
+    ThreadNode *node;
+
+    node = NULL;
+    error = JVMTI_FUNC_PTR(gdata->jvmti,GetThreadLocalStorage)
+            (gdata->jvmti, thread, (void**)&node);
+    if ( error == JVMTI_ERROR_THREAD_NOT_ALIVE ) {
+        /* Just return NULL, thread hasn't started yet */
+        return NULL;
+    } else if ( error != JVMTI_ERROR_NONE ) {
+        /* The jthread object must be valid, so this must be a fatal error */
+        EXIT_ERROR(error, "cannot get thread local storage");
+    }
+    return node;
+}
+
+/* Search list for nodes that don't have TLS set and match this thread.
+ *   It assumed that this logic is never dealing with terminated threads,
+ *   since the ThreadEnd events always delete the ThreadNode while the
+ *   jthread is still alive.  So we can only look at the ThreadNode's that
+ *   have never had their TLS set, making the search much faster.
+ *   But keep in mind, this kind of search should rarely be needed.
+ */
+static ThreadNode *
+nonTlsSearch(JNIEnv *env, ThreadList *list, jthread thread)
+{
+    ThreadNode *node;
+
+    for (node = list->first; node != NULL; node = node->next) {
+        if (isSameObject(env, node->thread, thread)) {
+            break;
+        }
+    }
+    return node;
+}
+
+/*
+ * These functions maintain the linked list of currently running threads.
+ * All assume that the threadLock is held before calling.
+ * If list==NULL, search both lists.
+ */
+static ThreadNode *
+findThread(ThreadList *list, jthread thread)
+{
+    ThreadNode *node;
+
+    /* Get thread local storage for quick thread -> node access */
+    node = getThreadLocalStorage(thread);
+
+    /* In some rare cases we might get NULL, so we check the list manually for
+     *   any threads that we could match.
+     */
+    if ( node == NULL ) {
+        JNIEnv *env;
+
+        env = getEnv();
+        if ( list != NULL ) {
+            node = nonTlsSearch(env, list, thread);
+        } else {
+            node = nonTlsSearch(env, &runningThreads, thread);
+            if ( node == NULL ) {
+                node = nonTlsSearch(env, &otherThreads, thread);
+            }
+        }
+        if ( node != NULL ) {
+            /* Here we make another attempt to set TLS, it's ok if this fails */
+            setThreadLocalStorage(thread, (void*)node);
+        }
+    }
+
+    /* If a list is supplied, only return ones in this list */
+    if ( node != NULL && list != NULL && node->list != list ) {
+        return NULL;
+    }
+    return node;
+}
+
+/* Remove a ThreadNode from a ThreadList */
+static void
+removeNode(ThreadList *list, ThreadNode *node)
+{
+    ThreadNode *prev;
+    ThreadNode *next;
+
+    prev = node->prev;
+    next = node->next;
+    if ( prev != NULL ) {
+        prev->next = next;
+    }
+    if ( next != NULL ) {
+        next->prev = prev;
+    }
+    if ( prev == NULL ) {
+        list->first = next;
+    }
+    node->next = NULL;
+    node->prev = NULL;
+    node->list = NULL;
+}
+
+/* Add a ThreadNode to a ThreadList */
+static void
+addNode(ThreadList *list, ThreadNode *node)
+{
+    node->next = NULL;
+    node->prev = NULL;
+    node->list = NULL;
+    if ( list->first == NULL ) {
+        list->first = node;
+    } else {
+        list->first->prev = node;
+        node->next = list->first;
+        list->first = node;
+    }
+    node->list = list;
+}
+
+static ThreadNode *
+insertThread(JNIEnv *env, ThreadList *list, jthread thread)
+{
+    ThreadNode *node;
+    struct bag *eventBag;
+
+    node = findThread(list, thread);
+    if (node == NULL) {
+        node = jvmtiAllocate(sizeof(*node));
+        if (node == NULL) {
+            EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"thread table entry");
+            return NULL;
+        }
+        (void)memset(node, 0, sizeof(*node));
+        eventBag = eventHelper_createEventBag();
+        if (eventBag == NULL) {
+            jvmtiDeallocate(node);
+            EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"thread table entry");
+            return NULL;
+        }
+
+        /*
+         * Init all flags false, all refs NULL, all counts 0
+         */
+
+        saveGlobalRef(env, thread, &(node->thread));
+        if (node->thread == NULL) {
+            jvmtiDeallocate(node);
+            bagDestroyBag(eventBag);
+            EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"thread table entry");
+            return NULL;
+        }
+        /*
+         * Remember if it is a debug thread
+         */
+        if (threadControl_isDebugThread(node->thread)) {
+            node->isDebugThread = JNI_TRUE;
+        } else if (suspendAllCount > 0){
+            /*
+             * If there is a pending suspendAll, all new threads should
+             * be initialized as if they were suspended by the suspendAll,
+             * and the thread will need to be suspended when it starts.
+             */
+            node->suspendCount = suspendAllCount;
+            node->suspendOnStart = JNI_TRUE;
+        }
+        node->current_ei = 0;
+        node->instructionStepMode = JVMTI_DISABLE;
+        node->eventBag = eventBag;
+        addNode(list, node);
+
+        /* Set thread local storage for quick thread -> node access.
+         *   Some threads may not be in a state that allows setting of TLS,
+         *   which is ok, see findThread, it deals with threads without TLS set.
+         */
+        setThreadLocalStorage(node->thread, (void*)node);
+    }
+
+    return node;
+}
+
+static void
+clearThread(JNIEnv *env, ThreadNode *node)
+{
+    if (node->pendingStop != NULL) {
+        tossGlobalRef(env, &(node->pendingStop));
+    }
+    stepControl_clearRequest(node->thread, &node->currentStep);
+    if (node->isDebugThread) {
+        (void)threadControl_removeDebugThread(node->thread);
+    }
+    /* Clear out TLS on this thread (just a cleanup action) */
+    setThreadLocalStorage(node->thread, NULL);
+    tossGlobalRef(env, &(node->thread));
+    bagDestroyBag(node->eventBag);
+    jvmtiDeallocate(node);
+}
+
+static void
+removeThread(JNIEnv *env, ThreadList *list, jthread thread)
+{
+    ThreadNode *node;
+
+    node = findThread(list, thread);
+    if (node != NULL) {
+        removeNode(list, node);
+        clearThread(env, node);
+    }
+}
+
+static void
+removeResumed(JNIEnv *env, ThreadList *list)
+{
+    ThreadNode *node;
+
+    node = list->first;
+    while (node != NULL) {
+        ThreadNode *temp = node->next;
+        if (node->suspendCount == 0) {
+            removeThread(env, list, node->thread);
+        }
+        node = temp;
+    }
+}
+
+static void
+moveNode(ThreadList *source, ThreadList *dest, ThreadNode *node)
+{
+    removeNode(source, node);
+    JDI_ASSERT(findThread(dest, node->thread) == NULL);
+    addNode(dest, node);
+}
+
+typedef jvmtiError (*ThreadEnumerateFunction)(JNIEnv *, ThreadNode *, void *);
+
+static jvmtiError
+enumerateOverThreadList(JNIEnv *env, ThreadList *list,
+                        ThreadEnumerateFunction function, void *arg)
+{
+    ThreadNode *node;
+    jvmtiError error = JVMTI_ERROR_NONE;
+
+    for (node = list->first; node != NULL; node = node->next) {
+        error = (*function)(env, node, arg);
+        if ( error != JVMTI_ERROR_NONE ) {
+            break;
+        }
+    }
+    return error;
+}
+
+static void
+insertEventMode(DeferredEventModeList *list, DeferredEventMode *eventMode)
+{
+    if (list->last != NULL) {
+        list->last->next = eventMode;
+    } else {
+        list->first = eventMode;
+    }
+    list->last = eventMode;
+}
+
+static void
+removeEventMode(DeferredEventModeList *list, DeferredEventMode *eventMode, DeferredEventMode *prev)
+{
+    if (prev == NULL) {
+        list->first = eventMode->next;
+    } else {
+        prev->next = eventMode->next;
+    }
+    if (eventMode->next == NULL) {
+        list->last = prev;
+    }
+}
+
+static jvmtiError
+addDeferredEventMode(JNIEnv *env, jvmtiEventMode mode, EventIndex ei, jthread thread)
+{
+    DeferredEventMode *eventMode;
+
+    /*LINTED*/
+    eventMode = jvmtiAllocate((jint)sizeof(DeferredEventMode));
+    if (eventMode == NULL) {
+        return AGENT_ERROR_OUT_OF_MEMORY;
+    }
+    eventMode->thread = NULL;
+    saveGlobalRef(env, thread, &(eventMode->thread));
+    eventMode->mode = mode;
+    eventMode->ei = ei;
+    eventMode->next = NULL;
+    insertEventMode(&deferredEventModes, eventMode);
+    return JVMTI_ERROR_NONE;
+}
+
+static void
+freeDeferredEventModes(JNIEnv *env)
+{
+    DeferredEventMode *eventMode;
+    eventMode = deferredEventModes.first;
+    while (eventMode != NULL) {
+        DeferredEventMode *next;
+        next = eventMode->next;
+        tossGlobalRef(env, &(eventMode->thread));
+        jvmtiDeallocate(eventMode);
+        eventMode = next;
+    }
+    deferredEventModes.first = NULL;
+    deferredEventModes.last = NULL;
+}
+
+static jvmtiError
+threadSetEventNotificationMode(ThreadNode *node,
+        jvmtiEventMode mode, EventIndex ei, jthread thread)
+{
+    jvmtiError error;
+
+    /* record single step mode */
+    if (ei == EI_SINGLE_STEP) {
+        node->instructionStepMode = mode;
+    }
+    error = JVMTI_FUNC_PTR(gdata->jvmti,SetEventNotificationMode)
+        (gdata->jvmti, mode, eventIndex2jvmti(ei), thread);
+    return error;
+}
+
+static void
+processDeferredEventModes(JNIEnv *env, jthread thread, ThreadNode *node)
+{
+    jvmtiError error;
+    DeferredEventMode *eventMode;
+    DeferredEventMode *prev;
+
+    prev = NULL;
+    eventMode = deferredEventModes.first;
+    while (eventMode != NULL) {
+        DeferredEventMode *next = eventMode->next;
+        if (isSameObject(env, thread, eventMode->thread)) {
+            error = threadSetEventNotificationMode(node,
+                    eventMode->mode, eventMode->ei, eventMode->thread);
+            if (error != JVMTI_ERROR_NONE) {
+                EXIT_ERROR(error, "cannot process deferred thread event notifications at thread start");
+            }
+            removeEventMode(&deferredEventModes, eventMode, prev);
+            tossGlobalRef(env, &(eventMode->thread));
+            jvmtiDeallocate(eventMode);
+        } else {
+            prev = eventMode;
+        }
+        eventMode = next;
+    }
+}
+
+static void
+getLocks(void)
+{
+    /*
+     * Anything which might be locked as part of the handling of
+     * a JVMTI event (which means: might be locked by an application
+     * thread) needs to be grabbed here. This allows thread control
+     * code to safely suspend and resume the application threads
+     * while ensuring they don't hold a critical lock.
+     */
+
+    eventHandler_lock();
+    invoker_lock();
+    eventHelper_lock();
+    stepControl_lock();
+    commonRef_lock();
+    debugMonitorEnter(threadLock);
+
+}
+
+static void
+releaseLocks(void)
+{
+    debugMonitorExit(threadLock);
+    commonRef_unlock();
+    stepControl_unlock();
+    eventHelper_unlock();
+    invoker_unlock();
+    eventHandler_unlock();
+}
+
+void
+threadControl_initialize(void)
+{
+    jlocation unused;
+    jvmtiError error;
+
+    suspendAllCount = 0;
+    runningThreads.first = NULL;
+    otherThreads.first = NULL;
+    debugThreadCount = 0;
+    threadLock = debugMonitorCreate("JDWP Thread Lock");
+    if (gdata->threadClass==NULL) {
+        EXIT_ERROR(AGENT_ERROR_NULL_POINTER, "no java.lang.thread class");
+    }
+    if (gdata->threadResume==0) {
+        EXIT_ERROR(AGENT_ERROR_NULL_POINTER, "cannot resume thread");
+    }
+    /* Get the java.lang.Thread.resume() method beginning location */
+    error = methodLocation(gdata->threadResume, &resumeLocation, &unused);
+    if (error != JVMTI_ERROR_NONE) {
+        EXIT_ERROR(error, "getting method location");
+    }
+}
+
+static jthread
+getResumee(jthread resumingThread)
+{
+    jthread resumee = NULL;
+    jvmtiError error;
+    jobject object;
+    FrameNumber fnum = 0;
+
+    error = JVMTI_FUNC_PTR(gdata->jvmti,GetLocalObject)
+                    (gdata->jvmti, resumingThread, fnum, 0, &object);
+    if (error == JVMTI_ERROR_NONE) {
+        resumee = object;
+    }
+    return resumee;
+}
+
+
+static jboolean
+pendingAppResume(jboolean includeSuspended)
+{
+    ThreadList *list;
+    ThreadNode *node;
+
+    list = &runningThreads;
+    node = list->first;
+    while (node != NULL) {
+        if (node->resumeFrameDepth > 0) {
+            if (includeSuspended) {
+                return JNI_TRUE;
+            } else {
+                jvmtiError error;
+                jint       state;
+
+                error = threadState(node->thread, &state);
+                if (error != JVMTI_ERROR_NONE) {
+                    EXIT_ERROR(error, "getting thread state");
+                }
+                if (!(state & JVMTI_THREAD_STATE_SUSPENDED)) {
+                    return JNI_TRUE;
+                }
+            }
+        }
+        node = node->next;
+    }
+    return JNI_FALSE;
+}
+
+static void
+notifyAppResumeComplete(void)
+{
+    debugMonitorNotifyAll(threadLock);
+    if (!pendingAppResume(JNI_TRUE)) {
+        if (framePopHandlerNode != NULL) {
+            (void)eventHandler_free(framePopHandlerNode);
+            framePopHandlerNode = NULL;
+        }
+        if (catchHandlerNode != NULL) {
+            (void)eventHandler_free(catchHandlerNode);
+            catchHandlerNode = NULL;
+        }
+    }
+}
+
+static void
+handleAppResumeCompletion(JNIEnv *env, EventInfo *evinfo,
+                          HandlerNode *handlerNode,
+                          struct bag *eventBag)
+{
+    ThreadNode *node;
+    jthread     thread;
+
+    thread = evinfo->thread;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        if (node->resumeFrameDepth > 0) {
+            jint compareDepth = getStackDepth(thread);
+            if (evinfo->ei == EI_FRAME_POP) {
+                compareDepth--;
+            }
+            if (compareDepth < node->resumeFrameDepth) {
+                node->resumeFrameDepth = 0;
+                notifyAppResumeComplete();
+            }
+        }
+    }
+
+    debugMonitorExit(threadLock);
+}
+
+static void
+blockOnDebuggerSuspend(jthread thread)
+{
+    ThreadNode *node;
+
+    node = findThread(NULL, thread);
+    if (node != NULL) {
+        while (node && node->suspendCount > 0) {
+            debugMonitorWait(threadLock);
+            node = findThread(NULL, thread);
+        }
+    }
+}
+
+static void
+trackAppResume(jthread thread)
+{
+    jvmtiError  error;
+    FrameNumber fnum;
+    ThreadNode *node;
+
+    fnum = 0;
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        JDI_ASSERT(node->resumeFrameDepth == 0);
+        error = JVMTI_FUNC_PTR(gdata->jvmti,NotifyFramePop)
+                        (gdata->jvmti, thread, fnum);
+        if (error == JVMTI_ERROR_NONE) {
+            jint frameDepth = getStackDepth(thread);
+            if ((frameDepth > 0) && (framePopHandlerNode == NULL)) {
+                framePopHandlerNode = eventHandler_createInternalThreadOnly(
+                                           EI_FRAME_POP,
+                                           handleAppResumeCompletion,
+                                           thread);
+                catchHandlerNode = eventHandler_createInternalThreadOnly(
+                                           EI_EXCEPTION_CATCH,
+                                           handleAppResumeCompletion,
+                                           thread);
+                if ((framePopHandlerNode == NULL) ||
+                    (catchHandlerNode == NULL)) {
+                    (void)eventHandler_free(framePopHandlerNode);
+                    framePopHandlerNode = NULL;
+                    (void)eventHandler_free(catchHandlerNode);
+                    catchHandlerNode = NULL;
+                }
+            }
+            if ((framePopHandlerNode != NULL) &&
+                (catchHandlerNode != NULL) &&
+                (frameDepth > 0)) {
+                node->resumeFrameDepth = frameDepth;
+            }
+        }
+    }
+}
+
+static void
+handleAppResumeBreakpoint(JNIEnv *env, EventInfo *evinfo,
+                          HandlerNode *handlerNode,
+                          struct bag *eventBag)
+{
+    jthread resumer = evinfo->thread;
+    jthread resumee = getResumee(resumer);
+
+    debugMonitorEnter(threadLock);
+    if (resumee != NULL) {
+        /*
+         * Hold up any attempt to resume as long as the debugger
+         * has suspended the resumee.
+         */
+        blockOnDebuggerSuspend(resumee);
+    }
+
+    if (resumer != NULL) {
+        /*
+         * Track the resuming thread by marking it as being within
+         * a resume and by setting up for notification on
+         * a frame pop or exception. We won't allow the debugger
+         * to suspend threads while any thread is within a
+         * call to resume. This (along with the block above)
+         * ensures that when the debugger
+         * suspends a thread it will remain suspended.
+         */
+        trackAppResume(resumer);
+    }
+
+    debugMonitorExit(threadLock);
+}
+
+void
+threadControl_onConnect(void)
+{
+    breakpointHandlerNode = eventHandler_createInternalBreakpoint(
+                 handleAppResumeBreakpoint, NULL,
+                 gdata->threadClass, gdata->threadResume, resumeLocation);
+}
+
+void
+threadControl_onDisconnect(void)
+{
+    if (breakpointHandlerNode != NULL) {
+        (void)eventHandler_free(breakpointHandlerNode);
+        breakpointHandlerNode = NULL;
+    }
+    if (framePopHandlerNode != NULL) {
+        (void)eventHandler_free(framePopHandlerNode);
+        framePopHandlerNode = NULL;
+    }
+    if (catchHandlerNode != NULL) {
+        (void)eventHandler_free(catchHandlerNode);
+        catchHandlerNode = NULL;
+    }
+}
+
+void
+threadControl_onHook(void)
+{
+    /*
+     * As soon as the event hook is in place, we need to initialize
+     * the thread list with already-existing threads. The threadLock
+     * has been held since initialize, so we don't need to worry about
+     * insertions or deletions from the event handlers while we do this
+     */
+    JNIEnv *env;
+
+    env = getEnv();
+
+    /*
+     * Prevent any event processing until OnHook has been called
+     */
+    debugMonitorEnter(threadLock);
+
+    WITH_LOCAL_REFS(env, 1) {
+
+        jint threadCount;
+        jthread *threads;
+
+        threads = allThreads(&threadCount);
+        if (threads == NULL) {
+            EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"thread table");
+        } else {
+
+            int i;
+
+            for (i = 0; i < threadCount; i++) {
+                ThreadNode *node;
+                jthread thread = threads[i];
+                node = insertThread(env, &runningThreads, thread);
+
+                /*
+                 * This is a tiny bit risky. We have to assume that the
+                 * pre-existing threads have been started because we
+                 * can't rely on a thread start event for them. The chances
+                 * of a problem related to this are pretty slim though, and
+                 * there's really no choice because without setting this flag
+                 * there is no way to enable stepping and other events on
+                 * the threads that already exist (e.g. the finalizer thread).
+                 */
+                node->isStarted = JNI_TRUE;
+            }
+        }
+
+    } END_WITH_LOCAL_REFS(env)
+
+    debugMonitorExit(threadLock);
+}
+
+static jvmtiError
+commonSuspendByNode(ThreadNode *node)
+{
+    jvmtiError error;
+
+    LOG_MISC(("thread=%p suspended", node->thread));
+    error = JVMTI_FUNC_PTR(gdata->jvmti,SuspendThread)
+                (gdata->jvmti, node->thread);
+
+    /*
+     * Mark for resume only if suspend succeeded
+     */
+    if (error == JVMTI_ERROR_NONE) {
+        node->toBeResumed = JNI_TRUE;
+    }
+
+    /*
+     * If the thread was suspended by another app thread,
+     * do nothing and report no error (we won't resume it later).
+     */
+     if (error == JVMTI_ERROR_THREAD_SUSPENDED) {
+        error = JVMTI_ERROR_NONE;
+     }
+
+     return error;
+}
+
+/*
+ * Deferred suspends happen when the suspend is attempted on a thread
+ * that is not started. Bookkeeping (suspendCount,etc.)
+ * is handled by the original request, and once the thread actually
+ * starts, an actual suspend is attempted. This function does the
+ * deferred suspend without changing the bookkeeping that is already
+ * in place.
+ */
+static jint
+deferredSuspendThreadByNode(ThreadNode *node)
+{
+    jvmtiError error;
+
+    error = JVMTI_ERROR_NONE;
+    if (node->isDebugThread) {
+        /* Ignore requests for suspending debugger threads */
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*
+     * Do the actual suspend only if a subsequent resume hasn't
+     * made it irrelevant.
+     */
+    if (node->suspendCount > 0) {
+        error = commonSuspendByNode(node);
+
+        /*
+         * Attempt to clean up from any error by decrementing the
+         * suspend count. This compensates for the increment that
+         * happens when suspendOnStart is set to true.
+         */
+        if (error != JVMTI_ERROR_NONE) {
+          node->suspendCount--;
+        }
+    }
+
+    node->suspendOnStart = JNI_FALSE;
+
+    debugMonitorNotifyAll(threadLock);
+
+    return error;
+}
+
+static jvmtiError
+suspendThreadByNode(ThreadNode *node)
+{
+    jvmtiError error = JVMTI_ERROR_NONE;
+    if (node->isDebugThread) {
+        /* Ignore requests for suspending debugger threads */
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*
+     * Just increment the suspend count if we are waiting
+     * for a deferred suspend.
+     */
+    if (node->suspendOnStart) {
+        node->suspendCount++;
+        return JVMTI_ERROR_NONE;
+    }
+
+    if (node->suspendCount == 0) {
+        error = commonSuspendByNode(node);
+
+        if (error == JVMTI_ERROR_THREAD_NOT_ALIVE) {
+            /*
+             * This error means that the thread is either a zombie or not yet
+             * started. In either case, we ignore the error. If the thread
+             * is a zombie, suspend/resume are no-ops. If the thread is not
+             * started, it will be suspended for real during the processing
+             * of its thread start event.
+             */
+            node->suspendOnStart = JNI_TRUE;
+            error = JVMTI_ERROR_NONE;
+        }
+    }
+
+    if (error == JVMTI_ERROR_NONE) {
+        node->suspendCount++;
+    }
+
+    debugMonitorNotifyAll(threadLock);
+
+    return error;
+}
+
+static jvmtiError
+resumeThreadByNode(ThreadNode *node)
+{
+    jvmtiError error = JVMTI_ERROR_NONE;
+
+    if (node->isDebugThread) {
+        /* never suspended by debugger => don't ever try to resume */
+        return JVMTI_ERROR_NONE;
+    }
+    if (node->suspendCount > 0) {
+        node->suspendCount--;
+        debugMonitorNotifyAll(threadLock);
+        if ((node->suspendCount == 0) && node->toBeResumed &&
+            !node->suspendOnStart) {
+            LOG_MISC(("thread=%p resumed", node->thread));
+            error = JVMTI_FUNC_PTR(gdata->jvmti,ResumeThread)
+                        (gdata->jvmti, node->thread);
+            node->frameGeneration++; /* Increment on each resume */
+            node->toBeResumed = JNI_FALSE;
+            if (error == JVMTI_ERROR_THREAD_NOT_ALIVE && !node->isStarted) {
+                /*
+                 * We successfully "suspended" this thread, but
+                 * we never received a THREAD_START event for it.
+                 * Since the thread never ran, we can ignore our
+                 * failure to resume the thread.
+                 */
+                error = JVMTI_ERROR_NONE;
+            }
+        }
+    }
+
+    return error;
+}
+
+/*
+ * Functions which respond to user requests to suspend/resume
+ * threads.
+ * Suspends and resumes add and subtract from a count respectively.
+ * The thread is only suspended when the count goes from 0 to 1 and
+ * resumed only when the count goes from 1 to 0.
+ *
+ * These functions suspend and resume application threads
+ * without changing the
+ * state of threads that were already suspended beforehand.
+ * They must not be called from an application thread because
+ * that thread may be suspended somewhere in the  middle of things.
+ */
+static void
+preSuspend(void)
+{
+    getLocks();                     /* Avoid debugger deadlocks */
+
+    /*
+     * Delay any suspend while a call to java.lang.Thread.resume is in
+     * progress (not including those in suspended threads). The wait is
+     * timed because the threads suspended through
+     * java.lang.Thread.suspend won't result in a notify even though
+     * it may change the result of pendingAppResume()
+     */
+    while (pendingAppResume(JNI_FALSE)) {
+        /*
+         * This is ugly but we need to release the locks from getLocks
+         * or else the notify will never happen. The locks must be
+         * released and reacquired in the right order. else deadlocks
+         * can happen. It is possible that, during this dance, the
+         * notify will be missed, but since the wait needs to be timed
+         * anyway, it won't be a disaster. Note that this code will
+         * execute only on very rare occasions anyway.
+         */
+        releaseLocks();
+
+        debugMonitorEnter(threadLock);
+        debugMonitorTimedWait(threadLock, 1000);
+        debugMonitorExit(threadLock);
+
+        getLocks();
+    }
+}
+
+static void
+postSuspend(void)
+{
+    releaseLocks();
+}
+
+/*
+ * This function must be called after preSuspend and before postSuspend.
+ */
+static jvmtiError
+commonSuspend(JNIEnv *env, jthread thread, jboolean deferred)
+{
+    ThreadNode *node;
+
+    /*
+     * If the thread is not between its start and end events, we should
+     * still suspend it. To keep track of things, add the thread
+     * to a separate list of threads so that we'll resume it later.
+     */
+    node = findThread(&runningThreads, thread);
+    if (node == NULL) {
+        node = insertThread(env, &otherThreads, thread);
+    }
+
+    if ( deferred ) {
+        return deferredSuspendThreadByNode(node);
+    } else {
+        return suspendThreadByNode(node);
+    }
+}
+
+
+static jvmtiError
+resumeCopyHelper(JNIEnv *env, ThreadNode *node, void *arg)
+{
+    if (node->isDebugThread) {
+        /* never suspended by debugger => don't ever try to resume */
+        return JVMTI_ERROR_NONE;
+    }
+
+    if (node->suspendCount > 1) {
+        node->suspendCount--;
+        /* nested suspend so just undo one level */
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*
+     * This thread was marked for suspension since its THREAD_START
+     * event came in during a suspendAll, but the helper hasn't
+     * completed the job yet. We decrement the count so the helper
+     * won't suspend this thread after we are done with the resumeAll.
+     * Another case to be handled here is when the debugger suspends
+     * the thread while the app has it suspended. In this case,
+     * the toBeResumed flag has been cleared indicating that
+     * the thread should not be resumed when the debugger does a resume.
+     * In this case, we also have to decrement the suspend count.
+     * If we don't then when the app resumes the thread and our Thread.resume
+     * bkpt handler is called, blockOnDebuggerSuspend will not resume
+     * the thread because suspendCount will be 1 meaning that the
+     * debugger has the thread suspended.  See bug 6224859.
+     */
+    if (node->suspendCount == 1 && (!node->toBeResumed || node->suspendOnStart)) {
+        node->suspendCount--;
+        return JVMTI_ERROR_NONE;
+    }
+
+    if (arg == NULL) {
+        /* nothing to hard resume so we're done */
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*
+     * This is tricky. A suspendCount of 1 and toBeResumed means that
+     * JVM/DI SuspendThread() or JVM/DI SuspendThreadList() was called
+     * on this thread. The check for !suspendOnStart is paranoia that
+     * we inherited from resumeThreadByNode().
+     */
+    if (node->suspendCount == 1 && node->toBeResumed && !node->suspendOnStart) {
+        jthread **listPtr = (jthread **)arg;
+
+        **listPtr = node->thread;
+        (*listPtr)++;
+    }
+    return JVMTI_ERROR_NONE;
+}
+
+
+static jvmtiError
+resumeCountHelper(JNIEnv *env, ThreadNode *node, void *arg)
+{
+    if (node->isDebugThread) {
+        /* never suspended by debugger => don't ever try to resume */
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*
+     * This is tricky. A suspendCount of 1 and toBeResumed means that
+     * JVM/DI SuspendThread() or JVM/DI SuspendThreadList() was called
+     * on this thread. The check for !suspendOnStart is paranoia that
+     * we inherited from resumeThreadByNode().
+     */
+    if (node->suspendCount == 1 && node->toBeResumed && !node->suspendOnStart) {
+        jint *counter = (jint *)arg;
+
+        (*counter)++;
+    }
+    return JVMTI_ERROR_NONE;
+}
+
+static void *
+newArray(jint length, size_t nbytes)
+{
+    void *ptr;
+    ptr = jvmtiAllocate(length*(jint)nbytes);
+    if ( ptr != NULL ) {
+        (void)memset(ptr, 0, length*nbytes);
+    }
+    return ptr;
+}
+
+static void
+deleteArray(void *ptr)
+{
+    jvmtiDeallocate(ptr);
+}
+
+/*
+ * This function must be called with the threadLock held.
+ *
+ * Two facts conspire to make this routine complicated:
+ *
+ * 1) the VM doesn't support nested external suspend
+ * 2) the original resumeAll code structure doesn't retrieve the
+ *    entire thread list from JVMTI so we use the runningThreads
+ *    list and two helpers to get the job done.
+ *
+ * Because we hold the threadLock, state seen by resumeCountHelper()
+ * is the same state seen in resumeCopyHelper(). resumeCountHelper()
+ * just counts up the number of threads to be hard resumed.
+ * resumeCopyHelper() does the accounting for nested suspends and
+ * special cases and, finally, populates the list of hard resume
+ * threads to be passed to ResumeThreadList().
+ *
+ * At first glance, you might think that the accounting could be done
+ * in resumeCountHelper(), but then resumeCopyHelper() would see
+ * "post-resume" state in the accounting values (suspendCount and
+ * toBeResumed) and would not be able to distinguish between a thread
+ * that needs a hard resume versus a thread that is already running.
+ */
+static jvmtiError
+commonResumeList(JNIEnv *env)
+{
+    jvmtiError   error;
+    jint         i;
+    jint         reqCnt;
+    jthread     *reqList;
+    jthread     *reqPtr;
+    jvmtiError  *results;
+
+    reqCnt = 0;
+
+    /* count number of threads to hard resume */
+    (void) enumerateOverThreadList(env, &runningThreads, resumeCountHelper,
+                                   &reqCnt);
+    if (reqCnt == 0) {
+        /* nothing to hard resume so do just the accounting part */
+        (void) enumerateOverThreadList(env, &runningThreads, resumeCopyHelper,
+                                       NULL);
+        return JVMTI_ERROR_NONE;
+    }
+
+    /*LINTED*/
+    reqList = newArray(reqCnt, sizeof(jthread));
+    if (reqList == NULL) {
+        EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"resume request list");
+    }
+    /*LINTED*/
+    results = newArray(reqCnt, sizeof(jvmtiError));
+    if (results == NULL) {
+        EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"resume list");
+    }
+
+    /* copy the jthread values for threads to hard resume */
+    reqPtr = reqList;
+    (void) enumerateOverThreadList(env, &runningThreads, resumeCopyHelper,
+                                   &reqPtr);
+
+    error = JVMTI_FUNC_PTR(gdata->jvmti,ResumeThreadList)
+                (gdata->jvmti, reqCnt, reqList, results);
+    for (i = 0; i < reqCnt; i++) {
+        ThreadNode *node;
+
+        node = findThread(&runningThreads, reqList[i]);
+        if (node == NULL) {
+            EXIT_ERROR(AGENT_ERROR_INVALID_THREAD,"missing entry in running thread table");
+        }
+        LOG_MISC(("thread=%p resumed as part of list", node->thread));
+
+        /*
+         * resumeThreadByNode() assumes that JVM/DI ResumeThread()
+         * always works and does all the accounting updates. We do
+         * the same here. We also don't clear the error.
+         */
+        node->suspendCount--;
+        node->toBeResumed = JNI_FALSE;
+        node->frameGeneration++; /* Increment on each resume */
+    }
+    deleteArray(results);
+    deleteArray(reqList);
+
+    debugMonitorNotifyAll(threadLock);
+
+    return error;
+}
+
+
+/*
+ * This function must be called after preSuspend and before postSuspend.
+ */
+static jvmtiError
+commonSuspendList(JNIEnv *env, jint initCount, jthread *initList)
+{
+    jvmtiError  error;
+    jint        i;
+    jint        reqCnt;
+    jthread    *reqList;
+
+    error   = JVMTI_ERROR_NONE;
+    reqCnt  = 0;
+    reqList = newArray(initCount, sizeof(jthread));
+    if (reqList == NULL) {
+        EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"request list");
+    }
+
+    /*
+     * Go through the initial list and see if we have anything to suspend.
+     */
+    for (i = 0; i < initCount; i++) {
+        ThreadNode *node;
+
+        /*
+         * If the thread is not between its start and end events, we should
+         * still suspend it. To keep track of things, add the thread
+         * to a separate list of threads so that we'll resume it later.
+         */
+        node = findThread(&runningThreads, initList[i]);
+        if (node == NULL) {
+            node = insertThread(env, &otherThreads, initList[i]);
+        }
+
+        if (node->isDebugThread) {
+            /* Ignore requests for suspending debugger threads */
+            continue;
+        }
+
+        /*
+         * Just increment the suspend count if we are waiting
+         * for a deferred suspend or if this is a nested suspend.
+         */
+        if (node->suspendOnStart || node->suspendCount > 0) {
+            node->suspendCount++;
+            continue;
+        }
+
+        if (node->suspendCount == 0) {
+            /* thread is not suspended yet so put it on the request list */
+            reqList[reqCnt++] = initList[i];
+        }
+    }
+
+    if (reqCnt > 0) {
+        jvmtiError *results = newArray(reqCnt, sizeof(jvmtiError));
+
+        if (results == NULL) {
+            EXIT_ERROR(AGENT_ERROR_OUT_OF_MEMORY,"suspend list results");
+        }
+
+        /*
+         * We have something to suspend so try to do it.
+         */
+        error = JVMTI_FUNC_PTR(gdata->jvmti,SuspendThreadList)
+                        (gdata->jvmti, reqCnt, reqList, results);
+        for (i = 0; i < reqCnt; i++) {
+            ThreadNode *node;
+
+            node = findThread(NULL, reqList[i]);
+            if (node == NULL) {
+                EXIT_ERROR(AGENT_ERROR_INVALID_THREAD,"missing entry in thread tables");
+            }
+            LOG_MISC(("thread=%p suspended as part of list", node->thread));
+
+            if (results[i] == JVMTI_ERROR_NONE) {
+                /* thread was suspended as requested */
+                node->toBeResumed = JNI_TRUE;
+            } else if (results[i] == JVMTI_ERROR_THREAD_SUSPENDED) {
+                /*
+                 * If the thread was suspended by another app thread,
+                 * do nothing and report no error (we won't resume it later).
+                 */
+                results[i] = JVMTI_ERROR_NONE;
+            } else if (results[i] == JVMTI_ERROR_THREAD_NOT_ALIVE) {
+                /*
+                 * This error means that the suspend request failed
+                 * because the thread is either a zombie or not yet
+                 * started. In either case, we ignore the error. If the
+                 * thread is a zombie, suspend/resume are no-ops. If the
+                 * thread is not started, it will be suspended for real
+                 * during the processing of its thread start event.
+                 */
+                node->suspendOnStart = JNI_TRUE;
+                results[i] = JVMTI_ERROR_NONE;
+            }
+
+            /* count real, app and deferred (suspendOnStart) suspensions */
+            if (results[i] == JVMTI_ERROR_NONE) {
+                node->suspendCount++;
+            }
+        }
+        deleteArray(results);
+    }
+    deleteArray(reqList);
+
+    debugMonitorNotifyAll(threadLock);
+
+    return error;
+}
+
+
+static jvmtiError
+commonResume(jthread thread)
+{
+    jvmtiError  error;
+    ThreadNode *node;
+
+    /*
+     * The thread is normally between its start and end events, but if
+     * not, check the auxiliary list used by threadControl_suspendThread.
+     */
+    node = findThread(NULL, thread);
+
+    /*
+     * If the node is in neither list, the debugger never suspended
+     * this thread, so do nothing.
+     */
+    error = JVMTI_ERROR_NONE;
+    if (node != NULL) {
+        error = resumeThreadByNode(node);
+    }
+    return error;
+}
+
+
+jvmtiError
+threadControl_suspendThread(jthread thread, jboolean deferred)
+{
+    jvmtiError error;
+    JNIEnv    *env;
+
+    env = getEnv();
+
+    log_debugee_location("threadControl_suspendThread()", thread, NULL, 0);
+
+    preSuspend();
+    error = commonSuspend(env, thread, deferred);
+    postSuspend();
+
+    return error;
+}
+
+jvmtiError
+threadControl_resumeThread(jthread thread, jboolean do_unblock)
+{
+    jvmtiError error;
+    JNIEnv    *env;
+
+    env = getEnv();
+
+    log_debugee_location("threadControl_resumeThread()", thread, NULL, 0);
+
+    eventHandler_lock(); /* for proper lock order */
+    debugMonitorEnter(threadLock);
+    error = commonResume(thread);
+    removeResumed(env, &otherThreads);
+    debugMonitorExit(threadLock);
+    eventHandler_unlock();
+
+    if (do_unblock) {
+        /* let eventHelper.c: commandLoop() know we resumed one thread */
+        unblockCommandLoop();
+    }
+
+    return error;
+}
+
+jvmtiError
+threadControl_suspendCount(jthread thread, jint *count)
+{
+    jvmtiError  error;
+    ThreadNode *node;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node == NULL) {
+        node = findThread(&otherThreads, thread);
+    }
+
+    error = JVMTI_ERROR_NONE;
+    if (node != NULL) {
+        *count = node->suspendCount;
+    } else {
+        /*
+         * If the node is in neither list, the debugger never suspended
+         * this thread, so the suspend count is 0.
+         */
+        *count = 0;
+    }
+
+    debugMonitorExit(threadLock);
+
+    return error;
+}
+
+static jboolean
+contains(JNIEnv *env, jthread *list, jint count, jthread item)
+{
+    int i;
+
+    for (i = 0; i < count; i++) {
+        if (isSameObject(env, list[i], item)) {
+            return JNI_TRUE;
+        }
+    }
+    return JNI_FALSE;
+}
+
+
+typedef struct {
+    jthread *list;
+    jint count;
+} SuspendAllArg;
+
+static jvmtiError
+suspendAllHelper(JNIEnv *env, ThreadNode *node, void *arg)
+{
+    SuspendAllArg *saArg = (SuspendAllArg *)arg;
+    jvmtiError error = JVMTI_ERROR_NONE;
+    jthread *list = saArg->list;
+    jint count = saArg->count;
+    if (!contains(env, list, count, node->thread)) {
+        error = commonSuspend(env, node->thread, JNI_FALSE);
+    }
+    return error;
+}
+
+jvmtiError
+threadControl_suspendAll(void)
+{
+    jvmtiError error;
+    JNIEnv    *env;
+
+    env = getEnv();
+
+    log_debugee_location("threadControl_suspendAll()", NULL, NULL, 0);
+
+    preSuspend();
+
+    /*
+     * Get a list of all threads and suspend them.
+     */
+    WITH_LOCAL_REFS(env, 1) {
+
+        jthread *threads;
+        jint count;
+
+        threads = allThreads(&count);
+        if (threads == NULL) {
+            error = AGENT_ERROR_OUT_OF_MEMORY;
+            goto err;
+        }
+        if (canSuspendResumeThreadLists()) {
+            error = commonSuspendList(env, count, threads);
+            if (error != JVMTI_ERROR_NONE) {
+                goto err;
+            }
+        } else {
+
+            int i;
+
+            for (i = 0; i < count; i++) {
+                error = commonSuspend(env, threads[i], JNI_FALSE);
+
+                if (error != JVMTI_ERROR_NONE) {
+                    goto err;
+                }
+            }
+        }
+
+        /*
+         * Update the suspend count of any threads not yet (or no longer)
+         * in the thread list above.
+         */
+        {
+            SuspendAllArg arg;
+            arg.list = threads;
+            arg.count = count;
+            error = enumerateOverThreadList(env, &otherThreads,
+                                            suspendAllHelper, &arg);
+        }
+
+        if (error == JVMTI_ERROR_NONE) {
+            suspendAllCount++;
+        }
+
+    err: ;
+
+    } END_WITH_LOCAL_REFS(env)
+
+    postSuspend();
+
+    return error;
+}
+
+static jvmtiError
+resumeHelper(JNIEnv *env, ThreadNode *node, void *ignored)
+{
+    /*
+     * Since this helper is called with the threadLock held, we
+     * don't need to recheck to see if the node is still on one
+     * of the two thread lists.
+     */
+    return resumeThreadByNode(node);
+}
+
+jvmtiError
+threadControl_resumeAll(void)
+{
+    jvmtiError error;
+    JNIEnv    *env;
+
+    env = getEnv();
+
+    log_debugee_location("threadControl_resumeAll()", NULL, NULL, 0);
+
+    eventHandler_lock(); /* for proper lock order */
+    debugMonitorEnter(threadLock);
+
+    /*
+     * Resume only those threads that the debugger has suspended. All
+     * such threads must have a node in one of the thread lists, so there's
+     * no need to get the whole thread list from JVMTI (unlike
+     * suspendAll).
+     */
+    if (canSuspendResumeThreadLists()) {
+        error = commonResumeList(env);
+    } else {
+        error = enumerateOverThreadList(env, &runningThreads,
+                                        resumeHelper, NULL);
+    }
+    if ((error == JVMTI_ERROR_NONE) && (otherThreads.first != NULL)) {
+        error = enumerateOverThreadList(env, &otherThreads,
+                                        resumeHelper, NULL);
+        removeResumed(env, &otherThreads);
+    }
+
+    if (suspendAllCount > 0) {
+        suspendAllCount--;
+    }
+
+    debugMonitorExit(threadLock);
+    eventHandler_unlock();
+    /* let eventHelper.c: commandLoop() know we are resuming */
+    unblockCommandLoop();
+
+    return error;
+}
+
+
+StepRequest *
+threadControl_getStepRequest(jthread thread)
+{
+    ThreadNode  *node;
+    StepRequest *step;
+
+    step = NULL;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        step = &node->currentStep;
+    }
+
+    debugMonitorExit(threadLock);
+
+    return step;
+}
+
+InvokeRequest *
+threadControl_getInvokeRequest(jthread thread)
+{
+    ThreadNode    *node;
+    InvokeRequest *request;
+
+    request = NULL;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+         request = &node->currentInvoke;
+    }
+
+    debugMonitorExit(threadLock);
+
+    return request;
+}
+
+jvmtiError
+threadControl_addDebugThread(jthread thread)
+{
+    jvmtiError error;
+
+    debugMonitorEnter(threadLock);
+    if (debugThreadCount >= MAX_DEBUG_THREADS) {
+        error = AGENT_ERROR_OUT_OF_MEMORY;
+    } else {
+        JNIEnv    *env;
+
+        env = getEnv();
+        debugThreads[debugThreadCount] = NULL;
+        saveGlobalRef(env, thread, &(debugThreads[debugThreadCount]));
+        if (debugThreads[debugThreadCount] == NULL) {
+            error = AGENT_ERROR_OUT_OF_MEMORY;
+        } else {
+            debugThreadCount++;
+            error = JVMTI_ERROR_NONE;
+        }
+    }
+    debugMonitorExit(threadLock);
+    return error;
+}
+
+static jvmtiError
+threadControl_removeDebugThread(jthread thread)
+{
+    jvmtiError error;
+    JNIEnv    *env;
+    int        i;
+
+    error = AGENT_ERROR_INVALID_THREAD;
+    env   = getEnv();
+
+    debugMonitorEnter(threadLock);
+    for (i = 0; i< debugThreadCount; i++) {
+        if (isSameObject(env, thread, debugThreads[i])) {
+            int j;
+
+            tossGlobalRef(env, &(debugThreads[i]));
+            for (j = i+1; j < debugThreadCount; j++) {
+                debugThreads[j-1] = debugThreads[j];
+            }
+            debugThreadCount--;
+            error = JVMTI_ERROR_NONE;
+            break;
+        }
+    }
+    debugMonitorExit(threadLock);
+    return error;
+}
+
+jboolean
+threadControl_isDebugThread(jthread thread)
+{
+    int      i;
+    jboolean rc;
+    JNIEnv  *env;
+
+    rc  = JNI_FALSE;
+    env = getEnv();
+
+    debugMonitorEnter(threadLock);
+    for (i = 0; i < debugThreadCount; i++) {
+        if (isSameObject(env, thread, debugThreads[i])) {
+            rc = JNI_TRUE;
+            break;
+        }
+    }
+    debugMonitorExit(threadLock);
+    return rc;
+}
+
+static void
+initLocks(void)
+{
+    if (popFrameEventLock == NULL) {
+        popFrameEventLock = debugMonitorCreate("JDWP PopFrame Event Lock");
+        popFrameProceedLock = debugMonitorCreate("JDWP PopFrame Proceed Lock");
+    }
+}
+
+static jboolean
+getPopFrameThread(jthread thread)
+{
+    jboolean popFrameThread;
+
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            popFrameThread = JNI_FALSE;
+        } else {
+            popFrameThread = node->popFrameThread;
+        }
+    }
+    debugMonitorExit(threadLock);
+
+    return popFrameThread;
+}
+
+static void
+setPopFrameThread(jthread thread, jboolean value)
+{
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"entry in thread table");
+        } else {
+            node->popFrameThread = value;
+        }
+    }
+    debugMonitorExit(threadLock);
+}
+
+static jboolean
+getPopFrameEvent(jthread thread)
+{
+    jboolean popFrameEvent;
+
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            popFrameEvent = JNI_FALSE;
+            EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"entry in thread table");
+        } else {
+            popFrameEvent = node->popFrameEvent;
+        }
+    }
+    debugMonitorExit(threadLock);
+
+    return popFrameEvent;
+}
+
+static void
+setPopFrameEvent(jthread thread, jboolean value)
+{
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"entry in thread table");
+        } else {
+            node->popFrameEvent = value;
+            node->frameGeneration++; /* Increment on each resume */
+        }
+    }
+    debugMonitorExit(threadLock);
+}
+
+static jboolean
+getPopFrameProceed(jthread thread)
+{
+    jboolean popFrameProceed;
+
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            popFrameProceed = JNI_FALSE;
+            EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"entry in thread table");
+        } else {
+            popFrameProceed = node->popFrameProceed;
+        }
+    }
+    debugMonitorExit(threadLock);
+
+    return popFrameProceed;
+}
+
+static void
+setPopFrameProceed(jthread thread, jboolean value)
+{
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+        if (node == NULL) {
+            EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"entry in thread table");
+        } else {
+            node->popFrameProceed = value;
+        }
+    }
+    debugMonitorExit(threadLock);
+}
+
+/**
+ * Special event handler for events on the popped thread
+ * that occur during the pop operation.
+ */
+static void
+popFrameCompleteEvent(jthread thread)
+{
+      debugMonitorEnter(popFrameProceedLock);
+      {
+          /* notify that we got the event */
+          debugMonitorEnter(popFrameEventLock);
+          {
+              setPopFrameEvent(thread, JNI_TRUE);
+              debugMonitorNotify(popFrameEventLock);
+          }
+          debugMonitorExit(popFrameEventLock);
+
+          /* make sure we get suspended again */
+          setPopFrameProceed(thread, JNI_FALSE);
+          while (getPopFrameProceed(thread) == JNI_FALSE) {
+              debugMonitorWait(popFrameProceedLock);
+          }
+      }
+      debugMonitorExit(popFrameProceedLock);
+}
+
+/**
+ * Pop one frame off the stack of thread.
+ * popFrameEventLock is already held
+ */
+static jvmtiError
+popOneFrame(jthread thread)
+{
+    jvmtiError error;
+
+    error = JVMTI_FUNC_PTR(gdata->jvmti,PopFrame)(gdata->jvmti, thread);
+    if (error != JVMTI_ERROR_NONE) {
+        return error;
+    }
+
+    /* resume the popped thread so that the pop occurs and so we */
+    /* will get the event (step or method entry) after the pop */
+    LOG_MISC(("thread=%p resumed in popOneFrame", thread));
+    error = JVMTI_FUNC_PTR(gdata->jvmti,ResumeThread)(gdata->jvmti, thread);
+    if (error != JVMTI_ERROR_NONE) {
+        return error;
+    }
+
+    /* wait for the event to occur */
+    setPopFrameEvent(thread, JNI_FALSE);
+    while (getPopFrameEvent(thread) == JNI_FALSE) {
+        debugMonitorWait(popFrameEventLock);
+    }
+
+    /* make sure not to suspend until the popped thread is on the wait */
+    debugMonitorEnter(popFrameProceedLock);
+    {
+        /* return popped thread to suspended state */
+        LOG_MISC(("thread=%p suspended in popOneFrame", thread));
+        error = JVMTI_FUNC_PTR(gdata->jvmti,SuspendThread)(gdata->jvmti, thread);
+
+        /* notify popped thread so it can proceed when resumed */
+        setPopFrameProceed(thread, JNI_TRUE);
+        debugMonitorNotify(popFrameProceedLock);
+    }
+    debugMonitorExit(popFrameProceedLock);
+
+    return error;
+}
+
+/**
+ * pop frames of the stack of 'thread' until 'frame' is popped.
+ */
+jvmtiError
+threadControl_popFrames(jthread thread, FrameNumber fnum)
+{
+    jvmtiError error;
+    jvmtiEventMode prevStepMode;
+    jint framesPopped = 0;
+    jint popCount;
+    jboolean prevInvokeRequestMode;
+
+    log_debugee_location("threadControl_popFrames()", thread, NULL, 0);
+
+    initLocks();
+
+    /* compute the number of frames to pop */
+    popCount = fnum+1;
+    if (popCount < 1) {
+        return AGENT_ERROR_NO_MORE_FRAMES;
+    }
+
+    /* enable instruction level single step, but first note prev value */
+    prevStepMode = threadControl_getInstructionStepMode(thread);
+
+    /*
+     * Fix bug 6517249.  The pop processing will disable invokes,
+     * so remember if invokes are enabled now and restore
+     * that state after we finish popping.
+     */
+    prevInvokeRequestMode = invoker_isEnabled(thread);
+
+    error = threadControl_setEventMode(JVMTI_ENABLE,
+                                       EI_SINGLE_STEP, thread);
+    if (error != JVMTI_ERROR_NONE) {
+        return error;
+    }
+
+    /* Inform eventHandler logic we are in a popFrame for this thread */
+    debugMonitorEnter(popFrameEventLock);
+    {
+        setPopFrameThread(thread, JNI_TRUE);
+        /* pop frames using single step */
+        while (framesPopped++ < popCount) {
+            error = popOneFrame(thread);
+            if (error != JVMTI_ERROR_NONE) {
+                break;
+            }
+        }
+        setPopFrameThread(thread, JNI_FALSE);
+    }
+    debugMonitorExit(popFrameEventLock);
+
+    /*  Reset StepRequest info (fromLine and stackDepth) after popframes
+     *  only if stepping is enabled.
+     */
+    if (prevStepMode == JVMTI_ENABLE) {
+        stepControl_resetRequest(thread);
+    }
+
+    if (prevInvokeRequestMode) {
+        invoker_enableInvokeRequests(thread);
+    }
+
+    /* restore state */
+    (void)threadControl_setEventMode(prevStepMode,
+                               EI_SINGLE_STEP, thread);
+
+    return error;
+}
+
+/* Check to see if any events are being consumed by a popFrame(). */
+static jboolean
+checkForPopFrameEvents(JNIEnv *env, EventIndex ei, jthread thread)
+{
+    if ( getPopFrameThread(thread) ) {
+        switch (ei) {
+            case EI_THREAD_START:
+                /* Excuse me? */
+                EXIT_ERROR(AGENT_ERROR_INTERNAL, "thread start during pop frame");
+                break;
+            case EI_THREAD_END:
+                /* Thread wants to end? let it. */
+                setPopFrameThread(thread, JNI_FALSE);
+                popFrameCompleteEvent(thread);
+                break;
+            case EI_SINGLE_STEP:
+                /* This is an event we requested to mark the */
+                /*        completion of the pop frame */
+                popFrameCompleteEvent(thread);
+                return JNI_TRUE;
+            case EI_BREAKPOINT:
+            case EI_EXCEPTION:
+            case EI_FIELD_ACCESS:
+            case EI_FIELD_MODIFICATION:
+            case EI_METHOD_ENTRY:
+            case EI_METHOD_EXIT:
+                /* Tell event handler to assume event has been consumed. */
+                return JNI_TRUE;
+            default:
+                break;
+        }
+    }
+    /* Pretend we were never called */
+    return JNI_FALSE;
+}
+
+struct bag *
+threadControl_onEventHandlerEntry(jbyte sessionID, EventIndex ei, jthread thread, jobject currentException)
+{
+    ThreadNode *node;
+    JNIEnv     *env;
+    struct bag *eventBag;
+    jthread     threadToSuspend;
+    jboolean    consumed;
+
+    env             = getEnv();
+    threadToSuspend = NULL;
+
+    log_debugee_location("threadControl_onEventHandlerEntry()", thread, NULL, 0);
+
+    /* Events during pop commands may need to be ignored here. */
+    consumed = checkForPopFrameEvents(env, ei, thread);
+    if ( consumed ) {
+        /* Always restore any exception (see below). */
+        if (currentException != NULL) {
+            JNI_FUNC_PTR(env,Throw)(env, currentException);
+        } else {
+            JNI_FUNC_PTR(env,ExceptionClear)(env);
+        }
+        return NULL;
+    }
+
+    debugMonitorEnter(threadLock);
+
+    /*
+     * Check the list of unknown threads maintained by suspend
+     * and resume. If this thread is currently present in the
+     * list, it should be
+     * moved to the runningThreads list, since it is a
+     * well-known thread now.
+     */
+    node = findThread(&otherThreads, thread);
+    if (node != NULL) {
+        moveNode(&otherThreads, &runningThreads, node);
+    } else {
+        /*
+         * Get a thread node for the reporting thread. For thread start
+         * events, or if this event precedes a thread start event,
+         * the thread node may need to be created.
+         *
+         * It is possible for certain events (notably method entry/exit)
+         * to precede thread start for some VM implementations.
+         */
+        node = insertThread(env, &runningThreads, thread);
+    }
+
+    if (ei == EI_THREAD_START) {
+        node->isStarted = JNI_TRUE;
+        processDeferredEventModes(env, thread, node);
+    }
+
+    node->current_ei = ei;
+    eventBag = node->eventBag;
+    if (node->suspendOnStart) {
+        threadToSuspend = node->thread;
+    }
+    debugMonitorExit(threadLock);
+
+    if (threadToSuspend != NULL) {
+        /*
+         * An attempt was made to suspend this thread before it started.
+         * We must suspend it now, before it starts to run. This must
+         * be done with no locks held.
+         */
+        eventHelper_suspendThread(sessionID, threadToSuspend);
+    }
+
+    return eventBag;
+}
+
+static void
+doPendingTasks(JNIEnv *env, ThreadNode *node)
+{
+    /*
+     * Take care of any pending interrupts/stops, and clear out
+     * info on pending interrupts/stops.
+     */
+    if (node->pendingInterrupt) {
+        JVMTI_FUNC_PTR(gdata->jvmti,InterruptThread)
+                        (gdata->jvmti, node->thread);
+        /*
+         * TO DO: Log error
+         */
+        node->pendingInterrupt = JNI_FALSE;
+    }
+
+    if (node->pendingStop != NULL) {
+        JVMTI_FUNC_PTR(gdata->jvmti,StopThread)
+                        (gdata->jvmti, node->thread, node->pendingStop);
+        /*
+         * TO DO: Log error
+         */
+        tossGlobalRef(env, &(node->pendingStop));
+    }
+}
+
+void
+threadControl_onEventHandlerExit(EventIndex ei, jthread thread,
+                                 struct bag *eventBag)
+{
+    ThreadNode *node;
+
+    log_debugee_location("threadControl_onEventHandlerExit()", thread, NULL, 0);
+
+    if (ei == EI_THREAD_END) {
+        eventHandler_lock(); /* for proper lock order */
+    }
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node == NULL) {
+        EXIT_ERROR(AGENT_ERROR_NULL_POINTER,"thread list corrupted");
+    } else {
+        JNIEnv *env;
+
+        env = getEnv();
+        if (ei == EI_THREAD_END) {
+            jboolean inResume = (node->resumeFrameDepth > 0);
+            removeThread(env, &runningThreads, thread);
+            node = NULL;   /* has been freed */
+
+            /*
+             * Clean up mechanism used to detect end of
+             * resume.
+             */
+            if (inResume) {
+                notifyAppResumeComplete();
+            }
+        } else {
+            /* No point in doing this if the thread is about to die.*/
+            doPendingTasks(env, node);
+            node->eventBag = eventBag;
+            node->current_ei = 0;
+        }
+    }
+
+    debugMonitorExit(threadLock);
+    if (ei == EI_THREAD_END) {
+        eventHandler_unlock();
+    }
+}
+
+/* Returns JDWP flavored status and status flags. */
+jvmtiError
+threadControl_applicationThreadStatus(jthread thread,
+                        jdwpThreadStatus *pstatus, jint *statusFlags)
+{
+    ThreadNode *node;
+    jvmtiError  error;
+    jint        state;
+
+    log_debugee_location("threadControl_applicationThreadStatus()", thread, NULL, 0);
+
+    debugMonitorEnter(threadLock);
+
+    error = threadState(thread, &state);
+    *pstatus = map2jdwpThreadStatus(state);
+    *statusFlags = map2jdwpSuspendStatus(state);
+
+    if (error == JVMTI_ERROR_NONE) {
+        node = findThread(&runningThreads, thread);
+        if ((node != NULL) && HANDLING_EVENT(node)) {
+            /*
+             * While processing an event, an application thread is always
+             * considered to be running even if its handler happens to be
+             * cond waiting on an internal debugger monitor, etc.
+             *
+             * Leave suspend status untouched since it is not possible
+             * to distinguish debugger suspends from app suspends.
+             */
+            *pstatus = JDWP_THREAD_STATUS(RUNNING);
+        }
+    }
+
+    debugMonitorExit(threadLock);
+
+    return error;
+}
+
+jvmtiError
+threadControl_interrupt(jthread thread)
+{
+    ThreadNode *node;
+    jvmtiError  error;
+
+    error = JVMTI_ERROR_NONE;
+
+    log_debugee_location("threadControl_interrupt()", thread, NULL, 0);
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if ((node == NULL) || !HANDLING_EVENT(node)) {
+        error = JVMTI_FUNC_PTR(gdata->jvmti,InterruptThread)
+                        (gdata->jvmti, thread);
+    } else {
+        /*
+         * Hold any interrupts until after the event is processed.
+         */
+        node->pendingInterrupt = JNI_TRUE;
+    }
+
+    debugMonitorExit(threadLock);
+
+    return error;
+}
+
+void
+threadControl_clearCLEInfo(JNIEnv *env, jthread thread)
+{
+    ThreadNode *node;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        node->cleInfo.ei = 0;
+        if (node->cleInfo.clazz != NULL) {
+            tossGlobalRef(env, &(node->cleInfo.clazz));
+        }
+    }
+
+    debugMonitorExit(threadLock);
+}
+
+jboolean
+threadControl_cmpCLEInfo(JNIEnv *env, jthread thread, jclass clazz,
+                         jmethodID method, jlocation location)
+{
+    ThreadNode *node;
+    jboolean    result;
+
+    result = JNI_FALSE;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL && node->cleInfo.ei != 0 &&
+        node->cleInfo.method == method &&
+        node->cleInfo.location == location &&
+        (isSameObject(env, node->cleInfo.clazz, clazz))) {
+        result = JNI_TRUE; /* we have a match */
+    }
+
+    debugMonitorExit(threadLock);
+
+    return result;
+}
+
+void
+threadControl_saveCLEInfo(JNIEnv *env, jthread thread, EventIndex ei,
+                          jclass clazz, jmethodID method, jlocation location)
+{
+    ThreadNode *node;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        node->cleInfo.ei = ei;
+        /* Create a class ref that will live beyond */
+        /* the end of this call */
+        saveGlobalRef(env, clazz, &(node->cleInfo.clazz));
+        /* if returned clazz is NULL, we just won't match */
+        node->cleInfo.method    = method;
+        node->cleInfo.location  = location;
+    }
+
+    debugMonitorExit(threadLock);
+}
+
+void
+threadControl_setPendingInterrupt(jthread thread)
+{
+    ThreadNode *node;
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        node->pendingInterrupt = JNI_TRUE;
+    }
+
+    debugMonitorExit(threadLock);
+}
+
+jvmtiError
+threadControl_stop(jthread thread, jobject throwable)
+{
+    ThreadNode *node;
+    jvmtiError  error;
+
+    error = JVMTI_ERROR_NONE;
+
+    log_debugee_location("threadControl_stop()", thread, NULL, 0);
+
+    debugMonitorEnter(threadLock);
+
+    node = findThread(&runningThreads, thread);
+    if ((node == NULL) || !HANDLING_EVENT(node)) {
+        error = JVMTI_FUNC_PTR(gdata->jvmti,StopThread)
+                        (gdata->jvmti, thread, throwable);
+    } else {
+        JNIEnv *env;
+
+        /*
+         * Hold any stops until after the event is processed.
+         */
+        env = getEnv();
+        saveGlobalRef(env, throwable, &(node->pendingStop));
+    }
+
+    debugMonitorExit(threadLock);
+
+    return error;
+}
+
+static jvmtiError
+detachHelper(JNIEnv *env, ThreadNode *node, void *arg)
+{
+    invoker_detach(&node->currentInvoke);
+    return JVMTI_ERROR_NONE;
+}
+
+void
+threadControl_detachInvokes(void)
+{
+    JNIEnv *env;
+
+    env = getEnv();
+    invoker_lock(); /* for proper lock order */
+    debugMonitorEnter(threadLock);
+    (void)enumerateOverThreadList(env, &runningThreads, detachHelper, NULL);
+    debugMonitorExit(threadLock);
+    invoker_unlock();
+}
+
+static jvmtiError
+resetHelper(JNIEnv *env, ThreadNode *node, void *arg)
+{
+    if (node->toBeResumed) {
+        LOG_MISC(("thread=%p resumed", node->thread));
+        (void)JVMTI_FUNC_PTR(gdata->jvmti,ResumeThread)(gdata->jvmti, node->thread);
+        node->frameGeneration++; /* Increment on each resume */
+    }
+    stepControl_clearRequest(node->thread, &node->currentStep);
+    node->toBeResumed = JNI_FALSE;
+    node->suspendCount = 0;
+    node->suspendOnStart = JNI_FALSE;
+
+    return JVMTI_ERROR_NONE;
+}
+
+void
+threadControl_reset(void)
+{
+    JNIEnv *env;
+
+    env = getEnv();
+    eventHandler_lock(); /* for proper lock order */
+    debugMonitorEnter(threadLock);
+    (void)enumerateOverThreadList(env, &runningThreads, resetHelper, NULL);
+    (void)enumerateOverThreadList(env, &otherThreads, resetHelper, NULL);
+
+    removeResumed(env, &otherThreads);
+
+    freeDeferredEventModes(env);
+
+    suspendAllCount = 0;
+
+    /* Everything should have been resumed */
+    JDI_ASSERT(otherThreads.first == NULL);
+
+    debugMonitorExit(threadLock);
+    eventHandler_unlock();
+}
+
+jvmtiEventMode
+threadControl_getInstructionStepMode(jthread thread)
+{
+    ThreadNode    *node;
+    jvmtiEventMode mode;
+
+    mode = JVMTI_DISABLE;
+
+    debugMonitorEnter(threadLock);
+    node = findThread(&runningThreads, thread);
+    if (node != NULL) {
+        mode = node->instructionStepMode;
+    }
+    debugMonitorExit(threadLock);
+    return mode;
+}
+
+jvmtiError
+threadControl_setEventMode(jvmtiEventMode mode, EventIndex ei, jthread thread)
+{
+    jvmtiError error;
+
+    /* Global event */
+    if ( thread == NULL ) {
+        error = JVMTI_FUNC_PTR(gdata->jvmti,SetEventNotificationMode)
+                    (gdata->jvmti, mode, eventIndex2jvmti(ei), thread);
+    } else {
+        /* Thread event */
+        ThreadNode *node;
+
+        debugMonitorEnter(threadLock);
+        {
+            node = findThread(&runningThreads, thread);
+            if ((node == NULL) || (!node->isStarted)) {
+                JNIEnv *env;
+
+                env = getEnv();
+                error = addDeferredEventMode(env, mode, ei, thread);
+            } else {
+                error = threadSetEventNotificationMode(node,
+                        mode, ei, thread);
+            }
+        }
+        debugMonitorExit(threadLock);
+
+    }
+    return error;
+}
+
+/*
+ * Returns the current thread, if the thread has generated at least
+ * one event, and has not generated a thread end event.
+ */
+jthread threadControl_currentThread(void)
+{
+    jthread thread;
+
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(&runningThreads, NULL);
+        thread = (node == NULL) ? NULL : node->thread;
+    }
+    debugMonitorExit(threadLock);
+
+    return thread;
+}
+
+jlong
+threadControl_getFrameGeneration(jthread thread)
+{
+    jlong frameGeneration = -1;
+
+    debugMonitorEnter(threadLock);
+    {
+        ThreadNode *node;
+
+        node = findThread(NULL, thread);
+
+        if (node != NULL) {
+            frameGeneration = node->frameGeneration;
+        }
+    }
+    debugMonitorExit(threadLock);
+
+    return frameGeneration;
+}