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

Dawit Alemayehu adawit at
Thu Aug 18 22:45:08 BST 2011

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(Updated Aug. 18, 2011, 9:45 p.m.)

Review request for kdelibs, David Faure and Thiago Macieira.


Removed the signal/slot connection in NameLookThread's ctor. It is no longer needed since the thread will be reused and only gotten rid of when its parent class is destroyed.


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 



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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