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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/121134/">https://git.reviewboard.kde.org/r/121134/</a>
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<p style="margin-top: 0;">On November 16th, 2014, 7:22 nachm. UTC, <b>Thomas Lübking</b> wrote:</p>
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<a href="https://git.reviewboard.kde.org/r/121134/diff/5/?file=328836#file328836line343" style="color: black; font-weight: bold; text-decoration: underline;">kdecore/kernel/kglobal.cpp</a>
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(Diff revision 5)
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">QString KGlobal::caption()</pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">s_allowQuit</span><span class="hl"> </span><span class="o"><span class="hl">=</span></span><span class="hl"> </span><span class="n">allowQuit</span><span class="p">;</span></pre></td>
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<td bgcolor="#fdfebc" width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span class="n">s_allowQuit</span><span class="p"><span class="hl">.</span></span><span class="n"><span class="hl">fetchAndStoreOrdered</span></span><span class="p"><span class="hl">(</span></span><span class="kt"><span class="hl">int</span></span><span class="p"><span class="hl">(</span></span><span class="n">allowQuit</span><span class="p"><span class="hl">))</span>;</span></pre></td>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Does this actually make sense?
The result is "undefined" when used from multiple threads anyway.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Should one enforce this to be called from the main thread only instead?</p></pre>
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<p>On November 16th, 2014, 8:08 nachm. UTC, <b>René J.V. Bertin</b> wrote:</p>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">How do you mean, undefined? The result will be the value set by whoever called the function last.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">You have a point that this doesn't make a lot of sense, there's something to say that the main (master...) thread ought to be the one deciding whether or not it can be quit by the reference counter.</p></pre>
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<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><blockquote style="text-rendering: inherit;padding: 0 0 0 1em;border-left: 1px solid #bbb;white-space: normal;margin: 0 0 0 0.5em;line-height: inherit;">
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">How do you mean, undefined?</p>
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<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">It's a write-only flag. If written from two threads with disagree, none has an idea about the current state - and there's no getter either.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">Since the client code somehow has to find agreement on the outcome, it needs a local mutex - or define who's in position to write this ("the one deciding whether or not it can be quit by the reference counter")</p></pre>
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<p>- Thomas</p>
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<p>On November 16th, 2014, 8:22 nachm. UTC, René J.V. Bertin wrote:</p>
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<div>Review request for KDE Software on Mac OS X, kdelibs and David Faure.</div>
<div>By René J.V. Bertin.</div>
<p style="color: grey;"><i>Updated Nov. 16, 2014, 8:22 nachm.</i></p>
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<b style="color: #575012; font-size: 10pt;">Repository: </b>
kdelibs
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">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 <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">KGlobal::deref</code> reaching a zero reference count and invoking <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">QCoreApplication::quit</code> 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.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">This patch introduces thread-safety to KGlobal's reference counting by turning the simple global <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">static int s_refCount</code> into a <code style="text-rendering: inherit;color: #4444cc;padding: 0;white-space: normal;margin: 0;line-height: inherit;">static QAtomicInt s_refCount</code>. I consider this an important bug fix regardless of whether it corrects the issue I have with KDevelop.</p></pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
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<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">On OS X 10.6.8 only for now.</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">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.</p></pre>
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<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
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<li>kdecore/kernel/kglobal.cpp <span style="color: grey">(cf003a4)</span></li>
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<p><a href="https://git.reviewboard.kde.org/r/121134/diff/" style="margin-left: 3em;">View Diff</a></p>
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