gecko-dev/xpcom/base/nsCycleCollector.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
//
// This file implements a garbage-cycle collector based on the paper
//
// Concurrent Cycle Collection in Reference Counted Systems
// Bacon & Rajan (2001), ECOOP 2001 / Springer LNCS vol 2072
//
// We are not using the concurrent or acyclic cases of that paper; so
// the green, red and orange colors are not used.
//
// The collector is based on tracking pointers of four colors:
//
// Black nodes are definitely live. If we ever determine a node is
// black, it's ok to forget about, drop from our records.
//
// White nodes are definitely garbage cycles. Once we finish with our
// scanning, we unlink all the white nodes and expect that by
// unlinking them they will self-destruct (since a garbage cycle is
// only keeping itself alive with internal links, by definition).
//
// Snow-white is an addition to the original algorithm. Snow-white object
// has reference count zero and is just waiting for deletion.
//
// Grey nodes are being scanned. Nodes that turn grey will turn
// either black if we determine that they're live, or white if we
// determine that they're a garbage cycle. After the main collection
// algorithm there should be no grey nodes.
//
// Purple nodes are *candidates* for being scanned. They are nodes we
// haven't begun scanning yet because they're not old enough, or we're
// still partway through the algorithm.
//
// XPCOM objects participating in garbage-cycle collection are obliged
// to inform us when they ought to turn purple; that is, when their
// refcount transitions from N+1 -> N, for nonzero N. Furthermore we
// require that *after* an XPCOM object has informed us of turning
// purple, they will tell us when they either transition back to being
// black (incremented refcount) or are ultimately deleted.
// Safety:
//
// An XPCOM object is either scan-safe or scan-unsafe, purple-safe or
// purple-unsafe.
//
// An nsISupports object is scan-safe if:
//
// - It can be QI'ed to |nsXPCOMCycleCollectionParticipant|, though
// this operation loses ISupports identity (like nsIClassInfo).
// - Additionally, the operation |traverse| on the resulting
// nsXPCOMCycleCollectionParticipant does not cause *any* refcount
// adjustment to occur (no AddRef / Release calls).
//
// A non-nsISupports ("native") object is scan-safe by explicitly
// providing its nsCycleCollectionParticipant.
//
// An object is purple-safe if it satisfies the following properties:
//
// - The object is scan-safe.
//
// When we receive a pointer |ptr| via
// |nsCycleCollector::suspect(ptr)|, we assume it is purple-safe. We
// can check the scan-safety, but have no way to ensure the
// purple-safety; objects must obey, or else the entire system falls
// apart. Don't involve an object in this scheme if you can't
// guarantee its purple-safety. The easiest way to ensure that an
// object is purple-safe is to use nsCycleCollectingAutoRefCnt.
//
// When we have a scannable set of purple nodes ready, we begin
// our walks. During the walks, the nodes we |traverse| should only
// feed us more scan-safe nodes, and should not adjust the refcounts
// of those nodes.
//
// We do not |AddRef| or |Release| any objects during scanning. We
// rely on the purple-safety of the roots that call |suspect| to
// hold, such that we will clear the pointer from the purple buffer
// entry to the object before it is destroyed. The pointers that are
// merely scan-safe we hold only for the duration of scanning, and
// there should be no objects released from the scan-safe set during
// the scan.
//
// We *do* call |Root| and |Unroot| on every white object, on
// either side of the calls to |Unlink|. This keeps the set of white
// objects alive during the unlinking.
//
#if !defined(__MINGW32__)
#ifdef WIN32
#include <crtdbg.h>
#include <errno.h>
#endif
#endif
#include "base/process_util.h"
/* This must occur *after* base/process_util.h to avoid typedefs conflicts. */
#include "mozilla/MemoryReporting.h"
#include "mozilla/Util.h"
#include "mozilla/CycleCollectedJSRuntime.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsDeque.h"
#include "nsCycleCollector.h"
#include "nsThreadUtils.h"
#include "prenv.h"
#include "nsPrintfCString.h"
#include "nsTArray.h"
#include "nsIConsoleService.h"
#include "mozilla/Attributes.h"
#include "nsICycleCollectorListener.h"
#include "nsIMemoryReporter.h"
#include "nsIFile.h"
#include "nsMemoryInfoDumper.h"
#include "xpcpublic.h"
#include "GeckoProfiler.h"
#include <stdint.h>
#include <stdio.h>
#include "mozilla/Likely.h"
#include "mozilla/mozPoisonWrite.h"
#include "mozilla/Telemetry.h"
#include "mozilla/ThreadLocal.h"
using namespace mozilla;
//#define COLLECT_TIME_DEBUG
// Enable assertions that are useful for diagnosing errors in graph construction.
//#define DEBUG_CC_GRAPH
#define DEFAULT_SHUTDOWN_COLLECTIONS 5
// One to do the freeing, then another to detect there is no more work to do.
#define NORMAL_SHUTDOWN_COLLECTIONS 2
// Cycle collector environment variables
//
// XPCOM_CC_LOG_ALL: If defined, always log cycle collector heaps.
//
// XPCOM_CC_LOG_SHUTDOWN: If defined, log cycle collector heaps at shutdown.
//
// XPCOM_CC_ALL_TRACES_AT_SHUTDOWN: If defined, any cycle collector
// logging done at shutdown will be WantAllTraces, which disables
// various cycle collector optimizations to give a fuller picture of
// the heap.
//
// XPCOM_CC_RUN_DURING_SHUTDOWN: In non-DEBUG or builds, if this is set,
// run cycle collections at shutdown.
//
// MOZ_CC_LOG_DIRECTORY: The directory in which logs are placed (such as
// logs from XPCOM_CC_LOG_ALL and XPCOM_CC_LOG_SHUTDOWN, or other uses
// of nsICycleCollectorListener)
MOZ_NEVER_INLINE void
CC_AbortIfNull(void *ptr)
{
if (!ptr)
MOZ_CRASH();
}
// Various parameters of this collector can be tuned using environment
// variables.
struct nsCycleCollectorParams
{
bool mLogAll;
bool mLogShutdown;
bool mAllTracesAtShutdown;
nsCycleCollectorParams() :
mLogAll (PR_GetEnv("XPCOM_CC_LOG_ALL") != NULL),
mLogShutdown (PR_GetEnv("XPCOM_CC_LOG_SHUTDOWN") != NULL),
mAllTracesAtShutdown (PR_GetEnv("XPCOM_CC_ALL_TRACES_AT_SHUTDOWN") != NULL)
{
}
};
#ifdef COLLECT_TIME_DEBUG
class TimeLog
{
public:
TimeLog() : mLastCheckpoint(TimeStamp::Now()) {}
void
Checkpoint(const char* aEvent)
{
TimeStamp now = TimeStamp::Now();
uint32_t dur = (uint32_t) ((now - mLastCheckpoint).ToMilliseconds());
if (dur > 0) {
printf("cc: %s took %dms\n", aEvent, dur);
}
mLastCheckpoint = now;
}
private:
TimeStamp mLastCheckpoint;
};
#else
class TimeLog
{
public:
TimeLog() {}
void Checkpoint(const char* aEvent) {}
};
#endif
////////////////////////////////////////////////////////////////////////
// Base types
////////////////////////////////////////////////////////////////////////
struct PtrInfo;
class EdgePool
{
public:
// EdgePool allocates arrays of void*, primarily to hold PtrInfo*.
// However, at the end of a block, the last two pointers are a null
// and then a void** pointing to the next block. This allows
// EdgePool::Iterators to be a single word but still capable of crossing
// block boundaries.
EdgePool()
{
mSentinelAndBlocks[0].block = nullptr;
mSentinelAndBlocks[1].block = nullptr;
}
~EdgePool()
{
MOZ_ASSERT(!mSentinelAndBlocks[0].block &&
!mSentinelAndBlocks[1].block,
"Didn't call Clear()?");
}
void Clear()
{
Block *b = Blocks();
while (b) {
Block *next = b->Next();
delete b;
b = next;
}
mSentinelAndBlocks[0].block = nullptr;
mSentinelAndBlocks[1].block = nullptr;
}
private:
struct Block;
union PtrInfoOrBlock {
// Use a union to avoid reinterpret_cast and the ensuing
// potential aliasing bugs.
PtrInfo *ptrInfo;
Block *block;
};
struct Block {
enum { BlockSize = 16 * 1024 };
PtrInfoOrBlock mPointers[BlockSize];
Block() {
mPointers[BlockSize - 2].block = nullptr; // sentinel
mPointers[BlockSize - 1].block = nullptr; // next block pointer
}
Block*& Next() { return mPointers[BlockSize - 1].block; }
PtrInfoOrBlock* Start() { return &mPointers[0]; }
PtrInfoOrBlock* End() { return &mPointers[BlockSize - 2]; }
};
// Store the null sentinel so that we can have valid iterators
// before adding any edges and without adding any blocks.
PtrInfoOrBlock mSentinelAndBlocks[2];
Block*& Blocks() { return mSentinelAndBlocks[1].block; }
Block* Blocks() const { return mSentinelAndBlocks[1].block; }
public:
class Iterator
{
public:
Iterator() : mPointer(nullptr) {}
Iterator(PtrInfoOrBlock *aPointer) : mPointer(aPointer) {}
Iterator(const Iterator& aOther) : mPointer(aOther.mPointer) {}
Iterator& operator++()
{
if (mPointer->ptrInfo == nullptr) {
// Null pointer is a sentinel for link to the next block.
mPointer = (mPointer + 1)->block->mPointers;
}
++mPointer;
return *this;
}
PtrInfo* operator*() const
{
if (mPointer->ptrInfo == nullptr) {
// Null pointer is a sentinel for link to the next block.
return (mPointer + 1)->block->mPointers->ptrInfo;
}
return mPointer->ptrInfo;
}
bool operator==(const Iterator& aOther) const
{ return mPointer == aOther.mPointer; }
bool operator!=(const Iterator& aOther) const
{ return mPointer != aOther.mPointer; }
#ifdef DEBUG_CC_GRAPH
bool Initialized() const
{
return mPointer != nullptr;
}
#endif
private:
PtrInfoOrBlock *mPointer;
};
class Builder;
friend class Builder;
class Builder {
public:
Builder(EdgePool &aPool)
: mCurrent(&aPool.mSentinelAndBlocks[0]),
mBlockEnd(&aPool.mSentinelAndBlocks[0]),
mNextBlockPtr(&aPool.Blocks())
{
}
Iterator Mark() { return Iterator(mCurrent); }
void Add(PtrInfo* aEdge) {
if (mCurrent == mBlockEnd) {
Block *b = new Block();
*mNextBlockPtr = b;
mCurrent = b->Start();
mBlockEnd = b->End();
mNextBlockPtr = &b->Next();
}
(mCurrent++)->ptrInfo = aEdge;
}
private:
// mBlockEnd points to space for null sentinel
PtrInfoOrBlock *mCurrent, *mBlockEnd;
Block **mNextBlockPtr;
};
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
size_t n = 0;
Block *b = Blocks();
while (b) {
n += aMallocSizeOf(b);
b = b->Next();
}
return n;
}
};
#ifdef DEBUG_CC_GRAPH
#define CC_GRAPH_ASSERT(b) MOZ_ASSERT(b)
#else
#define CC_GRAPH_ASSERT(b)
#endif
#define CC_TELEMETRY(_name, _value) \
PR_BEGIN_MACRO \
if (NS_IsMainThread()) { \
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR##_name, _value); \
} else { \
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_WORKER##_name, _value); \
} \
PR_END_MACRO
enum NodeColor { black, white, grey };
// This structure should be kept as small as possible; we may expect
// hundreds of thousands of them to be allocated and touched
// repeatedly during each cycle collection.
struct PtrInfo
{
void *mPointer;
nsCycleCollectionParticipant *mParticipant;
uint32_t mColor : 2;
uint32_t mInternalRefs : 30;
uint32_t mRefCount;
private:
EdgePool::Iterator mFirstChild;
public:
PtrInfo(void *aPointer, nsCycleCollectionParticipant *aParticipant)
: mPointer(aPointer),
mParticipant(aParticipant),
mColor(grey),
mInternalRefs(0),
mRefCount(0),
mFirstChild()
{
MOZ_ASSERT(aParticipant);
}
// Allow NodePool::Block's constructor to compile.
PtrInfo() {
NS_NOTREACHED("should never be called");
}
EdgePool::Iterator FirstChild()
{
CC_GRAPH_ASSERT(mFirstChild.Initialized());
return mFirstChild;
}
// this PtrInfo must be part of a NodePool
EdgePool::Iterator LastChild()
{
CC_GRAPH_ASSERT((this + 1)->mFirstChild.Initialized());
return (this + 1)->mFirstChild;
}
void SetFirstChild(EdgePool::Iterator aFirstChild)
{
CC_GRAPH_ASSERT(aFirstChild.Initialized());
mFirstChild = aFirstChild;
}
// this PtrInfo must be part of a NodePool
void SetLastChild(EdgePool::Iterator aLastChild)
{
CC_GRAPH_ASSERT(aLastChild.Initialized());
(this + 1)->mFirstChild = aLastChild;
}
};
/**
* A structure designed to be used like a linked list of PtrInfo, except
* that allocates the PtrInfo 32K-at-a-time.
*/
class NodePool
{
private:
enum { BlockSize = 8 * 1024 }; // could be int template parameter
struct Block {
// We create and destroy Block using NS_Alloc/NS_Free rather
// than new and delete to avoid calling its constructor and
// destructor.
Block() { NS_NOTREACHED("should never be called"); }
~Block() { NS_NOTREACHED("should never be called"); }
Block* mNext;
PtrInfo mEntries[BlockSize + 1]; // +1 to store last child of last node
};
public:
NodePool()
: mBlocks(nullptr),
mLast(nullptr)
{
}
~NodePool()
{
MOZ_ASSERT(!mBlocks, "Didn't call Clear()?");
}
void Clear()
{
Block *b = mBlocks;
while (b) {
Block *n = b->mNext;
NS_Free(b);
b = n;
}
mBlocks = nullptr;
mLast = nullptr;
}
class Builder;
friend class Builder;
class Builder {
public:
Builder(NodePool& aPool)
: mNextBlock(&aPool.mBlocks),
mNext(aPool.mLast),
mBlockEnd(nullptr)
{
MOZ_ASSERT(aPool.mBlocks == nullptr && aPool.mLast == nullptr,
"pool not empty");
}
PtrInfo *Add(void *aPointer, nsCycleCollectionParticipant *aParticipant)
{
if (mNext == mBlockEnd) {
Block *block = static_cast<Block*>(NS_Alloc(sizeof(Block)));
*mNextBlock = block;
mNext = block->mEntries;
mBlockEnd = block->mEntries + BlockSize;
block->mNext = nullptr;
mNextBlock = &block->mNext;
}
return new (mNext++) PtrInfo(aPointer, aParticipant);
}
private:
Block **mNextBlock;
PtrInfo *&mNext;
PtrInfo *mBlockEnd;
};
class Enumerator;
friend class Enumerator;
class Enumerator {
public:
Enumerator(NodePool& aPool)
: mFirstBlock(aPool.mBlocks),
mCurBlock(nullptr),
mNext(nullptr),
mBlockEnd(nullptr),
mLast(aPool.mLast)
{
}
bool IsDone() const
{
return mNext == mLast;
}
bool AtBlockEnd() const
{
return mNext == mBlockEnd;
}
PtrInfo* GetNext()
{
MOZ_ASSERT(!IsDone(), "calling GetNext when done");
if (mNext == mBlockEnd) {
Block *nextBlock = mCurBlock ? mCurBlock->mNext : mFirstBlock;
mNext = nextBlock->mEntries;
mBlockEnd = mNext + BlockSize;
mCurBlock = nextBlock;
}
return mNext++;
}
private:
// mFirstBlock is a reference to allow an Enumerator to be constructed
// for an empty graph.
Block *&mFirstBlock;
Block *mCurBlock;
// mNext is the next value we want to return, unless mNext == mBlockEnd
// NB: mLast is a reference to allow enumerating while building!
PtrInfo *mNext, *mBlockEnd, *&mLast;
};
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
// We don't measure the things pointed to by mEntries[] because those
// pointers are non-owning.
size_t n = 0;
Block *b = mBlocks;
while (b) {
n += aMallocSizeOf(b);
b = b->mNext;
}
return n;
}
private:
Block *mBlocks;
PtrInfo *mLast;
};
struct WeakMapping
{
// map and key will be null if the corresponding objects are GC marked
PtrInfo *mMap;
PtrInfo *mKey;
PtrInfo *mKeyDelegate;
PtrInfo *mVal;
};
class GCGraphBuilder;
struct GCGraph
{
NodePool mNodes;
EdgePool mEdges;
nsTArray<WeakMapping> mWeakMaps;
uint32_t mRootCount;
GCGraph() : mRootCount(0) {
}
~GCGraph() {
}
void Clear()
{
mNodes.Clear();
mEdges.Clear();
mWeakMaps.Clear();
mRootCount = 0;
}
void SizeOfExcludingThis(MallocSizeOf aMallocSizeOf,
size_t *aNodesSize, size_t *aEdgesSize,
size_t *aWeakMapsSize) const {
*aNodesSize = mNodes.SizeOfExcludingThis(aMallocSizeOf);
*aEdgesSize = mEdges.SizeOfExcludingThis(aMallocSizeOf);
// We don't measure what the WeakMappings point to, because the
// pointers are non-owning.
*aWeakMapsSize = mWeakMaps.SizeOfExcludingThis(aMallocSizeOf);
}
};
static nsISupports *
CanonicalizeXPCOMParticipant(nsISupports *in)
{
nsISupports* out;
in->QueryInterface(NS_GET_IID(nsCycleCollectionISupports),
reinterpret_cast<void**>(&out));
return out;
}
static inline void
ToParticipant(nsISupports *s, nsXPCOMCycleCollectionParticipant **cp);
static void
CanonicalizeParticipant(void **parti, nsCycleCollectionParticipant **cp)
{
// If the participant is null, this is an nsISupports participant,
// so we must QI to get the real participant.
if (!*cp) {
nsISupports *nsparti = static_cast<nsISupports*>(*parti);
nsparti = CanonicalizeXPCOMParticipant(nsparti);
NS_ASSERTION(nsparti,
"Don't add objects that don't participate in collection!");
nsXPCOMCycleCollectionParticipant *xcp;
ToParticipant(nsparti, &xcp);
*parti = nsparti;
*cp = xcp;
}
}
class nsCycleCollector;
struct nsPurpleBuffer
{
private:
struct Block {
Block *mNext;
// Try to match the size of a jemalloc bucket, to minimize slop bytes.
// - On 32-bit platforms sizeof(nsPurpleBufferEntry) is 12, so mEntries
// is 16,380 bytes, which leaves 4 bytes for mNext.
// - On 64-bit platforms sizeof(nsPurpleBufferEntry) is 24, so mEntries
// is 32,544 bytes, which leaves 8 bytes for mNext.
nsPurpleBufferEntry mEntries[1365];
Block() : mNext(nullptr) {
// Ensure Block is the right size (see above).
static_assert(
sizeof(Block) == 16384 || // 32-bit
sizeof(Block) == 32768, // 64-bit
"ill-sized nsPurpleBuffer::Block"
);
}
template <class PurpleVisitor>
void VisitEntries(nsPurpleBuffer &aBuffer, PurpleVisitor &aVisitor)
{
nsPurpleBufferEntry *eEnd = ArrayEnd(mEntries);
for (nsPurpleBufferEntry *e = mEntries; e != eEnd; ++e) {
if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
aVisitor.Visit(aBuffer, e);
}
}
}
};
// This class wraps a linked list of the elements in the purple
// buffer.
uint32_t mCount;
Block mFirstBlock;
nsPurpleBufferEntry *mFreeList;
public:
nsPurpleBuffer()
{
InitBlocks();
}
~nsPurpleBuffer()
{
FreeBlocks();
}
template <class PurpleVisitor>
void VisitEntries(PurpleVisitor &aVisitor)
{
for (Block *b = &mFirstBlock; b; b = b->mNext) {
b->VisitEntries(*this, aVisitor);
}
}
void InitBlocks()
{
mCount = 0;
mFreeList = nullptr;
StartBlock(&mFirstBlock);
}
void StartBlock(Block *aBlock)
{
NS_ABORT_IF_FALSE(!mFreeList, "should not have free list");
// Put all the entries in the block on the free list.
nsPurpleBufferEntry *entries = aBlock->mEntries;
mFreeList = entries;
for (uint32_t i = 1; i < ArrayLength(aBlock->mEntries); ++i) {
entries[i - 1].mNextInFreeList =
(nsPurpleBufferEntry*)(uintptr_t(entries + i) | 1);
}
entries[ArrayLength(aBlock->mEntries) - 1].mNextInFreeList =
(nsPurpleBufferEntry*)1;
}
void FreeBlocks()
{
if (mCount > 0)
UnmarkRemainingPurple(&mFirstBlock);
Block *b = mFirstBlock.mNext;
while (b) {
if (mCount > 0)
UnmarkRemainingPurple(b);
Block *next = b->mNext;
delete b;
b = next;
}
mFirstBlock.mNext = nullptr;
}
struct UnmarkRemainingPurpleVisitor
{
void
Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
{
if (aEntry->mRefCnt) {
aEntry->mRefCnt->RemoveFromPurpleBuffer();
aEntry->mRefCnt = nullptr;
}
aEntry->mObject = nullptr;
--aBuffer.mCount;
}
};
void UnmarkRemainingPurple(Block *b)
{
UnmarkRemainingPurpleVisitor visitor;
b->VisitEntries(*this, visitor);
}
void SelectPointers(GCGraphBuilder &builder);
// RemoveSkippable removes entries from the purple buffer synchronously
// (1) if aAsyncSnowWhiteFreeing is false and nsPurpleBufferEntry::mRefCnt is 0 or
// (2) if the object's nsXPCOMCycleCollectionParticipant::CanSkip() returns true or
// (3) if nsPurpleBufferEntry::mRefCnt->IsPurple() is false.
// (4) If removeChildlessNodes is true, then any nodes in the purple buffer
// that will have no children in the cycle collector graph will also be
// removed. CanSkip() may be run on these children.
void RemoveSkippable(nsCycleCollector* aCollector,
bool removeChildlessNodes,
bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb);
nsPurpleBufferEntry* NewEntry()
{
if (!mFreeList) {
Block *b = new Block;
StartBlock(b);
// Add the new block as the second block in the list.
b->mNext = mFirstBlock.mNext;
mFirstBlock.mNext = b;
}
nsPurpleBufferEntry *e = mFreeList;
mFreeList = (nsPurpleBufferEntry*)
(uintptr_t(mFreeList->mNextInFreeList) & ~uintptr_t(1));
return e;
}
void Put(void *p, nsCycleCollectionParticipant *cp,
nsCycleCollectingAutoRefCnt *aRefCnt)
{
nsPurpleBufferEntry *e = NewEntry();
++mCount;
e->mObject = p;
e->mRefCnt = aRefCnt;
e->mParticipant = cp;
}
void Remove(nsPurpleBufferEntry *e)
{
MOZ_ASSERT(mCount != 0, "must have entries");
if (e->mRefCnt) {
e->mRefCnt->RemoveFromPurpleBuffer();
e->mRefCnt = nullptr;
}
e->mNextInFreeList =
(nsPurpleBufferEntry*)(uintptr_t(mFreeList) | uintptr_t(1));
mFreeList = e;
--mCount;
}
uint32_t Count() const
{
return mCount;
}
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
{
size_t n = 0;
// Don't measure mFirstBlock because it's within |this|.
const Block *block = mFirstBlock.mNext;
while (block) {
n += aMallocSizeOf(block);
block = block->mNext;
}
// mFreeList is deliberately not measured because it points into
// the purple buffer, which is within mFirstBlock and thus within |this|.
//
// We also don't measure the things pointed to by mEntries[] because
// those pointers are non-owning.
return n;
}
};
static bool
AddPurpleRoot(GCGraphBuilder &aBuilder, void *aRoot, nsCycleCollectionParticipant *aParti);
struct SelectPointersVisitor
{
SelectPointersVisitor(GCGraphBuilder &aBuilder)
: mBuilder(aBuilder)
{}
void
Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
{
MOZ_ASSERT(aEntry->mObject, "Null object in purple buffer");
MOZ_ASSERT(aEntry->mRefCnt->get() != 0,
"SelectPointersVisitor: snow-white object in the purple buffer");
if (!aEntry->mRefCnt->IsPurple() ||
AddPurpleRoot(mBuilder, aEntry->mObject, aEntry->mParticipant)) {
aBuffer.Remove(aEntry);
}
}
private:
GCGraphBuilder &mBuilder;
};
void
nsPurpleBuffer::SelectPointers(GCGraphBuilder &aBuilder)
{
SelectPointersVisitor visitor(aBuilder);
VisitEntries(visitor);
NS_ASSERTION(mCount == 0, "AddPurpleRoot failed");
if (mCount == 0) {
FreeBlocks();
InitBlocks();
}
}
enum ccType {
ScheduledCC, /* Automatically triggered, based on time or the purple buffer. */
ManualCC, /* Explicitly triggered. */
ShutdownCC /* Shutdown CC, used for finding leaks. */
};
#ifdef MOZ_NUWA_PROCESS
#include "ipc/Nuwa.h"
#endif
////////////////////////////////////////////////////////////////////////
// Top level structure for the cycle collector.
////////////////////////////////////////////////////////////////////////
class nsCycleCollector
{
friend class GCGraphBuilder;
bool mCollectionInProgress;
// mScanInProgress should be false when we're collecting white objects.
bool mScanInProgress;
nsCycleCollectorResults *mResults;
TimeStamp mCollectionStart;
CycleCollectedJSRuntime *mJSRuntime;
GCGraph mGraph;
nsIThread* mThread;
nsCycleCollectorParams mParams;
nsTArray<PtrInfo*> *mWhiteNodes;
uint32_t mWhiteNodeCount;
// mVisitedRefCounted and mVisitedGCed are only used for telemetry
uint32_t mVisitedRefCounted;
uint32_t mVisitedGCed;
CC_BeforeUnlinkCallback mBeforeUnlinkCB;
CC_ForgetSkippableCallback mForgetSkippableCB;
nsCOMPtr<nsIMemoryReporter> mReporter;
nsPurpleBuffer mPurpleBuf;
uint32_t mUnmergedNeeded;
uint32_t mMergedInARow;
public:
nsCycleCollector();
~nsCycleCollector();
void RegisterJSRuntime(CycleCollectedJSRuntime *aJSRuntime);
void ForgetJSRuntime();
void SetBeforeUnlinkCallback(CC_BeforeUnlinkCallback aBeforeUnlinkCB)
{
CheckThreadSafety();
mBeforeUnlinkCB = aBeforeUnlinkCB;
}
void SetForgetSkippableCallback(CC_ForgetSkippableCallback aForgetSkippableCB)
{
CheckThreadSafety();
mForgetSkippableCB = aForgetSkippableCB;
}
void Suspect(void *n, nsCycleCollectionParticipant *cp,
nsCycleCollectingAutoRefCnt *aRefCnt);
uint32_t SuspectedCount();
void ForgetSkippable(bool aRemoveChildlessNodes, bool aAsyncSnowWhiteFreeing);
bool FreeSnowWhite(bool aUntilNoSWInPurpleBuffer);
bool Collect(ccType aCCType,
nsTArray<PtrInfo*> *aWhiteNodes,
nsCycleCollectorResults *aResults,
nsICycleCollectorListener *aManualListener);
void Shutdown();
void SizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
size_t *aObjectSize,
size_t *aGraphNodesSize,
size_t *aGraphEdgesSize,
size_t *aWeakMapsSize,
size_t *aWhiteNodeSize,
size_t *aPurpleBufferSize) const;
private:
void CheckThreadSafety();
void ShutdownCollect();
void PrepareForCollection(nsCycleCollectorResults *aResults,
nsTArray<PtrInfo*> *aWhiteNodes);
void FixGrayBits(bool aForceGC);
bool ShouldMergeZones(ccType aCCType);
void BeginCollection(ccType aCCType, nsICycleCollectorListener *aManualListener);
void MarkRoots(GCGraphBuilder &aBuilder);
void ScanRoots(nsICycleCollectorListener *aListener);
void ScanWeakMaps();
// returns whether anything was collected
bool CollectWhite();
void CleanupAfterCollection();
};
/**
* GraphWalker is templatized over a Visitor class that must provide
* the following two methods:
*
* bool ShouldVisitNode(PtrInfo const *pi);
* void VisitNode(PtrInfo *pi);
*/
template <class Visitor>
class GraphWalker
{
private:
Visitor mVisitor;
void DoWalk(nsDeque &aQueue);
void CheckedPush(nsDeque &aQueue, PtrInfo *pi)
{
CC_AbortIfNull(pi);
if (!aQueue.Push(pi, fallible_t())) {
mVisitor.Failed();
}
}
public:
void Walk(PtrInfo *s0);
void WalkFromRoots(GCGraph &aGraph);
// copy-constructing the visitor should be cheap, and less
// indirection than using a reference
GraphWalker(const Visitor aVisitor) : mVisitor(aVisitor) {}
};
////////////////////////////////////////////////////////////////////////
// The static collector struct
////////////////////////////////////////////////////////////////////////
struct CollectorData {
nsCycleCollector* mCollector;
CycleCollectedJSRuntime* mRuntime;
};
static mozilla::ThreadLocal<CollectorData*> sCollectorData;
////////////////////////////////////////////////////////////////////////
// Utility functions
////////////////////////////////////////////////////////////////////////
MOZ_NEVER_INLINE static void
Fault(const char *msg, const void *ptr=nullptr)
{
if (ptr)
printf("Fault in cycle collector: %s (ptr: %p)\n", msg, ptr);
else
printf("Fault in cycle collector: %s\n", msg);
NS_RUNTIMEABORT("cycle collector fault");
}
static void
Fault(const char *msg, PtrInfo *pi)
{
Fault(msg, pi->mPointer);
}
static inline void
ToParticipant(nsISupports *s, nsXPCOMCycleCollectionParticipant **cp)
{
// We use QI to move from an nsISupports to an
// nsXPCOMCycleCollectionParticipant, which is a per-class singleton helper
// object that implements traversal and unlinking logic for the nsISupports
// in question.
CallQueryInterface(s, cp);
}
template <class Visitor>
MOZ_NEVER_INLINE void
GraphWalker<Visitor>::Walk(PtrInfo *s0)
{
nsDeque queue;
CheckedPush(queue, s0);
DoWalk(queue);
}
template <class Visitor>
MOZ_NEVER_INLINE void
GraphWalker<Visitor>::WalkFromRoots(GCGraph& aGraph)
{
nsDeque queue;
NodePool::Enumerator etor(aGraph.mNodes);
for (uint32_t i = 0; i < aGraph.mRootCount; ++i) {
CheckedPush(queue, etor.GetNext());
}
DoWalk(queue);
}
template <class Visitor>
MOZ_NEVER_INLINE void
GraphWalker<Visitor>::DoWalk(nsDeque &aQueue)
{
// Use a aQueue to match the breadth-first traversal used when we
// built the graph, for hopefully-better locality.
while (aQueue.GetSize() > 0) {
PtrInfo *pi = static_cast<PtrInfo*>(aQueue.PopFront());
CC_AbortIfNull(pi);
if (mVisitor.ShouldVisitNode(pi)) {
mVisitor.VisitNode(pi);
for (EdgePool::Iterator child = pi->FirstChild(),
child_end = pi->LastChild();
child != child_end; ++child) {
CheckedPush(aQueue, *child);
}
}
}
}
struct CCGraphDescriber
{
CCGraphDescriber()
: mAddress("0x"), mToAddress("0x"), mCnt(0), mType(eUnknown) {}
enum Type
{
eRefCountedObject,
eGCedObject,
eGCMarkedObject,
eEdge,
eRoot,
eGarbage,
eUnknown
};
nsCString mAddress;
nsCString mToAddress;
nsCString mName;
uint32_t mCnt;
Type mType;
};
class nsCycleCollectorLogger MOZ_FINAL : public nsICycleCollectorListener
{
public:
nsCycleCollectorLogger() :
mStream(nullptr), mWantAllTraces(false),
mDisableLog(false), mWantAfterProcessing(false),
mNextIndex(0)
{
}
~nsCycleCollectorLogger()
{
if (mStream) {
MozillaUnRegisterDebugFILE(mStream);
fclose(mStream);
}
}
NS_DECL_ISUPPORTS
void SetAllTraces()
{
mWantAllTraces = true;
}
NS_IMETHOD AllTraces(nsICycleCollectorListener** aListener)
{
SetAllTraces();
NS_ADDREF(*aListener = this);
return NS_OK;
}
NS_IMETHOD GetWantAllTraces(bool* aAllTraces)
{
*aAllTraces = mWantAllTraces;
return NS_OK;
}
NS_IMETHOD GetDisableLog(bool* aDisableLog)
{
*aDisableLog = mDisableLog;
return NS_OK;
}
NS_IMETHOD SetDisableLog(bool aDisableLog)
{
mDisableLog = aDisableLog;
return NS_OK;
}
NS_IMETHOD GetWantAfterProcessing(bool* aWantAfterProcessing)
{
*aWantAfterProcessing = mWantAfterProcessing;
return NS_OK;
}
NS_IMETHOD SetWantAfterProcessing(bool aWantAfterProcessing)
{
mWantAfterProcessing = aWantAfterProcessing;
return NS_OK;
}
NS_IMETHOD GetFilenameIdentifier(nsAString& aIdentifier)
{
aIdentifier = mFilenameIdentifier;
return NS_OK;
}
NS_IMETHOD SetFilenameIdentifier(const nsAString& aIdentifier)
{
mFilenameIdentifier = aIdentifier;
return NS_OK;
}
NS_IMETHOD Begin()
{
mCurrentAddress.AssignLiteral("0x");
mDescribers.Clear();
mNextIndex = 0;
if (mDisableLog) {
return NS_OK;
}
// Initially create the log in a file starting with
// "incomplete-gc-edges". We'll move the file and strip off the
// "incomplete-" once the dump completes. (We do this because we don't
// want scripts which poll the filesystem looking for gc/cc dumps to
// grab a file before we're finished writing to it.)
nsCOMPtr<nsIFile> gcLogFile = CreateTempFile("incomplete-gc-edges");
NS_ENSURE_STATE(gcLogFile);
// Dump the JS heap.
FILE* gcLogANSIFile = nullptr;
gcLogFile->OpenANSIFileDesc("w", &gcLogANSIFile);
NS_ENSURE_STATE(gcLogANSIFile);
MozillaRegisterDebugFILE(gcLogANSIFile);
CollectorData *data = sCollectorData.get();
if (data && data->mRuntime)
data->mRuntime->DumpJSHeap(gcLogANSIFile);
MozillaUnRegisterDebugFILE(gcLogANSIFile);
fclose(gcLogANSIFile);
// Strip off "incomplete-".
nsCOMPtr<nsIFile> gcLogFileFinalDestination =
CreateTempFile("gc-edges");
NS_ENSURE_STATE(gcLogFileFinalDestination);
nsAutoString gcLogFileFinalDestinationName;
gcLogFileFinalDestination->GetLeafName(gcLogFileFinalDestinationName);
NS_ENSURE_STATE(!gcLogFileFinalDestinationName.IsEmpty());
gcLogFile->MoveTo(/* directory */ nullptr, gcLogFileFinalDestinationName);
// Log to the error console.
nsCOMPtr<nsIConsoleService> cs =
do_GetService(NS_CONSOLESERVICE_CONTRACTID);
if (cs) {
nsAutoString gcLogPath;
gcLogFileFinalDestination->GetPath(gcLogPath);
nsString msg = NS_LITERAL_STRING("Garbage Collector log dumped to ") +
gcLogPath;
cs->LogStringMessage(msg.get());
}
// Open a file for dumping the CC graph. We again prefix with
// "incomplete-".
mOutFile = CreateTempFile("incomplete-cc-edges");
NS_ENSURE_STATE(mOutFile);
MOZ_ASSERT(!mStream);
mOutFile->OpenANSIFileDesc("w", &mStream);
NS_ENSURE_STATE(mStream);
MozillaRegisterDebugFILE(mStream);
fprintf(mStream, "# WantAllTraces=%s\n", mWantAllTraces ? "true" : "false");
return NS_OK;
}
NS_IMETHOD NoteRefCountedObject(uint64_t aAddress, uint32_t refCount,
const char *aObjectDescription)
{
if (!mDisableLog) {
fprintf(mStream, "%p [rc=%u] %s\n", (void*)aAddress, refCount,
aObjectDescription);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = mDescribers.AppendElement();
mCurrentAddress.AssignLiteral("0x");
mCurrentAddress.AppendInt(aAddress, 16);
d->mType = CCGraphDescriber::eRefCountedObject;
d->mAddress = mCurrentAddress;
d->mCnt = refCount;
d->mName.Append(aObjectDescription);
}
return NS_OK;
}
NS_IMETHOD NoteGCedObject(uint64_t aAddress, bool aMarked,
const char *aObjectDescription)
{
if (!mDisableLog) {
fprintf(mStream, "%p [gc%s] %s\n", (void*)aAddress,
aMarked ? ".marked" : "", aObjectDescription);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = mDescribers.AppendElement();
mCurrentAddress.AssignLiteral("0x");
mCurrentAddress.AppendInt(aAddress, 16);
d->mType = aMarked ? CCGraphDescriber::eGCMarkedObject :
CCGraphDescriber::eGCedObject;
d->mAddress = mCurrentAddress;
d->mName.Append(aObjectDescription);
}
return NS_OK;
}
NS_IMETHOD NoteEdge(uint64_t aToAddress, const char *aEdgeName)
{
if (!mDisableLog) {
fprintf(mStream, "> %p %s\n", (void*)aToAddress, aEdgeName);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = mDescribers.AppendElement();
d->mType = CCGraphDescriber::eEdge;
d->mAddress = mCurrentAddress;
d->mToAddress.AppendInt(aToAddress, 16);
d->mName.Append(aEdgeName);
}
return NS_OK;
}
NS_IMETHOD NoteWeakMapEntry(uint64_t aMap, uint64_t aKey,
uint64_t aKeyDelegate, uint64_t aValue)
{
if (!mDisableLog) {
fprintf(mStream, "WeakMapEntry map=%p key=%p keyDelegate=%p value=%p\n",
(void*)aMap, (void*)aKey, (void*)aKeyDelegate, (void*)aValue);
}
// We don't support after-processing for weak map entries.
return NS_OK;
}
NS_IMETHOD BeginResults()
{
if (!mDisableLog) {
fputs("==========\n", mStream);
}
return NS_OK;
}
NS_IMETHOD DescribeRoot(uint64_t aAddress, uint32_t aKnownEdges)
{
if (!mDisableLog) {
fprintf(mStream, "%p [known=%u]\n", (void*)aAddress, aKnownEdges);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = mDescribers.AppendElement();
d->mType = CCGraphDescriber::eRoot;
d->mAddress.AppendInt(aAddress, 16);
d->mCnt = aKnownEdges;
}
return NS_OK;
}
NS_IMETHOD DescribeGarbage(uint64_t aAddress)
{
if (!mDisableLog) {
fprintf(mStream, "%p [garbage]\n", (void*)aAddress);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = mDescribers.AppendElement();
d->mType = CCGraphDescriber::eGarbage;
d->mAddress.AppendInt(aAddress, 16);
}
return NS_OK;
}
NS_IMETHOD End()
{
if (!mDisableLog) {
MOZ_ASSERT(mStream);
MOZ_ASSERT(mOutFile);
MozillaUnRegisterDebugFILE(mStream);
fclose(mStream);
mStream = nullptr;
// Strip off "incomplete-" from the log file's name.
nsCOMPtr<nsIFile> logFileFinalDestination =
CreateTempFile("cc-edges");
NS_ENSURE_STATE(logFileFinalDestination);
nsAutoString logFileFinalDestinationName;
logFileFinalDestination->GetLeafName(logFileFinalDestinationName);
NS_ENSURE_STATE(!logFileFinalDestinationName.IsEmpty());
mOutFile->MoveTo(/* directory = */ nullptr,
logFileFinalDestinationName);
mOutFile = nullptr;
// Log to the error console.
nsCOMPtr<nsIConsoleService> cs =
do_GetService(NS_CONSOLESERVICE_CONTRACTID);
if (cs) {
nsAutoString ccLogPath;
logFileFinalDestination->GetPath(ccLogPath);
nsString msg = NS_LITERAL_STRING("Cycle Collector log dumped to ") +
ccLogPath;
cs->LogStringMessage(msg.get());
}
}
return NS_OK;
}
NS_IMETHOD ProcessNext(nsICycleCollectorHandler* aHandler,
bool* aCanContinue)
{
NS_ENSURE_STATE(aHandler && mWantAfterProcessing);
if (mNextIndex < mDescribers.Length()) {
CCGraphDescriber& d = mDescribers[mNextIndex++];
switch (d.mType) {
case CCGraphDescriber::eRefCountedObject:
aHandler->NoteRefCountedObject(d.mAddress,
d.mCnt,
d.mName);
break;
case CCGraphDescriber::eGCedObject:
case CCGraphDescriber::eGCMarkedObject:
aHandler->NoteGCedObject(d.mAddress,
d.mType ==
CCGraphDescriber::eGCMarkedObject,
d.mName);
break;
case CCGraphDescriber::eEdge:
aHandler->NoteEdge(d.mAddress,
d.mToAddress,
d.mName);
break;
case CCGraphDescriber::eRoot:
aHandler->DescribeRoot(d.mAddress,
d.mCnt);
break;
case CCGraphDescriber::eGarbage:
aHandler->DescribeGarbage(d.mAddress);
break;
case CCGraphDescriber::eUnknown:
NS_NOTREACHED("CCGraphDescriber::eUnknown");
break;
}
}
if (!(*aCanContinue = mNextIndex < mDescribers.Length())) {
mCurrentAddress.AssignLiteral("0x");
mDescribers.Clear();
mNextIndex = 0;
}
return NS_OK;
}
private:
/**
* Create a new file named something like aPrefix.$PID.$IDENTIFIER.log in
* $MOZ_CC_LOG_DIRECTORY or in the system's temp directory. No existing
* file will be overwritten; if aPrefix.$PID.$IDENTIFIER.log exists, we'll
* try a file named something like aPrefix.$PID.$IDENTIFIER-1.log, and so
* on.
*/
already_AddRefed<nsIFile>
CreateTempFile(const char* aPrefix)
{
nsPrintfCString filename("%s.%d%s%s.log",
aPrefix,
base::GetCurrentProcId(),
mFilenameIdentifier.IsEmpty() ? "" : ".",
NS_ConvertUTF16toUTF8(mFilenameIdentifier).get());
// Get the log directory either from $MOZ_CC_LOG_DIRECTORY or from
// the fallback directories in OpenTempFile. We don't use an nsCOMPtr
// here because OpenTempFile uses an in/out param and getter_AddRefs
// wouldn't work.
nsIFile* logFile = nullptr;
if (char* env = PR_GetEnv("MOZ_CC_LOG_DIRECTORY")) {
NS_NewNativeLocalFile(nsCString(env), /* followLinks = */ true,
&logFile);
}
nsresult rv = nsMemoryInfoDumper::OpenTempFile(filename, &logFile);
if (NS_FAILED(rv)) {
NS_IF_RELEASE(logFile);
return nullptr;
}
return dont_AddRef(logFile);
}
FILE *mStream;
nsCOMPtr<nsIFile> mOutFile;
bool mWantAllTraces;
bool mDisableLog;
bool mWantAfterProcessing;
nsString mFilenameIdentifier;
nsCString mCurrentAddress;
nsTArray<CCGraphDescriber> mDescribers;
uint32_t mNextIndex;
};
NS_IMPL_ISUPPORTS1(nsCycleCollectorLogger, nsICycleCollectorListener)
nsresult
nsCycleCollectorLoggerConstructor(nsISupports* aOuter,
const nsIID& aIID,
void* *aInstancePtr)
{
NS_ENSURE_TRUE(!aOuter, NS_ERROR_NO_AGGREGATION);
nsISupports *logger = new nsCycleCollectorLogger();
return logger->QueryInterface(aIID, aInstancePtr);
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |MarkRoots| routine.
////////////////////////////////////////////////////////////////////////
struct PtrToNodeEntry : public PLDHashEntryHdr
{
// The key is mNode->mPointer
PtrInfo *mNode;
};
static bool
PtrToNodeMatchEntry(PLDHashTable *table,
const PLDHashEntryHdr *entry,
const void *key)
{
const PtrToNodeEntry *n = static_cast<const PtrToNodeEntry*>(entry);
return n->mNode->mPointer == key;
}
static PLDHashTableOps PtrNodeOps = {
PL_DHashAllocTable,
PL_DHashFreeTable,
PL_DHashVoidPtrKeyStub,
PtrToNodeMatchEntry,
PL_DHashMoveEntryStub,
PL_DHashClearEntryStub,
PL_DHashFinalizeStub,
nullptr
};
class GCGraphBuilder : public nsCycleCollectionTraversalCallback,
public nsCycleCollectionNoteRootCallback
{
private:
nsCycleCollector *mCollector;
NodePool::Builder mNodeBuilder;
EdgePool::Builder mEdgeBuilder;
nsTArray<WeakMapping> &mWeakMaps;
PLDHashTable mPtrToNodeMap;
PtrInfo *mCurrPi;
nsCycleCollectionParticipant *mJSParticipant;
nsCycleCollectionParticipant *mJSZoneParticipant;
nsCString mNextEdgeName;
nsICycleCollectorListener *mListener;
bool mMergeZones;
bool mRanOutOfMemory;
public:
GCGraphBuilder(nsCycleCollector *aCollector,
GCGraph &aGraph,
CycleCollectedJSRuntime *aJSRuntime,
nsICycleCollectorListener *aListener,
bool aMergeZones);
~GCGraphBuilder();
bool WantAllTraces() const
{
return nsCycleCollectionNoteRootCallback::WantAllTraces();
}
uint32_t Count() const { return mPtrToNodeMap.entryCount; }
PtrInfo* AddNode(void *aPtr, nsCycleCollectionParticipant *aParticipant);
PtrInfo* AddWeakMapNode(void* node);
void Traverse(PtrInfo* aPtrInfo);
void SetLastChild();
bool RanOutOfMemory() const { return mRanOutOfMemory; }
private:
void DescribeNode(uint32_t refCount, const char *objName)
{
mCurrPi->mRefCount = refCount;
}
public:
// nsCycleCollectionNoteRootCallback methods.
NS_IMETHOD_(void) NoteXPCOMRoot(nsISupports *root);
NS_IMETHOD_(void) NoteJSRoot(void *root);
NS_IMETHOD_(void) NoteNativeRoot(void *root, nsCycleCollectionParticipant *participant);
NS_IMETHOD_(void) NoteWeakMapping(void *map, void *key, void *kdelegate, void *val);
// nsCycleCollectionTraversalCallback methods.
NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refCount,
const char *objName);
NS_IMETHOD_(void) DescribeGCedNode(bool isMarked, const char *objName);
NS_IMETHOD_(void) NoteXPCOMChild(nsISupports *child);
NS_IMETHOD_(void) NoteJSChild(void *child);
NS_IMETHOD_(void) NoteNativeChild(void *child,
nsCycleCollectionParticipant *participant);
NS_IMETHOD_(void) NoteNextEdgeName(const char* name);
private:
NS_IMETHOD_(void) NoteRoot(void *root,
nsCycleCollectionParticipant *participant)
{
MOZ_ASSERT(root);
MOZ_ASSERT(participant);
if (!participant->CanSkipInCC(root) || MOZ_UNLIKELY(WantAllTraces())) {
AddNode(root, participant);
}
}
NS_IMETHOD_(void) NoteChild(void *child, nsCycleCollectionParticipant *cp,
nsCString edgeName)
{
PtrInfo *childPi = AddNode(child, cp);
if (!childPi)
return;
mEdgeBuilder.Add(childPi);
if (mListener) {
mListener->NoteEdge((uint64_t)child, edgeName.get());
}
++childPi->mInternalRefs;
}
JS::Zone *MergeZone(void *gcthing) {
if (!mMergeZones) {
return nullptr;
}
JS::Zone *zone = JS::GetGCThingZone(gcthing);
if (js::IsSystemZone(zone)) {
return nullptr;
}
return zone;
}
};
GCGraphBuilder::GCGraphBuilder(nsCycleCollector *aCollector,
GCGraph &aGraph,
CycleCollectedJSRuntime *aJSRuntime,
nsICycleCollectorListener *aListener,
bool aMergeZones)
: mCollector(aCollector),
mNodeBuilder(aGraph.mNodes),
mEdgeBuilder(aGraph.mEdges),
mWeakMaps(aGraph.mWeakMaps),
mJSParticipant(nullptr),
mJSZoneParticipant(nullptr),
mListener(aListener),
mMergeZones(aMergeZones),
mRanOutOfMemory(false)
{
if (!PL_DHashTableInit(&mPtrToNodeMap, &PtrNodeOps, nullptr,
sizeof(PtrToNodeEntry), 32768)) {
MOZ_CRASH();
}
if (aJSRuntime) {
mJSParticipant = aJSRuntime->GCThingParticipant();
mJSZoneParticipant = aJSRuntime->ZoneParticipant();
}
uint32_t flags = 0;
if (!flags && mListener) {
flags = nsCycleCollectionTraversalCallback::WANT_DEBUG_INFO;
bool all = false;
mListener->GetWantAllTraces(&all);
if (all) {
flags |= nsCycleCollectionTraversalCallback::WANT_ALL_TRACES;
mWantAllTraces = true; // for nsCycleCollectionNoteRootCallback
}
}
mFlags |= flags;
mMergeZones = mMergeZones && MOZ_LIKELY(!WantAllTraces());
MOZ_ASSERT(nsCycleCollectionNoteRootCallback::WantAllTraces() ==
nsCycleCollectionTraversalCallback::WantAllTraces());
}
GCGraphBuilder::~GCGraphBuilder()
{
if (mPtrToNodeMap.ops)
PL_DHashTableFinish(&mPtrToNodeMap);
}
PtrInfo*
GCGraphBuilder::AddNode(void *aPtr, nsCycleCollectionParticipant *aParticipant)
{
PtrToNodeEntry *e = static_cast<PtrToNodeEntry*>(PL_DHashTableOperate(&mPtrToNodeMap, aPtr, PL_DHASH_ADD));
if (!e) {
mRanOutOfMemory = true;
return nullptr;
}
PtrInfo *result;
if (!e->mNode) {
// New entry.
result = mNodeBuilder.Add(aPtr, aParticipant);
e->mNode = result;
NS_ASSERTION(result, "mNodeBuilder.Add returned null");
} else {
result = e->mNode;
MOZ_ASSERT(result->mParticipant == aParticipant,
"nsCycleCollectionParticipant shouldn't change!");
}
return result;
}
MOZ_NEVER_INLINE void
GCGraphBuilder::Traverse(PtrInfo* aPtrInfo)
{
mCurrPi = aPtrInfo;
mCurrPi->SetFirstChild(mEdgeBuilder.Mark());
nsresult rv = aPtrInfo->mParticipant->Traverse(aPtrInfo->mPointer, *this);
if (NS_FAILED(rv)) {
Fault("script pointer traversal failed", aPtrInfo);
}
}
void
GCGraphBuilder::SetLastChild()
{
mCurrPi->SetLastChild(mEdgeBuilder.Mark());
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteXPCOMRoot(nsISupports *root)
{
root = CanonicalizeXPCOMParticipant(root);
NS_ASSERTION(root,
"Don't add objects that don't participate in collection!");
nsXPCOMCycleCollectionParticipant *cp;
ToParticipant(root, &cp);
NoteRoot(root, cp);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteJSRoot(void *root)
{
if (JS::Zone *zone = MergeZone(root)) {
NoteRoot(zone, mJSZoneParticipant);
} else {
NoteRoot(root, mJSParticipant);
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteNativeRoot(void *root, nsCycleCollectionParticipant *participant)
{
NoteRoot(root, participant);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::DescribeRefCountedNode(nsrefcnt refCount, const char *objName)
{
if (refCount == 0)
Fault("zero refcount", mCurrPi);
if (refCount == UINT32_MAX)
Fault("overflowing refcount", mCurrPi);
mCollector->mVisitedRefCounted++;
if (mListener) {
mListener->NoteRefCountedObject((uint64_t)mCurrPi->mPointer, refCount,
objName);
}
DescribeNode(refCount, objName);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::DescribeGCedNode(bool isMarked, const char *objName)
{
uint32_t refCount = isMarked ? UINT32_MAX : 0;
mCollector->mVisitedGCed++;
if (mListener) {
mListener->NoteGCedObject((uint64_t)mCurrPi->mPointer, isMarked,
objName);
}
DescribeNode(refCount, objName);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteXPCOMChild(nsISupports *child)
{
nsCString edgeName;
if (WantDebugInfo()) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (!child || !(child = CanonicalizeXPCOMParticipant(child)))
return;
nsXPCOMCycleCollectionParticipant *cp;
ToParticipant(child, &cp);
if (cp && (!cp->CanSkipThis(child) || WantAllTraces())) {
NoteChild(child, cp, edgeName);
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteNativeChild(void *child,
nsCycleCollectionParticipant *participant)
{
nsCString edgeName;
if (WantDebugInfo()) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (!child)
return;
MOZ_ASSERT(participant, "Need a nsCycleCollectionParticipant!");
NoteChild(child, participant, edgeName);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteJSChild(void *child)
{
if (!child) {
return;
}
nsCString edgeName;
if (MOZ_UNLIKELY(WantDebugInfo())) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (xpc_GCThingIsGrayCCThing(child) || MOZ_UNLIKELY(WantAllTraces())) {
if (JS::Zone *zone = MergeZone(child)) {
NoteChild(zone, mJSZoneParticipant, edgeName);
} else {
NoteChild(child, mJSParticipant, edgeName);
}
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteNextEdgeName(const char* name)
{
if (WantDebugInfo()) {
mNextEdgeName = name;
}
}
PtrInfo*
GCGraphBuilder::AddWeakMapNode(void *node)
{
MOZ_ASSERT(node, "Weak map node should be non-null.");
if (!xpc_GCThingIsGrayCCThing(node) && !WantAllTraces())
return nullptr;
if (JS::Zone *zone = MergeZone(node)) {
return AddNode(zone, mJSZoneParticipant);
} else {
return AddNode(node, mJSParticipant);
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteWeakMapping(void *map, void *key, void *kdelegate, void *val)
{
// Don't try to optimize away the entry here, as we've already attempted to
// do that in TraceWeakMapping in nsXPConnect.
WeakMapping *mapping = mWeakMaps.AppendElement();
mapping->mMap = map ? AddWeakMapNode(map) : nullptr;
mapping->mKey = key ? AddWeakMapNode(key) : nullptr;
mapping->mKeyDelegate = kdelegate ? AddWeakMapNode(kdelegate) : mapping->mKey;
mapping->mVal = val ? AddWeakMapNode(val) : nullptr;
if (mListener) {
mListener->NoteWeakMapEntry((uint64_t)map, (uint64_t)key,
(uint64_t)kdelegate, (uint64_t)val);
}
}
static bool
AddPurpleRoot(GCGraphBuilder &aBuilder, void *aRoot, nsCycleCollectionParticipant *aParti)
{
CanonicalizeParticipant(&aRoot, &aParti);
if (aBuilder.WantAllTraces() || !aParti->CanSkipInCC(aRoot)) {
PtrInfo *pinfo = aBuilder.AddNode(aRoot, aParti);
if (!pinfo) {
return false;
}
}
return true;
}
// MayHaveChild() will be false after a Traverse if the object does
// not have any children the CC will visit.
class ChildFinder : public nsCycleCollectionTraversalCallback
{
public:
ChildFinder() : mMayHaveChild(false) {}
// The logic of the Note*Child functions must mirror that of their
// respective functions in GCGraphBuilder.
NS_IMETHOD_(void) NoteXPCOMChild(nsISupports *child);
NS_IMETHOD_(void) NoteNativeChild(void *child,
nsCycleCollectionParticipant *helper);
NS_IMETHOD_(void) NoteJSChild(void *child);
NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refcount,
const char *objname) {}
NS_IMETHOD_(void) DescribeGCedNode(bool ismarked,
const char *objname) {}
NS_IMETHOD_(void) NoteNextEdgeName(const char* name) {}
bool MayHaveChild() {
return mMayHaveChild;
}
private:
bool mMayHaveChild;
};
NS_IMETHODIMP_(void)
ChildFinder::NoteXPCOMChild(nsISupports *child)
{
if (!child || !(child = CanonicalizeXPCOMParticipant(child)))
return;
nsXPCOMCycleCollectionParticipant *cp;
ToParticipant(child, &cp);
if (cp && !cp->CanSkip(child, true))
mMayHaveChild = true;
}
NS_IMETHODIMP_(void)
ChildFinder::NoteNativeChild(void *child,
nsCycleCollectionParticipant *helper)
{
if (child)
mMayHaveChild = true;
}
NS_IMETHODIMP_(void)
ChildFinder::NoteJSChild(void *child)
{
if (child && xpc_GCThingIsGrayCCThing(child)) {
mMayHaveChild = true;
}
}
static bool
MayHaveChild(void *o, nsCycleCollectionParticipant* cp)
{
ChildFinder cf;
cp->Traverse(o, cf);
return cf.MayHaveChild();
}
struct SnowWhiteObject
{
void* mPointer;
nsCycleCollectionParticipant* mParticipant;
nsCycleCollectingAutoRefCnt* mRefCnt;
};
class SnowWhiteKiller
{
public:
SnowWhiteKiller(uint32_t aMaxCount)
{
while (true) {
if (mObjects.SetCapacity(aMaxCount)) {
break;
}
if (aMaxCount == 1) {
NS_RUNTIMEABORT("Not enough memory to even delete objects!");
}
aMaxCount /= 2;
}
}
~SnowWhiteKiller()
{
for (uint32_t i = 0; i < mObjects.Length(); ++i) {
SnowWhiteObject& o = mObjects[i];
if (!o.mRefCnt->get() && !o.mRefCnt->IsInPurpleBuffer()) {
o.mRefCnt->stabilizeForDeletion();
o.mParticipant->DeleteCycleCollectable(o.mPointer);
}
}
}
void
Visit(nsPurpleBuffer& aBuffer, nsPurpleBufferEntry* aEntry)
{
MOZ_ASSERT(aEntry->mObject, "Null object in purple buffer");
if (!aEntry->mRefCnt->get()) {
void *o = aEntry->mObject;
nsCycleCollectionParticipant *cp = aEntry->mParticipant;
CanonicalizeParticipant(&o, &cp);
SnowWhiteObject swo = { o, cp, aEntry->mRefCnt };
if (mObjects.AppendElement(swo)) {
aBuffer.Remove(aEntry);
}
}
}
bool HasSnowWhiteObjects() const
{
return mObjects.Length() > 0;
}
private:
FallibleTArray<SnowWhiteObject> mObjects;
};
class RemoveSkippableVisitor : public SnowWhiteKiller
{
public:
RemoveSkippableVisitor(nsCycleCollector* aCollector,
uint32_t aMaxCount, bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb)
: SnowWhiteKiller(aAsyncSnowWhiteFreeing ? 0 : aMaxCount),
mRemoveChildlessNodes(aRemoveChildlessNodes),
mAsyncSnowWhiteFreeing(aAsyncSnowWhiteFreeing),
mDispatchedDeferredDeletion(false),
mCallback(aCb)
{}
~RemoveSkippableVisitor()
{
// Note, we must call the callback before SnowWhiteKiller calls
// DeleteCycleCollectable!
if (mCallback) {
mCallback();
}
if (HasSnowWhiteObjects()) {
// Effectively a continuation.
nsCycleCollector_dispatchDeferredDeletion(true);
}
}
void
Visit(nsPurpleBuffer &aBuffer, nsPurpleBufferEntry *aEntry)
{
MOZ_ASSERT(aEntry->mObject, "null mObject in purple buffer");
if (!aEntry->mRefCnt->get()) {
if (!mAsyncSnowWhiteFreeing) {
SnowWhiteKiller::Visit(aBuffer, aEntry);
} else if (!mDispatchedDeferredDeletion) {
mDispatchedDeferredDeletion = true;
nsCycleCollector_dispatchDeferredDeletion(false);
}
return;
}
void *o = aEntry->mObject;
nsCycleCollectionParticipant *cp = aEntry->mParticipant;
CanonicalizeParticipant(&o, &cp);
if (aEntry->mRefCnt->IsPurple() && !cp->CanSkip(o, false) &&
(!mRemoveChildlessNodes || MayHaveChild(o, cp))) {
return;
}
aBuffer.Remove(aEntry);
}
private:
bool mRemoveChildlessNodes;
bool mAsyncSnowWhiteFreeing;
bool mDispatchedDeferredDeletion;
CC_ForgetSkippableCallback mCallback;
};
void
nsPurpleBuffer::RemoveSkippable(nsCycleCollector* aCollector,
bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb)
{
RemoveSkippableVisitor visitor(aCollector, Count(), aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing, aCb);
VisitEntries(visitor);
}
bool
nsCycleCollector::FreeSnowWhite(bool aUntilNoSWInPurpleBuffer)
{
CheckThreadSafety();
bool hadSnowWhiteObjects = false;
do {
SnowWhiteKiller visitor(mPurpleBuf.Count());
mPurpleBuf.VisitEntries(visitor);
hadSnowWhiteObjects = hadSnowWhiteObjects ||
visitor.HasSnowWhiteObjects();
if (!visitor.HasSnowWhiteObjects()) {
break;
}
} while (aUntilNoSWInPurpleBuffer);
return hadSnowWhiteObjects;
}
void
nsCycleCollector::ForgetSkippable(bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing)
{
CheckThreadSafety();
if (mJSRuntime) {
mJSRuntime->PrepareForForgetSkippable();
}
MOZ_ASSERT(!mScanInProgress, "Don't forget skippable or free snow-white while scan is in progress.");
mPurpleBuf.RemoveSkippable(this, aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing, mForgetSkippableCB);
}
MOZ_NEVER_INLINE void
nsCycleCollector::MarkRoots(GCGraphBuilder &aBuilder)
{
mGraph.mRootCount = aBuilder.Count();
// read the PtrInfo out of the graph that we are building
NodePool::Enumerator queue(mGraph.mNodes);
while (!queue.IsDone()) {
PtrInfo *pi = queue.GetNext();
CC_AbortIfNull(pi);
aBuilder.Traverse(pi);
if (queue.AtBlockEnd()) {
aBuilder.SetLastChild();
}
}
if (mGraph.mRootCount > 0) {
aBuilder.SetLastChild();
}
if (aBuilder.RanOutOfMemory()) {
NS_ASSERTION(false,
"Ran out of memory while building cycle collector graph");
CC_TELEMETRY(_OOM, true);
}
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |ScanRoots| routine.
////////////////////////////////////////////////////////////////////////
struct ScanBlackVisitor
{
ScanBlackVisitor(uint32_t &aWhiteNodeCount, bool &aFailed)
: mWhiteNodeCount(aWhiteNodeCount), mFailed(aFailed)
{
}
bool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor != black;
}
MOZ_NEVER_INLINE void VisitNode(PtrInfo *pi)
{
if (pi->mColor == white)
--mWhiteNodeCount;
pi->mColor = black;
}
void Failed()
{
mFailed = true;
}
private:
uint32_t &mWhiteNodeCount;
bool &mFailed;
};
struct scanVisitor
{
scanVisitor(uint32_t &aWhiteNodeCount, bool &aFailed)
: mWhiteNodeCount(aWhiteNodeCount), mFailed(aFailed)
{
}
bool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor == grey;
}
MOZ_NEVER_INLINE void VisitNode(PtrInfo *pi)
{
if (pi->mInternalRefs > pi->mRefCount && pi->mRefCount > 0)
Fault("traversed refs exceed refcount", pi);
if (pi->mInternalRefs == pi->mRefCount || pi->mRefCount == 0) {
pi->mColor = white;
++mWhiteNodeCount;
} else {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, mFailed)).Walk(pi);
MOZ_ASSERT(pi->mColor == black,
"Why didn't ScanBlackVisitor make pi black?");
}
}
void Failed() {
mFailed = true;
}
private:
uint32_t &mWhiteNodeCount;
bool &mFailed;
};
// Iterate over the WeakMaps. If we mark anything while iterating
// over the WeakMaps, we must iterate over all of the WeakMaps again.
void
nsCycleCollector::ScanWeakMaps()
{
bool anyChanged;
bool failed = false;
do {
anyChanged = false;
for (uint32_t i = 0; i < mGraph.mWeakMaps.Length(); i++) {
WeakMapping *wm = &mGraph.mWeakMaps[i];
// If any of these are null, the original object was marked black.
uint32_t mColor = wm->mMap ? wm->mMap->mColor : black;
uint32_t kColor = wm->mKey ? wm->mKey->mColor : black;
uint32_t kdColor = wm->mKeyDelegate ? wm->mKeyDelegate->mColor : black;
uint32_t vColor = wm->mVal ? wm->mVal->mColor : black;
// All non-null weak mapping maps, keys and values are
// roots (in the sense of WalkFromRoots) in the cycle
// collector graph, and thus should have been colored
// either black or white in ScanRoots().
MOZ_ASSERT(mColor != grey, "Uncolored weak map");
MOZ_ASSERT(kColor != grey, "Uncolored weak map key");
MOZ_ASSERT(kdColor != grey, "Uncolored weak map key delegate");
MOZ_ASSERT(vColor != grey, "Uncolored weak map value");
if (mColor == black && kColor != black && kdColor == black) {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, failed)).Walk(wm->mKey);
anyChanged = true;
}
if (mColor == black && kColor == black && vColor != black) {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount, failed)).Walk(wm->mVal);
anyChanged = true;
}
}
} while (anyChanged);
if (failed) {
NS_ASSERTION(false, "Ran out of memory in ScanWeakMaps");
CC_TELEMETRY(_OOM, true);
}
}
void
nsCycleCollector::ScanRoots(nsICycleCollectorListener *aListener)
{
mWhiteNodeCount = 0;
// On the assumption that most nodes will be black, it's
// probably faster to use a GraphWalker than a
// NodePool::Enumerator.
bool failed = false;
GraphWalker<scanVisitor>(scanVisitor(mWhiteNodeCount, failed)).WalkFromRoots(mGraph);
if (failed) {
NS_ASSERTION(false, "Ran out of memory in ScanRoots");
CC_TELEMETRY(_OOM, true);
}
ScanWeakMaps();
if (aListener) {
aListener->BeginResults();
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo *pi = etor.GetNext();
switch (pi->mColor) {
case black:
if (pi->mRefCount > 0 && pi->mRefCount < UINT32_MAX &&
pi->mInternalRefs != pi->mRefCount) {
aListener->DescribeRoot((uint64_t)pi->mPointer,
pi->mInternalRefs);
}
break;
case white:
aListener->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.
break;
}
}
aListener->End();
}
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |CollectWhite| routine, somewhat modified.
////////////////////////////////////////////////////////////////////////
bool
nsCycleCollector::CollectWhite()
{
// Explanation of "somewhat modified": we have no way to collect the
// set of whites "all at once", we have to ask each of them to drop
// their outgoing links and assume this will cause the garbage cycle
// to *mostly* self-destruct (except for the reference we continue
// to hold).
//
// To do this "safely" we must make sure that the white nodes we're
// operating on are stable for the duration of our operation. So we
// make 3 sets of calls to language runtimes:
//
// - Root(whites), which should pin the whites in memory.
// - Unlink(whites), which drops outgoing links on each white.
// - Unroot(whites), which returns the whites to normal GC.
TimeLog timeLog;
MOZ_ASSERT(mWhiteNodes->IsEmpty(),
"CleanupAfterCollection wasn't called?");
mWhiteNodes->SetCapacity(mWhiteNodeCount);
uint32_t numWhiteGCed = 0;
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone())
{
PtrInfo *pinfo = etor.GetNext();
if (pinfo->mColor == white) {
mWhiteNodes->AppendElement(pinfo);
pinfo->mParticipant->Root(pinfo->mPointer);
if (pinfo->mRefCount == 0) {
// only JS objects have a refcount of 0
++numWhiteGCed;
}
}
}
uint32_t count = mWhiteNodes->Length();
MOZ_ASSERT(numWhiteGCed <= count,
"More freed GCed nodes than total freed nodes.");
if (mResults) {
mResults->mFreedRefCounted += count - numWhiteGCed;
mResults->mFreedGCed += numWhiteGCed;
}
timeLog.Checkpoint("CollectWhite::Root");
if (mBeforeUnlinkCB) {
mBeforeUnlinkCB();
timeLog.Checkpoint("CollectWhite::BeforeUnlinkCB");
}
for (uint32_t i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
#ifdef DEBUG
if (mJSRuntime) {
mJSRuntime->SetObjectToUnlink(pinfo->mPointer);
}
#endif
pinfo->mParticipant->Unlink(pinfo->mPointer);
#ifdef DEBUG
if (mJSRuntime) {
mJSRuntime->SetObjectToUnlink(nullptr);
mJSRuntime->AssertNoObjectsToTrace(pinfo->mPointer);
}
#endif
}
timeLog.Checkpoint("CollectWhite::Unlink");
for (uint32_t i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
pinfo->mParticipant->Unroot(pinfo->mPointer);
}
timeLog.Checkpoint("CollectWhite::Unroot");
nsCycleCollector_dispatchDeferredDeletion(false);
return count > 0;
}
////////////////////////
// Memory reporter
////////////////////////
class CycleCollectorReporter MOZ_FINAL : public nsIMemoryReporter
{
public:
CycleCollectorReporter(nsCycleCollector* aCollector)
: mCollector(aCollector)
{}
NS_DECL_ISUPPORTS
NS_IMETHOD GetName(nsACString& name)
{
name.AssignLiteral("cycle-collector");
return NS_OK;
}
NS_IMETHOD CollectReports(nsIMemoryReporterCallback* aCb,
nsISupports* aClosure)
{
size_t objectSize, graphNodesSize, graphEdgesSize, weakMapsSize,
whiteNodesSize, purpleBufferSize;
mCollector->SizeOfIncludingThis(MallocSizeOf,
&objectSize,
&graphNodesSize, &graphEdgesSize,
&weakMapsSize,
&whiteNodesSize,
&purpleBufferSize);
#define REPORT(_path, _amount, _desc) \
do { \
size_t amount = _amount; /* evaluate |_amount| only once */ \
if (amount > 0) { \
nsresult rv; \
rv = aCb->Callback(EmptyCString(), NS_LITERAL_CSTRING(_path), \
nsIMemoryReporter::KIND_HEAP, \
nsIMemoryReporter::UNITS_BYTES, _amount, \
NS_LITERAL_CSTRING(_desc), aClosure); \
NS_ENSURE_SUCCESS(rv, rv); \
} \
} while (0)
REPORT("explicit/cycle-collector/collector-object", objectSize,
"Memory used for the cycle collector object itself.");
REPORT("explicit/cycle-collector/graph-nodes", graphNodesSize,
"Memory used for the nodes of the cycle collector's graph. "
"This should be zero when the collector is idle.");
REPORT("explicit/cycle-collector/graph-edges", graphEdgesSize,
"Memory used for the edges of the cycle collector's graph. "
"This should be zero when the collector is idle.");
REPORT("explicit/cycle-collector/weak-maps", weakMapsSize,
"Memory used for the representation of weak maps in the "
"cycle collector's graph. "
"This should be zero when the collector is idle.");
REPORT("explicit/cycle-collector/white-nodes", whiteNodesSize,
"Memory used for the cycle collector's white nodes array. "
"This should be zero when the collector is idle.");
REPORT("explicit/cycle-collector/purple-buffer", purpleBufferSize,
"Memory used for the cycle collector's purple buffer.");
#undef REPORT
return NS_OK;
}
private:
NS_MEMORY_REPORTER_MALLOC_SIZEOF_FUN(MallocSizeOf)
nsCycleCollector* mCollector;
};
NS_IMPL_ISUPPORTS1(CycleCollectorReporter, nsIMemoryReporter)
////////////////////////////////////////////////////////////////////////
// Collector implementation
////////////////////////////////////////////////////////////////////////
nsCycleCollector::nsCycleCollector() :
mCollectionInProgress(false),
mScanInProgress(false),
mResults(nullptr),
mJSRuntime(nullptr),
mThread(NS_GetCurrentThread()),
mWhiteNodes(nullptr),
mWhiteNodeCount(0),
mVisitedRefCounted(0),
mVisitedGCed(0),
mBeforeUnlinkCB(nullptr),
mForgetSkippableCB(nullptr),
mReporter(nullptr),
mUnmergedNeeded(0),
mMergedInARow(0)
{
}
nsCycleCollector::~nsCycleCollector()
{
NS_UnregisterMemoryReporter(mReporter);
}
void
nsCycleCollector::RegisterJSRuntime(CycleCollectedJSRuntime *aJSRuntime)
{
if (mJSRuntime)
Fault("multiple registrations of cycle collector JS runtime", aJSRuntime);
mJSRuntime = aJSRuntime;
// We can't register the reporter in nsCycleCollector() because that runs
// before the memory reporter manager is initialized. So we do it here
// instead.
static bool registered = false;
if (!registered) {
NS_RegisterMemoryReporter(new CycleCollectorReporter(this));
registered = true;
}
}
void
nsCycleCollector::ForgetJSRuntime()
{
if (!mJSRuntime)
Fault("forgetting non-registered cycle collector JS runtime");
mJSRuntime = nullptr;
}
#ifdef DEBUG
static bool
nsCycleCollector_isScanSafe(void *s, nsCycleCollectionParticipant *cp)
{
if (!s)
return false;
if (cp)
return true;
nsXPCOMCycleCollectionParticipant *xcp;
ToParticipant(static_cast<nsISupports*>(s), &xcp);
return xcp != nullptr;
}
#endif
void
nsCycleCollector::Suspect(void *n, nsCycleCollectionParticipant *cp,
nsCycleCollectingAutoRefCnt *aRefCnt)
{
CheckThreadSafety();
// Re-entering ::Suspect during collection used to be a fault, but
// we are canonicalizing nsISupports pointers using QI, so we will
// see some spurious refcount traffic here.
if (mScanInProgress)
return;
MOZ_ASSERT(nsCycleCollector_isScanSafe(n, cp),
"suspected a non-scansafe pointer");
mPurpleBuf.Put(n, cp, aRefCnt);
}
void
nsCycleCollector::CheckThreadSafety()
{
#ifdef DEBUG
nsIThread* currentThread = NS_GetCurrentThread();
// XXXkhuey we can be called so late in shutdown that NS_GetCurrentThread
// returns null (after the thread manager has shut down)
MOZ_ASSERT(mThread == currentThread || !currentThread);
#endif
}
// The cycle collector uses the mark bitmap to discover what JS objects
// were reachable only from XPConnect roots that might participate in
// cycles. We ask the JS runtime whether we need to force a GC before
// this CC. It returns true on startup (before the mark bits have been set),
// and also when UnmarkGray has run out of stack. We also force GCs on shut
// down to collect cycles involving both DOM and JS.
void
nsCycleCollector::FixGrayBits(bool aForceGC)
{
CheckThreadSafety();
if (!mJSRuntime)
return;
if (!aForceGC) {
mJSRuntime->FixWeakMappingGrayBits();
bool needGC = mJSRuntime->NeedCollect();
// Only do a telemetry ping for non-shutdown CCs.
CC_TELEMETRY(_NEED_GC, needGC);
if (!needGC)
return;
if (mResults)
mResults->mForcedGC = true;
}
TimeLog timeLog;
mJSRuntime->Collect(aForceGC ? JS::gcreason::SHUTDOWN_CC : JS::gcreason::CC_FORCED);
timeLog.Checkpoint("GC()");
}
void
nsCycleCollector::PrepareForCollection(nsCycleCollectorResults *aResults,
nsTArray<PtrInfo*> *aWhiteNodes)
{
TimeLog timeLog;
mCollectionStart = TimeStamp::Now();
mVisitedRefCounted = 0;
mVisitedGCed = 0;
mCollectionInProgress = true;
if (mJSRuntime) {
mJSRuntime->PrepareForCollection();
}
mResults = aResults;
mWhiteNodes = aWhiteNodes;
timeLog.Checkpoint("PrepareForCollection()");
}
void
nsCycleCollector::CleanupAfterCollection()
{
mWhiteNodes->Clear();
mWhiteNodes = nullptr;
mGraph.Clear();
mCollectionInProgress = false;
#ifdef XP_OS2
// Now that the cycle collector has freed some memory, we can try to
// force the C library to give back as much memory to the system as
// possible.
_heapmin();
#endif
uint32_t interval = (uint32_t) ((TimeStamp::Now() - mCollectionStart).ToMilliseconds());
#ifdef COLLECT_TIME_DEBUG
printf("cc: total cycle collector time was %ums\n", interval);
if (mResults) {
printf("cc: visited %u ref counted and %u GCed objects, freed %d ref counted and %d GCed objects.\n",
mVisitedRefCounted, mVisitedGCed,
mResults->mFreedRefCounted, mResults->mFreedGCed);
} else {
printf("cc: visited %u ref counted and %u GCed objects, freed %d.\n",
mVisitedRefCounted, mVisitedGCed, mWhiteNodeCount);
}
printf("cc: \n");
#endif
if (mResults) {
mResults->mVisitedRefCounted = mVisitedRefCounted;
mResults->mVisitedGCed = mVisitedGCed;
mResults = nullptr;
}
CC_TELEMETRY( , interval);
CC_TELEMETRY(_VISITED_REF_COUNTED, mVisitedRefCounted);
CC_TELEMETRY(_VISITED_GCED, mVisitedGCed);
CC_TELEMETRY(_COLLECTED, mWhiteNodeCount);
}
void
nsCycleCollector::ShutdownCollect()
{
nsAutoTArray<PtrInfo*, 4000> whiteNodes;
for (uint32_t i = 0; i < DEFAULT_SHUTDOWN_COLLECTIONS; ++i) {
NS_ASSERTION(i < NORMAL_SHUTDOWN_COLLECTIONS, "Extra shutdown CC");
if (!Collect(ShutdownCC, &whiteNodes, nullptr, nullptr)) {
break;
}
}
}
bool
nsCycleCollector::Collect(ccType aCCType,
nsTArray<PtrInfo*> *aWhiteNodes,
nsCycleCollectorResults *aResults,
nsICycleCollectorListener *aManualListener)
{
CheckThreadSafety();
// This can legitimately happen in a few cases. See bug 383651.
if (mCollectionInProgress) {
return false;
}
PrepareForCollection(aResults, aWhiteNodes);
BeginCollection(aCCType, aManualListener);
bool collectedAny = CollectWhite();
CleanupAfterCollection();
return collectedAny;
}
// Don't merge too many times in a row, and do at least a minimum
// number of unmerged CCs in a row.
static const uint32_t kMinConsecutiveUnmerged = 3;
static const uint32_t kMaxConsecutiveMerged = 3;
bool
nsCycleCollector::ShouldMergeZones(ccType aCCType)
{
if (!mJSRuntime) {
return false;
}
MOZ_ASSERT(mUnmergedNeeded <= kMinConsecutiveUnmerged);
MOZ_ASSERT(mMergedInARow <= kMaxConsecutiveMerged);
if (mMergedInARow == kMaxConsecutiveMerged) {
MOZ_ASSERT(mUnmergedNeeded == 0);
mUnmergedNeeded = kMinConsecutiveUnmerged;
}
if (mUnmergedNeeded > 0) {
mUnmergedNeeded--;
mMergedInARow = 0;
return false;
}
if (aCCType == ScheduledCC && mJSRuntime->UsefulToMergeZones()) {
mMergedInARow++;
return true;
} else {
mMergedInARow = 0;
return false;
}
}
void
nsCycleCollector::BeginCollection(ccType aCCType,
nsICycleCollectorListener *aManualListener)
{
TimeLog timeLog;
bool isShutdown = (aCCType == ShutdownCC);
// Set up the listener for this CC.
MOZ_ASSERT_IF(isShutdown, !aManualListener);
nsCOMPtr<nsICycleCollectorListener> listener(aManualListener);
aManualListener = nullptr;
if (!listener) {
if (mParams.mLogAll || (isShutdown && mParams.mLogShutdown)) {
nsRefPtr<nsCycleCollectorLogger> logger = new nsCycleCollectorLogger();
if (isShutdown && mParams.mAllTracesAtShutdown) {
logger->SetAllTraces();
}
listener = logger.forget();
}
}
bool forceGC = isShutdown;
if (!forceGC && listener) {
// On a WantAllTraces CC, force a synchronous global GC to prevent
// hijinks from ForgetSkippable and compartmental GCs.
listener->GetWantAllTraces(&forceGC);
}
FixGrayBits(forceGC);
FreeSnowWhite(true);
if (listener && NS_FAILED(listener->Begin())) {
listener = nullptr;
}
// Set up the data structures for building the graph.
bool mergeZones = ShouldMergeZones(aCCType);
if (mResults) {
mResults->mMergedZones = mergeZones;
}
GCGraphBuilder builder(this, mGraph, mJSRuntime, listener,
mergeZones);
if (mJSRuntime) {
mJSRuntime->BeginCycleCollection(builder);
timeLog.Checkpoint("mJSRuntime->BeginCycleCollection()");
}
mScanInProgress = true;
mPurpleBuf.SelectPointers(builder);
timeLog.Checkpoint("SelectPointers()");
// The main Bacon & Rajan collection algorithm.
MarkRoots(builder);
timeLog.Checkpoint("MarkRoots()");
ScanRoots(listener);
timeLog.Checkpoint("ScanRoots()");
mScanInProgress = false;
}
uint32_t
nsCycleCollector::SuspectedCount()
{
CheckThreadSafety();
return mPurpleBuf.Count();
}
void
nsCycleCollector::Shutdown()
{
CheckThreadSafety();
// Always delete snow white objects.
FreeSnowWhite(true);
#ifndef DEBUG
if (PR_GetEnv("XPCOM_CC_RUN_DURING_SHUTDOWN"))
#endif
{
ShutdownCollect();
}
}
void
nsCycleCollector::SizeOfIncludingThis(MallocSizeOf aMallocSizeOf,
size_t *aObjectSize,
size_t *aGraphNodesSize,
size_t *aGraphEdgesSize,
size_t *aWeakMapsSize,
size_t *aWhiteNodeSize,
size_t *aPurpleBufferSize) const
{
*aObjectSize = aMallocSizeOf(this);
mGraph.SizeOfExcludingThis(aMallocSizeOf, aGraphNodesSize, aGraphEdgesSize,
aWeakMapsSize);
// No need to measure what the entries point to; the pointers are
// non-owning.
*aWhiteNodeSize = mWhiteNodes
? mWhiteNodes->SizeOfIncludingThis(aMallocSizeOf)
: 0;
*aPurpleBufferSize = mPurpleBuf.SizeOfExcludingThis(aMallocSizeOf);
// These fields are deliberately not measured:
// - mResults: because it's tiny and only contains scalars.
// - mJSRuntime: because it's non-owning and measured by JS reporters.
// - mParams: because it only contains scalars.
}
////////////////////////////////////////////////////////////////////////
// Module public API (exported in nsCycleCollector.h)
// Just functions that redirect into the singleton, once it's built.
////////////////////////////////////////////////////////////////////////
void
nsCycleCollector_registerJSRuntime(CycleCollectedJSRuntime *rt)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
// But we shouldn't already have a runtime.
MOZ_ASSERT(!data->mRuntime);
data->mRuntime = rt;
data->mCollector->RegisterJSRuntime(rt);
}
void
nsCycleCollector_forgetJSRuntime()
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
// And we shouldn't have already forgotten our runtime.
MOZ_ASSERT(data->mRuntime);
// But it may have shutdown already.
if (data->mCollector) {
data->mCollector->ForgetJSRuntime();
data->mRuntime = nullptr;
} else {
data->mRuntime = nullptr;
delete data;
sCollectorData.set(nullptr);
}
}
/* static */ CycleCollectedJSRuntime*
CycleCollectedJSRuntime::Get()
{
CollectorData* data = sCollectorData.get();
if (data) {
return data->mRuntime;
}
return nullptr;
}
namespace mozilla {
namespace cyclecollector {
void
HoldJSObjectsImpl(void* aHolder, nsScriptObjectTracer* aTracer)
{
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
// And we should have a runtime.
MOZ_ASSERT(data->mRuntime);
data->mRuntime->AddJSHolder(aHolder, aTracer);
}
void
HoldJSObjectsImpl(nsISupports* aHolder)
{
nsXPCOMCycleCollectionParticipant* participant;
CallQueryInterface(aHolder, &participant);
MOZ_ASSERT(participant, "Failed to QI to nsXPCOMCycleCollectionParticipant!");
MOZ_ASSERT(participant->CheckForRightISupports(aHolder),
"The result of QIing a JS holder should be the same as ToSupports");
HoldJSObjectsImpl(aHolder, participant);
}
void
DropJSObjectsImpl(void* aHolder)
{
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now, and not completely
// shut down.
MOZ_ASSERT(data);
// And we should have a runtime.
MOZ_ASSERT(data->mRuntime);
data->mRuntime->RemoveJSHolder(aHolder);
}
void
DropJSObjectsImpl(nsISupports* aHolder)
{
#ifdef DEBUG
nsXPCOMCycleCollectionParticipant* participant;
CallQueryInterface(aHolder, &participant);
MOZ_ASSERT(participant, "Failed to QI to nsXPCOMCycleCollectionParticipant!");
MOZ_ASSERT(participant->CheckForRightISupports(aHolder),
"The result of QIing a JS holder should be the same as ToSupports");
#endif
DropJSObjectsImpl(static_cast<void*>(aHolder));
}
#ifdef DEBUG
bool
IsJSHolder(void* aHolder)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now, and not completely
// shut down.
MOZ_ASSERT(data);
// And we should have a runtime.
MOZ_ASSERT(data->mRuntime);
return data->mRuntime->IsJSHolder(aHolder);
}
#endif
void
DeferredFinalize(nsISupports* aSupports)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now, and not completely
// shut down.
MOZ_ASSERT(data);
// And we should have a runtime.
MOZ_ASSERT(data->mRuntime);
data->mRuntime->DeferredFinalize(aSupports);
}
void
DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
DeferredFinalizeFunction aFunc,
void* aThing)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now, and not completely
// shut down.
MOZ_ASSERT(data);
// And we should have a runtime.
MOZ_ASSERT(data->mRuntime);
data->mRuntime->DeferredFinalize(aAppendFunc, aFunc, aThing);
}
} // namespace cyclecollector
} // namespace mozilla
void
NS_CycleCollectorSuspect3(void *n, nsCycleCollectionParticipant *cp,
nsCycleCollectingAutoRefCnt *aRefCnt,
bool* aShouldDelete)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
if (!data->mCollector) {
if (aRefCnt->get() == 0) {
if (!aShouldDelete) {
CanonicalizeParticipant(&n, &cp);
aRefCnt->stabilizeForDeletion();
cp->DeleteCycleCollectable(n);
} else {
*aShouldDelete = true;
}
} else {
// Make sure we'll get called again.
aRefCnt->RemoveFromPurpleBuffer();
}
return;
}
return data->mCollector->Suspect(n, cp, aRefCnt);
}
uint32_t
nsCycleCollector_suspectedCount()
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
if (!data->mCollector) {
return 0;
}
return data->mCollector->SuspectedCount();
}
bool
nsCycleCollector_init()
{
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
MOZ_ASSERT(!sCollectorData.initialized(), "Called twice!?");
return sCollectorData.init();
}
void
nsCycleCollector_startup()
{
MOZ_ASSERT(sCollectorData.initialized(),
"Forgot to call nsCycleCollector_init!");
if (sCollectorData.get()) {
MOZ_CRASH();
}
nsAutoPtr<nsCycleCollector> collector(new nsCycleCollector());
nsAutoPtr<CollectorData> data(new CollectorData);
data->mRuntime = nullptr;
data->mCollector = collector.forget();
sCollectorData.set(data.forget());
}
void
nsCycleCollector_setBeforeUnlinkCallback(CC_BeforeUnlinkCallback aCB)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
data->mCollector->SetBeforeUnlinkCallback(aCB);
}
void
nsCycleCollector_setForgetSkippableCallback(CC_ForgetSkippableCallback aCB)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
data->mCollector->SetForgetSkippableCallback(aCB);
}
void
nsCycleCollector_forgetSkippable(bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
PROFILER_LABEL("CC", "nsCycleCollector_forgetSkippable");
TimeLog timeLog;
data->mCollector->ForgetSkippable(aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing);
timeLog.Checkpoint("ForgetSkippable()");
}
void
nsCycleCollector_dispatchDeferredDeletion(bool aContinuation)
{
CollectorData *data = sCollectorData.get();
if (!data || !data->mRuntime) {
return;
}
data->mRuntime->DispatchDeferredDeletion(aContinuation);
}
bool
nsCycleCollector_doDeferredDeletion()
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
MOZ_ASSERT(data->mRuntime);
return data->mCollector->FreeSnowWhite(false);
}
void
nsCycleCollector_collect(bool aManuallyTriggered,
nsCycleCollectorResults *aResults,
nsICycleCollectorListener *aManualListener)
{
CollectorData *data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
PROFILER_LABEL("CC", "nsCycleCollector_collect");
MOZ_ASSERT_IF(aManualListener, aManuallyTriggered);
nsAutoTArray<PtrInfo*, 4000> whiteNodes;
data->mCollector->Collect(aManuallyTriggered ? ManualCC : ScheduledCC,
&whiteNodes, aResults, aManualListener);
}
void
nsCycleCollector_shutdown()
{
CollectorData *data = sCollectorData.get();
if (data) {
MOZ_ASSERT(data->mCollector);
PROFILER_LABEL("CC", "nsCycleCollector_shutdown");
data->mCollector->Shutdown();
delete data->mCollector;
data->mCollector = nullptr;
if (!data->mRuntime) {
delete data;
sCollectorData.set(nullptr);
}
}
}