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QUdpSocket: avoid infinite read notifier blocking

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There was a small amount of time between the last readDatagram() call
and disabling a read notifier in case the socket had a pending
datagram. If a new datagram arrived in this period, this qualified as
absence of a datagram reader. Do not change the read notifier state
because it is disabled on canReadNotification() entry and always enabled
by the datagram reader.

Thanks to Peter Seiderer, who investigated the same: "Querying
hasPendingDatagrams() for enabling/disabling setReadNotificationEnabled()
is racy (a new datagram could arrive after readDatagam() is called and
before hasPendingDatagrams() is checked). But for unbuffered sockets the
ReadNotification is already disabled before the readReady signal is
emitted and should be re-enabled when calling read() or readDatagram()
from the user."

However, this patch does not completely solve the problem under Windows,
as the socket notifier may emit spurious notifications.

Task-number: QTBUG-46552
Change-Id: If7295d53ae2c788c39e86303502f38135c4d6180
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Alex Trotsenko 2015-02-11 20:02:07 +02:00
parent d75505facc
commit 378e26dd14
2 changed files with 57 additions and 9 deletions
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12
src/network/socket/qabstractsocket.cpp
View File

@ -739,15 +739,9 @@ bool QAbstractSocketPrivate::canReadNotification()
return true;
}
if (socketEngine) {
// turn the socket engine off if we've either:
// - got pending datagrams
// - reached the buffer size limit
if (isBuffered)
socketEngine->setReadNotificationEnabled(readBufferMaxSize == 0 || readBufferMaxSize > q->bytesAvailable());
else if (socketType != QAbstractSocket::TcpSocket)
socketEngine->setReadNotificationEnabled(!socketEngine->hasPendingDatagrams());
}
// turn the socket engine off if we've reached the buffer size limit
if (socketEngine && isBuffered)
socketEngine->setReadNotificationEnabled(readBufferMaxSize == 0 || readBufferMaxSize > q->bytesAvailable());
// reset the read socket notifier state if we reentered inside the
// readyRead() connected slot.

54
tests/auto/network/socket/qudpsocket/tst_qudpsocket.cpp
View File

@ -116,10 +116,12 @@ private slots:
void linkLocalIPv4();
void readyRead();
void readyReadForEmptyDatagram();
void asyncReadDatagram();
protected slots:
void empty_readyReadSlot();
void empty_connectedSlot();
void async_readDatagramSlot();
private:
#ifndef QT_NO_BEARERMANAGEMENT
@ -127,6 +129,8 @@ private:
QNetworkConfiguration networkConfiguration;
QSharedPointer<QNetworkSession> networkSession;
#endif
QUdpSocket *m_asyncSender;
QUdpSocket *m_asyncReceiver;
};
static QHostAddress makeNonAny(const QHostAddress &address, QHostAddress::SpecialAddress preferForAny = QHostAddress::LocalHost)
@ -1671,5 +1675,55 @@ void tst_QUdpSocket::readyReadForEmptyDatagram()
QCOMPARE(receiver.readDatagram(buf, sizeof buf), qint64(0));
}
void tst_QUdpSocket::async_readDatagramSlot()
{
char buf[1];
QVERIFY(m_asyncReceiver->hasPendingDatagrams());
QCOMPARE(m_asyncReceiver->pendingDatagramSize(), qint64(1));
QCOMPARE(m_asyncReceiver->bytesAvailable(), qint64(1));
QCOMPARE(m_asyncReceiver->readDatagram(buf, sizeof(buf)), qint64(1));
if (buf[0] == '2') {
QTestEventLoop::instance().exitLoop();
return;
}
m_asyncSender->writeDatagram("2", makeNonAny(m_asyncReceiver->localAddress()), m_asyncReceiver->localPort());
// wait a little to ensure that the datagram we've just sent
// will be delivered on receiver side.
QTest::qSleep(100);
}
void tst_QUdpSocket::asyncReadDatagram()
{
QFETCH_GLOBAL(bool, setProxy);
if (setProxy)
return;
m_asyncSender = new QUdpSocket;
m_asyncReceiver = new QUdpSocket;
#ifdef FORCE_SESSION
m_asyncSender->setProperty("_q_networksession", QVariant::fromValue(networkSession));
m_asyncReceiver->setProperty("_q_networksession", QVariant::fromValue(networkSession));
#endif
QVERIFY(m_asyncReceiver->bind(QHostAddress(QHostAddress::AnyIPv4), 0));
quint16 port = m_asyncReceiver->localPort();
QVERIFY(port != 0);
QSignalSpy spy(m_asyncReceiver, SIGNAL(readyRead()));
connect(m_asyncReceiver, SIGNAL(readyRead()), SLOT(async_readDatagramSlot()));
m_asyncSender->writeDatagram("1", makeNonAny(m_asyncReceiver->localAddress()), port);
QTestEventLoop::instance().enterLoop(1);
QVERIFY(!QTestEventLoop::instance().timeout());
QCOMPARE(spy.count(), 2);
delete m_asyncSender;
delete m_asyncReceiver;
}
QTEST_MAIN(tst_QUdpSocket)
#include "tst_qudpsocket.moc"