Review Request 121134: make KGlobal reference counting threadsafe
René J.V. Bertin
rjvbertin at gmail.com
Sun Nov 16 19:13:05 GMT 2014
> On Nov. 16, 2014, 8:05 p.m., Pino Toscano wrote:
> > kdecore/kernel/kglobal.cpp, lines 323-324
> > <https://git.reviewboard.kde.org/r/121134/diff/3/?file=328834#file328834line323>
> >
> > QAtomicInt is not a POD, so it is not safe to be used this way. You rather need to use the semi-private QBasicAtomicInt, which is not a POD, like:
> >
> > static QBasicAtomicInt s_allowQuit = Q_BASIC_ATOMIC_INITIALIZER(0);
> >
> > The API should be the same.
Personal education: what does POD stand for in this context?
- René J.V.
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https://git.reviewboard.kde.org/r/121134/#review70463
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On Nov. 16, 2014, 8:01 p.m., René J.V. Bertin wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/121134/
> -----------------------------------------------------------
>
> (Updated Nov. 16, 2014, 8:01 p.m.)
>
>
> Review request for KDE Software on Mac OS X and kdelibs.
>
>
> Repository: kdelibs
>
>
> Description
> -------
>
> I have been experiencing unexpected exits from KDevelop that were not due to any kind of error in the KDevelop code; it was as if someone told the application to exit normally. This happens mostly on OS X, but also sometimes on Linux.
> I finally traced this to `KGlobal::deref` reaching a zero reference count and invoking `QCoreApplication::quit` when called from one of KDevelop's KJob dtors. There does not appear to be a reference counting mismatch in the code, so the issue might be due to a race condition in KGlobal::ref/deref.
>
> This patch introduces thread-safety to KGlobal's reference counting by turning the simple global `static int s_refCount` into a `static QAtomicInt s_refCount`. I consider this an important bug fix regardless of whether it corrects the issue I have with KDevelop.
>
>
> Diffs
> -----
>
> kdecore/kernel/kglobal.cpp cf003a4
>
> Diff: https://git.reviewboard.kde.org/r/121134/diff/
>
>
> Testing
> -------
>
> On OS X 10.6.8 only for now.
>
> NB: Qt itself uses the QAtomicInt's parent class (QBasicAtomicInt) for its own reference counter used for implicit sharing. This is thus well-tested code that is unlikely to introduce regressions to a core KDE feature.
>
>
> Thanks,
>
> René J.V. Bertin
>
>
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