Review Request: Avoid terminating a QThread in kio/kio/hostinfo.cpp

Dawit Alemayehu adawit at
Wed Aug 17 06:40:51 BST 2011

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(Updated Aug. 17, 2011, 5:40 a.m.)

Review request for kdelibs, David Faure and Thiago Macieira.


- Modified the last patch so that the lookup thread is recycled and reused instead of being discarded.
- Moved the timeout based name lookup code into an overloaded function in HostInfoAgentPrivate.
- Changed keywords "signals" -> "Q_SIGNALS" and "slots" -> "Q_SLOTS".

Summary (updated)

The attached patch is an alternate approach to address the issue of crashes that arise from terminating an active thread than the one proposed at With this patch the function "QHostInfo::lookupHost(QString, int)" avoids the use of QThread::terminate with the following fairly simple changes:

- Connect its finished signal to its parent deleteLater slot in the ctor so that the thread is automatically deleted later.
- Store the looked up DNS info in  the global cache to avoid unnecessary queries for the same request.
- Check for cached DNS information and avoid doing reverse look ups before resorting to performing DNS queries in a separate thread.

Diffs (updated)

  kio/kio/hostinfo.cpp 344b1d8 


Testing (updated)

Tested with the following code based on Albert's post. 

#include "hostinfo_p.h"
#include <QtGui/QApplication>
#include <QtCore/QElapsedTimer>
#include <QtNetwork/QHostInfo>

int main(int a, char **b)
    QApplication app(a, b);
    QElapsedTimer t;
    qDebug() << KIO::HostInfo::lookupHost("", 0).addresses();
    qDebug() << "Time:" << t.elapsed() << "ms";



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