static void test1(void)
{
    RTTestISub("Three threads");

    /*
     * Create the threads and let them block on the event multi semaphore.
     */
    RTSEMEVENTMULTI hSem;
    RTTESTI_CHECK_RC_RETV(RTSemEventMultiCreate(&hSem), VINF_SUCCESS);

    RTTHREAD hThread2;
    RTTESTI_CHECK_RC_RETV(RTThreadCreate(&hThread2, test1Thread2, &hSem, 0, RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "test2"), VINF_SUCCESS);
    RTThreadSleep(100);

    RTTHREAD hThread1;
    RTTESTI_CHECK_RC_RETV(RTThreadCreate(&hThread1, test1Thread1, &hSem, 0, RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "test1"), VINF_SUCCESS);

    /* Force first thread (which has a timeout of 1 second) to timeout in the
     * first wait, and the second wait will succeed. */
    RTTESTI_CHECK_RC(RTThreadSleep(1500), VINF_SUCCESS);
    RTTESTI_CHECK_RC(RTSemEventMultiSignal(hSem), VINF_SUCCESS);
    RTTESTI_CHECK_RC(RTThreadWait(hThread1, 5000, NULL), VINF_SUCCESS);
    RTTESTI_CHECK_RC(RTThreadWait(hThread2, 5000, NULL), VINF_SUCCESS);
    RTTESTI_CHECK_RC(RTSemEventMultiDestroy(hSem), VINF_SUCCESS);
}

/**
 * Wait on the threads to complete.
 *
 * @returns Thread status (if collected), otherwise VINF_SUCCESS.
 * @param   cMillies        The period to wait on each thread.
 */
static int txsTcpConnectWaitOnThreads(RTMSINTERVAL cMillies)
{
    int rcRet = VINF_SUCCESS;

    if (g_hThreadTcpConnect != NIL_RTTHREAD)
    {
        int rcThread;
        int rc2 = RTThreadWait(g_hThreadTcpConnect, cMillies, &rcThread);
        if (RT_SUCCESS(rc2))
        {
            g_hThreadTcpConnect = NIL_RTTHREAD;
            rcRet = rcThread;
        }
    }

    if (g_hThreadTcpServer != NIL_RTTHREAD)
    {
        int rcThread;
        int rc2 = RTThreadWait(g_hThreadTcpServer, cMillies, &rcThread);
        if (RT_SUCCESS(rc2))
        {
            g_hThreadTcpServer = NIL_RTTHREAD;
            if (RT_SUCCESS(rc2))
                rcRet = rcThread;
        }
    }
    return rcRet;
}

void VBoxNetBaseService::shutdown(void)
{
    syncEnter();
    if (!m->fShutdown)
    {
        m->fShutdown = true;
        if (m->m_hThrRecv != NIL_RTTHREAD)
        {
            int rc = abortWait();
            AssertRC(rc == VINF_SUCCESS || rc == VERR_SEM_DESTROYED);
            rc = m->m_EventQ->interruptEventQueueProcessing();
            if (RT_SUCCESS(rc))
            {
                rc = RTThreadWait(m->m_hThrRecv, 60000, NULL);
                if (RT_FAILURE(rc))
                    Log1WarningFunc(("RTThreadWait(%RTthrd) -> %Rrc\n", m->m_hThrRecv, rc));
            }
            else
            {
                AssertMsgFailed(("interruptEventQueueProcessing() failed\n"));
                RTThreadWait(m->m_hThrRecv , 0, NULL);
            }
        }
    }
    syncLeave();
}

/**
 * Does a multi-threading list test. Several list additions, reading, replacing
 * and erasing are done simultaneous.
 *
 */
static void test2()
{
    RTTestISubF("MT test with 6 threads (%u tests per thread).", MTTESTITEMS);

    int                         rc;
    MTTESTLISTTYPE<MTTESTTYPE>  testList;
    RTTHREAD                    ahThreads[6];
    static PFNRTTHREAD          apfnThreads[6] =
    {
        MtTest1ThreadProc, MtTest2ThreadProc, MtTest3ThreadProc, MtTest4ThreadProc, MtTest5ThreadProc, MtTest6ThreadProc
    };

    for (unsigned i = 0; i < RT_ELEMENTS(ahThreads); i++)
    {
        RTTESTI_CHECK_RC_RETV(RTThreadCreateF(&ahThreads[i], apfnThreads[i], &testList, 0,
                                              RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "mttest%u", i), VINF_SUCCESS);
    }

    uint64_t tsMsDeadline = RTTimeMilliTS() + 60000;
    for (unsigned i = 0; i < RT_ELEMENTS(ahThreads); i++)
    {
        uint64_t tsNow = RTTimeMilliTS();
        uint32_t cWait = tsNow > tsMsDeadline ? 5000 : tsMsDeadline - tsNow;
        RTTESTI_CHECK_RC(RTThreadWait(ahThreads[i], tsNow, NULL), VINF_SUCCESS);
    }

    RTTESTI_CHECK_RETV(testList.size() == MTTESTITEMS * 2);
    for (size_t i = 0; i < testList.size(); ++i)
    {
        uint32_t a = testList.at(i);
        RTTESTI_CHECK(a == 0x0 || a == 0xFFFFFFFF || a == 0xF0F0F0F0 || a == 0xFF00FF00);
    }
}

VirtualBox::ClientWatcher::~ClientWatcher()
{
    if (mThread != NIL_RTTHREAD)
    {
        /* signal the client watcher thread, should be exiting now */
        update();
        /* wait for termination */
        RTThreadWait(mThread, RT_INDEFINITE_WAIT, NULL);
        mThread = NIL_RTTHREAD;
    }
    mProcesses.clear();
#if defined(RT_OS_WINDOWS)
    if (mUpdateReq != NULL)
    {
        ::CloseHandle(mUpdateReq);
        mUpdateReq = NULL;
    }
#elif defined(RT_OS_OS2) || defined(VBOX_WITH_SYS_V_IPC_SESSION_WATCHER) || defined(VBOX_WITH_GENERIC_SESSION_WATCHER)
    if (mUpdateReq != NIL_RTSEMEVENT)
    {
        RTSemEventDestroy(mUpdateReq);
        mUpdateReq = NIL_RTSEMEVENT;
    }
#else
# error "Port me!"
#endif
}

/**
 * Shutdowns all the watchers.
 */
void VirtualBoxSDS::i_shutdownAllWatchers(void)
{
    LogRel(("i_shutdownAllWatchers: %u watchers\n", m_cWatchers));

    /* Notify them all. */
    uint32_t i = m_cWatchers;
    while (i-- > 0)
    {
        ASMAtomicWriteBool(&m_papWatchers[i]->fShutdown, true);
        SetEvent(m_papWatchers[i]->aHandles[0]);
    }

    /* Wait for them to complete and destroy their data. */
    i = m_cWatchers;
    m_cWatchers = 0;
    while (i-- > 0)
    {
        VBoxSDSWatcher *pWatcher = m_papWatchers[i];
        if (pWatcher)
        {
            m_papWatchers[i] = NULL;

            int rc = RTThreadWait(pWatcher->hThread, RT_MS_1MIN / 2, NULL);
            if (RT_SUCCESS(rc))
                pWatcher->hThread = NIL_RTTHREAD;
            else
                LogRel(("i_shutdownAllWatchers: RTThreadWait failed on #%u: %Rrc\n", i, rc));

            if (ASMAtomicDecU32(&pWatcher->cRefs) == 0)
                RTMemFree(pWatcher);
        }
    }
}

int
VBoxCredProvPoller::Shutdown(void)
{
    VBoxCredProvVerbose(0, "VBoxCredProvPoller: Shutdown\n");

    if (m_hThreadPoller == NIL_RTTHREAD)
        return VINF_SUCCESS;

    /* Post termination event semaphore. */
    int rc = RTThreadUserSignal(m_hThreadPoller);
    if (RT_SUCCESS(rc))
    {
        VBoxCredProvVerbose(0, "VBoxCredProvPoller: Waiting for thread to terminate\n");
        /* Wait until the thread has terminated. */
        rc = RTThreadWait(m_hThreadPoller, RT_INDEFINITE_WAIT, NULL);
        if (RT_FAILURE(rc))
            VBoxCredProvVerbose(0, "VBoxCredProvPoller: Wait returned error rc=%Rrc\n", rc);
    }
    else
        VBoxCredProvVerbose(0, "VBoxCredProvPoller: Error waiting for thread shutdown, rc=%Rrc\n", rc);

    m_pProv = NULL;
    m_hThreadPoller = NIL_RTTHREAD;

    VBoxCredProvVerbose(0, "VBoxCredProvPoller: Shutdown returned with rc=%Rrc\n", rc);
    return rc;
}

/**
 *  Uninitializes the instance and sets the ready flag to FALSE.
 *  Called either from FinalRelease() or by the parent when it gets destroyed.
 */
void VirtualBoxClient::uninit()
{
    LogFlowThisFunc(("\n"));

    /* Enclose the state transition Ready->InUninit->NotReady */
    AutoUninitSpan autoUninitSpan(this);
    if (autoUninitSpan.uninitDone())
        return;

    if (mData.m_ThreadWatcher != NIL_RTTHREAD)
    {
        /* Signal the event semaphore and wait for the thread to terminate.
         * if it hangs for some reason exit anyway, this can cause a crash
         * though as the object will no longer be available. */
        RTSemEventSignal(mData.m_SemEvWatcher);
        RTThreadWait(mData.m_ThreadWatcher, 30000, NULL);
        mData.m_ThreadWatcher = NIL_RTTHREAD;
        RTSemEventDestroy(mData.m_SemEvWatcher);
        mData.m_SemEvWatcher = NIL_RTSEMEVENT;
    }

    mData.m_pVirtualBox.setNull();

    ASMAtomicDecU32(&g_cInstances);
}

int VBoxGINACredentialsPollerTerminate(void)
{
    if (gThreadPoller == NIL_RTTHREAD)
        return VINF_SUCCESS;

    VBoxGINAVerbose(0, "VBoxGINA::credentialsPollerTerminate\n");

    /* post termination event semaphore */
    int rc = RTThreadUserSignal(gThreadPoller);
    if (RT_SUCCESS(rc))
    {
        VBoxGINAVerbose(0, "VBoxGINA::credentialsPollerTerminate: waiting for thread to terminate\n");
        rc = RTThreadWait(gThreadPoller, RT_INDEFINITE_WAIT, NULL);
    }
    else
        VBoxGINAVerbose(0, "VBoxGINA::credentialsPollerTerminate: thread has terminated? wait rc = %Rrc\n",     rc);

    if (RT_SUCCESS(rc))
    {
        gThreadPoller = NIL_RTTHREAD;
    }

    VBoxGINAVerbose(0, "VBoxGINA::credentialsPollerTerminate: returned with rc=%Rrc)\n", rc);
    return rc;
}

/**
 * Destruct a char driver instance.
 *
 * Most VM resources are freed by the VM. This callback is provided so that
 * any non-VM resources can be freed correctly.
 *
 * @param   pDrvIns     The driver instance data.
 */
static DECLCALLBACK(void) drvCharDestruct(PPDMDRVINS pDrvIns)
{
    PDRVCHAR pThis = PDMINS_2_DATA(pDrvIns, PDRVCHAR);
    LogFlow(("%s: iInstance=%d\n", __FUNCTION__, pDrvIns->iInstance));
    PDMDRV_CHECK_VERSIONS_RETURN_VOID(pDrvIns);

    /*
     * Tell the threads to shut down.
     */
    pThis->fShutdown = true;
    if (pThis->SendSem != NIL_RTSEMEVENT)
    {
        RTSemEventSignal(pThis->SendSem);
        pThis->SendSem = NIL_RTSEMEVENT;
    }

    /*
     * Wait for the threads.
     * ASSUMES that PDM destroys the driver chain from the bottom and up.
     */
    if (pThis->ReceiveThread != NIL_RTTHREAD)
    {
        int rc = RTThreadWait(pThis->ReceiveThread, 30000, NULL);
        if (RT_SUCCESS(rc))
            pThis->ReceiveThread = NIL_RTTHREAD;
        else
            LogRel(("Char%d: receive thread did not terminate (%Rrc)\n", pDrvIns->iInstance, rc));
    }

    if (pThis->SendThread != NIL_RTTHREAD)
    {
        int rc = RTThreadWait(pThis->SendThread, 30000, NULL);
        if (RT_SUCCESS(rc))
            pThis->SendThread = NIL_RTTHREAD;
        else
            LogRel(("Char%d: send thread did not terminate (%Rrc)\n", pDrvIns->iInstance, rc));
    }

    if (pThis->SendSem != NIL_RTSEMEVENT)
    {
        RTSemEventDestroy(pThis->SendSem);
        pThis->SendSem = NIL_RTSEMEVENT;
    }
}

/**
 *  Entry point.
 */
extern "C" DECLEXPORT(int) TrustedMain(int argc, char **argv)
{
    /*
     * Instantiate the DHCP server and hand it the options.
     */
    VBoxNetDhcp *pDhcp = new VBoxNetDhcp();
    if (!pDhcp)
    {
        RTStrmPrintf(g_pStdErr, "VBoxNetDHCP: new VBoxNetDhcp failed!\n");
        return 1;
    }

    RTEXITCODE rcExit = (RTEXITCODE)pDhcp->parseArgs(argc - 1, argv + 1);
    if (rcExit != RTEXITCODE_SUCCESS)
        return rcExit;

#ifdef RT_OS_WINDOWS
    /* DIFx hack. */
    RTTHREAD hMakeUseKillableThread = NIL_RTTHREAD;
    int rc2 = RTThreadCreate(&hMakeUseKillableThread, DIFxKillableProcessThreadProc, NULL, 0,
                             RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "DIFxKill");
    if (RT_FAILURE(rc2))
        hMakeUseKillableThread = NIL_RTTHREAD;
#endif

    pDhcp->init();

    /*
     * Try connect the server to the network.
     */
    int rc = pDhcp->tryGoOnline();
    if (RT_SUCCESS(rc))
    {
        /*
         * Process requests.
         */
        g_pDhcp = pDhcp;
        rc = pDhcp->run();
        pDhcp->done();

        g_pDhcp = NULL;
    }
    delete pDhcp;

#ifdef RT_OS_WINDOWS
    /* Kill DIFx hack. */
    if (hMakeUseKillableThread != NIL_RTTHREAD)
    {
        g_fExitProcessOnQuit = false;
        PostThreadMessage((DWORD)RTThreadGetNative(hMakeUseKillableThread), WM_QUIT, 0, 0);
        RTThreadWait(hMakeUseKillableThread, RT_MS_1SEC * 5U, NULL);
    }
#endif

    return RT_SUCCESS(rc) ? RTEXITCODE_SUCCESS : RTEXITCODE_FAILURE;
}

static void test1(void)
{
    RTTestSub(g_hTest, "Interrupt RTThreadSleep");
    RTTHREAD hThread;
    RTTESTI_CHECK_RC_RETV(RTThreadCreate(&hThread, test1Thread, NULL, 0, RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "test1"),
                          VINF_SUCCESS);
    RTThreadSleep(500); RTThreadSleep(1500); /* fudge */
    RTTESTI_CHECK_RC(RTThreadPoke(hThread), VINF_SUCCESS);
    RTTESTI_CHECK_RC(RTThreadWait(hThread, RT_INDEFINITE_WAIT, NULL), VINF_SUCCESS);
}

int VDIoBackendMemDestroy(PVDIOBACKENDMEM pIoBackend)
{
    ASMAtomicXchgBool(&pIoBackend->fRunning, false);
    vdIoBackendMemThreadPoke(pIoBackend);

    RTThreadWait(pIoBackend->hThreadIo, RT_INDEFINITE_WAIT, NULL);
    RTSemEventDestroy(pIoBackend->EventSem);
    RTCircBufDestroy(pIoBackend->pRequestRing);
    RTMemFree(pIoBackend);

    return VINF_SUCCESS;
}

bool VBoxCredPoller::Shutdown(void)
{
    Log(("VBoxCredPoller::Shutdown\n"));

    if (m_hThreadPoller == NIL_RTTHREAD)
    {
        Log(("VBoxCredPoller::Shutdown: Either thread or exit sem is NULL!\n"));
        return false;
    }

    /* Post termination event semaphore. */
    int rc = RTThreadUserSignal(m_hThreadPoller);
    if (RT_SUCCESS(rc))
    {
        Log(("VBoxCredPoller::Shutdown: Waiting for thread to terminate\n"));
        /* Wait until the thread has terminated. */
        rc = RTThreadWait(m_hThreadPoller, RT_INDEFINITE_WAIT, NULL);
        Log(("VBoxCredPoller::Shutdown: Thread has (probably) terminated (rc = %Rrc)\n", rc));
    }
    else
    {
        /* Failed to signal the thread - very unlikely - so no point in waiting long. */
        Log(("VBoxCredPoller::Shutdown: Failed to signal semaphore, rc = %Rrc\n", rc));
        rc = RTThreadWait(m_hThreadPoller, 100, NULL);
        Log(("VBoxCredPoller::Shutdown: Thread has terminated? wait rc = %Rrc\n", rc));
    }

    if (m_pProv != NULL)
    {
        m_pProv->Release();
        m_pProv = NULL;
    }

    credentialsReset();
    RTCritSectDelete(&m_csCredUpate);

    m_hThreadPoller = NIL_RTTHREAD;
    return true;
}

HostPowerServiceWin::~HostPowerServiceWin()
{
    if (mHwnd)
    {
        Log(("HostPowerServiceWin::!HostPowerServiceWin: destroy window %x\n", mHwnd));

        /* Is this allowed from another thread? */
        SetWindowLongPtr(mHwnd, 0, 0);
        /* Poke the thread out of the event loop and wait for it to clean up. */
        PostMessage(mHwnd, WM_QUIT, 0, 0);
        RTThreadWait(mThread, 5000, NULL);
        mThread = NIL_RTTHREAD;
    }
}

/**
 * @interface_method_impl{PDMDEVREG,pfnDestruct}
 */
static DECLCALLBACK(int) gimdevR3Destruct(PPDMDEVINS pDevIns)
{
    PGIMDEV  pThis    = PDMINS_2_DATA(pDevIns, PGIMDEV);
    PVM      pVM      = PDMDevHlpGetVM(pDevIns);
    uint32_t cRegions = 0;

    PGIMMMIO2REGION pCur = GIMR3GetMmio2Regions(pVM, &cRegions);
    for (uint32_t i = 0; i < cRegions; i++, pCur++)
    {
        int rc = PDMDevHlpMMIOExDeregister(pDevIns, NULL, pCur->iRegion);
        if (RT_FAILURE(rc))
            return rc;
    }

    /*
     * Signal and wait for the debug thread to terminate.
     */
    if (pThis->hDbgRecvThread != NIL_RTTHREAD)
    {
        pThis->fDbgRecvThreadShutdown = true;
        if (pThis->Dbg.hDbgRecvThreadSem != NIL_RTSEMEVENT)
            RTSemEventMultiSignal(pThis->Dbg.hDbgRecvThreadSem);

        int rc = RTThreadWait(pThis->hDbgRecvThread, 20000, NULL /*prc*/);
        if (RT_SUCCESS(rc))
            pThis->hDbgRecvThread = NIL_RTTHREAD;
        else
        {
            LogRel(("GIMDev: Debug thread did not terminate, rc=%Rrc!\n", rc));
            return VERR_RESOURCE_BUSY;
        }
    }

    /*
     * Now clean up the semaphore & buffer now that the thread is gone.
     */
    if (pThis->Dbg.hDbgRecvThreadSem != NIL_RTSEMEVENT)
    {
        RTSemEventMultiDestroy(pThis->Dbg.hDbgRecvThreadSem);
        pThis->Dbg.hDbgRecvThreadSem = NIL_RTSEMEVENTMULTI;
    }
    if (pThis->Dbg.pvDbgRecvBuf)
    {
        RTMemFree(pThis->Dbg.pvDbgRecvBuf);
        pThis->Dbg.pvDbgRecvBuf = NULL;
    }

    return VINF_SUCCESS;
}

void vboxClipboardDestroy (void)
{
    Log(("vboxClipboardDestroy\n"));

    if (g_ctx.hwnd)
    {
        int rc = PostMessage (g_ctx.hwnd, WM_CLOSE, 0, 0);
    }

    CloseHandle (g_ctx.hRenderEvent);

    /* Wait for the window thread to terminate. */
    RTThreadWait (g_ctx.thread, RT_INDEFINITE_WAIT, NULL);

    g_ctx.thread = NIL_RTTHREAD;
}

/**
 * Send a signal to the thread function that it should exit
 */
int SeamlessMain::stopX11MonitorThread(void)
{
    int rc;

    mX11MonitorThreadStopping = true;
    if (!isX11MonitorThreadRunning())
        return VINF_SUCCESS;
    mX11Monitor.interruptEventWait();
    rc = RTThreadWait(mX11MonitorThread, RT_INDEFINITE_WAIT, NULL);
    if (RT_SUCCESS(rc))
        mX11MonitorThread = NIL_RTTHREAD;
    else
        LogRelThisFunc(("Failed to stop X11 monitor thread, rc=%Rrc!\n",
                        rc));
    return rc;
}

int main(int argc, char **argv)
{
    RTR3InitExe(argc, &argv, 0);
    if (argc == 2 && !strcmp(argv[1], "child"))
        return 42;

    RTPrintf("tstRTWait: spawning a child in a separate thread and waits for it in the main thread...\n");
    RTTHREAD  Thread;
    SPAWNERARGS Args = { NIL_RTPROCESS, argv[0] };
    int rc = RTThreadCreate(&Thread, SpawnerThread, &Args, 0, RTTHREADTYPE_DEFAULT, RTTHREADFLAGS_WAITABLE, "SPAWNER");
    if (RT_SUCCESS(rc))
    {
        /* Wait for it to complete. */
        int rc2;
        rc = RTThreadWait(Thread, RT_INDEFINITE_WAIT, &rc2);
        if (RT_SUCCESS(rc))
            rc = rc2;
        if (RT_SUCCESS(rc))
        {
            /* wait for the process to complete */
            RTPROCSTATUS Status;
            rc = RTProcWait(Args.Process, 0, &Status);
            if (RT_SUCCESS(rc))
            {
                if (    Status.enmReason == RTPROCEXITREASON_NORMAL
                    &&  Status.iStatus == 42)
                    RTPrintf("tstRTWait: Success!\n");
                else
                {
                    rc = VERR_GENERAL_FAILURE;
                    if (Status.enmReason != RTPROCEXITREASON_NORMAL)
                        RTPrintf("tstRTWait: Expected exit reason RTPROCEXITREASON_NORMAL, got %d.\n", Status.enmReason);
                    else
                        RTPrintf("tstRTWait: Expected exit status 42, got %d.\n", Status.iStatus);
                }
            }
            else
                RTPrintf("tstRTWait: RTProcWait failed with rc=%Rrc!\n", rc);
        }
        else
            RTPrintf("tstRTWait: RTThreadWait or SpawnerThread failed with rc=%Rrc!\n", rc);
    }
    else
        RTPrintf("tstRTWait: RTThreadCreate failed with rc=%Rrc!\n", rc);

    return RT_SUCCESS(rc) ? 0 : 1;
}

static void test1(void)
{
    RTTestSub(g_hTest, "Interrupt RTThreadSleep");
    RTTHREAD hThread[16];
    RTMSINTERVAL msWait = 1000;
    for (unsigned i = 0; i < RT_ELEMENTS(hThread); i++)
    {
        RTTESTI_CHECK_RC_RETV(RTThreadCreate(&hThread[i], testThread, NULL, 0, RTTHREADTYPE_DEFAULT,
                              RTTHREADFLAGS_WAITABLE, "test"), VINF_SUCCESS);
    }
    RTThreadSleep(500);
    RTPrintf("Waiting for %dms ...\n", msWait);
    RTThreadSleep(msWait);
    for (unsigned i = 0; i < RT_ELEMENTS(hThread); i++)
        RTTESTI_CHECK_RC(RTThreadWait(hThread[i], RT_INDEFINITE_WAIT, NULL), VINF_SUCCESS);

    RTPrintf("sum kernel = %lldms, sum user = %lldms\n", g_kernel, g_user);
}