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gecko/xpcom/base/nsCycleCollector.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set cindent tabstop=4 expandtab shiftwidth=4: */
/* 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).
//
// 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 object is scan-safe if:
//
// - It can be QI'ed to |nsXPCOMCycleCollectionParticipant|, though this
// operation loses ISupports identity (like nsIClassInfo).
// - The operation |traverse| on the resulting
// nsXPCOMCycleCollectionParticipant does not cause *any* refcount
// adjustment to occur (no AddRef / Release calls).
//
// An object is purple-safe if it satisfies the following properties:
//
// - The object is scan-safe.
// - If the object calls |nsCycleCollector::suspect(this)|,
// it will eventually call |nsCycleCollector::forget(this)|,
// exactly once per call to |suspect|, before being destroyed.
//
// 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.
//
// 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 purple-safety of the roots that call |suspect| and
// |forget| to hold, such that we will forget about a purple pointer
// 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 (there
// should be no threads involved).
//
// We *do* call |AddRef| and |Release| 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/Util.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollectorUtils.h"
#include "nsIProgrammingLanguage.h"
#include "nsBaseHashtable.h"
#include "nsHashKeys.h"
#include "nsDeque.h"
#include "nsCycleCollector.h"
#include "nsThreadUtils.h"
#include "prenv.h"
#include "prprf.h"
#include "plstr.h"
#include "nsPrintfCString.h"
#include "nsTArray.h"
#include "nsIObserverService.h"
#include "nsIConsoleService.h"
#include "nsServiceManagerUtils.h"
#include "nsThreadUtils.h"
#include "nsTArray.h"
#include "mozilla/Services.h"
#include "mozilla/Attributes.h"
#include "nsICycleCollectorListener.h"
#include "nsIXPConnect.h"
#include "nsIJSRuntimeService.h"
#include "nsIMemoryReporter.h"
#include "xpcpublic.h"
#include "nsXPCOMPrivate.h"
#include "sampler.h"
#include <stdio.h>
#include <string.h>
#ifdef WIN32
#include <io.h>
#include <process.h>
#endif
#ifdef XP_WIN
#include <windows.h>
#endif
#include "mozilla/Mutex.h"
#include "mozilla/CondVar.h"
#include "mozilla/StandardInteger.h"
#include "mozilla/Telemetry.h"
using namespace mozilla;
//#define COLLECT_TIME_DEBUG
#define DEFAULT_SHUTDOWN_COLLECTIONS 5
#ifdef DEBUG_CC
#define SHUTDOWN_COLLECTIONS(params) params.mShutdownCollections
#else
#define SHUTDOWN_COLLECTIONS(params) DEFAULT_SHUTDOWN_COLLECTIONS
#endif
#if defined(XP_WIN)
// Defined in nsThreadManager.cpp.
extern DWORD gTLSThreadIDIndex;
#elif defined(NS_TLS)
// Defined in nsThreadManager.cpp.
extern NS_TLS mozilla::threads::ID gTLSThreadID;
#else
PRThread* gCycleCollectorThread = nullptr;
#endif
// If true, always log cycle collector graphs.
const bool gAlwaysLogCCGraphs = false;
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 mDoNothing;
bool mLogGraphs;
#ifdef DEBUG_CC
bool mReportStats;
bool mLogPointers;
uint32_t mShutdownCollections;
#endif
nsCycleCollectorParams() :
#ifdef DEBUG_CC
mDoNothing (PR_GetEnv("XPCOM_CC_DO_NOTHING") != NULL),
mLogGraphs (gAlwaysLogCCGraphs ||
PR_GetEnv("XPCOM_CC_DRAW_GRAPHS") != NULL),
mReportStats (PR_GetEnv("XPCOM_CC_REPORT_STATS") != NULL),
mLogPointers (PR_GetEnv("XPCOM_CC_LOG_POINTERS") != NULL),
mShutdownCollections(DEFAULT_SHUTDOWN_COLLECTIONS)
#else
mDoNothing (false),
mLogGraphs (gAlwaysLogCCGraphs)
#endif
{
#ifdef DEBUG_CC
char *s = PR_GetEnv("XPCOM_CC_SHUTDOWN_COLLECTIONS");
if (s)
PR_sscanf(s, "%d", &mShutdownCollections);
#endif
}
};
#ifdef DEBUG_CC
// Various operations involving the collector are recorded in a
// statistics table. These are for diagnostics.
struct nsCycleCollectorStats
{
uint32_t mFailedQI;
uint32_t mSuccessfulQI;
uint32_t mVisitedNode;
uint32_t mWalkedGraph;
uint32_t mFreedBytes;
uint32_t mSetColorBlack;
uint32_t mSetColorWhite;
uint32_t mFailedUnlink;
uint32_t mCollectedNode;
uint32_t mSuspectNode;
uint32_t mForgetNode;
uint32_t mCollection;
nsCycleCollectorStats()
{
memset(this, 0, sizeof(nsCycleCollectorStats));
}
void Dump()
{
fprintf(stderr, "\f\n");
#define DUMP(entry) fprintf(stderr, "%30.30s: %-20.20d\n", #entry, entry)
DUMP(mFailedQI);
DUMP(mSuccessfulQI);
DUMP(mVisitedNode);
DUMP(mWalkedGraph);
DUMP(mFreedBytes);
DUMP(mSetColorBlack);
DUMP(mSetColorWhite);
DUMP(mFailedUnlink);
DUMP(mCollectedNode);
DUMP(mSuspectNode);
DUMP(mForgetNode);
DUMP(mCollection);
#undef DUMP
}
};
#endif
#ifdef DEBUG_CC
static bool nsCycleCollector_shouldSuppress(nsISupports *s);
#endif
#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;
mNumBlocks = 0;
}
~EdgePool()
{
NS_ASSERTION(!mSentinelAndBlocks[0].block &&
!mSentinelAndBlocks[1].block,
"Didn't call Clear()?");
}
void Clear()
{
Block *b = Blocks();
while (b) {
Block *next = b->Next();
delete b;
NS_ASSERTION(mNumBlocks > 0,
"Expected EdgePool mNumBlocks to be positive.");
mNumBlocks--;
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];
uint32_t mNumBlocks;
Block*& Blocks() { 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; }
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()),
mNumBlocks(aPool.mNumBlocks)
{
}
Iterator Mark() { return Iterator(mCurrent); }
void Add(PtrInfo* aEdge) {
if (mCurrent == mBlockEnd) {
Block *b = new Block();
if (!b) {
// This means we just won't collect (some) cycles.
NS_NOTREACHED("out of memory, ignoring edges");
return;
}
*mNextBlockPtr = b;
mCurrent = b->Start();
mBlockEnd = b->End();
mNextBlockPtr = &b->Next();
mNumBlocks++;
}
(mCurrent++)->ptrInfo = aEdge;
}
private:
// mBlockEnd points to space for null sentinel
PtrInfoOrBlock *mCurrent, *mBlockEnd;
Block **mNextBlockPtr;
uint32_t &mNumBlocks;
};
size_t BlocksSize() const {
return sizeof(Block) * mNumBlocks;
}
};
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:
#ifdef DEBUG_CC
char *mName;
#endif
PtrInfo(void *aPointer, nsCycleCollectionParticipant *aParticipant)
: mPointer(aPointer),
mParticipant(aParticipant),
mColor(grey),
mInternalRefs(0),
mRefCount(0),
mFirstChild()
#ifdef DEBUG_CC
, mName(nullptr)
#endif
{
MOZ_ASSERT(aParticipant);
}
#ifdef DEBUG_CC
void Destroy() {
PL_strfree(mName);
}
#endif
// Allow NodePool::Block's constructor to compile.
PtrInfo() {
NS_NOTREACHED("should never be called");
}
EdgePool::Iterator FirstChild()
{
return mFirstChild;
}
// this PtrInfo must be part of a NodePool
EdgePool::Iterator LastChild()
{
return (this + 1)->mFirstChild;
}
void SetFirstChild(EdgePool::Iterator aFirstChild)
{
mFirstChild = aFirstChild;
}
// this PtrInfo must be part of a NodePool
void SetLastChild(EdgePool::Iterator aLastChild)
{
(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),
mNumBlocks(0)
{
}
~NodePool()
{
NS_ASSERTION(!mBlocks, "Didn't call Clear()?");
}
void Clear()
{
#ifdef DEBUG_CC
{
Enumerator queue(*this);
while (!queue.IsDone()) {
queue.GetNext()->Destroy();
}
}
#endif
Block *b = mBlocks;
while (b) {
Block *n = b->mNext;
NS_Free(b);
NS_ASSERTION(mNumBlocks > 0,
"Expected NodePool mNumBlocks to be positive.");
mNumBlocks--;
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),
mNumBlocks(aPool.mNumBlocks)
{
NS_ASSERTION(aPool.mBlocks == nullptr && aPool.mLast == nullptr,
"pool not empty");
}
PtrInfo *Add(void *aPointer, nsCycleCollectionParticipant *aParticipant)
{
if (mNext == mBlockEnd) {
Block *block;
if (!(*mNextBlock = block =
static_cast<Block*>(NS_Alloc(sizeof(Block)))))
return nullptr;
mNext = block->mEntries;
mBlockEnd = block->mEntries + BlockSize;
block->mNext = nullptr;
mNextBlock = &block->mNext;
mNumBlocks++;
}
return new (mNext++) PtrInfo(aPointer, aParticipant);
}
private:
Block **mNextBlock;
PtrInfo *&mNext;
PtrInfo *mBlockEnd;
uint32_t &mNumBlocks;
};
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()
{
NS_ASSERTION(!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:
Block *mFirstBlock, *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 BlocksSize() const {
return sizeof(Block) * mNumBlocks;
}
private:
Block *mBlocks;
PtrInfo *mLast;
uint32_t mNumBlocks;
};
struct WeakMapping
{
// map and key will be null if the corresponding objects are GC marked
PtrInfo *mMap;
PtrInfo *mKey;
PtrInfo *mVal;
};
class GCGraphBuilder;
struct GCGraph
{
NodePool mNodes;
EdgePool mEdges;
nsTArray<WeakMapping> mWeakMaps;
uint32_t mRootCount;
GCGraph() : mRootCount(0) {
}
~GCGraph() {
}
size_t BlocksSize() const {
return mNodes.BlocksSize() + mEdges.BlocksSize();
}
};
// XXX Would be nice to have an nsHashSet<KeyType> API that has
// Add/Remove/Has rather than PutEntry/RemoveEntry/GetEntry.
typedef nsTHashtable<nsPtrHashKey<const void> > PointerSet;
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;
}
}
struct nsPurpleBuffer
{
private:
struct Block {
Block *mNext;
// Try to match the size of a jemalloc bucket.
nsPurpleBufferEntry mEntries[1360];
Block() : mNext(nullptr) {}
};
public:
// This class wraps a linked list of the elements in the purple
// buffer.
nsCycleCollectorParams &mParams;
uint32_t mNumBlocksAlloced;
uint32_t mCount;
Block mFirstBlock;
nsPurpleBufferEntry *mFreeList;
#ifdef DEBUG_CC
PointerSet mNormalObjects; // duplicates our blocks
nsCycleCollectorStats &mStats;
#endif
#ifdef DEBUG_CC
nsPurpleBuffer(nsCycleCollectorParams &params,
nsCycleCollectorStats &stats)
: mParams(params),
mStats(stats)
{
InitBlocks();
mNormalObjects.Init();
}
#else
nsPurpleBuffer(nsCycleCollectorParams &params)
: mParams(params)
{
InitBlocks();
}
#endif
~nsPurpleBuffer()
{
FreeBlocks();
}
void InitBlocks()
{
mNumBlocksAlloced = 0;
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;
NS_ASSERTION(mNumBlocksAlloced > 0,
"Expected positive mNumBlocksAlloced.");
mNumBlocksAlloced--;
}
mFirstBlock.mNext = nullptr;
}
void UnmarkRemainingPurple(Block *b)
{
for (nsPurpleBufferEntry *e = b->mEntries,
*eEnd = ArrayEnd(b->mEntries);
e != eEnd; ++e) {
if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
// This is a real entry (rather than something on the
// free list).
if (e->mObject) {
void *obj = e->mObject;
nsCycleCollectionParticipant *cp = e->mParticipant;
CanonicalizeParticipant(&obj, &cp);
cp->UnmarkIfPurple(obj);
}
if (--mCount == 0)
break;
}
}
}
void SelectPointers(GCGraphBuilder &builder);
// RemoveSkippable removes entries from the purple buffer if
// nsPurpleBufferEntry::mObject is null or if the object's
// nsXPCOMCycleCollectionParticipant::CanSkip() returns true or
// if nsPurpleBufferEntry::mNotPurple is true.
// 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(bool removeChildlessNodes);
#ifdef DEBUG_CC
bool Exists(void *p) const
{
return mNormalObjects.GetEntry(p);
}
#endif
nsPurpleBufferEntry* NewEntry()
{
if (!mFreeList) {
Block *b = new Block;
if (!b) {
return nullptr;
}
mNumBlocksAlloced++;
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;
}
nsPurpleBufferEntry* Put(void *p, nsCycleCollectionParticipant *cp)
{
nsPurpleBufferEntry *e = NewEntry();
if (!e) {
return nullptr;
}
++mCount;
e->mObject = p;
e->mParticipant = cp;
e->mNotPurple = false;
// Caller is responsible for filling in result's mRefCnt.
return e;
}
void Remove(nsPurpleBufferEntry *e)
{
NS_ASSERTION(mCount != 0, "must have entries");
#ifdef DEBUG_CC
mNormalObjects.RemoveEntry(e->mObject);
#endif
e->mNextInFreeList =
(nsPurpleBufferEntry*)(uintptr_t(mFreeList) | uintptr_t(1));
mFreeList = e;
--mCount;
}
uint32_t Count() const
{
return mCount;
}
size_t BlocksSize() const
{
return sizeof(Block) * mNumBlocksAlloced;
}
};
static bool
AddPurpleRoot(GCGraphBuilder &builder, void *root, nsCycleCollectionParticipant *cp);
void
nsPurpleBuffer::SelectPointers(GCGraphBuilder &aBuilder)
{
#ifdef DEBUG_CC
// Can't use mCount here, since it may include null entries.
uint32_t realCount = 0;
for (Block *b = &mFirstBlock; b; b = b->mNext) {
for (nsPurpleBufferEntry *e = b->mEntries,
*eEnd = ArrayEnd(b->mEntries);
e != eEnd; ++e) {
if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
if (e->mObject && !e->mNotPurple) {
++realCount;
}
}
}
}
NS_ABORT_IF_FALSE(mNormalObjects.Count() == realCount,
"count out of sync");
#endif
// Walk through all the blocks.
for (Block *b = &mFirstBlock; b; b = b->mNext) {
for (nsPurpleBufferEntry *e = b->mEntries,
*eEnd = ArrayEnd(b->mEntries);
e != eEnd; ++e) {
if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
// This is a real entry (rather than something on the
// free list).
if (e->mObject && e->mNotPurple) {
void* o = e->mObject;
nsCycleCollectionParticipant* cp = e->mParticipant;
CanonicalizeParticipant(&o, &cp);
cp->UnmarkIfPurple(o);
Remove(e);
} else if (!e->mObject || AddPurpleRoot(aBuilder, e->mObject,
e->mParticipant)) {
Remove(e);
}
}
}
}
NS_WARN_IF_FALSE(mCount == 0, "AddPurpleRoot failed");
if (mCount == 0) {
FreeBlocks();
InitBlocks();
}
}
////////////////////////////////////////////////////////////////////////
// Top level structure for the cycle collector.
////////////////////////////////////////////////////////////////////////
struct nsCycleCollector
{
bool mCollectionInProgress;
bool mScanInProgress;
bool mFollowupCollection;
nsCycleCollectorResults *mResults;
TimeStamp mCollectionStart;
nsCycleCollectionJSRuntime *mJSRuntime;
GCGraph mGraph;
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;
nsPurpleBuffer mPurpleBuf;
void RegisterJSRuntime(nsCycleCollectionJSRuntime *aJSRuntime);
void ForgetJSRuntime();
void SelectPurple(GCGraphBuilder &builder);
void MarkRoots(GCGraphBuilder &builder);
void ScanRoots();
void ScanWeakMaps();
void ForgetSkippable(bool removeChildlessNodes);
// returns whether anything was collected
bool CollectWhite(nsICycleCollectorListener *aListener);
nsCycleCollector();
~nsCycleCollector();
nsPurpleBufferEntry* Suspect2(void *n, nsCycleCollectionParticipant *cp);
bool Forget2(nsPurpleBufferEntry *e);
void Collect(bool aMergeCompartments,
nsCycleCollectorResults *aResults,
uint32_t aTryCollections,
nsICycleCollectorListener *aListener);
// Prepare for and cleanup after one or more collection(s).
bool PrepareForCollection(nsCycleCollectorResults *aResults,
nsTArray<PtrInfo*> *aWhiteNodes);
void GCIfNeeded(bool aForceGC);
void CleanupAfterCollection();
// Start and finish an individual collection.
bool BeginCollection(bool aMergeCompartments, nsICycleCollectorListener *aListener);
bool FinishCollection(nsICycleCollectorListener *aListener);
uint32_t SuspectedCount();
void Shutdown();
void ClearGraph()
{
mGraph.mNodes.Clear();
mGraph.mEdges.Clear();
mGraph.mWeakMaps.Clear();
mGraph.mRootCount = 0;
}
#ifdef DEBUG_CC
nsCycleCollectorStats mStats;
FILE *mPtrLog;
PointerSet mExpectedGarbage;
bool LogPurpleAddition(void* aObject, nsCycleCollectionParticipant *cp);
void LogPurpleRemoval(void* aObject);
void ShouldBeFreed(nsISupports *n);
void WasFreed(nsISupports *n);
#endif
};
/**
* 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);
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 object
////////////////////////////////////////////////////////////////////////
static nsCycleCollector *sCollector = nullptr;
////////////////////////////////////////////////////////////////////////
// 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");
}
#ifdef DEBUG_CC
static void
Fault(const char *msg, PtrInfo *pi)
{
printf("Fault in cycle collector: %s\n"
" while operating on pointer %p %s\n",
msg, pi->mPointer, pi->mName);
if (pi->mInternalRefs) {
printf(" which has internal references from:\n");
NodePool::Enumerator queue(sCollector->mGraph.mNodes);
while (!queue.IsDone()) {
PtrInfo *ppi = queue.GetNext();
for (EdgePool::Iterator e = ppi->FirstChild(),
e_end = ppi->LastChild();
e != e_end; ++e) {
if (*e == pi) {
printf(" %p %s\n", ppi->mPointer, ppi->mName);
}
}
}
}
Fault(msg, pi->mPointer);
}
#else
static void
Fault(const char *msg, PtrInfo *pi)
{
Fault(msg, pi->mPointer);
}
#endif
static inline void
AbortIfOffMainThreadIfCheckFast()
{
#if defined(XP_WIN) || defined(NS_TLS)
if (!NS_IsMainThread() && !NS_IsCycleCollectorThread()) {
NS_RUNTIMEABORT("Main-thread-only object used off the main thread");
}
#endif
}
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);
#ifdef DEBUG_CC
if (cp)
++sCollector->mStats.mSuccessfulQI;
else
++sCollector->mStats.mFailedQI;
#endif
}
template <class Visitor>
MOZ_NEVER_INLINE void
GraphWalker<Visitor>::Walk(PtrInfo *s0)
{
nsDeque queue;
CC_AbortIfNull(s0);
queue.Push(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) {
PtrInfo *pi = etor.GetNext();
CC_AbortIfNull(pi);
queue.Push(pi);
}
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) {
CC_AbortIfNull(*child);
aQueue.Push(*child);
}
}
};
#ifdef DEBUG_CC
sCollector->mStats.mWalkedGraph++;
#endif
}
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) {
fclose(mStream);
}
}
NS_DECL_ISUPPORTS
NS_IMETHOD AllTraces(nsICycleCollectorListener** aListener)
{
mWantAllTraces = true;
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 Begin()
{
mCurrentAddress.AssignLiteral("0x");
mDescribers.Clear();
mNextIndex = 0;
if (mDisableLog) {
return NS_OK;
}
char basename[MAXPATHLEN] = {'\0'};
char ccname[MAXPATHLEN] = {'\0'};
char* env;
if ((env = PR_GetEnv("MOZ_CC_LOG_DIRECTORY"))) {
strcpy(basename, env);
} else {
#ifdef XP_WIN
// On Windows, tmpnam returns useless stuff, such as "\\s164.".
// Therefore we need to call the APIs directly.
GetTempPathA(mozilla::ArrayLength(basename), basename);
#else
tmpnam(basename);
char *lastSlash = strrchr(basename, XPCOM_FILE_PATH_SEPARATOR[0]);
if (lastSlash) {
*lastSlash = '\0';
}
#endif
}
++gLogCounter;
// Dump the JS heap.
char gcname[MAXPATHLEN] = {'\0'};
sprintf(gcname, "%s%sgc-edges-%d.%d.log", basename,
XPCOM_FILE_PATH_SEPARATOR,
gLogCounter, base::GetCurrentProcId());
FILE* gcDumpFile = fopen(gcname, "w");
if (!gcDumpFile)
return NS_ERROR_FAILURE;
xpc::DumpJSHeap(gcDumpFile);
fclose(gcDumpFile);
// Open a file for dumping the CC graph.
sprintf(ccname, "%s%scc-edges-%d.%d.log", basename,
XPCOM_FILE_PATH_SEPARATOR,
gLogCounter, base::GetCurrentProcId());
mStream = fopen(ccname, "w");
if (!mStream)
return NS_ERROR_FAILURE;
nsCOMPtr<nsIConsoleService> cs =
do_GetService(NS_CONSOLESERVICE_CONTRACTID);
if (cs) {
nsString msg = NS_LITERAL_STRING("Cycle Collector log dumped to ");
AppendUTF8toUTF16(ccname, msg);
cs->LogStringMessage(msg.get());
msg = NS_LITERAL_STRING("Garbage Collector log dumped to ");
AppendUTF8toUTF16(gcname, msg);
cs->LogStringMessage(msg.get());
}
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();
NS_ENSURE_TRUE(d, NS_ERROR_OUT_OF_MEMORY);
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();
NS_ENSURE_TRUE(d, NS_ERROR_OUT_OF_MEMORY);
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();
NS_ENSURE_TRUE(d, NS_ERROR_OUT_OF_MEMORY);
d->mType = CCGraphDescriber::eEdge;
d->mAddress = mCurrentAddress;
d->mToAddress.AppendInt(aToAddress, 16);
d->mName.Append(aEdgeName);
}
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();
NS_ENSURE_TRUE(d, NS_ERROR_OUT_OF_MEMORY);
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();
NS_ENSURE_TRUE(d, NS_ERROR_OUT_OF_MEMORY);
d->mType = CCGraphDescriber::eGarbage;
d->mAddress.AppendInt(aAddress, 16);
}
return NS_OK;
}
NS_IMETHOD End()
{
if (!mDisableLog) {
fclose(mStream);
mStream = nullptr;
}
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:
FILE *mStream;
bool mWantAllTraces;
bool mDisableLog;
bool mWantAfterProcessing;
nsCString mCurrentAddress;
nsTArray<CCGraphDescriber> mDescribers;
uint32_t mNextIndex;
static uint32_t gLogCounter;
};
NS_IMPL_ISUPPORTS1(nsCycleCollectorLogger, nsICycleCollectorListener)
uint32_t nsCycleCollectorLogger::gLogCounter = 0;
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
{
private:
NodePool::Builder mNodeBuilder;
EdgePool::Builder mEdgeBuilder;
nsTArray<WeakMapping> &mWeakMaps;
PLDHashTable mPtrToNodeMap;
PtrInfo *mCurrPi;
nsCycleCollectionParticipant *mJSParticipant;
nsCycleCollectionParticipant *mJSCompParticipant;
nsCString mNextEdgeName;
nsICycleCollectorListener *mListener;
bool mMergeCompartments;
public:
GCGraphBuilder(GCGraph &aGraph,
nsCycleCollectionJSRuntime *aJSRuntime,
nsICycleCollectorListener *aListener,
bool aMergeCompartments);
~GCGraphBuilder();
bool Initialized();
uint32_t Count() const { return mPtrToNodeMap.entryCount; }
PtrInfo* AddNode(void *s, nsCycleCollectionParticipant *aParticipant);
PtrInfo* AddWeakMapNode(void* node);
void Traverse(PtrInfo* aPtrInfo);
void SetLastChild();
private:
void DescribeNode(uint32_t refCount, const char *objName)
{
mCurrPi->mRefCount = refCount;
#ifdef DEBUG_CC
mCurrPi->mName = PL_strdup(objName);
sCollector->mStats.mVisitedNode++;
#endif
}
public:
// nsCycleCollectionTraversalCallback methods.
NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refCount,
const char *objName);
NS_IMETHOD_(void) DescribeGCedNode(bool isMarked, const char *objName);
NS_IMETHOD_(void) NoteXPCOMRoot(nsISupports *root);
NS_IMETHOD_(void) NoteJSRoot(void *root);
NS_IMETHOD_(void) NoteNativeRoot(void *root, nsCycleCollectionParticipant *participant);
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);
NS_IMETHOD_(void) NoteWeakMapping(void *map, void *key, void *val);
private:
NS_IMETHOD_(void) NoteRoot(void *root,
nsCycleCollectionParticipant *participant)
{
MOZ_ASSERT(root);
MOZ_ASSERT(participant);
if (!participant->CanSkipInCC(root) || NS_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;
}
JSCompartment *MergeCompartment(void *gcthing) {
if (!mMergeCompartments) {
return nullptr;
}
JSCompartment *comp = js::GetGCThingCompartment(gcthing);
if (js::IsSystemCompartment(comp)) {
return nullptr;
}
return comp;
}
};
GCGraphBuilder::GCGraphBuilder(GCGraph &aGraph,
nsCycleCollectionJSRuntime *aJSRuntime,
nsICycleCollectorListener *aListener,
bool aMergeCompartments)
: mNodeBuilder(aGraph.mNodes),
mEdgeBuilder(aGraph.mEdges),
mWeakMaps(aGraph.mWeakMaps),
mJSParticipant(nullptr),
mJSCompParticipant(xpc_JSCompartmentParticipant()),
mListener(aListener),
mMergeCompartments(aMergeCompartments)
{
if (!PL_DHashTableInit(&mPtrToNodeMap, &PtrNodeOps, nullptr,
sizeof(PtrToNodeEntry), 32768))
mPtrToNodeMap.ops = nullptr;
if (aJSRuntime) {
mJSParticipant = aJSRuntime->GetParticipant();
}
uint32_t flags = 0;
#ifdef DEBUG_CC
flags = nsCycleCollectionTraversalCallback::WANT_DEBUG_INFO |
nsCycleCollectionTraversalCallback::WANT_ALL_TRACES;
#endif
if (!flags && mListener) {
flags = nsCycleCollectionTraversalCallback::WANT_DEBUG_INFO;
bool all = false;
mListener->GetWantAllTraces(&all);
if (all) {
flags |= nsCycleCollectionTraversalCallback::WANT_ALL_TRACES;
}
}
mFlags |= flags;
mMergeCompartments = mMergeCompartments && NS_LIKELY(!WantAllTraces());
}
GCGraphBuilder::~GCGraphBuilder()
{
if (mPtrToNodeMap.ops)
PL_DHashTableFinish(&mPtrToNodeMap);
}
bool
GCGraphBuilder::Initialized()
{
return !!mPtrToNodeMap.ops;
}
PtrInfo*
GCGraphBuilder::AddNode(void *s, nsCycleCollectionParticipant *aParticipant)
{
PtrToNodeEntry *e = static_cast<PtrToNodeEntry*>(PL_DHashTableOperate(&mPtrToNodeMap, s, PL_DHASH_ADD));
if (!e)
return nullptr;
PtrInfo *result;
if (!e->mNode) {
// New entry.
result = mNodeBuilder.Add(s, aParticipant);
if (!result) {
PL_DHashTableRawRemove(&mPtrToNodeMap, e);
return nullptr;
}
e->mNode = result;
} else {
result = e->mNode;
NS_ASSERTION(result->mParticipant == aParticipant,
"nsCycleCollectionParticipant shouldn't change!");
}
return result;
}
MOZ_NEVER_INLINE void
GCGraphBuilder::Traverse(PtrInfo* aPtrInfo)
{
mCurrPi = aPtrInfo;
#ifdef DEBUG_CC
if (!mCurrPi->mParticipant) {
Fault("unknown pointer during walk", aPtrInfo);
return;
}
#endif
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!");
#ifdef DEBUG_CC
if (nsCycleCollector_shouldSuppress(root))
return;
#endif
nsXPCOMCycleCollectionParticipant *cp;
ToParticipant(root, &cp);
NoteRoot(root, cp);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteJSRoot(void *root)
{
if (JSCompartment *comp = MergeCompartment(root)) {
NoteRoot(comp, mJSCompParticipant);
} 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 == PR_UINT32_MAX)
Fault("overflowing refcount", mCurrPi);
sCollector->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 ? PR_UINT32_MAX : 0;
sCollector->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;
#ifdef DEBUG_CC
if (nsCycleCollector_shouldSuppress(child))
return;
#endif
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;
NS_ASSERTION(participant, "Need a nsCycleCollectionParticipant!");
NoteChild(child, participant, edgeName);
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteJSChild(void *child)
{
if (!child) {
return;
}
nsCString edgeName;
if (NS_UNLIKELY(WantDebugInfo())) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (xpc_GCThingIsGrayCCThing(child) || NS_UNLIKELY(WantAllTraces())) {
if (JSCompartment *comp = MergeCompartment(child)) {
NoteChild(comp, mJSCompParticipant, edgeName);
} else {
NoteChild(child, mJSParticipant, edgeName);
}
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteNextEdgeName(const char* name)
{
if (WantDebugInfo()) {
mNextEdgeName = name;
}
}
PtrInfo*
GCGraphBuilder::AddWeakMapNode(void *node)
{
NS_ASSERTION(node, "Weak map node should be non-null.");
if (!xpc_GCThingIsGrayCCThing(node) && !WantAllTraces())
return nullptr;
if (JSCompartment *comp = MergeCompartment(node)) {
return AddNode(comp, mJSCompParticipant);
} else {
return AddNode(node, mJSParticipant);
}
}
NS_IMETHODIMP_(void)
GCGraphBuilder::NoteWeakMapping(void *map, void *key, void *val)
{
PtrInfo *valNode = AddWeakMapNode(val);
if (!valNode)
return;
WeakMapping *mapping = mWeakMaps.AppendElement();
mapping->mMap = map ? AddWeakMapNode(map) : nullptr;
mapping->mKey = key ? AddWeakMapNode(key) : nullptr;
mapping->mVal = valNode;
}
static bool
AddPurpleRoot(GCGraphBuilder &builder, void *root, nsCycleCollectionParticipant *cp)
{
CanonicalizeParticipant(&root, &cp);
if (builder.WantAllTraces() || !cp->CanSkipInCC(root)) {
PtrInfo *pinfo = builder.AddNode(root, cp);
if (!pinfo) {
return false;
}
}
cp->UnmarkIfPurple(root);
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) NoteXPCOMRoot(nsISupports *root) {}
NS_IMETHOD_(void) NoteJSRoot(void *root) {}
NS_IMETHOD_(void) NoteNativeRoot(void *root,
nsCycleCollectionParticipant *helper) {}
NS_IMETHOD_(void) NoteNextEdgeName(const char* name) {}
NS_IMETHOD_(void) NoteWeakMapping(void *map, void *key, void *val) {}
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();
}
void
nsPurpleBuffer::RemoveSkippable(bool removeChildlessNodes)
{
// Walk through all the blocks.
for (Block *b = &mFirstBlock; b; b = b->mNext) {
for (nsPurpleBufferEntry *e = b->mEntries,
*eEnd = ArrayEnd(b->mEntries);
e != eEnd; ++e) {
if (!(uintptr_t(e->mObject) & uintptr_t(1))) {
// This is a real entry (rather than something on the
// free list).
if (e->mObject) {
void *o = e->mObject;
nsCycleCollectionParticipant *cp = e->mParticipant;
CanonicalizeParticipant(&o, &cp);
if (!e->mNotPurple && !cp->CanSkip(o, false) &&
(!removeChildlessNodes || MayHaveChild(o, cp))) {
continue;
}
cp->UnmarkIfPurple(o);
}
Remove(e);
}
}
}
}
void
nsCycleCollector::SelectPurple(GCGraphBuilder &builder)
{
mPurpleBuf.SelectPointers(builder);
}
void
nsCycleCollector::ForgetSkippable(bool removeChildlessNodes)
{
nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
if (obs) {
obs->NotifyObservers(nullptr, "cycle-collector-forget-skippable", nullptr);
}
mPurpleBuf.RemoveSkippable(removeChildlessNodes);
if (mForgetSkippableCB) {
mForgetSkippableCB();
}
}
MOZ_NEVER_INLINE void
nsCycleCollector::MarkRoots(GCGraphBuilder &builder)
{
mGraph.mRootCount = builder.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);
builder.Traverse(pi);
if (queue.AtBlockEnd())
builder.SetLastChild();
}
if (mGraph.mRootCount > 0)
builder.SetLastChild();
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |ScanRoots| routine.
////////////////////////////////////////////////////////////////////////
struct ScanBlackVisitor
{
ScanBlackVisitor(uint32_t &aWhiteNodeCount)
: mWhiteNodeCount(aWhiteNodeCount)
{
}
bool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor != black;
}
MOZ_NEVER_INLINE void VisitNode(PtrInfo *pi)
{
if (pi->mColor == white)
--mWhiteNodeCount;
pi->mColor = black;
#ifdef DEBUG_CC
sCollector->mStats.mSetColorBlack++;
#endif
}
uint32_t &mWhiteNodeCount;
};
struct scanVisitor
{
scanVisitor(uint32_t &aWhiteNodeCount) : mWhiteNodeCount(aWhiteNodeCount)
{
}
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;
#ifdef DEBUG_CC
sCollector->mStats.mSetColorWhite++;
#endif
} else {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount)).Walk(pi);
NS_ASSERTION(pi->mColor == black,
"Why didn't ScanBlackVisitor make pi black?");
}
}
uint32_t &mWhiteNodeCount;
};
// 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;
do {
anyChanged = false;
for (uint32_t i = 0; i < mGraph.mWeakMaps.Length(); i++) {
WeakMapping *wm = &mGraph.mWeakMaps[i];
// If mMap or mKey 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;
PtrInfo *v = wm->mVal;
// 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().
NS_ASSERTION(mColor != grey, "Uncolored weak map");
NS_ASSERTION(kColor != grey, "Uncolored weak map key");
NS_ASSERTION(v->mColor != grey, "Uncolored weak map value");
if (mColor == black && kColor == black && v->mColor != black) {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(mWhiteNodeCount)).Walk(v);
anyChanged = true;
}
}
} while (anyChanged);
}
void
nsCycleCollector::ScanRoots()
{
mWhiteNodeCount = 0;
// On the assumption that most nodes will be black, it's
// probably faster to use a GraphWalker than a
// NodePool::Enumerator.
GraphWalker<scanVisitor>(scanVisitor(mWhiteNodeCount)).WalkFromRoots(mGraph);
ScanWeakMaps();
#ifdef DEBUG_CC
// Sanity check: scan should have colored all grey nodes black or
// white. So we ensure we have no grey nodes at this point.
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone())
{
PtrInfo *pinfo = etor.GetNext();
if (pinfo->mColor == grey) {
Fault("valid grey node after scanning", pinfo);
}
}
#endif
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |CollectWhite| routine, somewhat modified.
////////////////////////////////////////////////////////////////////////
bool
nsCycleCollector::CollectWhite(nsICycleCollectorListener *aListener)
{
// 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.
nsresult rv;
TimeLog timeLog;
NS_ASSERTION(mWhiteNodes->IsEmpty(),
"FinishCollection 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)) {
rv = pinfo->mParticipant->Root(pinfo->mPointer);
if (NS_FAILED(rv)) {
Fault("Failed root call while unlinking", pinfo);
mWhiteNodes->RemoveElementAt(mWhiteNodes->Length() - 1);
} else if (pinfo->mRefCount == 0) {
// only JS objects have a refcount of 0
++numWhiteGCed;
}
}
}
uint32_t count = mWhiteNodes->Length();
NS_ASSERTION(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");
}
#if defined(DEBUG_CC) && !defined(__MINGW32__) && defined(WIN32)
struct _CrtMemState ms1, ms2;
_CrtMemCheckpoint(&ms1);
#endif
if (aListener) {
for (uint32_t i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
aListener->DescribeGarbage((uint64_t)pinfo->mPointer);
}
aListener->End();
}
for (uint32_t i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
rv = pinfo->mParticipant->Unlink(pinfo->mPointer);
if (NS_FAILED(rv)) {
Fault("Failed unlink call while unlinking", pinfo);
#ifdef DEBUG_CC
mStats.mFailedUnlink++;
#endif
}
else {
#ifdef DEBUG_CC
++mStats.mCollectedNode;
#endif
}
}
timeLog.Checkpoint("CollectWhite::Unlink");
for (uint32_t i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
rv = pinfo->mParticipant->Unroot(pinfo->mPointer);
if (NS_FAILED(rv))
Fault("Failed unroot call while unlinking", pinfo);
}
timeLog.Checkpoint("CollectWhite::Unroot");
#if defined(DEBUG_CC) && !defined(__MINGW32__) && defined(WIN32)
_CrtMemCheckpoint(&ms2);
if (ms2.lTotalCount < ms1.lTotalCount)
mStats.mFreedBytes += (ms1.lTotalCount - ms2.lTotalCount);
#endif
return count > 0;
}
////////////////////////////////////////////////////////////////////////
// Collector implementation
////////////////////////////////////////////////////////////////////////
nsCycleCollector::nsCycleCollector() :
mCollectionInProgress(false),
mScanInProgress(false),
mResults(nullptr),
mJSRuntime(nullptr),
mWhiteNodes(nullptr),
mWhiteNodeCount(0),
mVisitedRefCounted(0),
mVisitedGCed(0),
mBeforeUnlinkCB(nullptr),
mForgetSkippableCB(nullptr),
#ifdef DEBUG_CC
mPurpleBuf(mParams, mStats),
mPtrLog(nullptr)
#else
mPurpleBuf(mParams)
#endif
{
#ifdef DEBUG_CC
mExpectedGarbage.Init();
#endif
}
nsCycleCollector::~nsCycleCollector()
{
}
void
nsCycleCollector::RegisterJSRuntime(nsCycleCollectionJSRuntime *aJSRuntime)
{
if (mParams.mDoNothing)
return;
if (mJSRuntime)
Fault("multiple registrations of cycle collector JS runtime", aJSRuntime);
mJSRuntime = aJSRuntime;
}
void
nsCycleCollector::ForgetJSRuntime()
{
if (mParams.mDoNothing)
return;
if (!mJSRuntime)
Fault("forgetting non-registered cycle collector JS runtime");
mJSRuntime = nullptr;
}
#ifdef DEBUG_CC
class Suppressor :
public nsCycleCollectionTraversalCallback
{
protected:
static char *sSuppressionList;
static bool sInitialized;
bool mSuppressThisNode;
public:
Suppressor()
{
}
bool shouldSuppress(nsISupports *s)
{
if (!sInitialized) {
sSuppressionList = PR_GetEnv("XPCOM_CC_SUPPRESS");
sInitialized = true;
}
if (sSuppressionList == nullptr) {
mSuppressThisNode = false;
} else {
nsresult rv;
nsXPCOMCycleCollectionParticipant *cp;
rv = CallQueryInterface(s, &cp);
if (NS_FAILED(rv)) {
Fault("checking suppression on wrong type of pointer", s);
return true;
}
cp->Traverse(s, *this);
}
return mSuppressThisNode;
}
NS_IMETHOD_(void) DescribeRefCountedNode(nsrefcnt refCount,
const char *objName)
{
mSuppressThisNode = (PL_strstr(sSuppressionList, objName) != nullptr);
}
NS_IMETHOD_(void) DescribeGCedNode(bool isMarked, const char *objName)
{
mSuppressThisNode = (PL_strstr(sSuppressionList, objName) != nullptr);
}
NS_IMETHOD_(void) NoteXPCOMRoot(nsISupports *root) {}
NS_IMETHOD_(void) NoteJSRoot(void *root) {}
NS_IMETHOD_(void) NoteNativeRoot(void *root,
nsCycleCollectionParticipant *participant) {}
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) {}
NS_IMETHOD_(void) NoteWeakMapping(void *map, void *key, void *val) {}
};
char *Suppressor::sSuppressionList = nullptr;
bool Suppressor::sInitialized = false;
static bool
nsCycleCollector_shouldSuppress(nsISupports *s)
{
Suppressor supp;
return supp.shouldSuppress(s);
}
#endif
#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
nsPurpleBufferEntry*
nsCycleCollector::Suspect2(void *n, nsCycleCollectionParticipant *cp)
{
AbortIfOffMainThreadIfCheckFast();
// 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 nullptr;
NS_ASSERTION(nsCycleCollector_isScanSafe(n, cp),
"suspected a non-scansafe pointer");
if (mParams.mDoNothing)
return nullptr;
#ifdef DEBUG_CC
if (!LogPurpleAddition(n, cp))
return nullptr;
#endif
// Caller is responsible for filling in result's mRefCnt.
return mPurpleBuf.Put(n, cp);
}
bool
nsCycleCollector::Forget2(nsPurpleBufferEntry *e)
{
AbortIfOffMainThreadIfCheckFast();
// Re-entering ::Forget 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 false;
#ifdef DEBUG_CC
LogPurpleRemoval(e->mObject);
#endif
mPurpleBuf.Remove(e);
return true;
}
#ifdef DEBUG_CC
void
nsCycleCollector_logPurpleAddition(void* aObject,
nsCycleCollectionParticipant *cp)
{
if (sCollector) {
sCollector->LogPurpleAddition(aObject, cp);
}
}
bool
nsCycleCollector::LogPurpleAddition(void* aObject,
nsCycleCollectionParticipant *cp)
{
if (mScanInProgress)
return false;
if (mParams.mDoNothing)
return false;
mStats.mSuspectNode++;
if (!cp &&
nsCycleCollector_shouldSuppress(static_cast<nsISupports *>(aObject)))
return false;
if (mParams.mLogPointers) {
if (!mPtrLog)
mPtrLog = fopen("pointer_log", "w");
fprintf(mPtrLog, "S %p\n", static_cast<void*>(aObject));
}
mPurpleBuf.mNormalObjects.PutEntry(aObject);
return true;
}
void
nsCycleCollector_logPurpleRemoval(void* aObject)
{
if (sCollector) {
sCollector->LogPurpleRemoval(aObject);
}
}
void
nsCycleCollector::LogPurpleRemoval(void* aObject)
{
AbortIfOffMainThreadIfCheckFast();
mStats.mForgetNode++;
if (mParams.mLogPointers) {
if (!mPtrLog)
mPtrLog = fopen("pointer_log", "w");
fprintf(mPtrLog, "F %p\n", aObject);
}
mPurpleBuf.mNormalObjects.RemoveEntry(aObject);
}
#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::GCIfNeeded(bool aForceGC)
{
NS_ASSERTION(NS_IsMainThread(),
"nsCycleCollector::GCIfNeeded() must be called on the main thread.");
if (mParams.mDoNothing)
return;
if (!mJSRuntime)
return;
if (!aForceGC) {
bool needGC = mJSRuntime->NeedCollect();
// Only do a telemetry ping for non-shutdown CCs.
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_NEED_GC, needGC);
if (!needGC)
return;
if (mResults)
mResults->mForcedGC = true;
}
TimeLog timeLog;
// mJSRuntime->Collect() must be called from the main thread,
// because it invokes XPCJSRuntime::GCCallback(cx, JSGC_BEGIN)
// which returns false if not in the main thread.
mJSRuntime->Collect(aForceGC ? js::gcreason::SHUTDOWN_CC : js::gcreason::CC_FORCED);
timeLog.Checkpoint("GC()");
}
bool
nsCycleCollector::PrepareForCollection(nsCycleCollectorResults *aResults,
nsTArray<PtrInfo*> *aWhiteNodes)
{
// This can legitimately happen in a few cases. See bug 383651.
if (mCollectionInProgress)
return false;
TimeLog timeLog;
mCollectionStart = TimeStamp::Now();
mVisitedRefCounted = 0;
mVisitedGCed = 0;
mCollectionInProgress = true;
nsCOMPtr<nsIObserverService> obs =
mozilla::services::GetObserverService();
if (obs)
obs->NotifyObservers(nullptr, "cycle-collector-begin", nullptr);
mFollowupCollection = false;
mResults = aResults;
mWhiteNodes = aWhiteNodes;
timeLog.Checkpoint("PrepareForCollection()");
return true;
}
void
nsCycleCollector::CleanupAfterCollection()
{
mWhiteNodes = nullptr;
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;
}
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR, interval);
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_VISITED_REF_COUNTED, mVisitedRefCounted);
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_VISITED_GCED, mVisitedGCed);
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_COLLECTED, mWhiteNodeCount);
}
void
nsCycleCollector::Collect(bool aMergeCompartments,
nsCycleCollectorResults *aResults,
uint32_t aTryCollections,
nsICycleCollectorListener *aListener)
{
nsAutoTArray<PtrInfo*, 4000> whiteNodes;
if (!PrepareForCollection(aResults, &whiteNodes))
return;
uint32_t totalCollections = 0;
while (aTryCollections > totalCollections) {
// Synchronous cycle collection. Always force a JS GC beforehand.
GCIfNeeded(true);
if (aListener && NS_FAILED(aListener->Begin()))
aListener = nullptr;
if (!(BeginCollection(aMergeCompartments, aListener) &&
FinishCollection(aListener)))
break;
++totalCollections;
}
CleanupAfterCollection();
}
bool
nsCycleCollector::BeginCollection(bool aMergeCompartments,
nsICycleCollectorListener *aListener)
{
// aListener should be Begin()'d before this
TimeLog timeLog;
if (mParams.mDoNothing)
return false;
GCGraphBuilder builder(mGraph, mJSRuntime, aListener, aMergeCompartments);
if (!builder.Initialized())
return false;
if (mJSRuntime) {
mJSRuntime->BeginCycleCollection(builder);
timeLog.Checkpoint("mJSRuntime->BeginCycleCollection()");
}
#ifdef DEBUG_CC
uint32_t purpleStart = builder.Count();
#endif
mScanInProgress = true;
SelectPurple(builder);
#ifdef DEBUG_CC
uint32_t purpleEnd = builder.Count();
if (purpleStart != purpleEnd) {
if (mParams.mLogPointers && !mPtrLog)
mPtrLog = fopen("pointer_log", "w");
uint32_t i = 0;
NodePool::Enumerator queue(mGraph.mNodes);
while (i++ < purpleStart) {
queue.GetNext();
}
while (i++ < purpleEnd) {
mStats.mForgetNode++;
if (mParams.mLogPointers)
fprintf(mPtrLog, "F %p\n", queue.GetNext()->mPointer);
}
}
#endif
timeLog.Checkpoint("SelectPurple()");
if (builder.Count() > 0) {
// The main Bacon & Rajan collection algorithm.
MarkRoots(builder);
timeLog.Checkpoint("MarkRoots()");
ScanRoots();
timeLog.Checkpoint("ScanRoots()");
mScanInProgress = false;
if (aListener) {
aListener->BeginResults();
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo *pi = etor.GetNext();
if (pi->mColor == black &&
pi->mRefCount > 0 && pi->mRefCount < PR_UINT32_MAX &&
pi->mInternalRefs != pi->mRefCount) {
aListener->DescribeRoot((uint64_t)pi->mPointer,
pi->mInternalRefs);
}
}
}
#ifdef DEBUG_CC
if (mFollowupCollection && purpleStart != purpleEnd) {
uint32_t i = 0;
NodePool::Enumerator queue(mGraph.mNodes);
while (i++ < purpleStart) {
queue.GetNext();
}
while (i++ < purpleEnd) {
PtrInfo *pi = queue.GetNext();
if (pi->mColor == white) {
printf("nsCycleCollector: a later shutdown collection collected the additional\n"
" suspect %p %s\n"
" (which could be fixed by improving traversal)\n",
pi->mPointer, pi->mName);
}
}
}
#endif
if (mJSRuntime) {
mJSRuntime->FinishTraverse();
timeLog.Checkpoint("mJSRuntime->FinishTraverse()");
}
} else {
mScanInProgress = false;
}
return true;
}
bool
nsCycleCollector::FinishCollection(nsICycleCollectorListener *aListener)
{
TimeLog timeLog;
bool collected = CollectWhite(aListener);
timeLog.Checkpoint("CollectWhite()");
#ifdef DEBUG_CC
mStats.mCollection++;
if (mParams.mReportStats)
mStats.Dump();
#endif
mFollowupCollection = true;
#ifdef DEBUG_CC
uint32_t i, count = mWhiteNodes->Length();
for (i = 0; i < count; ++i) {
PtrInfo *pinfo = mWhiteNodes->ElementAt(i);
if (mPurpleBuf.Exists(pinfo->mPointer)) {
printf("nsCycleCollector: %s object @%p is still alive after\n"
" calling RootAndUnlinkJSObjects, Unlink, and Unroot on"
" it! This probably\n"
" means the Unlink implementation was insufficient.\n",
pinfo->mName, pinfo->mPointer);
}
}
#endif
mWhiteNodes->Clear();
ClearGraph();
timeLog.Checkpoint("ClearGraph()");
mParams.mDoNothing = false;
return collected;
}
uint32_t
nsCycleCollector::SuspectedCount()
{
return mPurpleBuf.Count();
}
void
nsCycleCollector::Shutdown()
{
// Here we want to run a final collection and then permanently
// disable the collector because the program is shutting down.
nsCOMPtr<nsCycleCollectorLogger> listener;
if (mParams.mLogGraphs) {
listener = new nsCycleCollectorLogger();
}
Collect(false, nullptr, SHUTDOWN_COLLECTIONS(mParams), listener);
#ifdef DEBUG_CC
GCGraphBuilder builder(mGraph, mJSRuntime, nullptr, false);
mScanInProgress = true;
SelectPurple(builder);
mScanInProgress = false;
if (builder.Count() != 0) {
printf("Might have been able to release more cycles if the cycle collector would "
"run once more at shutdown.\n");
}
ClearGraph();
#endif
mParams.mDoNothing = true;
}
#ifdef DEBUG_CC
void
nsCycleCollector::ShouldBeFreed(nsISupports *n)
{
if (n) {
mExpectedGarbage.PutEntry(n);
}
}
void
nsCycleCollector::WasFreed(nsISupports *n)
{
if (n) {
mExpectedGarbage.RemoveEntry(n);
}
}
#endif
////////////////////////
// Memory reporter
////////////////////////
static int64_t
GetCycleCollectorSize()
{
if (!sCollector)
return 0;
int64_t size = sizeof(nsCycleCollector) +
sCollector->mPurpleBuf.BlocksSize() +
sCollector->mGraph.BlocksSize();
if (sCollector->mWhiteNodes)
size += sCollector->mWhiteNodes->Capacity() * sizeof(PtrInfo*);
return size;
}
NS_MEMORY_REPORTER_IMPLEMENT(CycleCollector,
"explicit/cycle-collector",
KIND_HEAP,
UNITS_BYTES,
GetCycleCollectorSize,
"Memory used by the cycle collector. This "
"includes the cycle collector structure, the "
"purple buffer, the graph, and the white nodes. "
"The latter two are expected to be empty when the "
"cycle collector is idle.")
////////////////////////////////////////////////////////////////////////
// Module public API (exported in nsCycleCollector.h)
// Just functions that redirect into the singleton, once it's built.
////////////////////////////////////////////////////////////////////////
void
nsCycleCollector_registerJSRuntime(nsCycleCollectionJSRuntime *rt)
{
static bool regMemReport = true;
if (sCollector)
sCollector->RegisterJSRuntime(rt);
if (regMemReport) {
regMemReport = false;
NS_RegisterMemoryReporter(new NS_MEMORY_REPORTER_NAME(CycleCollector));
}
}
void
nsCycleCollector_forgetJSRuntime()
{
if (sCollector)
sCollector->ForgetJSRuntime();
}
nsPurpleBufferEntry*
NS_CycleCollectorSuspect2(void *n, nsCycleCollectionParticipant *cp)
{
if (sCollector)
return sCollector->Suspect2(n, cp);
return nullptr;
}
bool
NS_CycleCollectorForget2(nsPurpleBufferEntry *e)
{
return sCollector ? sCollector->Forget2(e) : true;
}
uint32_t
nsCycleCollector_suspectedCount()
{
return sCollector ? sCollector->SuspectedCount() : 0;
}
#ifdef DEBUG
void
nsCycleCollector_DEBUG_shouldBeFreed(nsISupports *n)
{
#ifdef DEBUG_CC
if (sCollector)
sCollector->ShouldBeFreed(n);
#endif
}
void
nsCycleCollector_DEBUG_wasFreed(nsISupports *n)
{
#ifdef DEBUG_CC
if (sCollector)
sCollector->WasFreed(n);
#endif
}
#endif
class nsCycleCollectorRunner : public nsRunnable
{
nsCycleCollector *mCollector;
nsICycleCollectorListener *mListener;
Mutex mLock;
CondVar mRequest;
CondVar mReply;
bool mRunning;
bool mShutdown;
bool mCollected;
bool mMergeCompartments;
public:
NS_IMETHOD Run()
{
PR_SetCurrentThreadName("XPCOM CC");
#ifdef XP_WIN
TlsSetValue(gTLSThreadIDIndex,
(void*) mozilla::threads::CycleCollector);
#elif defined(NS_TLS)
gTLSThreadID = mozilla::threads::CycleCollector;
#else
gCycleCollectorThread = PR_GetCurrentThread();
#endif
NS_ASSERTION(NS_IsCycleCollectorThread() && !NS_IsMainThread(),
"Wrong thread!");
MutexAutoLock autoLock(mLock);
if (mShutdown)
return NS_OK;
mRunning = true;
while (1) {
mRequest.Wait();
if (!mRunning) {
mReply.Notify();
return NS_OK;
}
mCollector->mJSRuntime->NotifyEnterCycleCollectionThread();
mCollected = mCollector->BeginCollection(mMergeCompartments, mListener);
mCollector->mJSRuntime->NotifyLeaveCycleCollectionThread();
mReply.Notify();
}
return NS_OK;
}
nsCycleCollectorRunner(nsCycleCollector *collector)
: mCollector(collector),
mListener(nullptr),
mLock("cycle collector lock"),
mRequest(mLock, "cycle collector request condvar"),
mReply(mLock, "cycle collector reply condvar"),
mRunning(false),
mShutdown(false),
mCollected(false),
mMergeCompartments(false)
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
}
void Collect(bool aMergeCompartments,
nsCycleCollectorResults *aResults,
nsICycleCollectorListener *aListener)
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
// On a WantAllTraces CC, force a synchronous global GC to prevent
// hijinks from ForgetSkippable and compartmental GCs.
bool wantAllTraces = false;
if (aListener) {
aListener->GetWantAllTraces(&wantAllTraces);
}
mCollector->GCIfNeeded(wantAllTraces);
MutexAutoLock autoLock(mLock);
if (!mRunning)
return;
nsAutoTArray<PtrInfo*, 4000> whiteNodes;
if (!mCollector->PrepareForCollection(aResults, &whiteNodes))
return;
NS_ASSERTION(!mListener, "Should have cleared this already!");
if (aListener && NS_FAILED(aListener->Begin()))
aListener = nullptr;
mListener = aListener;
mMergeCompartments = aMergeCompartments;
if (mCollector->mJSRuntime->NotifyLeaveMainThread()) {
mRequest.Notify();
mReply.Wait();
mCollector->mJSRuntime->NotifyEnterMainThread();
} else {
mCollected = mCollector->BeginCollection(aMergeCompartments, mListener);
}
mListener = nullptr;
if (mCollected) {
mCollector->FinishCollection(aListener);
mCollector->CleanupAfterCollection();
}
}
void Shutdown()
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
MutexAutoLock autoLock(mLock);
mShutdown = true;
if (!mRunning)
return;
mRunning = false;
mRequest.Notify();
mReply.Wait();
}
};
// Holds a reference.
static nsCycleCollectorRunner* sCollectorRunner;
// Holds a reference.
static nsIThread* sCollectorThread;
nsresult
nsCycleCollector_startup()
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
NS_ASSERTION(!sCollector, "Forgot to call nsCycleCollector_shutdown?");
sCollector = new nsCycleCollector();
nsRefPtr<nsCycleCollectorRunner> runner =
new nsCycleCollectorRunner(sCollector);
nsCOMPtr<nsIThread> thread;
nsresult rv = NS_NewThread(getter_AddRefs(thread), runner);
NS_ENSURE_SUCCESS(rv, rv);
runner.swap(sCollectorRunner);
thread.swap(sCollectorThread);
return rv;
}
void
nsCycleCollector_setBeforeUnlinkCallback(CC_BeforeUnlinkCallback aCB)
{
if (sCollector) {
sCollector->mBeforeUnlinkCB = aCB;
}
}
void
nsCycleCollector_setForgetSkippableCallback(CC_ForgetSkippableCallback aCB)
{
if (sCollector) {
sCollector->mForgetSkippableCB = aCB;
}
}
void
nsCycleCollector_forgetSkippable(bool aRemoveChildlessNodes)
{
if (sCollector) {
SAMPLE_LABEL("CC", "nsCycleCollector_forgetSkippable");
TimeLog timeLog;
sCollector->ForgetSkippable(aRemoveChildlessNodes);
timeLog.Checkpoint("ForgetSkippable()");
}
}
void
nsCycleCollector_collect(bool aMergeCompartments,
nsCycleCollectorResults *aResults,
nsICycleCollectorListener *aListener)
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
SAMPLE_LABEL("CC", "nsCycleCollector_collect");
nsCOMPtr<nsICycleCollectorListener> listener(aListener);
if (!aListener && sCollector && sCollector->mParams.mLogGraphs) {
listener = new nsCycleCollectorLogger();
}
if (sCollectorRunner) {
sCollectorRunner->Collect(aMergeCompartments, aResults, listener);
} else if (sCollector) {
sCollector->Collect(aMergeCompartments, aResults, 1, listener);
}
}
void
nsCycleCollector_shutdownThreads()
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
if (sCollectorRunner) {
nsRefPtr<nsCycleCollectorRunner> runner;
runner.swap(sCollectorRunner);
runner->Shutdown();
}
if (sCollectorThread) {
nsCOMPtr<nsIThread> thread;
thread.swap(sCollectorThread);
thread->Shutdown();
}
}
void
nsCycleCollector_shutdown()
{
NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
NS_ASSERTION(!sCollectorRunner, "Should have finished before!");
NS_ASSERTION(!sCollectorThread, "Should have finished before!");
if (sCollector) {
SAMPLE_LABEL("CC", "nsCycleCollector_shutdown");
sCollector->Shutdown();
delete sCollector;
sCollector = nullptr;
}
}
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