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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/207071">207071</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2016-10-11 02:23:28 -0700 (Tue, 11 Oct 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/205859">r205859</a> - ParkingLot is going to have a bad time with threads dying
https://bugs.webkit.org/show_bug.cgi?id=161893
Reviewed by Michael Saboff.
If a thread dies right as it falls out of parkConditionally, then unparkOne() and friends
might die because they will dereference a deallocated ThreadData.
The solution is to ref-count ThreadData's. When unparkOne() and friends want to hold onto a
ThreadData past the queue lock, they can use RefPtr<>.
* wtf/ParkingLot.cpp:
(WTF::ParkingLot::unparkOne):
(WTF::ParkingLot::unparkOneImpl):
(WTF::ParkingLot::unparkAll):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit214SourceWTFChangeLog">releases/WebKitGTK/webkit-2.14/Source/WTF/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit214SourceWTFwtfParkingLotcpp">releases/WebKitGTK/webkit-2.14/Source/WTF/wtf/ParkingLot.cpp</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit214SourceWTFChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.14/Source/WTF/ChangeLog (207070 => 207071)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.14/Source/WTF/ChangeLog 2016-10-11 09:18:15 UTC (rev 207070)
+++ releases/WebKitGTK/webkit-2.14/Source/WTF/ChangeLog 2016-10-11 09:23:28 UTC (rev 207071)
</span><span class="lines">@@ -1,3 +1,21 @@
</span><ins>+2016-09-12 Filip Pizlo <fpizlo@apple.com>
+
+ ParkingLot is going to have a bad time with threads dying
+ https://bugs.webkit.org/show_bug.cgi?id=161893
+
+ Reviewed by Michael Saboff.
+
+ If a thread dies right as it falls out of parkConditionally, then unparkOne() and friends
+ might die because they will dereference a deallocated ThreadData.
+
+ The solution is to ref-count ThreadData's. When unparkOne() and friends want to hold onto a
+ ThreadData past the queue lock, they can use RefPtr<>.
+
+ * wtf/ParkingLot.cpp:
+ (WTF::ParkingLot::unparkOne):
+ (WTF::ParkingLot::unparkOneImpl):
+ (WTF::ParkingLot::unparkAll):
+
</ins><span class="cx"> 2016-09-12 Yusuke Suzuki <utatane.tea@gmail.com>
</span><span class="cx">
</span><span class="cx"> [WTF] HashTable's rehash is not compatible to Ref<T> and ASan
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit214SourceWTFwtfParkingLotcpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.14/Source/WTF/wtf/ParkingLot.cpp (207070 => 207071)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.14/Source/WTF/wtf/ParkingLot.cpp 2016-10-11 09:18:15 UTC (rev 207070)
+++ releases/WebKitGTK/webkit-2.14/Source/WTF/wtf/ParkingLot.cpp 2016-10-11 09:23:28 UTC (rev 207071)
</span><span class="lines">@@ -45,7 +45,7 @@
</span><span class="cx">
</span><span class="cx"> const bool verbose = false;
</span><span class="cx">
</span><del>-struct ThreadData {
</del><ins>+struct ThreadData : public ThreadSafeRefCounted<ThreadData> {
</ins><span class="cx"> WTF_MAKE_FAST_ALLOCATED;
</span><span class="cx"> public:
</span><span class="cx">
</span><span class="lines">@@ -245,7 +245,6 @@
</span><span class="cx"> }
</span><span class="cx"> };
</span><span class="cx">
</span><del>-ThreadSpecific<ThreadData>* threadData;
</del><span class="cx"> Atomic<Hashtable*> hashtable;
</span><span class="cx"> Atomic<unsigned> numThreads;
</span><span class="cx">
</span><span class="lines">@@ -448,14 +447,20 @@
</span><span class="cx">
</span><span class="cx"> ThreadData* myThreadData()
</span><span class="cx"> {
</span><ins>+ static ThreadSpecific<RefPtr<ThreadData>>* threadData;
</ins><span class="cx"> static std::once_flag initializeOnce;
</span><span class="cx"> std::call_once(
</span><span class="cx"> initializeOnce,
</span><span class="cx"> [] {
</span><del>- threadData = new ThreadSpecific<ThreadData>();
</del><ins>+ threadData = new ThreadSpecific<RefPtr<ThreadData>>();
</ins><span class="cx"> });
</span><del>-
- return *threadData;
</del><ins>+
+ RefPtr<ThreadData>& result = **threadData;
+
+ if (!result)
+ result = adoptRef(new ThreadData());
+
+ return result.get();
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> template<typename Functor>
</span><span class="lines">@@ -659,7 +664,7 @@
</span><span class="cx">
</span><span class="cx"> UnparkResult result;
</span><span class="cx">
</span><del>- ThreadData* threadData = nullptr;
</del><ins>+ RefPtr<ThreadData> threadData;
</ins><span class="cx"> result.mayHaveMoreThreads = dequeue(
</span><span class="cx"> address,
</span><span class="cx"> BucketMode::EnsureNonEmpty,
</span><span class="lines">@@ -697,7 +702,7 @@
</span><span class="cx"> if (verbose)
</span><span class="cx"> dataLog(toString(currentThread(), ": unparking one the hard way.\n"));
</span><span class="cx">
</span><del>- ThreadData* threadData = nullptr;
</del><ins>+ RefPtr<ThreadData> threadData;
</ins><span class="cx"> bool timeToBeFair = false;
</span><span class="cx"> dequeue(
</span><span class="cx"> address,
</span><span class="lines">@@ -738,7 +743,7 @@
</span><span class="cx"> if (verbose)
</span><span class="cx"> dataLog(toString(currentThread(), ": unparking all from ", RawPointer(address), ".\n"));
</span><span class="cx">
</span><del>- Vector<ThreadData*, 8> threadDatas;
</del><ins>+ Vector<RefPtr<ThreadData>, 8> threadDatas;
</ins><span class="cx"> dequeue(
</span><span class="cx"> address,
</span><span class="cx"> BucketMode::IgnoreEmpty,
</span><span class="lines">@@ -752,9 +757,9 @@
</span><span class="cx"> },
</span><span class="cx"> [] (bool) { });
</span><span class="cx">
</span><del>- for (ThreadData* threadData : threadDatas) {
</del><ins>+ for (RefPtr<ThreadData>& threadData : threadDatas) {
</ins><span class="cx"> if (verbose)
</span><del>- dataLog(toString(currentThread(), ": unparking ", RawPointer(threadData), " with address ", RawPointer(threadData->address), "\n"));
</del><ins>+ dataLog(toString(currentThread(), ": unparking ", RawPointer(threadData.get()), " with address ", RawPointer(threadData->address), "\n"));
</ins><span class="cx"> ASSERT(threadData->address);
</span><span class="cx"> {
</span><span class="cx"> std::unique_lock<std::mutex> locker(threadData->parkingLock);
</span></span></pre>
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