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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/191921">191921</a></dd>
<dt>Author</dt> <dd>cdumez@apple.com</dd>
<dt>Date</dt> <dd>2015-11-02 16:14:36 -0800 (Mon, 02 Nov 2015)</dd>
</dl>

<h3>Log Message</h3>
<pre>Regression(<a href="http://trac.webkit.org/projects/webkit/changeset/191673">r191673</a>): Crash in RunLoopTimer::schedule()
https://bugs.webkit.org/show_bug.cgi?id=150816
&lt;rdar://problem/23335285&gt;

Reviewed by Anders Carlsson.

The crash was happening when the RunLoopTimer would fire during the
call to RunLoopTimer::schedule(), which can happen because we are
calling schedule() from a background thread. In such case, the
timerFired() callback execution would cause |this| to get destroyed.

To avoid this issue, DecodingResultDispatcher is now ref-counted. The
object is ref'd while calling startTimer() so that the object cannot go
away during the execution of this method. Also, we explicitly ref the
object when starting the timer to keep the object alive until the
RunLoopTimer has fired, at which point we explicitely de-ref.

This should handle correctly the cases where the RunLoopTimer fires
during AND after the execution of startTimer().

* platform/network/DataURLDecoder.cpp:
(WebCore::DataURLDecoder::DecodingResultDispatcher::dispatch):
(WebCore::DataURLDecoder::DecodingResultDispatcher::startTimer):
(WebCore::DataURLDecoder::DecodingResultDispatcher::timerFired):</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreplatformnetworkDataURLDecodercpp">trunk/Source/WebCore/platform/network/DataURLDecoder.cpp</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (191920 => 191921)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog        2015-11-03 00:11:19 UTC (rev 191920)
+++ trunk/Source/WebCore/ChangeLog        2015-11-03 00:14:36 UTC (rev 191921)
</span><span class="lines">@@ -1,3 +1,30 @@
</span><ins>+2015-11-02  Chris Dumez  &lt;cdumez@apple.com&gt;
+
+        Regression(r191673): Crash in RunLoopTimer::schedule()
+        https://bugs.webkit.org/show_bug.cgi?id=150816
+        &lt;rdar://problem/23335285&gt;
+
+        Reviewed by Anders Carlsson.
+
+        The crash was happening when the RunLoopTimer would fire during the
+        call to RunLoopTimer::schedule(), which can happen because we are
+        calling schedule() from a background thread. In such case, the
+        timerFired() callback execution would cause |this| to get destroyed.
+
+        To avoid this issue, DecodingResultDispatcher is now ref-counted. The
+        object is ref'd while calling startTimer() so that the object cannot go
+        away during the execution of this method. Also, we explicitly ref the
+        object when starting the timer to keep the object alive until the
+        RunLoopTimer has fired, at which point we explicitely de-ref.
+
+        This should handle correctly the cases where the RunLoopTimer fires
+        during AND after the execution of startTimer().
+
+        * platform/network/DataURLDecoder.cpp:
+        (WebCore::DataURLDecoder::DecodingResultDispatcher::dispatch):
+        (WebCore::DataURLDecoder::DecodingResultDispatcher::startTimer):
+        (WebCore::DataURLDecoder::DecodingResultDispatcher::timerFired):
+
</ins><span class="cx"> 2015-11-02  Andy Estes  &lt;aestes@apple.com&gt;
</span><span class="cx"> 
</span><span class="cx">         [Cocoa] Add tvOS and watchOS to SUPPORTED_PLATFORMS
</span></span></pre></div>
<a id="trunkSourceWebCoreplatformnetworkDataURLDecodercpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/platform/network/DataURLDecoder.cpp (191920 => 191921)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/platform/network/DataURLDecoder.cpp        2015-11-03 00:11:19 UTC (rev 191920)
+++ trunk/Source/WebCore/platform/network/DataURLDecoder.cpp        2015-11-03 00:14:36 UTC (rev 191921)
</span><span class="lines">@@ -56,12 +56,12 @@
</span><span class="cx"> 
</span><span class="cx"> #if HAVE(RUNLOOP_TIMER)
</span><span class="cx"> 
</span><del>-class DecodingResultDispatcher {
</del><ins>+class DecodingResultDispatcher : public ThreadSafeRefCounted&lt;DecodingResultDispatcher&gt; {
</ins><span class="cx"> public:
</span><span class="cx">     static void dispatch(std::unique_ptr&lt;DecodeTask&gt; decodeTask)
</span><span class="cx">     {
</span><del>-        auto&amp; dispatcher = *new DecodingResultDispatcher(WTF::move(decodeTask));
-        dispatcher.startTimer();
</del><ins>+        Ref&lt;DecodingResultDispatcher&gt; dispatcher = adoptRef(*new DecodingResultDispatcher(WTF::move(decodeTask)));
+        dispatcher-&gt;startTimer();
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx"> private:
</span><span class="lines">@@ -73,6 +73,8 @@
</span><span class="cx"> 
</span><span class="cx">     void startTimer()
</span><span class="cx">     {
</span><ins>+        // Keep alive until the timer has fired.
+        ref();
</ins><span class="cx">         m_timer.startOneShot(0);
</span><span class="cx">         m_timer.schedule(m_decodeTask-&gt;scheduleContext.scheduledPairs);
</span><span class="cx">     }
</span><span class="lines">@@ -84,7 +86,7 @@
</span><span class="cx">         else
</span><span class="cx">             m_decodeTask-&gt;completionHandler({ });
</span><span class="cx"> 
</span><del>-        delete this;
</del><ins>+        deref();
</ins><span class="cx">     }
</span><span class="cx"> 
</span><span class="cx">     RunLoopTimer&lt;DecodingResultDispatcher&gt; m_timer;
</span></span></pre>
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