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Bug 1023758, part 2 - Dead traversed objects should be treated as incremental roots and colored. r=smaug

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This commit is contained in:
Andrew McCreight 2014-06-30 16:18:47 -07:00
parent 5f198d2ee6
commit 65e1d8fde8
1 changed files with 31 additions and 12 deletions
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43
xpcom/base/nsCycleCollector.cpp
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@ -556,6 +556,8 @@ struct PtrInfo
private:
EdgePool::Iterator mFirstChild;
static const uint32_t kInitialRefCount = UINT32_MAX - 1;
public:
PtrInfo(void* aPointer, nsCycleCollectionParticipant* aParticipant)
@ -563,7 +565,7 @@ public:
mParticipant(aParticipant),
mColor(grey),
mInternalRefs(0),
mRefCount(UINT32_MAX - 1),
mRefCount(kInitialRefCount),
mFirstChild()
{
MOZ_ASSERT(aParticipant);
@ -590,6 +592,11 @@ public:
return mRefCount == UINT32_MAX;
}
bool WasTraversed() const
{
return mRefCount != kInitialRefCount;
}
EdgePool::Iterator FirstChild() const
{
CC_GRAPH_ASSERT(mFirstChild.Initialized());
@ -1449,7 +1456,7 @@ GraphWalker<Visitor>::DoWalk(nsDeque& aQueue)
while (aQueue.GetSize() > 0) {
PtrInfo* pi = static_cast<PtrInfo*>(aQueue.PopFront());
if (pi->mParticipant && mVisitor.ShouldVisitNode(pi)) {
if (pi->WasTraversed() && mVisitor.ShouldVisitNode(pi)) {
mVisitor.VisitNode(pi);
for (EdgePool::Iterator child = pi->FirstChild(),
child_end = pi->LastChild();
@ -2886,7 +2893,7 @@ static void
FloodBlackNode(uint32_t& aWhiteNodeCount, bool& aFailed, PtrInfo* aPi)
{
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(aWhiteNodeCount, aFailed)).Walk(aPi);
MOZ_ASSERT(aPi->mColor == black || !aPi->mParticipant,
MOZ_ASSERT(aPi->mColor == black || !aPi->WasTraversed(),
"FloodBlackNode should make aPi black");
}
@ -3034,6 +3041,17 @@ nsCycleCollector::ScanIncrementalRoots()
} else {
MOZ_ASSERT(false, "Non-JS thing with 0 refcount? Treating as live.");
}
} else if (!pi->mParticipant && pi->WasTraversed()) {
// Dead traversed refcounted objects:
// If the object was traversed, it must have been alive at the start of
// the CC, and thus had a positive refcount. It is dead now, so its
// refcount must have decreased at some point during the CC. Therefore,
// it would be in the purple buffer if it wasn't dead, so treat it as an
// incremental root.
//
// This should not cause leaks because as the object died it should have
// released anything it held onto, which will add them to the purple
// buffer, which will cause them to be considered in the next CC.
} else {
continue;
}
@ -3043,14 +3061,15 @@ nsCycleCollector::ScanIncrementalRoots()
// If there's a listener, tell it about this root. We don't bother with the
// optimization of skipping the Walk() if pi is black: it will just return
// without doing anything and there's no need to make this case faster.
if (MOZ_UNLIKELY(hasListener)) {
if (MOZ_UNLIKELY(hasListener) && pi->mPointer) {
// Dead objects aren't logged. See bug 1031370.
mListener->NoteIncrementalRoot((uint64_t)pi->mPointer);
}
FloodBlackNode(mWhiteNodeCount, failed, pi);
}
timeLog.Checkpoint("ScanIncrementalRoots::fix JS");
timeLog.Checkpoint("ScanIncrementalRoots::fix nodes");
if (failed) {
NS_ASSERTION(false, "Ran out of memory in ScanIncrementalRoots");
@ -3077,9 +3096,10 @@ nsCycleCollector::ScanWhiteNodes(bool aFullySynchGraphBuild)
}
MOZ_ASSERT(pi->mColor == grey);
if (!pi->mParticipant) {
// This node has been deleted, so it could be in a mangled state, but
// that's okay because we're not going to look at it again.
if (!pi->WasTraversed()) {
// This node was deleted before it was traversed, so there's no reason
// to look at it.
MOZ_ASSERT(!pi->mParticipant, "Live nodes should all have been traversed");
continue;
}
@ -3109,7 +3129,7 @@ nsCycleCollector::ScanBlackNodes()
NodePool::Enumerator nodeEnum(mGraph.mNodes);
while (!nodeEnum.IsDone()) {
PtrInfo* pi = nodeEnum.GetNext();
if (pi->mColor == grey && pi->mParticipant) {
if (pi->mColor == grey && pi->WasTraversed()) {
FloodBlackNode(mWhiteNodeCount, failed, pi);
}
}
@ -3150,7 +3170,7 @@ nsCycleCollector::ScanRoots(bool aFullySynchGraphBuild)
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo* pi = etor.GetNext();
if (!pi->mParticipant) {
if (!pi->WasTraversed()) {
continue;
}
switch (pi->mColor) {
@ -3165,8 +3185,7 @@ nsCycleCollector::ScanRoots(bool aFullySynchGraphBuild)
mListener->DescribeGarbage((uint64_t)pi->mPointer);
break;
case grey:
// With incremental CC, we can end up with a grey object after
// scanning if it is only reachable from an object that gets freed.
MOZ_ASSERT(false, "All traversed objects should be black or white");
break;
}
}