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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/204070">204070</a></dd>
<dt>Author</dt> <dd>bshafiei@apple.com</dd>
<dt>Date</dt> <dd>2016-08-02 23:15:59 -0700 (Tue, 02 Aug 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/204057">r204057</a>. rdar://problem/27534205</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#branchessafari602branchSourceWebKit2ChangeLog">branches/safari-602-branch/Source/WebKit2/ChangeLog</a></li>
<li><a href="#branchessafari602branchSourceWebKit2UIProcessmacRemoteLayerTreeDrawingAreaProxyh">branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.h</a></li>
<li><a href="#branchessafari602branchSourceWebKit2UIProcessmacRemoteLayerTreeDrawingAreaProxymm">branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.mm</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="branchessafari602branchSourceWebKit2ChangeLog"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/WebKit2/ChangeLog (204069 => 204070)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/WebKit2/ChangeLog 2016-08-03 06:15:56 UTC (rev 204069)
+++ branches/safari-602-branch/Source/WebKit2/ChangeLog 2016-08-03 06:15:59 UTC (rev 204070)
</span><span class="lines">@@ -1,3 +1,48 @@
</span><ins>+2016-08-02 Babak Shafiei <bshafiei@apple.com>
+
+ Merge r204057. rdar://problem/27534205
+
+ 2016-08-02 Tim Horton <timothy_horton@apple.com>
+
+ REGRESSION (r203385): Frequent RELEASE_ASSERT in WebKit::RemoteLayerTreeDrawingArea::flushLayers()
+ https://bugs.webkit.org/show_bug.cgi?id=160481
+ <rdar://problem/27534205>
+
+ Reviewed by Simon Fraser.
+
+ * UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.h:
+ * UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.mm:
+ (WebKit::RemoteLayerTreeDrawingAreaProxy::commitLayerTree):
+ (WebKit::RemoteLayerTreeDrawingAreaProxy::didRefreshDisplay):
+ (WebKit::RemoteLayerTreeDrawingAreaProxy::waitForDidUpdateViewState):
+ If the UI process sends a didUpdate message while the Web process is in
+ the middle of flushing on a background thread, the drawing area will
+ allow another commit to start on the main thread, which then (rightfully)
+ causes the RELEASE_ASSERT.
+
+ This is normally not a problem, because didRefreshDisplay (which sends the didUpdate)
+ bails if m_didUpdateMessageState is anything other than NotSent, and m_didUpdateMessageState
+ is only NotSent if the Web process has sent a commit (and thus will not commit again until
+ it gets a didUpdate). This is the fundamental mechanism that avoids multiple commits being
+ in flight at once.
+
+ In r203385, I added a path where didRefreshDisplay could be called
+ before the first commit arrived (by way of
+ _applicationWillEnterForeground -> viewStateDidChange -> waitForDidUpdateViewState).
+
+ This caused trouble because m_didUpdateMessageState is initialized to NotSent,
+ which means that we could end up sending a didUpdate immediately, before the first
+ commit arrives - even worse, while the first commit is being flushed on a background thread,
+ leading the aforementioned RELEASE_ASSERT to fire.
+
+ Instead, initialize it to Sent (which I've renamed to DoesNotNeedDidUpdate), so that
+ we won't send a didUpdate until after the first commit arrives (at which point
+ the two processes are in agreement about the order of things).
+
+ It's not currently possible to API test this for multiple reasons, though it is fairly
+ easy to write a test app that reproduces reliably (by simulating suspend/resume notifications
+ inside the didFinishNavigation: callback).
+
</ins><span class="cx"> 2016-07-31 Babak Shafiei <bshafiei@apple.com>
</span><span class="cx">
</span><span class="cx"> Merge r203842. rdar://problem/27553464
</span></span></pre></div>
<a id="branchessafari602branchSourceWebKit2UIProcessmacRemoteLayerTreeDrawingAreaProxyh"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.h (204069 => 204070)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.h 2016-08-03 06:15:56 UTC (rev 204069)
+++ branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.h 2016-08-03 06:15:59 UTC (rev 204070)
</span><span class="lines">@@ -91,8 +91,8 @@
</span><span class="cx">
</span><span class="cx"> RemoteLayerTreeHost m_remoteLayerTreeHost;
</span><span class="cx"> bool m_isWaitingForDidUpdateGeometry { false };
</span><del>- enum DidUpdateMessageState { NotSent, Sent, MissedCommit };
- DidUpdateMessageState m_didUpdateMessageState { NotSent };
</del><ins>+ enum DidUpdateMessageState { DoesNotNeedDidUpdate, NeedsDidUpdate, MissedCommit };
+ DidUpdateMessageState m_didUpdateMessageState { DoesNotNeedDidUpdate };
</ins><span class="cx">
</span><span class="cx"> WebCore::IntSize m_lastSentSize;
</span><span class="cx">
</span></span></pre></div>
<a id="branchessafari602branchSourceWebKit2UIProcessmacRemoteLayerTreeDrawingAreaProxymm"></a>
<div class="modfile"><h4>Modified: branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.mm (204069 => 204070)</h4>
<pre class="diff"><span>
<span class="info">--- branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.mm 2016-08-03 06:15:56 UTC (rev 204069)
+++ branches/safari-602-branch/Source/WebKit2/UIProcess/mac/RemoteLayerTreeDrawingAreaProxy.mm 2016-08-03 06:15:59 UTC (rev 204070)
</span><span class="lines">@@ -227,11 +227,11 @@
</span><span class="cx"> m_webPageProxy.layerTreeCommitComplete();
</span><span class="cx">
</span><span class="cx"> #if PLATFORM(IOS)
</span><del>- if (std::exchange(m_didUpdateMessageState, NotSent) == MissedCommit)
</del><ins>+ if (std::exchange(m_didUpdateMessageState, NeedsDidUpdate) == MissedCommit)
</ins><span class="cx"> didRefreshDisplay(monotonicallyIncreasingTime());
</span><span class="cx"> [m_displayLinkHandler schedule];
</span><span class="cx"> #else
</span><del>- m_didUpdateMessageState = NotSent;
</del><ins>+ m_didUpdateMessageState = NeedsDidUpdate;
</ins><span class="cx"> didRefreshDisplay(monotonicallyIncreasingTime());
</span><span class="cx"> #endif
</span><span class="cx">
</span><span class="lines">@@ -399,7 +399,7 @@
</span><span class="cx"> if (!m_webPageProxy.isValid())
</span><span class="cx"> return;
</span><span class="cx">
</span><del>- if (m_didUpdateMessageState != NotSent) {
</del><ins>+ if (m_didUpdateMessageState != NeedsDidUpdate) {
</ins><span class="cx"> m_didUpdateMessageState = MissedCommit;
</span><span class="cx"> #if PLATFORM(IOS)
</span><span class="cx"> [m_displayLinkHandler pause];
</span><span class="lines">@@ -407,7 +407,7 @@
</span><span class="cx"> return;
</span><span class="cx"> }
</span><span class="cx">
</span><del>- m_didUpdateMessageState = Sent;
</del><ins>+ m_didUpdateMessageState = DoesNotNeedDidUpdate;
</ins><span class="cx">
</span><span class="cx"> TraceScope tracingScope(RAFDidRefreshDisplayStart, RAFDidRefreshDisplayEnd);
</span><span class="cx">
</span><span class="lines">@@ -425,7 +425,7 @@
</span><span class="cx"> {
</span><span class="cx"> // We must send the didUpdate message before blocking on the next commit, otherwise
</span><span class="cx"> // we can be guaranteed that the next commit won't come until after the waitForAndDispatchImmediately times out.
</span><del>- if (m_didUpdateMessageState != Sent)
</del><ins>+ if (m_didUpdateMessageState != DoesNotNeedDidUpdate)
</ins><span class="cx"> didRefreshDisplay(monotonicallyIncreasingTime());
</span><span class="cx">
</span><span class="cx"> static std::chrono::milliseconds viewStateUpdateTimeout = [] {
</span></span></pre>
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