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

[Dawit Alemayehu]

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http://git.reviewboard.kde.org/r/102238/
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(Updated Aug. 18, 2011, 9:45 p.m.)


Review request for kdelibs, David Faure and Thiago Macieira.


Changes
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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.


Summary
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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 https://git.reviewboard.kde.org/r/102179/. 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)
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  kio/kio/hostinfo.cpp 344b1d8 

Diff: http://git.reviewboard.kde.org/r/102238/diff


Testing
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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;
    t.start();
    qDebug() << KIO::HostInfo::lookupHost("www.kde.org", 0).addresses();
    qDebug() << "Time:" << t.elapsed() << "ms";
}


Thanks,

Dawit

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