path: root/src/corelib/kernel/qeventdispatcher_unix.cpp

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**
** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (qt-info@nokia.com)
**
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** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
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** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
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**
** In addition, as a special exception, Nokia gives you certain additional
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**
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****************************************************************************/

#include "qplatformdefs.h"

#include "qcoreapplication.h"
#include "qpair.h"
#include "qsocketnotifier.h"
#include "qthread.h"
#include "qelapsedtimer.h"

#include "qeventdispatcher_unix_p.h"
#include <private/qthread_p.h>
#include <private/qcoreapplication_p.h>
#include <private/qcore_unix_p.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

// VxWorks doesn't correctly set the _POSIX_... options
#if defined(Q_OS_VXWORKS)
#  if defined(_POSIX_MONOTONIC_CLOCK) && (_POSIX_MONOTONIC_CLOCK <= 0)
#    undef _POSIX_MONOTONIC_CLOCK
#    define _POSIX_MONOTONIC_CLOCK 1
#  endif
#  include <pipeDrv.h>
#  include <selectLib.h>
#endif

#if (_POSIX_MONOTONIC_CLOCK-0 <= 0) || defined(QT_BOOTSTRAPPED)
#  include <sys/times.h>
#endif

QT_BEGIN_NAMESPACE

Q_CORE_EXPORT bool qt_disable_lowpriority_timers=false;

/*****************************************************************************
 UNIX signal handling
 *****************************************************************************/

static sig_atomic_t signal_received;
static sig_atomic_t signals_fired[NSIG];

static void signalHandler(int sig)
{
    signals_fired[sig] = 1;
    signal_received = 1;
}


#if defined(Q_OS_INTEGRITY) || defined(Q_OS_VXWORKS)
static void initThreadPipeFD(int fd)
{
    int ret = fcntl(fd, F_SETFD, FD_CLOEXEC);
    if (ret == -1)
        perror("QEventDispatcherUNIXPrivate: Unable to init thread pipe");

    int flags = fcntl(fd, F_GETFL);
    if (flags == -1)
        perror("QEventDispatcherUNIXPrivate: Unable to get flags on thread pipe");

    ret = fcntl(fd, F_SETFL, flags | O_NONBLOCK);
    if (ret == -1)
        perror("QEventDispatcherUNIXPrivate: Unable to set flags on thread pipe");
}
#endif

QEventDispatcherUNIXPrivate::QEventDispatcherUNIXPrivate()
{
    extern Qt::HANDLE qt_application_thread_id;
    mainThread = (QThread::currentThreadId() == qt_application_thread_id);
    bool pipefail = false;

    // initialize the common parts of the event loop
#if defined(Q_OS_INTEGRITY)
    // INTEGRITY doesn't like a "select" on pipes, so use socketpair instead
    if (socketpair(AF_INET, SOCK_STREAM, PF_INET, thread_pipe) == -1) {
        perror("QEventDispatcherUNIXPrivate(): Unable to create socket pair");
        pipefail = true;
    } else {
        initThreadPipeFD(thread_pipe[0]);
        initThreadPipeFD(thread_pipe[1]);
    }
#elif defined(Q_OS_VXWORKS)
    char name[20];
    qsnprintf(name, sizeof(name), "/pipe/qt_%08x", int(taskIdCurrent));

    // make sure there is no pipe with this name
    pipeDevDelete(name, true);
    // create the pipe
    if (pipeDevCreate(name, 128 /*maxMsg*/, 1 /*maxLength*/) != OK) {
        perror("QEventDispatcherUNIXPrivate(): Unable to create thread pipe device");
        pipefail = true;
    } else {
        if ((thread_pipe[0] = open(name, O_RDWR, 0)) < 0) {
            perror("QEventDispatcherUNIXPrivate(): Unable to create thread pipe");
            pipefail = true;
        } else {
            initThreadPipeFD(thread_pipe[0]);
            thread_pipe[1] = thread_pipe[0];
        }
    }
#else
    if (qt_safe_pipe(thread_pipe, O_NONBLOCK) == -1) {
        perror("QEventDispatcherUNIXPrivate(): Unable to create thread pipe");
        pipefail = true;
    }
#endif

    if (pipefail)
        qFatal("QEventDispatcherUNIXPrivate(): Can not continue without a thread pipe");

    sn_highest = -1;

    interrupt = false;
}

QEventDispatcherUNIXPrivate::~QEventDispatcherUNIXPrivate()
{
#if defined(Q_OS_VXWORKS)
    close(thread_pipe[0]);

    char name[20];
    qsnprintf(name, sizeof(name), "/pipe/qt_%08x", int(taskIdCurrent));

    pipeDevDelete(name, true);
#else
    // cleanup the common parts of the event loop
    close(thread_pipe[0]);
    close(thread_pipe[1]);
#endif

    // cleanup timers
    qDeleteAll(timerList);
}

int QEventDispatcherUNIXPrivate::doSelect(QEventLoop::ProcessEventsFlags flags, timeval *timeout)
{
    Q_Q(QEventDispatcherUNIX);

    // needed in QEventDispatcherUNIX::select()
    timerList.updateCurrentTime();

    int nsel;
    do {
        if (mainThread) {
            while (signal_received) {
                signal_received = 0;
                for (int i = 0; i < NSIG; ++i) {
                    if (signals_fired[i]) {
                        signals_fired[i] = 0;
                        emit QCoreApplication::instance()->unixSignal(i);
                    }
                }
            }
        }

        // Process timers and socket notifiers - the common UNIX stuff
        int highest = 0;
        if (! (flags & QEventLoop::ExcludeSocketNotifiers) && (sn_highest >= 0)) {
            // return the highest fd we can wait for input on
                sn_vec[0].select_fds = sn_vec[0].enabled_fds;
                sn_vec[1].select_fds = sn_vec[1].enabled_fds;
                sn_vec[2].select_fds = sn_vec[2].enabled_fds;
            highest = sn_highest;
        } else {
            FD_ZERO(&sn_vec[0].select_fds);
            FD_ZERO(&sn_vec[1].select_fds);
            FD_ZERO(&sn_vec[2].select_fds);
        }

        FD_SET(thread_pipe[0], &sn_vec[0].select_fds);
        highest = qMax(highest, thread_pipe[0]);

        nsel = q->select(highest + 1,
                         &sn_vec[0].select_fds,
                         &sn_vec[1].select_fds,
                         &sn_vec[2].select_fds,
                         timeout);
    } while (nsel == -1 && (errno == EINTR || errno == EAGAIN));

    if (nsel == -1) {
        if (errno == EBADF) {
            // it seems a socket notifier has a bad fd... find out
            // which one it is and disable it
            fd_set fdset;
            timeval tm;
            tm.tv_sec = tm.tv_usec = 0l;

            for (int type = 0; type < 3; ++type) {
                QSockNotType::List &list = sn_vec[type].list;
                if (list.size() == 0)
                    continue;

                for (int i = 0; i < list.size(); ++i) {
                    QSockNot *sn = list[i];

                    FD_ZERO(&fdset);
                    FD_SET(sn->fd, &fdset);

                    int ret = -1;
                    do {
                        switch (type) {
                        case 0: // read
                            ret = select(sn->fd + 1, &fdset, 0, 0, &tm);
                            break;
                        case 1: // write
                            ret = select(sn->fd + 1, 0, &fdset, 0, &tm);
                            break;
                        case 2: // except
                            ret = select(sn->fd + 1, 0, 0, &fdset, &tm);
                            break;
                        }
                    } while (ret == -1 && (errno == EINTR || errno == EAGAIN));

                    if (ret == -1 && errno == EBADF) {
                        // disable the invalid socket notifier
                        static const char *t[] = { "Read", "Write", "Exception" };
                        qWarning("QSocketNotifier: Invalid socket %d and type '%s', disabling...",
                                 sn->fd, t[type]);
                        sn->obj->setEnabled(false);
                    }
                }
            }
        } else {
            // EINVAL... shouldn't happen, so let's complain to stderr
            // and hope someone sends us a bug report
            perror("select");
        }
    }

    // some other thread woke us up... consume the data on the thread pipe so that
    // select doesn't immediately return next time
    int nevents = 0;
    if (nsel > 0 && FD_ISSET(thread_pipe[0], &sn_vec[0].select_fds)) {
#if defined(Q_OS_VXWORKS)
        char c[16];
        ::read(thread_pipe[0], c, sizeof(c));
        ::ioctl(thread_pipe[0], FIOFLUSH, 0);
#else
        char c[16];
        while (::read(thread_pipe[0], c, sizeof(c)) > 0)
            ;
#endif
        if (!wakeUps.testAndSetRelease(1, 0)) {
            // hopefully, this is dead code
            qWarning("QEventDispatcherUNIX: internal error, wakeUps.testAndSetRelease(1, 0) failed!");
        }
        ++nevents;
    }

    // activate socket notifiers
    if (! (flags & QEventLoop::ExcludeSocketNotifiers) && nsel > 0 && sn_highest >= 0) {
        // if select says data is ready on any socket, then set the socket notifier
        // to pending
        for (int i=0; i<3; i++) {
            QSockNotType::List &list = sn_vec[i].list;
            for (int j = 0; j < list.size(); ++j) {
                QSockNot *sn = list[j];
                if (FD_ISSET(sn->fd, &sn_vec[i].select_fds))
                    q->setSocketNotifierPending(sn->obj);
            }
        }
    }
    return (nevents + q->activateSocketNotifiers());
}

/*
 * Internal functions for manipulating timer data structures.  The
 * timerBitVec array is used for keeping track of timer identifiers.
 */

QTimerInfoList::QTimerInfoList()
{
#if (_POSIX_MONOTONIC_CLOCK-0 <= 0) && !defined(Q_OS_MAC)
    if (!QElapsedTimer::isMonotonic()) {
        // not using monotonic timers, initialize the timeChanged() machinery
        previousTime = qt_gettime();

        tms unused;
        previousTicks = times(&unused);

        ticksPerSecond = sysconf(_SC_CLK_TCK);
        msPerTick = 1000/ticksPerSecond;
    } else {
        // detected monotonic timers
        previousTime.tv_sec = previousTime.tv_usec = 0;
        previousTicks = 0;
        ticksPerSecond = 0;
        msPerTick = 0;
    }
#endif

    firstTimerInfo = 0;
}

timeval QTimerInfoList::updateCurrentTime()
{
    return (currentTime = qt_gettime());
}

#if ((_POSIX_MONOTONIC_CLOCK-0 <= 0) && !defined(Q_OS_MAC)) || defined(QT_BOOTSTRAPPED)

template <>
timeval qAbs(const timeval &t)
{
    timeval tmp = t;
    if (tmp.tv_sec < 0) {
        tmp.tv_sec = -tmp.tv_sec - 1;
        tmp.tv_usec -= 1000000;
    }
    if (tmp.tv_sec == 0 && tmp.tv_usec < 0) {
        tmp.tv_usec = -tmp.tv_usec;
    }
    return normalizedTimeval(tmp);
}

/*
  Returns true if the real time clock has changed by more than 10%
  relative to the processor time since the last time this function was
  called. This presumably means that the system time has been changed.

  If /a delta is nonzero, delta is set to our best guess at how much the system clock was changed.
*/
bool QTimerInfoList::timeChanged(timeval *delta)
{
    struct tms unused;
    clock_t currentTicks = times(&unused);

    clock_t elapsedTicks = currentTicks - previousTicks;
    timeval elapsedTime = currentTime - previousTime;

    timeval elapsedTimeTicks;
    elapsedTimeTicks.tv_sec = elapsedTicks / ticksPerSecond;
    elapsedTimeTicks.tv_usec = (((elapsedTicks * 1000) / ticksPerSecond) % 1000) * 1000;

    timeval dummy;
    if (!delta)
        delta = &dummy;
    *delta = elapsedTime - elapsedTimeTicks;

    previousTicks = currentTicks;
    previousTime = currentTime;

    // If tick drift is more than 10% off compared to realtime, we assume that the clock has
    // been set. Of course, we have to allow for the tick granularity as well.
    timeval tickGranularity;
    tickGranularity.tv_sec = 0;
    tickGranularity.tv_usec = msPerTick * 1000;
    return elapsedTimeTicks < ((qAbs(*delta) - tickGranularity) * 10);
}

void QTimerInfoList::repairTimersIfNeeded()
{
    if (QElapsedTimer::isMonotonic())
        return;
    timeval delta;
    if (timeChanged(&delta))
        timerRepair(delta);
}

#else // !(_POSIX_MONOTONIC_CLOCK-0 <= 0) && !defined(QT_BOOTSTRAPPED)

void QTimerInfoList::repairTimersIfNeeded()
{
}

#endif

/*
  insert timer info into list
*/
void QTimerInfoList::timerInsert(QTimerInfo *ti)
{
    int index = size();
    while (index--) {
        register const QTimerInfo * const t = at(index);
        if (!(ti->timeout < t->timeout))
            break;
    }
    insert(index+1, ti);
}

/*
  repair broken timer
*/
void QTimerInfoList::timerRepair(const timeval &diff)
{
    // repair all timers
    for (int i = 0; i < size(); ++i) {
        register QTimerInfo *t = at(i);
        t->timeout = t->timeout + diff;
    }
}

/*
  Returns the time to wait for the next timer, or null if no timers
  are waiting.
*/
bool QTimerInfoList::timerWait(timeval &tm)
{
    timeval currentTime = updateCurrentTime();
    repairTimersIfNeeded();

    // Find first waiting timer not already active
    QTimerInfo *t = 0;
    for (QTimerInfoList::const_iterator it = constBegin(); it != constEnd(); ++it) {
        if (!(*it)->activateRef) {
            t = *it;
            break;
        }
    }

    if (!t)
      return false;

    if (currentTime < t->timeout) {
        // time to wait
        tm = t->timeout - currentTime;
    } else {
        // no time to wait
        tm.tv_sec  = 0;
        tm.tv_usec = 0;
    }

    return true;
}

void QTimerInfoList::registerTimer(int timerId, int interval, QObject *object)
{
    QTimerInfo *t = new QTimerInfo;
    t->id = timerId;
    t->interval.tv_sec  = interval / 1000;
    t->interval.tv_usec = (interval % 1000) * 1000;
    t->timeout = updateCurrentTime() + t->interval;
    t->obj = object;
    t->activateRef = 0;

    timerInsert(t);
}

bool QTimerInfoList::unregisterTimer(int timerId)
{
    // set timer inactive
    for (int i = 0; i < count(); ++i) {
        register QTimerInfo *t = at(i);
        if (t->id == timerId) {
            // found it
            removeAt(i);
            if (t == firstTimerInfo)
                firstTimerInfo = 0;
            if (t->activateRef)
                *(t->activateRef) = 0;

            // release the timer id
            if (!QObjectPrivate::get(t->obj)->inThreadChangeEvent)
                QAbstractEventDispatcherPrivate::releaseTimerId(timerId);

            delete t;
            return true;
        }
    }
    // id not found
    return false;
}

bool QTimerInfoList::unregisterTimers(QObject *object)
{
    if (isEmpty())
        return false;
    for (int i = 0; i < count(); ++i) {
        register QTimerInfo *t = at(i);
        if (t->obj == object) {
            // object found
            removeAt(i);
            if (t == firstTimerInfo)
                firstTimerInfo = 0;
            if (t->activateRef)
                *(t->activateRef) = 0;

            // release the timer id
            if (!QObjectPrivate::get(t->obj)->inThreadChangeEvent)
                QAbstractEventDispatcherPrivate::releaseTimerId(t->id);

            delete t;
            // move back one so that we don't skip the new current item
            --i;
        }
    }
    return true;
}

QList<QPair<int, int> > QTimerInfoList::registeredTimers(QObject *object) const
{
    QList<QPair<int, int> > list;
    for (int i = 0; i < count(); ++i) {
        register const QTimerInfo * const t = at(i);
        if (t->obj == object)
            list << QPair<int, int>(t->id, t->interval.tv_sec * 1000 + t->interval.tv_usec / 1000);
    }
    return list;
}

/*
    Activate pending timers, returning how many where activated.
*/
int QTimerInfoList::activateTimers()
{
    if (qt_disable_lowpriority_timers || isEmpty())
        return 0; // nothing to do

    int n_act = 0, maxCount = 0;
    firstTimerInfo = 0;

    timeval currentTime = updateCurrentTime();
    repairTimersIfNeeded();


    // Find out how many timer have expired
    for (QTimerInfoList::const_iterator it = constBegin(); it != constEnd(); ++it) {
        if (currentTime < (*it)->timeout)
            break;
        maxCount++;
    }

    //fire the timers.
    while (maxCount--) {
        if (isEmpty())
            break;

        QTimerInfo *currentTimerInfo = first();
        if (currentTime < currentTimerInfo->timeout)
            break; // no timer has expired

        if (!firstTimerInfo) {
            firstTimerInfo = currentTimerInfo;
        } else if (firstTimerInfo == currentTimerInfo) {
            // avoid sending the same timer multiple times
            break;
        } else if (currentTimerInfo->interval <  firstTimerInfo->interval
                   || currentTimerInfo->interval == firstTimerInfo->interval) {
            firstTimerInfo = currentTimerInfo;
        }

        // remove from list
        removeFirst();

        // determine next timeout time
        currentTimerInfo->timeout += currentTimerInfo->interval;
        if (currentTimerInfo->timeout < currentTime)
            currentTimerInfo->timeout = currentTime + currentTimerInfo->interval;

        // reinsert timer
        timerInsert(currentTimerInfo);
        if (currentTimerInfo->interval.tv_usec > 0 || currentTimerInfo->interval.tv_sec > 0)
            n_act++;

        if (!currentTimerInfo->activateRef) {
            // send event, but don't allow it to recurse
            currentTimerInfo->activateRef = &currentTimerInfo;

            QTimerEvent e(currentTimerInfo->id);
            QCoreApplication::sendEvent(currentTimerInfo->obj, &e);

            if (currentTimerInfo)
                currentTimerInfo->activateRef = 0;
        }
    }

    firstTimerInfo = 0;
    return n_act;
}

QEventDispatcherUNIX::QEventDispatcherUNIX(QObject *parent)
    : QAbstractEventDispatcher(*new QEventDispatcherUNIXPrivate, parent)
{ }

QEventDispatcherUNIX::QEventDispatcherUNIX(QEventDispatcherUNIXPrivate &dd, QObject *parent)
    : QAbstractEventDispatcher(dd, parent)
{ }

QEventDispatcherUNIX::~QEventDispatcherUNIX()
{
    Q_D(QEventDispatcherUNIX);
    d->threadData->eventDispatcher = 0;
}

int QEventDispatcherUNIX::select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
                                 timeval *timeout)
{
    return qt_safe_select(nfds, readfds, writefds, exceptfds, timeout);
}

/*!
    \internal
*/
void QEventDispatcherUNIX::registerTimer(int timerId, int interval, QObject *obj)
{
#ifndef QT_NO_DEBUG
    if (timerId < 1 || interval < 0 || !obj) {
        qWarning("QEventDispatcherUNIX::registerTimer: invalid arguments");
        return;
    } else if (obj->thread() != thread() || thread() != QThread::currentThread()) {
        qWarning("QObject::startTimer: timers cannot be started from another thread");
        return;
    }
#endif

    Q_D(QEventDispatcherUNIX);
    d->timerList.registerTimer(timerId, interval, obj);
}

/*!
    \internal
*/
bool QEventDispatcherUNIX::unregisterTimer(int timerId)
{
#ifndef QT_NO_DEBUG
    if (timerId < 1) {
        qWarning("QEventDispatcherUNIX::unregisterTimer: invalid argument");
        return false;
    } else if (thread() != QThread::currentThread()) {
        qWarning("QObject::killTimer: timers cannot be stopped from another thread");
        return false;
    }
#endif

    Q_D(QEventDispatcherUNIX);
    return d->timerList.unregisterTimer(timerId);
}

/*!
    \internal
*/
bool QEventDispatcherUNIX::unregisterTimers(QObject *object)
{
#ifndef QT_NO_DEBUG
    if (!object) {
        qWarning("QEventDispatcherUNIX::unregisterTimers: invalid argument");
        return false;
    } else if (object->thread() != thread() || thread() != QThread::currentThread()) {
        qWarning("QObject::killTimers: timers cannot be stopped from another thread");
        return false;
    }
#endif

    Q_D(QEventDispatcherUNIX);
    return d->timerList.unregisterTimers(object);
}

QList<QEventDispatcherUNIX::TimerInfo>
QEventDispatcherUNIX::registeredTimers(QObject *object) const
{
    if (!object) {
        qWarning("QEventDispatcherUNIX:registeredTimers: invalid argument");
        return QList<TimerInfo>();
    }

    Q_D(const QEventDispatcherUNIX);
    return d->timerList.registeredTimers(object);
}

/*****************************************************************************
 Socket notifier type
 *****************************************************************************/
QSockNotType::QSockNotType()
{
    FD_ZERO(&select_fds);
    FD_ZERO(&enabled_fds);
    FD_ZERO(&pending_fds);
}

QSockNotType::~QSockNotType()
{
    for (int i = 0; i < list.size(); ++i)
        delete list[i];
}

/*****************************************************************************
 QEventDispatcher implementations for UNIX
 *****************************************************************************/

void QEventDispatcherUNIX::registerSocketNotifier(QSocketNotifier *notifier)
{
    Q_ASSERT(notifier);
    int sockfd = notifier->socket();
    int type = notifier->type();
#ifndef QT_NO_DEBUG
    if (sockfd < 0
        || unsigned(sockfd) >= FD_SETSIZE) {
        qWarning("QSocketNotifier: Internal error");
        return;
    } else if (notifier->thread() != thread()
               || thread() != QThread::currentThread()) {
        qWarning("QSocketNotifier: socket notifiers cannot be enabled from another thread");
        return;
    }
#endif

    Q_D(QEventDispatcherUNIX);
    QSockNotType::List &list = d->sn_vec[type].list;
    fd_set *fds  = &d->sn_vec[type].enabled_fds;
    QSockNot *sn;

    sn = new QSockNot;
    sn->obj = notifier;
    sn->fd = sockfd;
    sn->queue = &d->sn_vec[type].pending_fds;

    int i;
    for (i = 0; i < list.size(); ++i) {
        QSockNot *p = list[i];
        if (p->fd < sockfd)
            break;
        if (p->fd == sockfd) {
            static const char *t[] = { "Read", "Write", "Exception" };
            qWarning("QSocketNotifier: Multiple socket notifiers for "
                      "same socket %d and type %s", sockfd, t[type]);
        }
    }
    list.insert(i, sn);

    FD_SET(sockfd, fds);
    d->sn_highest = qMax(d->sn_highest, sockfd);
}

void QEventDispatcherUNIX::unregisterSocketNotifier(QSocketNotifier *notifier)
{
    Q_ASSERT(notifier);
    int sockfd = notifier->socket();
    int type = notifier->type();
#ifndef QT_NO_DEBUG
    if (sockfd < 0
        || unsigned(sockfd) >= FD_SETSIZE) {
        qWarning("QSocketNotifier: Internal error");
        return;
    } else if (notifier->thread() != thread()
               || thread() != QThread::currentThread()) {
        qWarning("QSocketNotifier: socket notifiers cannot be disabled from another thread");
        return;
    }
#endif

    Q_D(QEventDispatcherUNIX);
    QSockNotType::List &list = d->sn_vec[type].list;
    fd_set *fds  =  &d->sn_vec[type].enabled_fds;
    QSockNot *sn = 0;
    int i;
    for (i = 0; i < list.size(); ++i) {
        sn = list[i];
        if(sn->obj == notifier && sn->fd == sockfd)
            break;
    }
    if (i == list.size()) // not found
        return;

    FD_CLR(sockfd, fds);                        // clear fd bit
    FD_CLR(sockfd, sn->queue);
    d->sn_pending_list.removeAll(sn);                // remove from activation list
    list.removeAt(i);                                // remove notifier found above
    delete sn;

    if (d->sn_highest == sockfd) {                // find highest fd
        d->sn_highest = -1;
        for (int i=0; i<3; i++) {
            if (!d->sn_vec[i].list.isEmpty())
                d->sn_highest = qMax(d->sn_highest,  // list is fd-sorted
                                     d->sn_vec[i].list[0]->fd);
        }
    }
}

void QEventDispatcherUNIX::setSocketNotifierPending(QSocketNotifier *notifier)
{
    Q_ASSERT(notifier);
    int sockfd = notifier->socket();
    int type = notifier->type();
#ifndef QT_NO_DEBUG
    if (sockfd < 0
        || unsigned(sockfd) >= FD_SETSIZE) {
        qWarning("QSocketNotifier: Internal error");
        return;
    }
    Q_ASSERT(notifier->thread() == thread() && thread() == QThread::currentThread());
#endif

    Q_D(QEventDispatcherUNIX);
    QSockNotType::List &list = d->sn_vec[type].list;
    QSockNot *sn = 0;
    int i;
    for (i = 0; i < list.size(); ++i) {
        sn = list[i];
        if(sn->obj == notifier && sn->fd == sockfd)
            break;
    }
    if (i == list.size()) // not found
        return;

    // We choose a random activation order to be more fair under high load.
    // If a constant order is used and a peer early in the list can
    // saturate the IO, it might grab our attention completely.
    // Also, if we're using a straight list, the callback routines may
    // delete other entries from the list before those other entries are
    // processed.
    if (! FD_ISSET(sn->fd, sn->queue)) {
        if (d->sn_pending_list.isEmpty()) {
            d->sn_pending_list.append(sn);
        } else {
            d->sn_pending_list.insert((qrand() & 0xff) %
                                      (d->sn_pending_list.size()+1), sn);
        }
        FD_SET(sn->fd, sn->queue);
    }
}

int QEventDispatcherUNIX::activateTimers()
{
    Q_ASSERT(thread() == QThread::currentThread());
    Q_D(QEventDispatcherUNIX);
    return d->timerList.activateTimers();
}

int QEventDispatcherUNIX::activateSocketNotifiers()
{
    Q_D(QEventDispatcherUNIX);
    if (d->sn_pending_list.isEmpty())
        return 0;

    // activate entries
    int n_act = 0;
    QEvent event(QEvent::SockAct);
    while (!d->sn_pending_list.isEmpty()) {
        QSockNot *sn = d->sn_pending_list.takeFirst();
        if (FD_ISSET(sn->fd, sn->queue)) {
            FD_CLR(sn->fd, sn->queue);
            QCoreApplication::sendEvent(sn->obj, &event);
            ++n_act;
        }
    }
    return n_act;
}

bool QEventDispatcherUNIX::processEvents(QEventLoop::ProcessEventsFlags flags)
{
    Q_D(QEventDispatcherUNIX);
    d->interrupt = false;

    // we are awake, broadcast it
    emit awake();
    QCoreApplicationPrivate::sendPostedEvents(0, 0, d->threadData);

    int nevents = 0;
    const bool canWait = (d->threadData->canWait
                          && !d->interrupt
                          && (flags & QEventLoop::WaitForMoreEvents));

    if (canWait)
        emit aboutToBlock();

    if (!d->interrupt) {
        // return the maximum time we can wait for an event.
        timeval *tm = 0;
        timeval wait_tm = { 0l, 0l };
        if (!(flags & QEventLoop::X11ExcludeTimers)) {
            if (d->timerList.timerWait(wait_tm))
                tm = &wait_tm;
        }

        if (!canWait) {
            if (!tm)
                tm = &wait_tm;

            // no time to wait
            tm->tv_sec  = 0l;
            tm->tv_usec = 0l;
        }

        nevents = d->doSelect(flags, tm);

        // activate timers
        if (! (flags & QEventLoop::X11ExcludeTimers)) {
            nevents += activateTimers();
        }
    }
    // return true if we handled events, false otherwise
    return (nevents > 0);
}

bool QEventDispatcherUNIX::hasPendingEvents()
{
    extern uint qGlobalPostedEventsCount(); // from qapplication.cpp
    return qGlobalPostedEventsCount();
}

void QEventDispatcherUNIX::wakeUp()
{
    Q_D(QEventDispatcherUNIX);
    if (d->wakeUps.testAndSetAcquire(0, 1)) {
        char c = 0;
        qt_safe_write( d->thread_pipe[1], &c, 1 );
    }
}

void QEventDispatcherUNIX::interrupt()
{
    Q_D(QEventDispatcherUNIX);
    d->interrupt = true;
    wakeUp();
}

void QEventDispatcherUNIX::flush()
{ }




void QCoreApplication::watchUnixSignal(int sig, bool watch)
{
    if (sig < NSIG) {
        struct sigaction sa;
        sigemptyset(&(sa.sa_mask));
        sa.sa_flags = 0;
        if (watch)
            sa.sa_handler = signalHandler;
        else
            sa.sa_handler = SIG_DFL;
        sigaction(sig, &sa, 0);
    }
}

QT_END_NAMESPACE