mozilla-central/xpcom/base/nsCycleCollector.cpp (file symbol)

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 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. A snow-white node
// 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.
// Incremental cycle collection
//
// Beyond the simple state machine required to implement incremental
// collection, the CC needs to be able to compensate for things the browser
// is doing during the collection. There are two kinds of problems. For each
// of these, there are two cases to deal with: purple-buffered C++ objects
// and JS objects.
// The first problem is that an object in the CC's graph can become garbage.
// This is bad because the CC touches the objects in its graph at every
// stage of its operation.
//
// All cycle collected C++ objects that die during a cycle collection
// will end up actually getting deleted by the SnowWhiteKiller. Before
// the SWK deletes an object, it checks if an ICC is running, and if so,
// if the object is in the graph. If it is, the CC clears mPointer and
// mParticipant so it does not point to the raw object any more. Because
// objects could die any time the CC returns to the mutator, any time the CC
// accesses a PtrInfo it must perform a null check on mParticipant to
// ensure the object has not gone away.
//
// JS objects don't always run finalizers, so the CC can't remove them from
// the graph when they die. Fortunately, JS objects can only die during a GC,
// so if a GC is begun during an ICC, the browser synchronously finishes off
// the ICC, which clears the entire CC graph. If the GC and CC are scheduled
// properly, this should be rare.
//
// The second problem is that objects in the graph can be changed, say by
// being addrefed or released, or by having a field updated, after the object
// has been added to the graph. The problem is that ICC can miss a newly
// created reference to an object, and end up unlinking an object that is
// actually alive.
//
// The basic idea of the solution, from "An on-the-fly Reference Counting
// Garbage Collector for Java" by Levanoni and Petrank, is to notice if an
// object has had an additional reference to it created during the collection,
// and if so, don't collect it during the current collection. This avoids having
// to rerun the scan as in Bacon & Rajan 2001.
//
// For cycle collected C++ objects, we modify AddRef to place the object in
// the purple buffer, in addition to Release. Then, in the CC, we treat any
// objects in the purple buffer as being alive, after graph building has
// completed. Because they are in the purple buffer, they will be suspected
// in the next CC, so there's no danger of leaks. This is imprecise, because
// we will treat as live an object that has been Released but not AddRefed
// during graph building, but that's probably rare enough that the additional
// bookkeeping overhead is not worthwhile.
//
// For JS objects, the cycle collector is only looking at gray objects. If a
// gray object is touched during ICC, it will be made black by UnmarkGray.
// Thus, if a JS object has become black during the ICC, we treat it as live.
// Merged JS zones have to be handled specially: we scan all zone globals.
// If any are black, we treat the zone as being black.
// 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"
#include "mozilla/ArrayUtils.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/CycleCollectedJSRuntime.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/HashFunctions.h"
#include "mozilla/HashTable.h"
#include "mozilla/HoldDropJSObjects.h"
#include "mozilla/Maybe.h"
/* This must occur *after* base/process_util.h to avoid typedefs conflicts. */
#include <stdint.h>
#include <stdio.h>
#include <utility>
#include "js/SliceBudget.h"
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"
#include "mozilla/LinkedList.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/MruCache.h"
#include "mozilla/PoisonIOInterposer.h"
#include "mozilla/ProfilerLabels.h"
#include "mozilla/SegmentedVector.h"
#include "mozilla/Telemetry.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/UniquePtr.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollector.h"
#include "nsDeque.h"
#include "nsDumpUtils.h"
#include "nsExceptionHandler.h"
#include "nsIConsoleService.h"
#include "nsICycleCollectorListener.h"
#include "nsIFile.h"
#include "nsIMemoryReporter.h"
#include "nsISerialEventTarget.h"
#include "nsPrintfCString.h"
#include "nsTArray.h"
#include "nsThreadUtils.h"
#include "nsXULAppAPI.h"
#include "prenv.h"
#include "xpcpublic.h"
using namespace mozilla;
struct NurseryPurpleBufferEntry {
void* mPtr;
nsCycleCollectionParticipant* mParticipant;
nsCycleCollectingAutoRefCnt* mRefCnt;
};
#define NURSERY_PURPLE_BUFFER_SIZE 2048
bool gNurseryPurpleBufferEnabled = true;
NurseryPurpleBufferEntry gNurseryPurpleBufferEntry[NURSERY_PURPLE_BUFFER_SIZE];
uint32_t gNurseryPurpleBufferEntryCount = 0;
void ClearNurseryPurpleBuffer();
static void SuspectUsingNurseryPurpleBuffer(
void* aPtr, nsCycleCollectionParticipant* aCp,
nsCycleCollectingAutoRefCnt* aRefCnt) {
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
MOZ_ASSERT(gNurseryPurpleBufferEnabled);
if (gNurseryPurpleBufferEntryCount == NURSERY_PURPLE_BUFFER_SIZE) {
ClearNurseryPurpleBuffer();
}
gNurseryPurpleBufferEntry[gNurseryPurpleBufferEntryCount] = {aPtr, aCp,
aRefCnt};
++gNurseryPurpleBufferEntryCount;
}
// #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
//
// MOZ_CC_LOG_ALL: If defined, always log cycle collector heaps.
//
// MOZ_CC_LOG_SHUTDOWN: If defined, log cycle collector heaps at shutdown.
//
// MOZ_CC_LOG_SHUTDOWN_SKIP: If set to a non-negative integer value n, then
// skip logging for the first n shutdown CCs. This implies MOZ_CC_LOG_SHUTDOWN.
// The first log or two are much larger than the rest, so it can be useful to
// reduce the total size of logs if you know already that the initial logs
// aren't interesting.
//
// MOZ_CC_LOG_THREAD: If set to "main", only automatically log main thread
// CCs. If set to "worker", only automatically log worker CCs. If set to "all",
// log either. The default value is "all". This must be used with either
// MOZ_CC_LOG_ALL or MOZ_CC_LOG_SHUTDOWN for it to do anything.
//
// MOZ_CC_LOG_PROCESS: If set to "main", only automatically log main process
// CCs. If set to "content", only automatically log tab CCs. If set to "all",
// log everything. The default value is "all". This must be used with either
// MOZ_CC_LOG_ALL or MOZ_CC_LOG_SHUTDOWN for it to do anything.
//
// MOZ_CC_ALL_TRACES: If set to "all", any cycle collector
// logging done will be WantAllTraces, which disables
// various cycle collector optimizations to give a fuller picture of
// the heap. If set to "shutdown", only shutdown logging will be WantAllTraces.
// The default is none.
//
// MOZ_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 MOZ_CC_LOG_ALL and MOZ_CC_LOG_SHUTDOWN, or other uses
// of nsICycleCollectorListener)
//
// MOZ_CC_DISABLE_GC_LOG: If defined, don't make a GC log whenever we make a
// cycle collector log. This can be useful for leaks that go away when shutdown
// gets slower, when the JS heap is not involved in the leak. The default is to
// make the GC log.
// Various parameters of this collector can be tuned using environment
// variables.
struct nsCycleCollectorParams {
bool mLogAll;
bool mLogShutdown;
bool mAllTracesAll;
bool mAllTracesShutdown;
bool mLogThisThread;
bool mLogGC;
int32_t mLogShutdownSkip = 0;
nsCycleCollectorParams()
: mLogAll(PR_GetEnv("MOZ_CC_LOG_ALL") != nullptr),
mLogShutdown(PR_GetEnv("MOZ_CC_LOG_SHUTDOWN") != nullptr),
mAllTracesAll(false),
mAllTracesShutdown(false),
mLogGC(!PR_GetEnv("MOZ_CC_DISABLE_GC_LOG")) {
if (const char* lssEnv = PR_GetEnv("MOZ_CC_LOG_SHUTDOWN_SKIP")) {
mLogShutdown = true;
nsDependentCString lssString(lssEnv);
nsresult rv;
int32_t lss = lssString.ToInteger(&rv);
if (NS_SUCCEEDED(rv) && lss >= 0) {
mLogShutdownSkip = lss;
}
}
const char* logThreadEnv = PR_GetEnv("MOZ_CC_LOG_THREAD");
bool threadLogging = true;
if (logThreadEnv && !!strcmp(logThreadEnv, "all")) {
if (NS_IsMainThread()) {
threadLogging = !strcmp(logThreadEnv, "main");
} else {
threadLogging = !strcmp(logThreadEnv, "worker");
}
}
const char* logProcessEnv = PR_GetEnv("MOZ_CC_LOG_PROCESS");
bool processLogging = true;
if (logProcessEnv && !!strcmp(logProcessEnv, "all")) {
switch (XRE_GetProcessType()) {
case GeckoProcessType_Default:
processLogging = !strcmp(logProcessEnv, "main");
break;
case GeckoProcessType_Content:
processLogging = !strcmp(logProcessEnv, "content");
break;
default:
processLogging = false;
break;
}
}
mLogThisThread = threadLogging && processLogging;
const char* allTracesEnv = PR_GetEnv("MOZ_CC_ALL_TRACES");
if (allTracesEnv) {
if (!strcmp(allTracesEnv, "all")) {
mAllTracesAll = true;
} else if (!strcmp(allTracesEnv, "shutdown")) {
mAllTracesShutdown = true;
}
}
}
// aShutdownCount is how many shutdown CCs we've started.
// For non-shutdown CCs, we'll pass in 0.
// For the first shutdown CC, we'll pass in 1.
bool LogThisCC(int32_t aShutdownCount) {
if (mLogAll) {
return mLogThisThread;
}
if (aShutdownCount == 0 || !mLogShutdown) {
return false;
}
if (aShutdownCount <= mLogShutdownSkip) {
return false;
}
return mLogThisThread;
}
bool AllTracesThisCC(bool aIsShutdown) {
return mAllTracesAll || (aIsShutdown && mAllTracesShutdown);
}
bool LogThisGC() const { return mLogGC; }
};
#ifdef COLLECT_TIME_DEBUG
class TimeLog {
public:
TimeLog() : mLastCheckpoint(TimeStamp::Now()) {}
void Checkpoint(const char* aEvent) {
TimeStamp now = TimeStamp::Now();
double dur = (now - mLastCheckpoint).ToMilliseconds();
if (dur >= 0.5) {
printf("cc: %s took %.1fms\n", aEvent, dur);
}
mLastCheckpoint = now;
}
private:
TimeStamp mLastCheckpoint;
};
#else
class TimeLog {
public:
TimeLog() = default;
void Checkpoint(const char* aEvent) {}
};
#endif
////////////////////////////////////////////////////////////////////////
// Base types
////////////////////////////////////////////////////////////////////////
class 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() {
EdgeBlock* b = EdgeBlocks();
while (b) {
EdgeBlock* next = b->Next();
delete b;
b = next;
}
mSentinelAndBlocks[0].block = nullptr;
mSentinelAndBlocks[1].block = nullptr;
}
#ifdef DEBUG
bool IsEmpty() {
return !mSentinelAndBlocks[0].block && !mSentinelAndBlocks[1].block;
}
#endif
private:
struct EdgeBlock;
union PtrInfoOrBlock {
// Use a union to avoid reinterpret_cast and the ensuing
// potential aliasing bugs.
PtrInfo* ptrInfo;
EdgeBlock* block;
};
struct EdgeBlock {
enum { EdgeBlockSize = 16 * 1024 };
PtrInfoOrBlock mPointers[EdgeBlockSize];
EdgeBlock() {
mPointers[EdgeBlockSize - 2].block = nullptr; // sentinel
mPointers[EdgeBlockSize - 1].block = nullptr; // next block pointer
}
EdgeBlock*& Next() { return mPointers[EdgeBlockSize - 1].block; }
PtrInfoOrBlock* Start() { return &mPointers[0]; }
PtrInfoOrBlock* End() { return &mPointers[EdgeBlockSize - 2]; }
};
// Store the null sentinel so that we can have valid iterators
// before adding any edges and without adding any blocks.
PtrInfoOrBlock mSentinelAndBlocks[2];
EdgeBlock*& EdgeBlocks() { return mSentinelAndBlocks[1].block; }
EdgeBlock* EdgeBlocks() const { return mSentinelAndBlocks[1].block; }
public:
class Iterator {
public:
Iterator() : mPointer(nullptr) {}
explicit Iterator(PtrInfoOrBlock* aPointer) : mPointer(aPointer) {}
Iterator(const Iterator& aOther) = default;
Iterator& operator++() {
if (!mPointer->ptrInfo) {
// 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) {
// 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:
explicit Builder(EdgePool& aPool)
: mCurrent(&aPool.mSentinelAndBlocks[0]),
mBlockEnd(&aPool.mSentinelAndBlocks[0]),
mNextBlockPtr(&aPool.EdgeBlocks()) {}
Iterator Mark() { return Iterator(mCurrent); }
void Add(PtrInfo* aEdge) {
if (mCurrent == mBlockEnd) {
EdgeBlock* b = new EdgeBlock();
*mNextBlockPtr = b;
mCurrent = b->Start();
mBlockEnd = b->End();
mNextBlockPtr = &b->Next();
}
(mCurrent++)->ptrInfo = aEdge;
}
private:
// mBlockEnd points to space for null sentinel
PtrInfoOrBlock* mCurrent;
PtrInfoOrBlock* mBlockEnd;
EdgeBlock** mNextBlockPtr;
};
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
size_t n = 0;
EdgeBlock* b = EdgeBlocks();
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) \
do { \
if (NS_IsMainThread()) { \
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR##_name, _value); \
} else { \
Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_WORKER##_name, _value); \
} \
} while (0)
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.
class PtrInfo final {
public:
// mParticipant knows a more concrete type.
void* mPointer;
nsCycleCollectionParticipant* mParticipant;
uint32_t mColor : 2;
uint32_t mInternalRefs : 30;
uint32_t mRefCount;
private:
EdgePool::Iterator mFirstChild;
static const uint32_t kInitialRefCount = UINT32_MAX - 1;
public:
PtrInfo(void* aPointer, nsCycleCollectionParticipant* aParticipant)
: mPointer(aPointer),
mParticipant(aParticipant),
mColor(grey),
mInternalRefs(0),
mRefCount(kInitialRefCount) {
MOZ_ASSERT(aParticipant);
// We initialize mRefCount to a large non-zero value so
// that it doesn't look like a JS object to the cycle collector
// in the case where the object dies before being traversed.
MOZ_ASSERT(!IsGrayJS() && !IsBlackJS());
}
// Allow NodePool::NodeBlock's constructor to compile.
PtrInfo()
: mPointer{nullptr},
mParticipant{nullptr},
mColor{0},
mInternalRefs{0},
mRefCount{0} {
MOZ_ASSERT_UNREACHABLE("should never be called");
}
bool IsGrayJS() const { return mRefCount == 0; }
bool IsBlackJS() const { return mRefCount == UINT32_MAX; }
bool WasTraversed() const { return mRefCount != kInitialRefCount; }
EdgePool::Iterator FirstChild() const {
CC_GRAPH_ASSERT(mFirstChild.Initialized());
return mFirstChild;
}
// this PtrInfo must be part of a NodePool
EdgePool::Iterator LastChild() const {
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;
}
void AnnotatedReleaseAssert(bool aCondition, const char* aMessage);
};
void PtrInfo::AnnotatedReleaseAssert(bool aCondition, const char* aMessage) {
if (aCondition) {
return;
}
const char* piName = "Unknown";
if (mParticipant) {
piName = mParticipant->ClassName();
}
nsPrintfCString msg("%s, for class %s", aMessage, piName);
NS_WARNING(msg.get());
CrashReporter::RecordAnnotationNSCString(
CrashReporter::Annotation::CycleCollector, msg);
MOZ_CRASH();
}
/**
* A structure designed to be used like a linked list of PtrInfo, except
* it allocates many PtrInfos at a time.
*/
class NodePool {
private:
// The -2 allows us to use |NodeBlockSize + 1| for |mEntries|, and fit
// |mNext|, all without causing slop.
enum { NodeBlockSize = 4 * 1024 - 2 };
struct NodeBlock {
// We create and destroy NodeBlock using moz_xmalloc/free rather than new
// and delete to avoid calling its constructor and destructor.
NodeBlock() : mNext{nullptr} {
MOZ_ASSERT_UNREACHABLE("should never be called");
// Ensure NodeBlock is the right size (see the comment on NodeBlockSize
// above).
static_assert(
sizeof(NodeBlock) == 81904 || // 32-bit; equals 19.996 x 4 KiB pages
sizeof(NodeBlock) ==
131048, // 64-bit; equals 31.994 x 4 KiB pages
"ill-sized NodeBlock");
}
~NodeBlock() { MOZ_ASSERT_UNREACHABLE("should never be called"); }
NodeBlock* mNext;
PtrInfo mEntries[NodeBlockSize + 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() {
NodeBlock* b = mBlocks;
while (b) {
NodeBlock* n = b->mNext;
free(b);
b = n;
}
mBlocks = nullptr;
mLast = nullptr;
}
#ifdef DEBUG
bool IsEmpty() { return !mBlocks && !mLast; }
#endif
class Builder;
friend class Builder;
class Builder {
public:
explicit Builder(NodePool& aPool)
: mNextBlock(&aPool.mBlocks), mNext(aPool.mLast), mBlockEnd(nullptr) {
MOZ_ASSERT(!aPool.mBlocks && !aPool.mLast, "pool not empty");
}
PtrInfo* Add(void* aPointer, nsCycleCollectionParticipant* aParticipant) {
if (mNext == mBlockEnd) {
NodeBlock* block = static_cast<NodeBlock*>(malloc(sizeof(NodeBlock)));
if (!block) {
return nullptr;
}
*mNextBlock = block;
mNext = block->mEntries;
mBlockEnd = block->mEntries + NodeBlockSize;
block->mNext = nullptr;
mNextBlock = &block->mNext;
}
return new (mozilla::KnownNotNull, mNext++)
PtrInfo(aPointer, aParticipant);
}
private:
NodeBlock** mNextBlock;
PtrInfo*& mNext;
PtrInfo* mBlockEnd;
};
class Enumerator;
friend class Enumerator;
class Enumerator {
public:
explicit 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) {
NodeBlock* nextBlock = mCurBlock ? mCurBlock->mNext : mFirstBlock;
mNext = nextBlock->mEntries;
mBlockEnd = mNext + NodeBlockSize;
mCurBlock = nextBlock;
}
return mNext++;
}
private:
// mFirstBlock is a reference to allow an Enumerator to be constructed
// for an empty graph.
NodeBlock*& mFirstBlock;
NodeBlock* 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;
PtrInfo* mBlockEnd;
PtrInfo*& 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;
NodeBlock* b = mBlocks;
while (b) {
n += aMallocSizeOf(b);
b = b->mNext;
}
return n;
}
private:
NodeBlock* mBlocks;
PtrInfo* mLast;
};
struct PtrToNodeHashPolicy {
using Key = PtrInfo*;
using Lookup = void*;
static js::HashNumber hash(const Lookup& aLookup) {
return mozilla::HashGeneric(aLookup);
}
static bool match(const Key& aKey, const Lookup& aLookup) {
return aKey->mPointer == aLookup;
}
};
struct WeakMapping {
// map and key will be null if the corresponding objects are GC marked
PtrInfo* mMap;
PtrInfo* mKey;
PtrInfo* mKeyDelegate;
PtrInfo* mVal;
};
class CCGraphBuilder;
struct CCGraph {
NodePool mNodes;
EdgePool mEdges;
nsTArray<WeakMapping> mWeakMaps;
uint32_t mRootCount;
private:
friend CCGraphBuilder;
mozilla::HashSet<PtrInfo*, PtrToNodeHashPolicy> mPtrInfoMap;
bool mOutOfMemory;
static const uint32_t kInitialMapLength = 16384;
public:
CCGraph()
: mRootCount(0), mPtrInfoMap(kInitialMapLength), mOutOfMemory(false) {}
~CCGraph() = default;
void Init() { MOZ_ASSERT(IsEmpty(), "Failed to call CCGraph::Clear"); }
void Clear() {
mNodes.Clear();
mEdges.Clear();
mWeakMaps.Clear();
mRootCount = 0;
mPtrInfoMap.clearAndCompact();
mOutOfMemory = false;
}
#ifdef DEBUG
bool IsEmpty() {
return mNodes.IsEmpty() && mEdges.IsEmpty() && mWeakMaps.IsEmpty() &&
mRootCount == 0 && mPtrInfoMap.empty();
}
#endif
PtrInfo* FindNode(void* aPtr);
void RemoveObjectFromMap(void* aObject);
uint32_t MapCount() const { return mPtrInfoMap.count(); }
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
size_t n = 0;
n += mNodes.SizeOfExcludingThis(aMallocSizeOf);
n += mEdges.SizeOfExcludingThis(aMallocSizeOf);
// We don't measure what the WeakMappings point to, because the
// pointers are non-owning.
n += mWeakMaps.ShallowSizeOfExcludingThis(aMallocSizeOf);
n += mPtrInfoMap.shallowSizeOfExcludingThis(aMallocSizeOf);
return n;
}
};
PtrInfo* CCGraph::FindNode(void* aPtr) {
auto p = mPtrInfoMap.lookup(aPtr);
return p ? *p : nullptr;
}
void CCGraph::RemoveObjectFromMap(void* aObj) {
auto p = mPtrInfoMap.lookup(aObj);
if (p) {
PtrInfo* pinfo = *p;
pinfo->mPointer = nullptr;
pinfo->mParticipant = nullptr;
mPtrInfoMap.remove(p);
}
}
static nsISupports* CanonicalizeXPCOMParticipant(nsISupports* aIn) {
nsISupports* out = nullptr;
aIn->QueryInterface(NS_GET_IID(nsCycleCollectionISupports),
reinterpret_cast<void**>(&out));
return out;
}
struct nsPurpleBufferEntry {
nsPurpleBufferEntry(void* aObject, nsCycleCollectingAutoRefCnt* aRefCnt,
nsCycleCollectionParticipant* aParticipant)
: mObject(aObject), mRefCnt(aRefCnt), mParticipant(aParticipant) {}
nsPurpleBufferEntry(nsPurpleBufferEntry&& aOther)
: mObject(nullptr), mRefCnt(nullptr), mParticipant(nullptr) {
Swap(aOther);
}
void Swap(nsPurpleBufferEntry& aOther) {
std::swap(mObject, aOther.mObject);
std::swap(mRefCnt, aOther.mRefCnt);
std::swap(mParticipant, aOther.mParticipant);
}
void Clear() {
mRefCnt->RemoveFromPurpleBuffer();
mRefCnt = nullptr;
mObject = nullptr;
mParticipant = nullptr;
}
~nsPurpleBufferEntry() {
if (mRefCnt) {
mRefCnt->RemoveFromPurpleBuffer();
}
}
void* mObject;
nsCycleCollectingAutoRefCnt* mRefCnt;
nsCycleCollectionParticipant* mParticipant; // nullptr for nsISupports
};
class nsCycleCollector;
struct nsPurpleBuffer {
private:
uint32_t mCount;
// Try to match the size of a jemalloc bucket, to minimize slop bytes.
// - On 32-bit platforms sizeof(nsPurpleBufferEntry) is 12, so mEntries'
// Segment is 16,372 bytes.
// - On 64-bit platforms sizeof(nsPurpleBufferEntry) is 24, so mEntries'
// Segment is 32,760 bytes.
static const uint32_t kEntriesPerSegment = 1365;
static const size_t kSegmentSize =
sizeof(nsPurpleBufferEntry) * kEntriesPerSegment;
typedef SegmentedVector<nsPurpleBufferEntry, kSegmentSize,
InfallibleAllocPolicy>
PurpleBufferVector;
PurpleBufferVector mEntries;
public:
nsPurpleBuffer() : mCount(0) {
static_assert(
sizeof(PurpleBufferVector::Segment) == 16372 || // 32-bit
sizeof(PurpleBufferVector::Segment) == 32760 || // 64-bit
sizeof(PurpleBufferVector::Segment) == 32744, // 64-bit Windows
"ill-sized nsPurpleBuffer::mEntries");
}
~nsPurpleBuffer() = default;
// This method compacts mEntries.
template <class PurpleVisitor>
void VisitEntries(PurpleVisitor& aVisitor) {
Maybe<AutoRestore<bool>> ar;
if (NS_IsMainThread()) {
ar.emplace(gNurseryPurpleBufferEnabled);
gNurseryPurpleBufferEnabled = false;
ClearNurseryPurpleBuffer();
}
if (mEntries.IsEmpty()) {
return;
}
uint32_t oldLength = mEntries.Length();
uint32_t keptLength = 0;
auto revIter = mEntries.IterFromLast();
auto iter = mEntries.Iter();
// After iteration this points to the first empty entry.
auto firstEmptyIter = mEntries.Iter();
auto iterFromLastEntry = mEntries.IterFromLast();
for (; !iter.Done(); iter.Next()) {
nsPurpleBufferEntry& e = iter.Get();
if (e.mObject) {
if (!aVisitor.Visit(*this, &e)) {
return;
}
}
// Visit call above may have cleared the entry, or the entry was empty
// already.
if (!e.mObject) {
// Try to find a non-empty entry from the end of the vector.
for (; !revIter.Done(); revIter.Prev()) {
nsPurpleBufferEntry& otherEntry = revIter.Get();
if (&e == &otherEntry) {
break;
}
if (otherEntry.mObject) {
if (!aVisitor.Visit(*this, &otherEntry)) {
return;
}
// Visit may have cleared otherEntry.
if (otherEntry.mObject) {
e.Swap(otherEntry);
revIter.Prev(); // We've swapped this now empty entry.
break;
}
}
}
}
// Entry is non-empty even after the Visit call, ensure it is kept
// in mEntries.
if (e.mObject) {
firstEmptyIter.Next();
++keptLength;
}
if (&e == &revIter.Get()) {
break;
}
}
// There were some empty entries.
if (oldLength != keptLength) {
// While visiting entries, some new ones were possibly added. This can
// happen during CanSkip. Move all such new entries to be after other
// entries. Note, we don't call Visit on newly added entries!
if (&iterFromLastEntry.Get() != &mEntries.GetLast()) {
iterFromLastEntry.Next(); // Now pointing to the first added entry.
auto& iterForNewEntries = iterFromLastEntry;
while (!iterForNewEntries.Done()) {
MOZ_ASSERT(!firstEmptyIter.Done());
MOZ_ASSERT(!firstEmptyIter.Get().mObject);
firstEmptyIter.Get().Swap(iterForNewEntries.Get());
firstEmptyIter.Next();
iterForNewEntries.Next();
}
}
mEntries.PopLastN(oldLength - keptLength);
}
}
void FreeBlocks() {
mCount = 0;
mEntries.Clear();
}
void SelectPointers(CCGraphBuilder& aBuilder);
// RemoveSkippable removes entries from the purple buffer synchronously
// (1) if !aAsyncSnowWhiteFreeing and nsPurpleBufferEntry::mRefCnt is 0 or
// (2) if nsXPCOMCycleCollectionParticipant::CanSkip() for the obj or
// (3) if nsPurpleBufferEntry::mRefCnt->IsPurple() is false.
// (4) If aRemoveChildlessNodes 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, js::SliceBudget& aBudget,
bool aRemoveChildlessNodes, bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb);
MOZ_ALWAYS_INLINE void Put(void* aObject, nsCycleCollectionParticipant* aCp,
nsCycleCollectingAutoRefCnt* aRefCnt) {
nsPurpleBufferEntry entry(aObject, aRefCnt, aCp);
Unused << mEntries.Append(std::move(entry));
MOZ_ASSERT(!entry.mRefCnt, "Move didn't work!");
++mCount;
}
void Remove(nsPurpleBufferEntry* aEntry) {
MOZ_ASSERT(mCount != 0, "must have entries");
--mCount;
aEntry->Clear();
}
uint32_t Count() const { return mCount; }
size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
return mEntries.SizeOfExcludingThis(aMallocSizeOf);
}
};
static bool AddPurpleRoot(CCGraphBuilder& aBuilder, void* aRoot,
nsCycleCollectionParticipant* aParti);
struct SelectPointersVisitor {
explicit SelectPointersVisitor(CCGraphBuilder& aBuilder)
: mBuilder(aBuilder) {}
bool 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);
}
return true;
}
private:
CCGraphBuilder& mBuilder;
};
void nsPurpleBuffer::SelectPointers(CCGraphBuilder& aBuilder) {
SelectPointersVisitor visitor(aBuilder);
VisitEntries(visitor);
MOZ_ASSERT(mCount == 0, "AddPurpleRoot failed");
if (mCount == 0) {
FreeBlocks();
}
}
enum ccPhase {
IdlePhase,
GraphBuildingPhase,
ScanAndCollectWhitePhase,
CleanupPhase
};
enum ccIsManual { CCIsNotManual = false, CCIsManual = true };
////////////////////////////////////////////////////////////////////////
// Top level structure for the cycle collector.
////////////////////////////////////////////////////////////////////////
using js::SliceBudget;
class JSPurpleBuffer;
class nsCycleCollector : public nsIMemoryReporter {
public:
NS_DECL_ISUPPORTS
NS_DECL_NSIMEMORYREPORTER
private:
bool mActivelyCollecting;
bool mFreeingSnowWhite;
// mScanInProgress should be false when we're collecting white objects.
bool mScanInProgress;
CycleCollectorResults mResults;
TimeStamp mCollectionStart;
CycleCollectedJSRuntime* mCCJSRuntime;
ccPhase mIncrementalPhase;
int32_t mShutdownCount = 0;
CCGraph mGraph;
UniquePtr<CCGraphBuilder> mBuilder;
RefPtr<nsCycleCollectorLogger> mLogger;
#ifdef DEBUG
nsISerialEventTarget* mEventTarget;
#endif
nsCycleCollectorParams mParams;
uint32_t mWhiteNodeCount;
CC_BeforeUnlinkCallback mBeforeUnlinkCB;
CC_ForgetSkippableCallback mForgetSkippableCB;
nsPurpleBuffer mPurpleBuf;
uint32_t mUnmergedNeeded;
uint32_t mMergedInARow;
RefPtr<JSPurpleBuffer> mJSPurpleBuffer;
private:
virtual ~nsCycleCollector();
public:
nsCycleCollector();
void SetCCJSRuntime(CycleCollectedJSRuntime* aCCRuntime);
void ClearCCJSRuntime();
void SetBeforeUnlinkCallback(CC_BeforeUnlinkCallback aBeforeUnlinkCB) {
CheckThreadSafety();
mBeforeUnlinkCB = aBeforeUnlinkCB;
}
void SetForgetSkippableCallback(
CC_ForgetSkippableCallback aForgetSkippableCB) {
CheckThreadSafety();
mForgetSkippableCB = aForgetSkippableCB;
}
void Suspect(void* aPtr, nsCycleCollectionParticipant* aCp,
nsCycleCollectingAutoRefCnt* aRefCnt);
void SuspectNurseryEntries();
uint32_t SuspectedCount();
void ForgetSkippable(js::SliceBudget& aBudget, bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing);
bool FreeSnowWhite(bool aUntilNoSWInPurpleBuffer);
bool FreeSnowWhiteWithBudget(js::SliceBudget& aBudget);
// This method assumes its argument is already canonicalized.
void RemoveObjectFromGraph(void* aPtr);
void PrepareForGarbageCollection();
void FinishAnyCurrentCollection(CCReason aReason);
bool Collect(CCReason aReason, ccIsManual aIsManual, SliceBudget& aBudget,
nsICycleCollectorListener* aManualListener,
bool aPreferShorterSlices = false);
MOZ_CAN_RUN_SCRIPT
void Shutdown(bool aDoCollect);
bool IsIdle() const { return mIncrementalPhase == IdlePhase; }
void SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
size_t* aObjectSize, size_t* aGraphSize,
size_t* aPurpleBufferSize) const;
JSPurpleBuffer* GetJSPurpleBuffer();
CycleCollectedJSRuntime* Runtime() { return mCCJSRuntime; }
private:
void CheckThreadSafety();
MOZ_CAN_RUN_SCRIPT
void ShutdownCollect();
void FixGrayBits(bool aIsShutdown, TimeLog& aTimeLog);
bool IsIncrementalGCInProgress();
void FinishAnyIncrementalGCInProgress();
bool ShouldMergeZones(ccIsManual aIsManual);
void BeginCollection(CCReason aReason, ccIsManual aIsManual,
nsICycleCollectorListener* aManualListener);
void MarkRoots(SliceBudget& aBudget);
void ScanRoots(bool aFullySynchGraphBuild);
void ScanIncrementalRoots();
void ScanWhiteNodes(bool aFullySynchGraphBuild);
void ScanBlackNodes();
void ScanWeakMaps();
// returns whether anything was collected
bool CollectWhite();
void CleanupAfterCollection();
};
NS_IMPL_ISUPPORTS(nsCycleCollector, nsIMemoryReporter)
/**
* 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<PtrInfo>& aQueue);
void CheckedPush(nsDeque<PtrInfo>& aQueue, PtrInfo* aPi) {
if (!aPi) {
MOZ_CRASH();
}
if (!aQueue.Push(aPi, fallible)) {
mVisitor.Failed();
}
}
public:
void Walk(PtrInfo* aPi);
void WalkFromRoots(CCGraph& aGraph);
// copy-constructing the visitor should be cheap, and less
// indirection than using a reference
explicit GraphWalker(const Visitor aVisitor) : mVisitor(aVisitor) {}
};
////////////////////////////////////////////////////////////////////////
// The static collector struct
////////////////////////////////////////////////////////////////////////
struct CollectorData {
RefPtr<nsCycleCollector> mCollector;
CycleCollectedJSContext* mContext;
};
static MOZ_THREAD_LOCAL(CollectorData*) sCollectorData;
////////////////////////////////////////////////////////////////////////
// Utility functions
////////////////////////////////////////////////////////////////////////
static inline void ToParticipant(nsISupports* aPtr,
nsXPCOMCycleCollectionParticipant** aCp) {
// 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.
*aCp = nullptr;
CallQueryInterface(aPtr, aCp);
}
static void ToParticipant(void* aParti, nsCycleCollectionParticipant** aCp) {
// If the participant is null, this is an nsISupports participant,
// so we must QI to get the real participant.
if (!*aCp) {
nsISupports* nsparti = static_cast<nsISupports*>(aParti);
MOZ_ASSERT(CanonicalizeXPCOMParticipant(nsparti) == nsparti);
nsXPCOMCycleCollectionParticipant* xcp;
ToParticipant(nsparti, &xcp);
*aCp = xcp;
}
}
template <class Visitor>
MOZ_NEVER_INLINE void GraphWalker<Visitor>::Walk(PtrInfo* aPi) {
nsDeque<PtrInfo> queue;
CheckedPush(queue, aPi);
DoWalk(queue);
}
template <class Visitor>
MOZ_NEVER_INLINE void GraphWalker<Visitor>::WalkFromRoots(CCGraph& aGraph) {
nsDeque<PtrInfo> 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<PtrInfo>& 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 = aQueue.PopFront();
if (pi->WasTraversed() && 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 : public LinkedListElement<CCGraphDescriber> {
CCGraphDescriber() : mAddress("0x"), mCnt(0), mType(eUnknown) {}
enum Type {
eRefCountedObject,
eGCedObject,
eGCMarkedObject,
eEdge,
eRoot,
eGarbage,
eUnknown
};
nsCString mAddress;
nsCString mName;
nsCString mCompartmentOrToAddress;
uint32_t mCnt;
Type mType;
};
class LogStringMessageAsync : public DiscardableRunnable {
public:
explicit LogStringMessageAsync(const nsAString& aMsg)
: mozilla::DiscardableRunnable("LogStringMessageAsync"), mMsg(aMsg) {}
NS_IMETHOD Run() override {
nsCOMPtr<nsIConsoleService> cs =
do_GetService(NS_CONSOLESERVICE_CONTRACTID);
if (cs) {
cs->LogStringMessage(mMsg.get());
}
return NS_OK;
}
private:
nsString mMsg;
};
class nsCycleCollectorLogSinkToFile final : public nsICycleCollectorLogSink {
public:
NS_DECL_ISUPPORTS
explicit nsCycleCollectorLogSinkToFile(bool aLogGC)
: mProcessIdentifier(base::GetCurrentProcId()), mCCLog("cc-edges") {
if (aLogGC) {
mGCLog.emplace("gc-edges");
}
}
NS_IMETHOD GetFilenameIdentifier(nsAString& aIdentifier) override {
aIdentifier = mFilenameIdentifier;
return NS_OK;
}
NS_IMETHOD SetFilenameIdentifier(const nsAString& aIdentifier) override {
mFilenameIdentifier = aIdentifier;
return NS_OK;
}
NS_IMETHOD GetProcessIdentifier(int32_t* aIdentifier) override {
*aIdentifier = mProcessIdentifier;
return NS_OK;
}
NS_IMETHOD SetProcessIdentifier(int32_t aIdentifier) override {
mProcessIdentifier = aIdentifier;
return NS_OK;
}
NS_IMETHOD GetGcLog(nsIFile** aPath) override {
if (mGCLog.isNothing()) {
return NS_ERROR_UNEXPECTED;
}
NS_IF_ADDREF(*aPath = mGCLog.ref().mFile);
return NS_OK;
}
NS_IMETHOD GetCcLog(nsIFile** aPath) override {
NS_IF_ADDREF(*aPath = mCCLog.mFile);
return NS_OK;
}
NS_IMETHOD Open(FILE** aGCLog, FILE** aCCLog) override {
nsresult rv;
if (mCCLog.mStream) {
return NS_ERROR_UNEXPECTED;
}
if (mGCLog.isSome()) {
if (mGCLog.ref().mStream) {
return NS_ERROR_UNEXPECTED;
}
rv = OpenLog(&mGCLog.ref());
NS_ENSURE_SUCCESS(rv, rv);
*aGCLog = mGCLog.ref().mStream;
} else {
*aGCLog = nullptr;
}
rv = OpenLog(&mCCLog);
NS_ENSURE_SUCCESS(rv, rv);
*aCCLog = mCCLog.mStream;
return NS_OK;
}
NS_IMETHOD CloseGCLog() override {
if (mGCLog.isNothing()) {
return NS_OK;
}
if (!mGCLog.ref().mStream) {
return NS_ERROR_UNEXPECTED;
}
CloseLog(&mGCLog.ref(), u"Garbage"_ns);
return NS_OK;
}
NS_IMETHOD CloseCCLog() override {
if (!mCCLog.mStream) {
return NS_ERROR_UNEXPECTED;
}
CloseLog(&mCCLog, u"Cycle"_ns);
return NS_OK;
}
private:
~nsCycleCollectorLogSinkToFile() {
if (mGCLog.isSome() && mGCLog.ref().mStream) {
MozillaUnRegisterDebugFILE(mGCLog.ref().mStream);
fclose(mGCLog.ref().mStream);
}
if (mCCLog.mStream) {
MozillaUnRegisterDebugFILE(mCCLog.mStream);
fclose(mCCLog.mStream);
}
}
struct FileInfo {
const char* const mPrefix;
nsCOMPtr<nsIFile> mFile;
FILE* mStream;
explicit FileInfo(const char* aPrefix)
: mPrefix(aPrefix), mStream(nullptr) {}
};
/**
* 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, mProcessIdentifier,
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);
}
// On Android or B2G, this function will open a file named
// aFilename under a memory-reporting-specific folder
// (/data/local/tmp/memory-reports). Otherwise, it will open a
// file named aFilename under "NS_OS_TEMP_DIR".
nsresult rv =
nsDumpUtils::OpenTempFile(filename, &logFile, "memory-reports"_ns);
if (NS_FAILED(rv)) {
NS_IF_RELEASE(logFile);
return nullptr;
}
return dont_AddRef(logFile);
}
nsresult OpenLog(FileInfo* aLog) {
// Initially create the log in a file starting with "incomplete-".
// 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.)
nsAutoCString incomplete;
incomplete += "incomplete-";
incomplete += aLog->mPrefix;
MOZ_ASSERT(!aLog->mFile);
aLog->mFile = CreateTempFile(incomplete.get());
if (NS_WARN_IF(!aLog->mFile)) {
return NS_ERROR_UNEXPECTED;
}
MOZ_ASSERT(!aLog->mStream);
nsresult rv = aLog->mFile->OpenANSIFileDesc("w", &aLog->mStream);
if (NS_WARN_IF(NS_FAILED(rv))) {
return NS_ERROR_UNEXPECTED;
}
MozillaRegisterDebugFILE(aLog->mStream);
return NS_OK;
}
nsresult CloseLog(FileInfo* aLog, const nsAString& aCollectorKind) {
MOZ_ASSERT(aLog->mStream);
MOZ_ASSERT(aLog->mFile);
MozillaUnRegisterDebugFILE(aLog->mStream);
fclose(aLog->mStream);
aLog->mStream = nullptr;
// Strip off "incomplete-".
nsCOMPtr<nsIFile> logFileFinalDestination = CreateTempFile(aLog->mPrefix);
if (NS_WARN_IF(!logFileFinalDestination)) {
return NS_ERROR_UNEXPECTED;
}
nsAutoString logFileFinalDestinationName;
logFileFinalDestination->GetLeafName(logFileFinalDestinationName);
if (NS_WARN_IF(logFileFinalDestinationName.IsEmpty())) {
return NS_ERROR_UNEXPECTED;
}
aLog->mFile->MoveTo(/* directory */ nullptr, logFileFinalDestinationName);
// Save the file path.
aLog->mFile = logFileFinalDestination;
// Log to the error console.
nsAutoString logPath;
logFileFinalDestination->GetPath(logPath);
nsAutoString msg =
aCollectorKind + u" Collector log dumped to "_ns + logPath;
// We don't want any JS to run between ScanRoots and CollectWhite calls,
// and since ScanRoots calls this method, better to log the message
// asynchronously.
RefPtr<LogStringMessageAsync> log = new LogStringMessageAsync(msg);
NS_DispatchToCurrentThread(log);
return NS_OK;
}
int32_t mProcessIdentifier;
nsString mFilenameIdentifier;
Maybe<FileInfo> mGCLog;
FileInfo mCCLog;
};
NS_IMPL_ISUPPORTS(nsCycleCollectorLogSinkToFile, nsICycleCollectorLogSink)
class nsCycleCollectorLogger final : public nsICycleCollectorListener {
~nsCycleCollectorLogger() { ClearDescribers(); }
public:
explicit nsCycleCollectorLogger(bool aLogGC)
: mLogSink(nsCycleCollector_createLogSink(aLogGC)),
mWantAllTraces(false),
mDisableLog(false),
mWantAfterProcessing(false),
mCCLog(nullptr) {}
NS_DECL_ISUPPORTS
void SetAllTraces() { mWantAllTraces = true; }
bool IsAllTraces() { return mWantAllTraces; }
NS_IMETHOD AllTraces(nsICycleCollectorListener** aListener) override {
SetAllTraces();
NS_ADDREF(*aListener = this);
return NS_OK;
}
NS_IMETHOD GetWantAllTraces(bool* aAllTraces) override {
*aAllTraces = mWantAllTraces;
return NS_OK;
}
NS_IMETHOD GetDisableLog(bool* aDisableLog) override {
*aDisableLog = mDisableLog;
return NS_OK;
}
NS_IMETHOD SetDisableLog(bool aDisableLog) override {
mDisableLog = aDisableLog;
return NS_OK;
}
NS_IMETHOD GetWantAfterProcessing(bool* aWantAfterProcessing) override {
*aWantAfterProcessing = mWantAfterProcessing;
return NS_OK;
}
NS_IMETHOD SetWantAfterProcessing(bool aWantAfterProcessing) override {
mWantAfterProcessing = aWantAfterProcessing;
return NS_OK;
}
NS_IMETHOD GetLogSink(nsICycleCollectorLogSink** aLogSink) override {
NS_ADDREF(*aLogSink = mLogSink);
return NS_OK;
}
NS_IMETHOD SetLogSink(nsICycleCollectorLogSink* aLogSink) override {
if (!aLogSink) {
return NS_ERROR_INVALID_ARG;
}
mLogSink = aLogSink;
return NS_OK;
}
nsresult Begin() {
nsresult rv;
mCurrentAddress.AssignLiteral("0x");
ClearDescribers();
if (mDisableLog) {
return NS_OK;
}
FILE* gcLog;
rv = mLogSink->Open(&gcLog, &mCCLog);
NS_ENSURE_SUCCESS(rv, rv);
// Dump the JS heap.
if (gcLog) {
CollectorData* data = sCollectorData.get();
if (data && data->mContext) {
data->mContext->Runtime()->DumpJSHeap(gcLog);
}
rv = mLogSink->CloseGCLog();
NS_ENSURE_SUCCESS(rv, rv);
}
fprintf(mCCLog, "# WantAllTraces=%s\n", mWantAllTraces ? "true" : "false");
return NS_OK;
}
void NoteRefCountedObject(uint64_t aAddress, uint32_t aRefCount,
const char* aObjectDescription) {
if (!mDisableLog) {
fprintf(mCCLog, "%p [rc=%u] %s\n", (void*)aAddress, aRefCount,
aObjectDescription);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = new CCGraphDescriber();
mDescribers.insertBack(d);
mCurrentAddress.AssignLiteral("0x");
mCurrentAddress.AppendInt(aAddress, 16);
d->mType = CCGraphDescriber::eRefCountedObject;
d->mAddress = mCurrentAddress;
d->mCnt = aRefCount;
d->mName.Append(aObjectDescription);
}
}
void NoteGCedObject(uint64_t aAddress, bool aMarked,
const char* aObjectDescription,
uint64_t aCompartmentAddress) {
if (!mDisableLog) {
fprintf(mCCLog, "%p [gc%s] %s\n", (void*)aAddress,
aMarked ? ".marked" : "", aObjectDescription);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = new CCGraphDescriber();
mDescribers.insertBack(d);
mCurrentAddress.AssignLiteral("0x");
mCurrentAddress.AppendInt(aAddress, 16);
d->mType = aMarked ? CCGraphDescriber::eGCMarkedObject
: CCGraphDescriber::eGCedObject;
d->mAddress = mCurrentAddress;
d->mName.Append(aObjectDescription);
if (aCompartmentAddress) {
d->mCompartmentOrToAddress.AssignLiteral("0x");
d->mCompartmentOrToAddress.AppendInt(aCompartmentAddress, 16);
} else {
d->mCompartmentOrToAddress.SetIsVoid(true);
}
}
}
void NoteEdge(uint64_t aToAddress, const char* aEdgeName) {
if (!mDisableLog) {
fprintf(mCCLog, "> %p %s\n", (void*)aToAddress, aEdgeName);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = new CCGraphDescriber();
mDescribers.insertBack(d);
d->mType = CCGraphDescriber::eEdge;
d->mAddress = mCurrentAddress;
d->mCompartmentOrToAddress.AssignLiteral("0x");
d->mCompartmentOrToAddress.AppendInt(aToAddress, 16);
d->mName.Append(aEdgeName);
}
}
void NoteWeakMapEntry(uint64_t aMap, uint64_t aKey, uint64_t aKeyDelegate,
uint64_t aValue) {
if (!mDisableLog) {
fprintf(mCCLog, "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.
}
void NoteIncrementalRoot(uint64_t aAddress) {
if (!mDisableLog) {
fprintf(mCCLog, "IncrementalRoot %p\n", (void*)aAddress);
}
// We don't support after-processing for incremental roots.
}
void BeginResults() {
if (!mDisableLog) {
fputs("==========\n", mCCLog);
}
}
void DescribeRoot(uint64_t aAddress, uint32_t aKnownEdges) {
if (!mDisableLog) {
fprintf(mCCLog, "%p [known=%u]\n", (void*)aAddress, aKnownEdges);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = new CCGraphDescriber();
mDescribers.insertBack(d);
d->mType = CCGraphDescriber::eRoot;
d->mAddress.AppendInt(aAddress, 16);
d->mCnt = aKnownEdges;
}
}
void DescribeGarbage(uint64_t aAddress) {
if (!mDisableLog) {
fprintf(mCCLog, "%p [garbage]\n", (void*)aAddress);
}
if (mWantAfterProcessing) {
CCGraphDescriber* d = new CCGraphDescriber();
mDescribers.insertBack(d);
d->mType = CCGraphDescriber::eGarbage;
d->mAddress.AppendInt(aAddress, 16);
}
}
void End() {
if (!mDisableLog) {
mCCLog = nullptr;
Unused << NS_WARN_IF(NS_FAILED(mLogSink->CloseCCLog()));
}
}
NS_IMETHOD ProcessNext(nsICycleCollectorHandler* aHandler,
bool* aCanContinue) override {
if (NS_WARN_IF(!aHandler) || NS_WARN_IF(!mWantAfterProcessing)) {
return NS_ERROR_UNEXPECTED;
}
CCGraphDescriber* d = mDescribers.popFirst();
if (d) {
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, d->mCompartmentOrToAddress);
break;
case CCGraphDescriber::eEdge:
aHandler->NoteEdge(d->mAddress, d->mCompartmentOrToAddress, d->mName);
break;
case CCGraphDescriber::eRoot:
aHandler->DescribeRoot(d->mAddress, d->mCnt);
break;
case CCGraphDescriber::eGarbage:
aHandler->DescribeGarbage(d->mAddress);
break;
case CCGraphDescriber::eUnknown:
MOZ_ASSERT_UNREACHABLE("CCGraphDescriber::eUnknown");
break;
}
delete d;
}
if (!(*aCanContinue = !mDescribers.isEmpty())) {
mCurrentAddress.AssignLiteral("0x");
}
return NS_OK;
}
NS_IMETHOD AsLogger(nsCycleCollectorLogger** aRetVal) override {
RefPtr<nsCycleCollectorLogger> rval = this;
rval.forget(aRetVal);
return NS_OK;
}
private:
void ClearDescribers() {
CCGraphDescriber* d;
while ((d = mDescribers.popFirst())) {
delete d;
}
}
nsCOMPtr<nsICycleCollectorLogSink> mLogSink;
bool mWantAllTraces;
bool mDisableLog;
bool mWantAfterProcessing;
nsCString mCurrentAddress;
mozilla::LinkedList<CCGraphDescriber> mDescribers;
FILE* mCCLog;
};
NS_IMPL_ISUPPORTS(nsCycleCollectorLogger, nsICycleCollectorListener)
already_AddRefed<nsICycleCollectorListener> nsCycleCollector_createLogger() {
nsCOMPtr<nsICycleCollectorListener> logger =
new nsCycleCollectorLogger(/* aLogGC = */ true);
return logger.forget();
}
static bool GCThingIsGrayCCThing(JS::GCCellPtr thing) {
return JS::IsCCTraceKind(thing.kind()) && JS::GCThingIsMarkedGrayInCC(thing);
}
static bool ValueIsGrayCCThing(const JS::Value& value) {
return JS::IsCCTraceKind(value.traceKind()) &&
JS::GCThingIsMarkedGray(value.toGCCellPtr());
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |MarkRoots| routine.
////////////////////////////////////////////////////////////////////////
class CCGraphBuilder final : public nsCycleCollectionTraversalCallback,
public nsCycleCollectionNoteRootCallback {
private:
CCGraph& mGraph;
CycleCollectorResults& mResults;
NodePool::Builder mNodeBuilder;
EdgePool::Builder mEdgeBuilder;
MOZ_INIT_OUTSIDE_CTOR PtrInfo* mCurrPi;
nsCycleCollectionParticipant* mJSParticipant;
nsCycleCollectionParticipant* mJSZoneParticipant;
nsCString mNextEdgeName;
RefPtr<nsCycleCollectorLogger> mLogger;
bool mMergeZones;
UniquePtr<NodePool::Enumerator> mCurrNode;
uint32_t mNoteChildCount;
struct PtrInfoCache : public MruCache<void*, PtrInfo*, PtrInfoCache, 491> {
static HashNumber Hash(const void* aKey) { return HashGeneric(aKey); }
static bool Match(const void* aKey, const PtrInfo* aVal) {
return aVal->mPointer == aKey;
}
};
PtrInfoCache mGraphCache;
public:
CCGraphBuilder(CCGraph& aGraph, CycleCollectorResults& aResults,
CycleCollectedJSRuntime* aCCRuntime,
nsCycleCollectorLogger* aLogger, bool aMergeZones);
virtual ~CCGraphBuilder();
bool WantAllTraces() const {
return nsCycleCollectionNoteRootCallback::WantAllTraces();
}
bool AddPurpleRoot(void* aRoot, nsCycleCollectionParticipant* aParti);
// This is called when all roots have been added to the graph, to prepare for
// BuildGraph().
void DoneAddingRoots();
// Do some work traversing nodes in the graph. Returns true if this graph
// building is finished.
bool BuildGraph(SliceBudget& aBudget);
void RemoveCachedEntry(void* aPtr) { mGraphCache.Remove(aPtr); }
private:
PtrInfo* AddNode(void* aPtr, nsCycleCollectionParticipant* aParticipant);
PtrInfo* AddWeakMapNode(JS::GCCellPtr aThing);
PtrInfo* AddWeakMapNode(JSObject* aObject);
void SetFirstChild() { mCurrPi->SetFirstChild(mEdgeBuilder.Mark()); }
void SetLastChild() { mCurrPi->SetLastChild(mEdgeBuilder.Mark()); }
public:
// nsCycleCollectionNoteRootCallback methods.
NS_IMETHOD_(void)
NoteXPCOMRoot(nsISupports* aRoot,
nsCycleCollectionParticipant* aParticipant) override;
NS_IMETHOD_(void) NoteJSRoot(JSObject* aRoot) override;
NS_IMETHOD_(void)
NoteNativeRoot(void* aRoot,
nsCycleCollectionParticipant* aParticipant) override;
NS_IMETHOD_(void)
NoteWeakMapping(JSObject* aMap, JS::GCCellPtr aKey, JSObject* aKdelegate,
JS::GCCellPtr aVal) override;
// This is used to create synthetic non-refcounted references to
// nsXPCWrappedJS from their wrapped JS objects. No map is needed, because
// the SubjectToFinalization list is like a known-black weak map, and
// no delegate is needed because the keys are all unwrapped objects.
NS_IMETHOD_(void)
NoteWeakMapping(JSObject* aKey, nsISupports* aVal,
nsCycleCollectionParticipant* aValParticipant) override;
// nsCycleCollectionTraversalCallback methods.
NS_IMETHOD_(void)
DescribeRefCountedNode(nsrefcnt aRefCount, const char* aObjName) override;
NS_IMETHOD_(void)
DescribeGCedNode(bool aIsMarked, const char* aObjName,
uint64_t aCompartmentAddress) override;
NS_IMETHOD_(void) NoteXPCOMChild(nsISupports* aChild) override;
NS_IMETHOD_(void) NoteJSChild(JS::GCCellPtr aThing) override;
NS_IMETHOD_(void)
NoteNativeChild(void* aChild,
nsCycleCollectionParticipant* aParticipant) override;
NS_IMETHOD_(void) NoteNextEdgeName(const char* aName) override;
private:
NS_IMETHOD_(void)
NoteRoot(void* aRoot, nsCycleCollectionParticipant* aParticipant) {
MOZ_ASSERT(aRoot);
MOZ_ASSERT(aParticipant);
if (!aParticipant->CanSkipInCC(aRoot) || MOZ_UNLIKELY(WantAllTraces())) {
AddNode(aRoot, aParticipant);
}
}
NS_IMETHOD_(void)
NoteChild(void* aChild, nsCycleCollectionParticipant* aCp,
nsCString& aEdgeName) {
PtrInfo* childPi = AddNode(aChild, aCp);
if (!childPi) {
return;
}
mEdgeBuilder.Add(childPi);
if (mLogger) {
mLogger->NoteEdge((uint64_t)aChild, aEdgeName.get());
}
++childPi->mInternalRefs;
}
JS::Zone* MergeZone(JS::GCCellPtr aGcthing) {
if (!mMergeZones) {
return nullptr;
}
JS::Zone* zone = JS::GetTenuredGCThingZone(aGcthing);
if (js::IsSystemZone(zone)) {
return nullptr;
}
return zone;
}
};
CCGraphBuilder::CCGraphBuilder(CCGraph& aGraph, CycleCollectorResults& aResults,
CycleCollectedJSRuntime* aCCRuntime,
nsCycleCollectorLogger* aLogger,
bool aMergeZones)
: mGraph(aGraph),
mResults(aResults),
mNodeBuilder(aGraph.mNodes),
mEdgeBuilder(aGraph.mEdges),
mJSParticipant(nullptr),
mJSZoneParticipant(nullptr),
mLogger(aLogger),
mMergeZones(aMergeZones),
mNoteChildCount(0) {
// 4096 is an allocation bucket size.
static_assert(sizeof(CCGraphBuilder) <= 4096,
"Don't create too large CCGraphBuilder objects");
if (aCCRuntime) {
mJSParticipant = aCCRuntime->GCThingParticipant();
mJSZoneParticipant = aCCRuntime->ZoneParticipant();
}
if (mLogger) {
mFlags |= nsCycleCollectionTraversalCallback::WANT_DEBUG_INFO;
if (mLogger->IsAllTraces()) {
mFlags |= nsCycleCollectionTraversalCallback::WANT_ALL_TRACES;
mWantAllTraces = true; // for nsCycleCollectionNoteRootCallback
}
}
mMergeZones = mMergeZones && MOZ_LIKELY(!WantAllTraces());
MOZ_ASSERT(nsCycleCollectionNoteRootCallback::WantAllTraces() ==
nsCycleCollectionTraversalCallback::WantAllTraces());
}
CCGraphBuilder::~CCGraphBuilder() = default;
PtrInfo* CCGraphBuilder::AddNode(void* aPtr,
nsCycleCollectionParticipant* aParticipant) {
if (mGraph.mOutOfMemory) {
return nullptr;
}
PtrInfoCache::Entry cached = mGraphCache.Lookup(aPtr);
if (cached) {
#ifdef DEBUG
if (cached.Data()->mParticipant != aParticipant) {
auto* parti1 = cached.Data()->mParticipant;
auto* parti2 = aParticipant;
NS_WARNING(
nsPrintfCString("cached participant: %s; AddNode participant: %s\n",
parti1 ? parti1->ClassName() : "null",
parti2 ? parti2->ClassName() : "null")
.get());
}
#endif
MOZ_ASSERT(cached.Data()->mParticipant == aParticipant,
"nsCycleCollectionParticipant shouldn't change!");
return cached.Data();
}
PtrInfo* result;
auto p = mGraph.mPtrInfoMap.lookupForAdd(aPtr);
if (!p) {
// New entry
result = mNodeBuilder.Add(aPtr, aParticipant);
if (!result) {
return nullptr;
}
if (!mGraph.mPtrInfoMap.add(p, result)) {
// `result` leaks here, but we can't free it because it's
// pool-allocated within NodePool.
mGraph.mOutOfMemory = true;
MOZ_ASSERT(false, "OOM while building cycle collector graph");
return nullptr;
}
} else {
result = *p;
MOZ_ASSERT(result->mParticipant == aParticipant,
"nsCycleCollectionParticipant shouldn't change!");
}
cached.Set(result);
return result;
}
bool CCGraphBuilder::AddPurpleRoot(void* aRoot,
nsCycleCollectionParticipant* aParti) {
ToParticipant(aRoot, &aParti);
if (WantAllTraces() || !aParti->CanSkipInCC(aRoot)) {
PtrInfo* pinfo = AddNode(aRoot, aParti);
if (!pinfo) {
return false;
}
}
return true;
}
void CCGraphBuilder::DoneAddingRoots() {
// We've finished adding roots, and everything in the graph is a root.
mGraph.mRootCount = mGraph.MapCount();
mCurrNode = MakeUnique<NodePool::Enumerator>(mGraph.mNodes);
}
MOZ_NEVER_INLINE bool CCGraphBuilder::BuildGraph(SliceBudget& aBudget) {
MOZ_ASSERT(mCurrNode);
while (!aBudget.isOverBudget() && !mCurrNode->IsDone()) {
mNoteChildCount = 0;
PtrInfo* pi = mCurrNode->GetNext();
if (!pi) {
MOZ_CRASH();
}
mCurrPi = pi;
// We need to call SetFirstChild() even on deleted nodes, to set their
// firstChild() that may be read by a prior non-deleted neighbor.
SetFirstChild();
if (pi->mParticipant) {
nsresult rv = pi->mParticipant->TraverseNativeAndJS(pi->mPointer, *this);
MOZ_RELEASE_ASSERT(!NS_FAILED(rv),
"Cycle collector Traverse method failed");
}
if (mCurrNode->AtBlockEnd()) {
SetLastChild();
}
aBudget.step(mNoteChildCount + 1);
}
if (!mCurrNode->IsDone()) {
return false;
}
if (mGraph.mRootCount > 0) {
SetLastChild();
}
mCurrNode = nullptr;
return true;
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteXPCOMRoot(nsISupports* aRoot,
nsCycleCollectionParticipant* aParticipant) {
MOZ_ASSERT(aRoot == CanonicalizeXPCOMParticipant(aRoot));
#ifdef DEBUG
nsXPCOMCycleCollectionParticipant* cp;
ToParticipant(aRoot, &cp);
MOZ_ASSERT(aParticipant == cp);
#endif
NoteRoot(aRoot, aParticipant);
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteJSRoot(JSObject* aRoot) {
if (JS::Zone* zone = MergeZone(JS::GCCellPtr(aRoot))) {
NoteRoot(zone, mJSZoneParticipant);
} else {
NoteRoot(aRoot, mJSParticipant);
}
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteNativeRoot(void* aRoot,
nsCycleCollectionParticipant* aParticipant) {
NoteRoot(aRoot, aParticipant);
}
NS_IMETHODIMP_(void)
CCGraphBuilder::DescribeRefCountedNode(nsrefcnt aRefCount,
const char* aObjName) {
mCurrPi->AnnotatedReleaseAssert(aRefCount != 0,
"CCed refcounted object has zero refcount");
mCurrPi->AnnotatedReleaseAssert(
aRefCount != UINT32_MAX,
"CCed refcounted object has overflowing refcount");
mResults.mVisitedRefCounted++;
if (mLogger) {
mLogger->NoteRefCountedObject((uint64_t)mCurrPi->mPointer, aRefCount,
aObjName);
}
mCurrPi->mRefCount = aRefCount;
}
NS_IMETHODIMP_(void)
CCGraphBuilder::DescribeGCedNode(bool aIsMarked, const char* aObjName,
uint64_t aCompartmentAddress) {
uint32_t refCount = aIsMarked ? UINT32_MAX : 0;
mResults.mVisitedGCed++;
if (mLogger) {
mLogger->NoteGCedObject((uint64_t)mCurrPi->mPointer, aIsMarked, aObjName,
aCompartmentAddress);
}
mCurrPi->mRefCount = refCount;
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteXPCOMChild(nsISupports* aChild) {
nsCString edgeName;
if (WantDebugInfo()) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (!aChild || !(aChild = CanonicalizeXPCOMParticipant(aChild))) {
return;
}
++mNoteChildCount;
nsXPCOMCycleCollectionParticipant* cp;
ToParticipant(aChild, &cp);
if (cp && (!cp->CanSkipThis(aChild) || WantAllTraces())) {
NoteChild(aChild, cp, edgeName);
}
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteNativeChild(void* aChild,
nsCycleCollectionParticipant* aParticipant) {
nsCString edgeName;
if (WantDebugInfo()) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (!aChild) {
return;
}
++mNoteChildCount;
MOZ_ASSERT(aParticipant, "Need a nsCycleCollectionParticipant!");
if (!aParticipant->CanSkipThis(aChild) || WantAllTraces()) {
NoteChild(aChild, aParticipant, edgeName);
}
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteJSChild(JS::GCCellPtr aChild) {
if (!aChild) {
return;
}
++mNoteChildCount;
nsCString edgeName;
if (MOZ_UNLIKELY(WantDebugInfo())) {
edgeName.Assign(mNextEdgeName);
mNextEdgeName.Truncate();
}
if (GCThingIsGrayCCThing(aChild) || MOZ_UNLIKELY(WantAllTraces())) {
if (JS::Zone* zone = MergeZone(aChild)) {
NoteChild(zone, mJSZoneParticipant, edgeName);
} else {
NoteChild(aChild.asCell(), mJSParticipant, edgeName);
}
}
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteNextEdgeName(const char* aName) {
if (WantDebugInfo()) {
mNextEdgeName = aName;
}
}
PtrInfo* CCGraphBuilder::AddWeakMapNode(JS::GCCellPtr aNode) {
MOZ_ASSERT(aNode, "Weak map node should be non-null.");
if (!GCThingIsGrayCCThing(aNode) && !WantAllTraces()) {
return nullptr;
}
if (JS::Zone* zone = MergeZone(aNode)) {
return AddNode(zone, mJSZoneParticipant);
}
return AddNode(aNode.asCell(), mJSParticipant);
}
PtrInfo* CCGraphBuilder::AddWeakMapNode(JSObject* aObject) {
return AddWeakMapNode(JS::GCCellPtr(aObject));
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteWeakMapping(JSObject* aMap, JS::GCCellPtr aKey,
JSObject* aKdelegate, JS::GCCellPtr aVal) {
// Don't try to optimize away the entry here, as we've already attempted to
// do that in TraceWeakMapping in nsXPConnect.
WeakMapping* mapping = mGraph.mWeakMaps.AppendElement();
mapping->mMap = aMap ? AddWeakMapNode(aMap) : nullptr;
mapping->mKey = aKey ? AddWeakMapNode(aKey) : nullptr;
mapping->mKeyDelegate =
aKdelegate ? AddWeakMapNode(aKdelegate) : mapping->mKey;
mapping->mVal = aVal ? AddWeakMapNode(aVal) : nullptr;
if (mLogger) {
mLogger->NoteWeakMapEntry((uint64_t)aMap, aKey ? aKey.unsafeAsInteger() : 0,
(uint64_t)aKdelegate,
aVal ? aVal.unsafeAsInteger() : 0);
}
}
NS_IMETHODIMP_(void)
CCGraphBuilder::NoteWeakMapping(JSObject* aKey, nsISupports* aVal,
nsCycleCollectionParticipant* aValParticipant) {
MOZ_ASSERT(aKey, "Don't call NoteWeakMapping with a null key");
MOZ_ASSERT(aVal, "Don't call NoteWeakMapping with a null value");
WeakMapping* mapping = mGraph.mWeakMaps.AppendElement();
mapping->mMap = nullptr;
mapping->mKey = AddWeakMapNode(aKey);
mapping->mKeyDelegate = mapping->mKey;
MOZ_ASSERT(js::UncheckedUnwrapWithoutExpose(aKey) == aKey);
mapping->mVal = AddNode(aVal, aValParticipant);
if (mLogger) {
mLogger->NoteWeakMapEntry(0, (uint64_t)aKey, 0, (uint64_t)aVal);
}
}
static bool AddPurpleRoot(CCGraphBuilder& aBuilder, void* aRoot,
nsCycleCollectionParticipant* aParti) {
return aBuilder.AddPurpleRoot(aRoot, aParti);
}
// 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 CCGraphBuilder.
NS_IMETHOD_(void) NoteXPCOMChild(nsISupports* aChild) override;
NS_IMETHOD_(void)
NoteNativeChild(void* aChild, nsCycleCollectionParticipant* aHelper) override;
NS_IMETHOD_(void) NoteJSChild(JS::GCCellPtr aThing) override;
NS_IMETHOD_(void)
NoteWeakMapping(JSObject* aKey, nsISupports* aVal,
nsCycleCollectionParticipant* aValParticipant) override {}
NS_IMETHOD_(void)
DescribeRefCountedNode(nsrefcnt aRefcount, const char* aObjname) override {}
NS_IMETHOD_(void)
DescribeGCedNode(bool aIsMarked, const char* aObjname,
uint64_t aCompartmentAddress) override {}
NS_IMETHOD_(void) NoteNextEdgeName(const char* aName) override {}
bool MayHaveChild() { return mMayHaveChild; }
private:
bool mMayHaveChild;
};
NS_IMETHODIMP_(void)
ChildFinder::NoteXPCOMChild(nsISupports* aChild) {
if (!aChild || !(aChild = CanonicalizeXPCOMParticipant(aChild))) {
return;
}
nsXPCOMCycleCollectionParticipant* cp;
ToParticipant(aChild, &cp);
if (cp && !cp->CanSkip(aChild, true)) {
mMayHaveChild = true;
}
}
NS_IMETHODIMP_(void)
ChildFinder::NoteNativeChild(void* aChild,
nsCycleCollectionParticipant* aHelper) {
if (!aChild) {
return;
}
MOZ_ASSERT(aHelper, "Native child must have a participant");
if (!aHelper->CanSkip(aChild, true)) {
mMayHaveChild = true;
}
}
NS_IMETHODIMP_(void)
ChildFinder::NoteJSChild(JS::GCCellPtr aChild) {
if (aChild && JS::GCThingIsMarkedGray(aChild)) {
mMayHaveChild = true;
}
}
static bool MayHaveChild(void* aObj, nsCycleCollectionParticipant* aCp) {
ChildFinder cf;
aCp->TraverseNativeAndJS(aObj, cf);
return cf.MayHaveChild();
}
// JSPurpleBuffer keeps references to GCThings which might affect the
// next cycle collection. It is owned only by itself and during unlink its
// self reference is broken down and the object ends up killing itself.
// If GC happens before CC, references to GCthings and the self reference are
// removed.
class JSPurpleBuffer {
~JSPurpleBuffer() {
MOZ_ASSERT(mValues.IsEmpty());
MOZ_ASSERT(mObjects.IsEmpty());
}
public:
explicit JSPurpleBuffer(RefPtr<JSPurpleBuffer>& aReferenceToThis)
: mReferenceToThis(aReferenceToThis),
mValues(kSegmentSize),
mObjects(kSegmentSize) {
mReferenceToThis = this;
mozilla::HoldJSObjects(this);
}
void Destroy() {
RefPtr<JSPurpleBuffer> referenceToThis;
mReferenceToThis.swap(referenceToThis);
mValues.Clear();
mObjects.Clear();
mozilla::DropJSObjects(this);
}
NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(JSPurpleBuffer)
NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(JSPurpleBuffer)
RefPtr<JSPurpleBuffer>& mReferenceToThis;
// These are raw pointers instead of Heap<T> because we only need Heap<T> for
// pointers which may point into the nursery. The purple buffer never contains
// pointers to the nursery because nursery gcthings can never be gray and only
// gray things can be inserted into the purple buffer.
static const size_t kSegmentSize = 512;
SegmentedVector<JS::Value, kSegmentSize, InfallibleAllocPolicy> mValues;
SegmentedVector<JSObject*, kSegmentSize, InfallibleAllocPolicy> mObjects;
};
NS_IMPL_CYCLE_COLLECTION_CLASS(JSPurpleBuffer)
NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(JSPurpleBuffer)
tmp->Destroy();
NS_IMPL_CYCLE_COLLECTION_UNLINK_END
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(JSPurpleBuffer)
CycleCollectionNoteChild(cb, tmp, "self");
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
#define NS_TRACE_SEGMENTED_ARRAY(_field, _type) \
{ \
for (auto iter = tmp->_field.Iter(); !iter.Done(); iter.Next()) { \
js::gc::CallTraceCallbackOnNonHeap<_type, TraceCallbacks>( \
&iter.Get(), aCallbacks, #_field, aClosure); \
} \
}
NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(JSPurpleBuffer)
NS_TRACE_SEGMENTED_ARRAY(mValues, JS::Value)
NS_TRACE_SEGMENTED_ARRAY(mObjects, JSObject*)
NS_IMPL_CYCLE_COLLECTION_TRACE_END
class SnowWhiteKiller : public TraceCallbacks {
struct SnowWhiteObject {
void* mPointer;
nsCycleCollectionParticipant* mParticipant;
nsCycleCollectingAutoRefCnt* mRefCnt;
};
// Segments are 4 KiB on 32-bit and 8 KiB on 64-bit.
static const size_t kSegmentSize = sizeof(void*) * 1024;
typedef SegmentedVector<SnowWhiteObject, kSegmentSize, InfallibleAllocPolicy>
ObjectsVector;
public:
SnowWhiteKiller(nsCycleCollector* aCollector, js::SliceBudget* aBudget)
: mCollector(aCollector),
mObjects(kSegmentSize),
mBudget(aBudget),
mSawSnowWhiteObjects(false) {
MOZ_ASSERT(mCollector, "Calling SnowWhiteKiller after nsCC went away");
}
explicit SnowWhiteKiller(nsCycleCollector* aCollector)
: SnowWhiteKiller(aCollector, nullptr) {}
~SnowWhiteKiller() {
for (auto iter = mObjects.Iter(); !iter.Done(); iter.Next()) {
SnowWhiteObject& o = iter.Get();
MaybeKillObject(o);
}
}
private:
void MaybeKillObject(SnowWhiteObject& aObject) {
if (!aObject.mRefCnt->get() && !aObject.mRefCnt->IsInPurpleBuffer()) {
mCollector->RemoveObjectFromGraph(aObject.mPointer);
aObject.mRefCnt->stabilizeForDeletion();
{
JS::AutoEnterCycleCollection autocc(mCollector->Runtime()->Runtime());
aObject.mParticipant->Trace(aObject.mPointer, *this, nullptr);
}
aObject.mParticipant->DeleteCycleCollectable(aObject.mPointer);
}
}
public:
bool Visit(nsPurpleBuffer& aBuffer, nsPurpleBufferEntry* aEntry) {
if (mBudget) {
if (mBudget->isOverBudget()) {
return false;
}
mBudget->step();
}
MOZ_ASSERT(aEntry->mObject, "Null object in purple buffer");
if (!aEntry->mRefCnt->get()) {
mSawSnowWhiteObjects = true;
void* o = aEntry->mObject;
nsCycleCollectionParticipant* cp = aEntry->mParticipant;
ToParticipant(o, &cp);
SnowWhiteObject swo = {o, cp, aEntry->mRefCnt};
if (!mBudget) {
mObjects.InfallibleAppend(swo);
}
aBuffer.Remove(aEntry);
if (mBudget) {
MaybeKillObject(swo);
}
}
return true;
}
bool HasSnowWhiteObjects() const { return !mObjects.IsEmpty(); }
bool SawSnowWhiteObjects() const { return mSawSnowWhiteObjects; }
virtual void Trace(JS::Heap<JS::Value>* aValue, const char* aName,
void* aClosure) const override {
const JS::Value& val = aValue->unbarrieredGet();
if (val.isGCThing() && ValueIsGrayCCThing(val)) {
MOZ_ASSERT(!js::gc::IsInsideNursery(val.toGCThing()));
mCollector->GetJSPurpleBuffer()->mValues.InfallibleAppend(val);
}
}
virtual void Trace(JS::Heap<jsid>* aId, const char* aName,
void* aClosure) const override {}
void AppendJSObjectToPurpleBuffer(JSObject* obj) const {
if (obj && JS::ObjectIsMarkedGray(obj)) {
MOZ_ASSERT(JS::ObjectIsTenured(obj));
mCollector->GetJSPurpleBuffer()->mObjects.InfallibleAppend(obj);
}
}
virtual void Trace(JS::Heap<JSObject*>* aObject, const char* aName,
void* aClosure) const override {
AppendJSObjectToPurpleBuffer(aObject->unbarrieredGet());
}
virtual void Trace(nsWrapperCache* aWrapperCache, const char* aName,
void* aClosure) const override {
AppendJSObjectToPurpleBuffer(aWrapperCache->GetWrapperPreserveColor());
}
virtual void Trace(JS::TenuredHeap<JSObject*>* aObject, const char* aName,
void* aClosure) const override {
AppendJSObjectToPurpleBuffer(aObject->unbarrieredGetPtr());
}
virtual void Trace(JS::Heap<JSString*>* aString, const char* aName,
void* aClosure) const override {}
virtual void Trace(JS::Heap<JSScript*>* aScript, const char* aName,
void* aClosure) const override {}
virtual void Trace(JS::Heap<JSFunction*>* aFunction, const char* aName,
void* aClosure) const override {}
private:
RefPtr<nsCycleCollector> mCollector;
ObjectsVector mObjects;
js::SliceBudget* mBudget;
bool mSawSnowWhiteObjects;
};
class RemoveSkippableVisitor : public SnowWhiteKiller {
public:
RemoveSkippableVisitor(nsCycleCollector* aCollector, js::SliceBudget& aBudget,
bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb)
: SnowWhiteKiller(aCollector),
mBudget(aBudget),
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);
}
}
bool Visit(nsPurpleBuffer& aBuffer, nsPurpleBufferEntry* aEntry) {
if (mBudget.isOverBudget()) {
return false;
}
// CanSkip calls can be a bit slow, so increase the likelihood that
// isOverBudget actually checks whether we're over the time budget.
mBudget.step(5);
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 true;
}
void* o = aEntry->mObject;
nsCycleCollectionParticipant* cp = aEntry->mParticipant;
ToParticipant(o, &cp);
if (aEntry->mRefCnt->IsPurple() && !cp->CanSkip(o, false) &&
(!mRemoveChildlessNodes || MayHaveChild(o, cp))) {
return true;
}
aBuffer.Remove(aEntry);
return true;
}
private:
js::SliceBudget& mBudget;
bool mRemoveChildlessNodes;
bool mAsyncSnowWhiteFreeing;
bool mDispatchedDeferredDeletion;
CC_ForgetSkippableCallback mCallback;
};
void nsPurpleBuffer::RemoveSkippable(nsCycleCollector* aCollector,
js::SliceBudget& aBudget,
bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing,
CC_ForgetSkippableCallback aCb) {
RemoveSkippableVisitor visitor(aCollector, aBudget, aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing, aCb);
VisitEntries(visitor);
}
bool nsCycleCollector::FreeSnowWhite(bool aUntilNoSWInPurpleBuffer) {
CheckThreadSafety();
if (mFreeingSnowWhite) {
return false;
}
AUTO_PROFILER_LABEL_CATEGORY_PAIR(GCCC_FreeSnowWhite);
AutoRestore<bool> ar(mFreeingSnowWhite);
mFreeingSnowWhite = true;
bool hadSnowWhiteObjects = false;
do {
SnowWhiteKiller visitor(this);
mPurpleBuf.VisitEntries(visitor);
hadSnowWhiteObjects = hadSnowWhiteObjects || visitor.HasSnowWhiteObjects();
if (!visitor.HasSnowWhiteObjects()) {
break;
}
} while (aUntilNoSWInPurpleBuffer);
return hadSnowWhiteObjects;
}
bool nsCycleCollector::FreeSnowWhiteWithBudget(js::SliceBudget& aBudget) {
CheckThreadSafety();
if (mFreeingSnowWhite) {
return false;
}
AUTO_PROFILER_LABEL_CATEGORY_PAIR(GCCC_FreeSnowWhite);
AutoRestore<bool> ar(mFreeingSnowWhite);
mFreeingSnowWhite = true;
SnowWhiteKiller visitor(this, &aBudget);
mPurpleBuf.VisitEntries(visitor);
return visitor.SawSnowWhiteObjects();
;
}
void nsCycleCollector::ForgetSkippable(js::SliceBudget& aBudget,
bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing) {
CheckThreadSafety();
if (mFreeingSnowWhite) {
return;
}
// If we remove things from the purple buffer during graph building, we may
// lose track of an object that was mutated during graph building.
MOZ_ASSERT(IsIdle());
if (mCCJSRuntime) {
mCCJSRuntime->PrepareForForgetSkippable();
}
MOZ_ASSERT(
!mScanInProgress,
"Don't forget skippable or free snow-white while scan is in progress.");
mPurpleBuf.RemoveSkippable(this, aBudget, aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing, mForgetSkippableCB);
}
MOZ_NEVER_INLINE void nsCycleCollector::MarkRoots(SliceBudget& aBudget) {
JS::AutoAssertNoGC nogc;
TimeLog timeLog;
AutoRestore<bool> ar(mScanInProgress);
MOZ_RELEASE_ASSERT(!mScanInProgress);
mScanInProgress = true;
MOZ_ASSERT(mIncrementalPhase == GraphBuildingPhase);
AUTO_PROFILER_LABEL_CATEGORY_PAIR(GCCC_BuildGraph);
JS::AutoEnterCycleCollection autocc(Runtime()->Runtime());
bool doneBuilding = mBuilder->BuildGraph(aBudget);
if (!doneBuilding) {
timeLog.Checkpoint("MarkRoots()");
return;
}
mBuilder = nullptr;
mIncrementalPhase = ScanAndCollectWhitePhase;
timeLog.Checkpoint("MarkRoots()");
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |ScanRoots| routine.
////////////////////////////////////////////////////////////////////////
struct ScanBlackVisitor {
ScanBlackVisitor(uint32_t& aWhiteNodeCount, bool& aFailed)
: mWhiteNodeCount(aWhiteNodeCount), mFailed(aFailed) {}
bool ShouldVisitNode(PtrInfo const* aPi) { return aPi->mColor != black; }
MOZ_NEVER_INLINE void VisitNode(PtrInfo* aPi) {
if (aPi->mColor == white) {
--mWhiteNodeCount;
}
aPi->mColor = black;
}
void Failed() { mFailed = true; }
private:
uint32_t& mWhiteNodeCount;
bool& mFailed;
};
static void FloodBlackNode(uint32_t& aWhiteNodeCount, bool& aFailed,
PtrInfo* aPi) {
GraphWalker<ScanBlackVisitor>(ScanBlackVisitor(aWhiteNodeCount, aFailed))
.Walk(aPi);
MOZ_ASSERT(aPi->mColor == black || !aPi->WasTraversed(),
"FloodBlackNode should make aPi black");
}
// 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;
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) {
FloodBlackNode(mWhiteNodeCount, failed, wm->mKey);
anyChanged = true;
}
if (mColor == black && kColor == black && vColor != black) {
FloodBlackNode(mWhiteNodeCount, failed, wm->mVal);
anyChanged = true;
}
}
} while (anyChanged);
if (failed) {
MOZ_ASSERT(false, "Ran out of memory in ScanWeakMaps");
CC_TELEMETRY(_OOM, true);
}
}
// Flood black from any objects in the purple buffer that are in the CC graph.
class PurpleScanBlackVisitor {
public:
PurpleScanBlackVisitor(CCGraph& aGraph, nsCycleCollectorLogger* aLogger,
uint32_t& aCount, bool& aFailed)
: mGraph(aGraph), mLogger(aLogger), mCount(aCount), mFailed(aFailed) {}
bool Visit(nsPurpleBuffer& aBuffer, nsPurpleBufferEntry* aEntry) {
MOZ_ASSERT(aEntry->mObject,
"Entries with null mObject shouldn't be in the purple buffer.");
MOZ_ASSERT(aEntry->mRefCnt->get() != 0,
"Snow-white objects shouldn't be in the purple buffer.");
void* obj = aEntry->mObject;
MOZ_ASSERT(
aEntry->mParticipant ||
CanonicalizeXPCOMParticipant(static_cast<nsISupports*>(obj)) == obj,
"Suspect nsISupports pointer must be canonical");
PtrInfo* pi = mGraph.FindNode(obj);
if (!pi) {
return true;
}
MOZ_ASSERT(pi->mParticipant,
"No dead objects should be in the purple buffer.");
if (MOZ_UNLIKELY(mLogger)) {
mLogger->NoteIncrementalRoot((uint64_t)pi->mPointer);
}
if (pi->mColor == black) {
return true;
}
FloodBlackNode(mCount, mFailed, pi);
return true;
}
private:
CCGraph& mGraph;
RefPtr<nsCycleCollectorLogger> mLogger;
uint32_t& mCount;
bool& mFailed;
};
// Objects that have been stored somewhere since the start of incremental graph
// building must be treated as live for this cycle collection, because we may
// not have accurate information about who holds references to them.
void nsCycleCollector::ScanIncrementalRoots() {
TimeLog timeLog;
// Reference counted objects:
// We cleared the purple buffer at the start of the current ICC, so if a
// refcounted object is purple, it may have been AddRef'd during the current
// ICC. (It may also have only been released.) If that is the case, we cannot
// be sure that the set of things pointing to the object in the CC graph
// is accurate. Therefore, for safety, we treat any purple objects as being
// live during the current CC. We don't remove anything from the purple
// buffer here, so these objects will be suspected and freed in the next CC
// if they are garbage.
bool failed = false;
PurpleScanBlackVisitor purpleScanBlackVisitor(mGraph, mLogger,
mWhiteNodeCount, failed);
mPurpleBuf.VisitEntries(purpleScanBlackVisitor);
timeLog.Checkpoint("ScanIncrementalRoots::fix purple");
bool hasJSRuntime = !!mCCJSRuntime;
nsCycleCollectionParticipant* jsParticipant =
hasJSRuntime ? mCCJSRuntime->GCThingParticipant() : nullptr;
nsCycleCollectionParticipant* zoneParticipant =
hasJSRuntime ? mCCJSRuntime->ZoneParticipant() : nullptr;
bool hasLogger = !!mLogger;
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo* pi = etor.GetNext();
// As an optimization, if an object has already been determined to be live,
// don't consider it further. We can't do this if there is a listener,
// because the listener wants to know the complete set of incremental roots.
if (pi->mColor == black && MOZ_LIKELY(!hasLogger)) {
continue;
}
// Garbage collected objects:
// If a GCed object was added to the graph with a refcount of zero, and is
// now marked black by the GC, it was probably gray before and was exposed
// to active JS, so it may have been stored somewhere, so it needs to be
// treated as live.
if (pi->IsGrayJS() && MOZ_LIKELY(hasJSRuntime)) {
// If the object is still marked gray by the GC, nothing could have gotten
// hold of it, so it isn't an incremental root.
if (pi->mParticipant == jsParticipant) {
JS::GCCellPtr ptr(pi->mPointer, JS::GCThingTraceKind(pi->mPointer));
if (GCThingIsGrayCCThing(ptr)) {
continue;
}
} else if (pi->mParticipant == zoneParticipant) {
JS::Zone* zone = static_cast<JS::Zone*>(pi->mPointer);
if (js::ZoneGlobalsAreAllGray(zone)) {
continue;
}
} else {
MOZ_ASSERT(false, "Non-JS thing with 0 refcount? Treating as live.");
}
} else if (!pi->mParticipant && pi->WasTraversed()) {
// Dead traversed refcounted objects:
// If the object was traversed, it must have been alive at the start of
// the CC, and thus had a positive refcount. It is dead now, so its
// refcount must have decreased at some point during the CC. Therefore,
// it would be in the purple buffer if it wasn't dead, so treat it as an
// incremental root.
//
// This should not cause leaks because as the object died it should have
// released anything it held onto, which will add them to the purple
// buffer, which will cause them to be considered in the next CC.
} else {
continue;
}
// At this point, pi must be an incremental root.
// If there's a listener, tell it about this root. We don't bother with the
// optimization of skipping the Walk() if pi is black: it will just return
// without doing anything and there's no need to make this case faster.
if (MOZ_UNLIKELY(hasLogger) && pi->mPointer) {
// Dead objects aren't logged. See bug 1031370.
mLogger->NoteIncrementalRoot((uint64_t)pi->mPointer);
}
FloodBlackNode(mWhiteNodeCount, failed, pi);
}
timeLog.Checkpoint("ScanIncrementalRoots::fix nodes");
if (failed) {
NS_ASSERTION(false, "Ran out of memory in ScanIncrementalRoots");
CC_TELEMETRY(_OOM, true);
}
}
// Mark nodes white and make sure their refcounts are ok.
// No nodes are marked black during this pass to ensure that refcount
// checking is run on all nodes not marked black by ScanIncrementalRoots.
void nsCycleCollector::ScanWhiteNodes(bool aFullySynchGraphBuild) {
NodePool::Enumerator nodeEnum(mGraph.mNodes);
while (!nodeEnum.IsDone()) {
PtrInfo* pi = nodeEnum.GetNext();
if (pi->mColor == black) {
// Incremental roots can be in a nonsensical state, so don't
// check them. This will miss checking nodes that are merely
// reachable from incremental roots.
MOZ_ASSERT(!aFullySynchGraphBuild,
"In a synch CC, no nodes should be marked black early on.");
continue;
}
MOZ_ASSERT(pi->mColor == grey);
if (!pi->WasTraversed()) {
// This node was deleted before it was traversed, so there's no reason
// to look at it.
MOZ_ASSERT(!pi->mParticipant,
"Live nodes should all have been traversed");
continue;
}
if (pi->mInternalRefs == pi->mRefCount || pi->IsGrayJS()) {
pi->mColor = white;
++mWhiteNodeCount;
continue;
}
pi->AnnotatedReleaseAssert(
pi->mInternalRefs <= pi->mRefCount,
"More references to an object than its refcount");
// This node will get marked black in the next pass.
}
}
// Any remaining grey nodes that haven't already been deleted must be alive,
// so mark them and their children black. Any nodes that are black must have
// already had their children marked black, so there's no need to look at them
// again. This pass may turn some white nodes to black.
void nsCycleCollector::ScanBlackNodes() {
bool failed = false;
NodePool::Enumerator nodeEnum(mGraph.mNodes);
while (!nodeEnum.IsDone()) {
PtrInfo* pi = nodeEnum.GetNext();
if (pi->mColor == grey && pi->WasTraversed()) {
FloodBlackNode(mWhiteNodeCount, failed, pi);
}
}
if (failed) {
NS_ASSERTION(false, "Ran out of memory in ScanBlackNodes");
CC_TELEMETRY(_OOM, true);
}
}
void nsCycleCollector::ScanRoots(bool aFullySynchGraphBuild) {
JS::AutoAssertNoGC nogc;
AutoRestore<bool> ar(mScanInProgress);
MOZ_RELEASE_ASSERT(!mScanInProgress);
mScanInProgress = true;
mWhiteNodeCount = 0;
MOZ_ASSERT(mIncrementalPhase == ScanAndCollectWhitePhase);
JS::AutoEnterCycleCollection autocc(Runtime()->Runtime());
if (!aFullySynchGraphBuild) {
ScanIncrementalRoots();
}
TimeLog timeLog;
ScanWhiteNodes(aFullySynchGraphBuild);
timeLog.Checkpoint("ScanRoots::ScanWhiteNodes");
ScanBlackNodes();
timeLog.Checkpoint("ScanRoots::ScanBlackNodes");
// Scanning weak maps must be done last.
ScanWeakMaps();
timeLog.Checkpoint("ScanRoots::ScanWeakMaps");
if (mLogger) {
mLogger->BeginResults();
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo* pi = etor.GetNext();
if (!pi->WasTraversed()) {
continue;
}
switch (pi->mColor) {
case black:
if (!pi->IsGrayJS() && !pi->IsBlackJS() &&
pi->mInternalRefs != pi->mRefCount) {
mLogger->DescribeRoot((uint64_t)pi->mPointer, pi->mInternalRefs);
}
break;
case white:
mLogger->DescribeGarbage((uint64_t)pi->mPointer);
break;
case grey:
MOZ_ASSERT(false, "All traversed objects should be black or white");
break;
}
}
mLogger->End();
mLogger = nullptr;
timeLog.Checkpoint("ScanRoots::listener");
}
}
////////////////////////////////////////////////////////////////////////
// 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.
// Segments are 4 KiB on 32-bit and 8 KiB on 64-bit.
static const size_t kSegmentSize = sizeof(void*) * 1024;
SegmentedVector<PtrInfo*, kSegmentSize, InfallibleAllocPolicy> whiteNodes(
kSegmentSize);
TimeLog timeLog;
MOZ_ASSERT(mIncrementalPhase == ScanAndCollectWhitePhase);
uint32_t numWhiteNodes = 0;
uint32_t numWhiteGCed = 0;
uint32_t numWhiteJSZones = 0;
{
JS::AutoAssertNoGC nogc;
bool hasJSRuntime = !!mCCJSRuntime;
nsCycleCollectionParticipant* zoneParticipant =
hasJSRuntime ? mCCJSRuntime->ZoneParticipant() : nullptr;
NodePool::Enumerator etor(mGraph.mNodes);
while (!etor.IsDone()) {
PtrInfo* pinfo = etor.GetNext();
if (pinfo->mColor == white && pinfo->mParticipant) {
if (pinfo->IsGrayJS()) {
MOZ_ASSERT(mCCJSRuntime);
++numWhiteGCed;
JS::Zone* zone;
if (MOZ_UNLIKELY(pinfo->mParticipant == zoneParticipant)) {
++numWhiteJSZones;
zone = static_cast<JS::Zone*>(pinfo->mPointer);
} else {
JS::GCCellPtr ptr(pinfo->mPointer,
JS::GCThingTraceKind(pinfo->mPointer));
zone = JS::GetTenuredGCThingZone(ptr);
}
mCCJSRuntime->AddZoneWaitingForGC(zone);
} else {
whiteNodes.InfallibleAppend(pinfo);
pinfo->mParticipant->Root(pinfo->mPointer);
++numWhiteNodes;
}
}
}
}
mResults.mFreedRefCounted += numWhiteNodes;
mResults.mFreedGCed += numWhiteGCed;
mResults.mFreedJSZones += numWhiteJSZones;
timeLog.Checkpoint("CollectWhite::Root");
if (mBeforeUnlinkCB) {
mBeforeUnlinkCB();
timeLog.Checkpoint("CollectWhite::BeforeUnlinkCB");
}
// Unlink() can trigger a GC, so do not touch any JS or anything
// else not in whiteNodes after here.
for (auto iter = whiteNodes.Iter(); !iter.Done(); iter.Next()) {
PtrInfo* pinfo = iter.Get();
MOZ_ASSERT(pinfo->mParticipant,
"Unlink shouldn't see objects removed from graph.");
pinfo->mParticipant->Unlink(pinfo->mPointer);
#ifdef DEBUG
if (mCCJSRuntime) {
mCCJSRuntime->AssertNoObjectsToTrace(pinfo->mPointer);
}
#endif
}
timeLog.Checkpoint("CollectWhite::Unlink");
JS::AutoAssertNoGC nogc;
for (auto iter = whiteNodes.Iter(); !iter.Done(); iter.Next()) {
PtrInfo* pinfo = iter.Get();
MOZ_ASSERT(pinfo->mParticipant,
"Unroot shouldn't see objects removed from graph.");
pinfo->mParticipant->Unroot(pinfo->mPointer);
}
timeLog.Checkpoint("CollectWhite::Unroot");
nsCycleCollector_dispatchDeferredDeletion(false, true);
timeLog.Checkpoint("CollectWhite::dispatchDeferredDeletion");
mIncrementalPhase = CleanupPhase;
return numWhiteNodes > 0 || numWhiteGCed > 0 || numWhiteJSZones > 0;
}
////////////////////////
// Memory reporting
////////////////////////
MOZ_DEFINE_MALLOC_SIZE_OF(CycleCollectorMallocSizeOf)
NS_IMETHODIMP
nsCycleCollector::CollectReports(nsIHandleReportCallback* aHandleReport,
nsISupports* aData, bool aAnonymize) {
size_t objectSize, graphSize, purpleBufferSize;
SizeOfIncludingThis(CycleCollectorMallocSizeOf, &objectSize, &graphSize,
&purpleBufferSize);
if (objectSize > 0) {
MOZ_COLLECT_REPORT("explicit/cycle-collector/collector-object", KIND_HEAP,
UNITS_BYTES, objectSize,
"Memory used for the cycle collector object itself.");
}
if (graphSize > 0) {
MOZ_COLLECT_REPORT(
"explicit/cycle-collector/graph", KIND_HEAP, UNITS_BYTES, graphSize,
"Memory used for the cycle collector's graph. This should be zero when "
"the collector is idle.");
}
if (purpleBufferSize > 0) {
MOZ_COLLECT_REPORT("explicit/cycle-collector/purple-buffer", KIND_HEAP,
UNITS_BYTES, purpleBufferSize,
"Memory used for the cycle collector's purple buffer.");
}
return NS_OK;
};
////////////////////////////////////////////////////////////////////////
// Collector implementation
////////////////////////////////////////////////////////////////////////
nsCycleCollector::nsCycleCollector()
: mActivelyCollecting(false),
mFreeingSnowWhite(false),
mScanInProgress(false),
mCCJSRuntime(nullptr),
mIncrementalPhase(IdlePhase),
#ifdef DEBUG
mEventTarget(GetCurrentSerialEventTarget()),
#endif
mWhiteNodeCount(0),
mBeforeUnlinkCB(nullptr),
mForgetSkippableCB(nullptr),
mUnmergedNeeded(0),
mMergedInARow(0) {
}
nsCycleCollector::~nsCycleCollector() {
MOZ_ASSERT(!mJSPurpleBuffer, "Didn't call JSPurpleBuffer::Destroy?");
UnregisterWeakMemoryReporter(this);
}
void nsCycleCollector::SetCCJSRuntime(CycleCollectedJSRuntime* aCCRuntime) {
MOZ_RELEASE_ASSERT(
!mCCJSRuntime,
"Multiple registrations of CycleCollectedJSRuntime in cycle collector");
mCCJSRuntime = aCCRuntime;
if (!NS_IsMainThread()) {
return;
}
// We can't register as a reporter in nsCycleCollector() because that runs
// before the memory reporter manager is initialized. So we do it here
// instead.
RegisterWeakMemoryReporter(this);
}
void nsCycleCollector::ClearCCJSRuntime() {
MOZ_RELEASE_ASSERT(mCCJSRuntime,
"Clearing CycleCollectedJSRuntime in cycle collector "
"before a runtime was registered");
mCCJSRuntime = nullptr;
}
#ifdef DEBUG
static bool HasParticipant(void* aPtr, nsCycleCollectionParticipant* aParti) {
if (aParti) {
return true;
}
nsXPCOMCycleCollectionParticipant* xcp;
ToParticipant(static_cast<nsISupports*>(aPtr), &xcp);
return xcp != nullptr;
}
#endif
MOZ_ALWAYS_INLINE void nsCycleCollector::Suspect(
void* aPtr, nsCycleCollectionParticipant* aParti,
nsCycleCollectingAutoRefCnt* aRefCnt) {
CheckThreadSafety();
// Don't call AddRef or Release of a CCed object in a Traverse() method.
MOZ_ASSERT(!mScanInProgress,
"Attempted to call Suspect() while a scan was in progress");
if (MOZ_UNLIKELY(mScanInProgress)) {
return;
}
MOZ_ASSERT(aPtr, "Don't suspect null pointers");
MOZ_ASSERT(HasParticipant(aPtr, aParti),
"Suspected nsISupports pointer must QI to "
"nsXPCOMCycleCollectionParticipant");
MOZ_ASSERT(aParti || CanonicalizeXPCOMParticipant(
static_cast<nsISupports*>(aPtr)) == aPtr,
"Suspect nsISupports pointer must be canonical");
mPurpleBuf.Put(aPtr, aParti, aRefCnt);
}
void nsCycleCollector::SuspectNurseryEntries() {
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
while (gNurseryPurpleBufferEntryCount) {
NurseryPurpleBufferEntry& entry =
gNurseryPurpleBufferEntry[--gNurseryPurpleBufferEntryCount];
if (!entry.mRefCnt->IsPurple() && IsIdle()) {
entry.mRefCnt->RemoveFromPurpleBuffer();
} else {
mPurpleBuf.Put(entry.mPtr, entry.mParticipant, entry.mRefCnt);
}
}
}
void nsCycleCollector::CheckThreadSafety() {
#ifdef DEBUG
MOZ_ASSERT(mEventTarget->IsOnCurrentThread());
#endif
}
// The cycle collector uses the mark bitmap to discover what JS objects are
// 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 should only
// be true when UnmarkGray has run out of stack. We also force GCs on shutdown
// to collect cycles involving both DOM and JS, and in WantAllTraces CCs to
// prevent hijinks from ForgetSkippable and compartmental GCs.
void nsCycleCollector::FixGrayBits(bool aIsShutdown, TimeLog& aTimeLog) {
CheckThreadSafety();
if (!mCCJSRuntime) {
return;
}
// If we're not forcing a GC anyways due to shutdown or an all traces CC,
// check to see if we still need to do one to fix the gray bits.
if (!(aIsShutdown || (mLogger && mLogger->IsAllTraces()))) {
mCCJSRuntime->FixWeakMappingGrayBits();
aTimeLog.Checkpoint("FixWeakMappingGrayBits");
bool needGC = !mCCJSRuntime->AreGCGrayBitsValid();
// Only do a telemetry ping for non-shutdown CCs.
CC_TELEMETRY(_NEED_GC, needGC);
if (!needGC) {
return;
}
}
mResults.mForcedGC = true;
uint32_t count = 0;
do {
if (aIsShutdown) {
mCCJSRuntime->GarbageCollect(JS::GCOptions::Shutdown,
JS::GCReason::SHUTDOWN_CC);
} else {
mCCJSRuntime->GarbageCollect(JS::GCOptions::Normal,
JS::GCReason::CC_FORCED);
}
mCCJSRuntime->FixWeakMappingGrayBits();
// It's possible that FixWeakMappingGrayBits will hit OOM when unmarking
// gray and we will have to go round again. The second time there should not
// be any weak mappings to fix up so the loop body should run at most twice.
MOZ_RELEASE_ASSERT(count < 2);
count++;
} while (!mCCJSRuntime->AreGCGrayBitsValid());
aTimeLog.Checkpoint("FixGrayBits");
}
bool nsCycleCollector::IsIncrementalGCInProgress() {
return mCCJSRuntime && JS::IsIncrementalGCInProgress(mCCJSRuntime->Runtime());
}
void nsCycleCollector::FinishAnyIncrementalGCInProgress() {
if (IsIncrementalGCInProgress()) {
NS_WARNING("Finishing incremental GC in progress during CC");
JSContext* cx = CycleCollectedJSContext::Get()->Context();
JS::PrepareForIncrementalGC(cx);
JS::FinishIncrementalGC(cx, JS::GCReason::CC_FORCED);
}
}
void nsCycleCollector::CleanupAfterCollection() {
TimeLog timeLog;
MOZ_ASSERT(mIncrementalPhase == CleanupPhase);
MOZ_RELEASE_ASSERT(!mScanInProgress);
mGraph.Clear();
timeLog.Checkpoint("CleanupAfterCollection::mGraph.Clear()");
uint32_t interval =
(uint32_t)((TimeStamp::Now() - mCollectionStart).ToMilliseconds());
#ifdef COLLECT_TIME_DEBUG
printf("cc: total cycle collector time was %ums in %u slices\n", interval,
mResults.mNumSlices);
printf(
"cc: visited %u ref counted and %u GCed objects, freed %d ref counted "
"and %d GCed objects",
mResults.mVisitedRefCounted, mResults.mVisitedGCed,
mResults.mFreedRefCounted, mResults.mFreedGCed);
uint32_t numVisited = mResults.mVisitedRefCounted + mResults.mVisitedGCed;
if (numVisited > 1000) {
uint32_t numFreed = mResults.mFreedRefCounted + mResults.mFreedGCed;
printf(" (%d%%)", 100 * numFreed / numVisited);
}
printf(".\ncc: \n");
#endif
CC_TELEMETRY(, interval);
CC_TELEMETRY(_VISITED_REF_COUNTED, mResults.mVisitedRefCounted);
CC_TELEMETRY(_VISITED_GCED, mResults.mVisitedGCed);
CC_TELEMETRY(_COLLECTED, mWhiteNodeCount);
timeLog.Checkpoint("CleanupAfterCollection::telemetry");
if (mCCJSRuntime) {
mCCJSRuntime->FinalizeDeferredThings(
mResults.mAnyManual ? CycleCollectedJSRuntime::FinalizeNow
: CycleCollectedJSRuntime::FinalizeIncrementally);
mCCJSRuntime->EndCycleCollectionCallback(mResults);
timeLog.Checkpoint("CleanupAfterCollection::EndCycleCollectionCallback()");
}
mIncrementalPhase = IdlePhase;
}
void nsCycleCollector::ShutdownCollect() {
FinishAnyIncrementalGCInProgress();
CycleCollectedJSContext* ccJSContext = CycleCollectedJSContext::Get();
JS::ShutdownAsyncTasks(ccJSContext->Context());
SliceBudget unlimitedBudget = SliceBudget::unlimited();
uint32_t i;
bool collectedAny = true;
for (i = 0; i < DEFAULT_SHUTDOWN_COLLECTIONS && collectedAny; ++i) {
collectedAny = Collect(CCReason::SHUTDOWN, ccIsManual::CCIsManual,
unlimitedBudget, nullptr);
// Run any remaining tasks that may have been enqueued via RunInStableState
// or DispatchToMicroTask. These can hold alive CCed objects, and we want to
// clear them out before we run the CC again or finish shutting down.
ccJSContext->PerformMicroTaskCheckPoint(true);
ccJSContext->ProcessStableStateQueue();
}
// This warning would happen very frequently, so don't do it unless we're
// logging this CC, so we might care about how many CCs there are.
NS_WARNING_ASSERTION(
!mParams.LogThisCC(mShutdownCount) || i < NORMAL_SHUTDOWN_COLLECTIONS,
"Extra shutdown CC");
}
static void PrintPhase(const char* aPhase) {
#ifdef DEBUG_PHASES
printf("cc: begin %s on %s\n", aPhase,
NS_IsMainThread() ? "mainthread" : "worker");
#endif
}
bool nsCycleCollector::Collect(CCReason aReason, ccIsManual aIsManual,
SliceBudget& aBudget,
nsICycleCollectorListener* aManualListener,
bool aPreferShorterSlices) {
AUTO_PROFILER_LABEL_RELEVANT_FOR_JS("Incremental CC", GCCC);
CheckThreadSafety();
// This can legitimately happen in a few cases. See bug 383651.
if (mActivelyCollecting || mFreeingSnowWhite) {
return false;
}
mActivelyCollecting = true;
MOZ_ASSERT(!IsIncrementalGCInProgress());
bool startedIdle = IsIdle();
bool collectedAny = false;
// If the CC started idle, it will call BeginCollection, which
// will do FreeSnowWhite, so it doesn't need to be done here.
if (!startedIdle) {
TimeLog timeLog;
FreeSnowWhite(true);
timeLog.Checkpoint("Collect::FreeSnowWhite");
}
if (aIsManual == ccIsManual::CCIsManual) {
mResults.mAnyManual = true;
}
++mResults.mNumSlices;
bool continueSlice = aBudget.isUnlimited() || !aPreferShorterSlices;
do {
switch (mIncrementalPhase) {
case IdlePhase:
PrintPhase("BeginCollection");
BeginCollection(aReason, aIsManual, aManualListener);
break;
case GraphBuildingPhase:
PrintPhase("MarkRoots");
MarkRoots(aBudget);
// Only continue this slice if we're running synchronously or the
// next phase will probably be short, to reduce the max pause for this
// collection.
// (There's no need to check if we've finished graph building, because
// if we haven't, we've already exceeded our budget, and will finish
// this slice anyways.)
continueSlice = aBudget.isUnlimited() ||
(mResults.mNumSlices < 3 && !aPreferShorterSlices);
break;
case ScanAndCollectWhitePhase:
// We do ScanRoots and CollectWhite in a single slice to ensure
// that we won't unlink a live object if a weak reference is
// promoted to a strong reference after ScanRoots has finished.
// See bug 926533.
{
AUTO_PROFILER_LABEL_CATEGORY_PAIR(GCCC_ScanRoots);
PrintPhase("ScanRoots");
ScanRoots(startedIdle);
}
{
AUTO_PROFILER_LABEL_CATEGORY_PAIR(GCCC_CollectWhite);
PrintPhase("CollectWhite");
collectedAny = CollectWhite();
}
break;
case CleanupPhase:
PrintPhase("CleanupAfterCollection");
CleanupAfterCollection();
continueSlice = false;
break;
}
if (continueSlice) {
aBudget.forceCheck();
continueSlice = !aBudget.isOverBudget();
}
} while (continueSlice);
// Clear mActivelyCollecting here to ensure that a recursive call to
// Collect() does something.
mActivelyCollecting = false;
if (aIsManual && !startedIdle) {
// We were in the middle of an incremental CC (using its own listener).
// Somebody has forced a CC, so after having finished out the current CC,
// run the CC again using the new listener.
MOZ_ASSERT(IsIdle());
if (Collect(aReason, ccIsManual::CCIsManual, aBudget, aManualListener)) {
collectedAny = true;
}
}
MOZ_ASSERT_IF(aIsManual == CCIsManual, IsIdle());
return collectedAny;
}
// Any JS objects we have in the graph could die when we GC, but we
// don't want to abandon the current CC, because the graph contains
// information about purple roots. So we synchronously finish off
// the current CC.
void nsCycleCollector::PrepareForGarbageCollection() {
if (IsIdle()) {
MOZ_ASSERT(mGraph.IsEmpty(), "Non-empty graph when idle");
MOZ_ASSERT(!mBuilder, "Non-null builder when idle");
if (mJSPurpleBuffer) {
mJSPurpleBuffer->Destroy();
}
return;
}
FinishAnyCurrentCollection(CCReason::GC_WAITING);
}
void nsCycleCollector::FinishAnyCurrentCollection(CCReason aReason) {
if (IsIdle()) {
return;
}
SliceBudget unlimitedBudget = SliceBudget::unlimited();
PrintPhase("FinishAnyCurrentCollection");
// Use CCIsNotManual because we only want to finish the CC in progress.
Collect(aReason, ccIsManual::CCIsNotManual, unlimitedBudget, nullptr);
// It is only okay for Collect() to have failed to finish the
// current CC if we're reentering the CC at some point past
// graph building. We need to be past the point where the CC will
// look at JS objects so that it is safe to GC.
MOZ_ASSERT(IsIdle() || (mActivelyCollecting &&
mIncrementalPhase != GraphBuildingPhase),
"Reentered CC during graph building");
}
// 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(ccIsManual aIsManual) {
if (!mCCJSRuntime) {
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 (aIsManual == CCIsNotManual && mCCJSRuntime->UsefulToMergeZones()) {
mMergedInARow++;
return true;
} else {
mMergedInARow = 0;
return false;
}
}
void nsCycleCollector::BeginCollection(
CCReason aReason, ccIsManual aIsManual,
nsICycleCollectorListener* aManualListener) {
TimeLog timeLog;
MOZ_ASSERT(IsIdle());
MOZ_RELEASE_ASSERT(!mScanInProgress);
mCollectionStart = TimeStamp::Now();
if (mCCJSRuntime) {
mCCJSRuntime->BeginCycleCollectionCallback(aReason);
timeLog.Checkpoint("BeginCycleCollectionCallback()");
}
bool isShutdown = (aReason == CCReason::SHUTDOWN);
if (isShutdown) {
mShutdownCount += 1;
}
// Set up the listener for this CC.
MOZ_ASSERT_IF(isShutdown, !aManualListener);
MOZ_ASSERT(!mLogger, "Forgot to clear a previous listener?");
if (aManualListener) {
aManualListener->AsLogger(getter_AddRefs(mLogger));
}
aManualListener = nullptr;
if (!mLogger && mParams.LogThisCC(mShutdownCount)) {
mLogger = new nsCycleCollectorLogger(mParams.LogThisGC());
if (mParams.AllTracesThisCC(isShutdown)) {
mLogger->SetAllTraces();
}
}
// BeginCycleCollectionCallback() might have started an IGC, and we need
// to finish it before we run FixGrayBits.
FinishAnyIncrementalGCInProgress();
timeLog.Checkpoint("Pre-FixGrayBits finish IGC");
FixGrayBits(isShutdown, timeLog);
if (mCCJSRuntime) {
mCCJSRuntime->CheckGrayBits();
}
FreeSnowWhite(true);
timeLog.Checkpoint("BeginCollection FreeSnowWhite");
if (mLogger && NS_FAILED(mLogger->Begin())) {
mLogger = nullptr;
}
// FreeSnowWhite could potentially have started an IGC, which we need
// to finish before we look at any JS roots.
FinishAnyIncrementalGCInProgress();
timeLog.Checkpoint("Post-FreeSnowWhite finish IGC");
// Set up the data structures for building the graph.
JS::AutoAssertNoGC nogc;
JS::AutoEnterCycleCollection autocc(mCCJSRuntime->Runtime());
mGraph.Init();
mResults.Init();
mResults.mSuspectedAtCCStart = SuspectedCount();
mResults.mAnyManual = aIsManual;
bool mergeZones = ShouldMergeZones(aIsManual);
mResults.mMergedZones = mergeZones;
MOZ_ASSERT(!mBuilder, "Forgot to clear mBuilder");
mBuilder = MakeUnique<CCGraphBuilder>(mGraph, mResults, mCCJSRuntime, mLogger,
mergeZones);
timeLog.Checkpoint("BeginCollection prepare graph builder");
if (mCCJSRuntime) {
mCCJSRuntime->TraverseRoots(*mBuilder);
timeLog.Checkpoint("mJSContext->TraverseRoots()");
}
AutoRestore<bool> ar(mScanInProgress);
MOZ_RELEASE_ASSERT(!mScanInProgress);
mScanInProgress = true;
mPurpleBuf.SelectPointers(*mBuilder);
timeLog.Checkpoint("SelectPointers()");
mBuilder->DoneAddingRoots();
mIncrementalPhase = GraphBuildingPhase;
}
uint32_t nsCycleCollector::SuspectedCount() {
CheckThreadSafety();
if (NS_IsMainThread()) {
return gNurseryPurpleBufferEntryCount + mPurpleBuf.Count();
}
return mPurpleBuf.Count();
}
void nsCycleCollector::Shutdown(bool aDoCollect) {
CheckThreadSafety();
if (NS_IsMainThread()) {
gNurseryPurpleBufferEnabled = false;
}
// Always delete snow white objects.
FreeSnowWhite(true);
if (aDoCollect) {
ShutdownCollect();
}
if (mJSPurpleBuffer) {
mJSPurpleBuffer->Destroy();
}
}
void nsCycleCollector::RemoveObjectFromGraph(void* aObj) {
if (IsIdle()) {
return;
}
mGraph.RemoveObjectFromMap(aObj);
if (mBuilder) {
mBuilder->RemoveCachedEntry(aObj);
}
}
void nsCycleCollector::SizeOfIncludingThis(mozilla::MallocSizeOf aMallocSizeOf,
size_t* aObjectSize,
size_t* aGraphSize,
size_t* aPurpleBufferSize) const {
*aObjectSize = aMallocSizeOf(this);
*aGraphSize = mGraph.SizeOfExcludingThis(aMallocSizeOf);
*aPurpleBufferSize = mPurpleBuf.SizeOfExcludingThis(aMallocSizeOf);
// These fields are deliberately not measured:
// - mCCJSRuntime: because it's non-owning and measured by JS reporters.
// - mParams: because it only contains scalars.
}
JSPurpleBuffer* nsCycleCollector::GetJSPurpleBuffer() {
if (!mJSPurpleBuffer) {
// The Release call here confuses the GC analysis.
JS::AutoSuppressGCAnalysis nogc;
// JSPurpleBuffer keeps itself alive, but we need to create it in such way
// that it ends up in the normal purple buffer. That happens when
// nsRefPtr goes out of the scope and calls Release.
RefPtr<JSPurpleBuffer> pb = new JSPurpleBuffer(mJSPurpleBuffer);
}
return mJSPurpleBuffer;
}
////////////////////////////////////////////////////////////////////////
// Module public API (exported in nsCycleCollector.h)
// Just functions that redirect into the singleton, once it's built.
////////////////////////////////////////////////////////////////////////
void nsCycleCollector_registerJSContext(CycleCollectedJSContext* aCx) {
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 context.
MOZ_ASSERT(!data->mContext);
data->mContext = aCx;
data->mCollector->SetCCJSRuntime(aCx->Runtime());
}
void nsCycleCollector_forgetJSContext() {
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
// And we shouldn't have already forgotten our context.
MOZ_ASSERT(data->mContext);
// But it may have shutdown already.
if (data->mCollector) {
data->mCollector->ClearCCJSRuntime();
data->mContext = nullptr;
} else {
data->mContext = nullptr;
delete data;
sCollectorData.set(nullptr);
}
}
/* static */
CycleCollectedJSContext* CycleCollectedJSContext::Get() {
CollectorData* data = sCollectorData.get();
if (data) {
return data->mContext;
}
return nullptr;
}
MOZ_NEVER_INLINE static void SuspectAfterShutdown(
void* aPtr, nsCycleCollectionParticipant* aCp,
nsCycleCollectingAutoRefCnt* aRefCnt, bool* aShouldDelete) {
if (aRefCnt->get() == 0) {
if (!aShouldDelete) {
// The CC is shut down, so we can't be in the middle of an ICC.
ToParticipant(aPtr, &aCp);
aRefCnt->stabilizeForDeletion();
aCp->DeleteCycleCollectable(aPtr);
} else {
*aShouldDelete = true;
}
} else {
// Make sure we'll get called again.
aRefCnt->RemoveFromPurpleBuffer();
}
}
void NS_CycleCollectorSuspect3(void* aPtr, nsCycleCollectionParticipant* aCp,
nsCycleCollectingAutoRefCnt* aRefCnt,
bool* aShouldDelete) {
if ((
#ifdef HAVE_64BIT_BUILD
aRefCnt->IsOnMainThread() ||
#endif
NS_IsMainThread()) &&
gNurseryPurpleBufferEnabled) {
// The next time the object is passed to the purple buffer, we can do faster
// IsOnMainThread() check.
aRefCnt->SetIsOnMainThread();
SuspectUsingNurseryPurpleBuffer(aPtr, aCp, aRefCnt);
return;
}
CollectorData* data = sCollectorData.get();
// This assertion will happen if you AddRef or Release a cycle collected
// object on a thread that does not have an active cycle collector.
// This can happen in a few situations:
// 1. We never cycle collect on this thread. (The cycle collector is only
// run on the main thread and DOM worker threads.)
// 2. The cycle collector hasn't been initialized on this thread yet.
// 3. The cycle collector has already been shut down on this thread.
MOZ_DIAGNOSTIC_ASSERT(
data,
"Cycle collected object used on a thread without a cycle collector.");
if (MOZ_LIKELY(data->mCollector)) {
data->mCollector->Suspect(aPtr, aCp, aRefCnt);
return;
}
SuspectAfterShutdown(aPtr, aCp, aRefCnt, aShouldDelete);
}
void ClearNurseryPurpleBuffer() {
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
CollectorData* data = sCollectorData.get();
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
data->mCollector->SuspectNurseryEntries();
}
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() {
#ifdef DEBUG
static bool sInitialized;
MOZ_ASSERT(NS_IsMainThread(), "Wrong thread!");
MOZ_ASSERT(!sInitialized, "Called twice!?");
sInitialized = true;
#endif
return sCollectorData.init();
}
void nsCycleCollector_startup() {
if (sCollectorData.get()) {
MOZ_CRASH();
}
CollectorData* data = new CollectorData;
data->mCollector = new nsCycleCollector();
data->mContext = nullptr;
sCollectorData.set(data);
}
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(js::SliceBudget& aBudget,
bool aRemoveChildlessNodes,
bool aAsyncSnowWhiteFreeing) {
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
TimeLog timeLog;
data->mCollector->ForgetSkippable(aBudget, aRemoveChildlessNodes,
aAsyncSnowWhiteFreeing);
timeLog.Checkpoint("ForgetSkippable()");
}
void nsCycleCollector_dispatchDeferredDeletion(bool aContinuation,
bool aPurge) {
CycleCollectedJSRuntime* rt = CycleCollectedJSRuntime::Get();
if (rt) {
rt->DispatchDeferredDeletion(aContinuation, aPurge);
}
}
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->mContext);
return data->mCollector->FreeSnowWhite(false);
}
bool nsCycleCollector_doDeferredDeletionWithBudget(js::SliceBudget& aBudget) {
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
MOZ_ASSERT(data->mContext);
return data->mCollector->FreeSnowWhiteWithBudget(aBudget);
}
already_AddRefed<nsICycleCollectorLogSink> nsCycleCollector_createLogSink(
bool aLogGC) {
nsCOMPtr<nsICycleCollectorLogSink> sink =
new nsCycleCollectorLogSinkToFile(aLogGC);
return sink.forget();
}
bool nsCycleCollector_collect(CCReason aReason,
nsICycleCollectorListener* aManualListener) {
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
AUTO_PROFILER_LABEL("nsCycleCollector_collect", GCCC);
SliceBudget unlimitedBudget = SliceBudget::unlimited();
return data->mCollector->Collect(aReason, ccIsManual::CCIsManual,
unlimitedBudget, aManualListener);
}
void nsCycleCollector_collectSlice(SliceBudget& budget, CCReason aReason,
bool aPreferShorterSlices) {
CollectorData* data = sCollectorData.get();
// We should have started the cycle collector by now.
MOZ_ASSERT(data);
MOZ_ASSERT(data->mCollector);
AUTO_PROFILER_LABEL("nsCycleCollector_collectSlice", GCCC);
data->mCollector->Collect(aReason, ccIsManual::CCIsNotManual, budget, nullptr,
aPreferShorterSlices);
}
void nsCycleCollector_prepareForGarbageCollection() {
CollectorData* data = sCollectorData.get();
MOZ_ASSERT(data);
if (!data->mCollector) {
return;
}
data->mCollector->PrepareForGarbageCollection();
}
void nsCycleCollector_finishAnyCurrentCollection() {
CollectorData* data = sCollectorData.get();
MOZ_ASSERT(data);
if (!data->mCollector) {
return;
}
data->mCollector->FinishAnyCurrentCollection(CCReason::API);
}
void nsCycleCollector_shutdown(bool aDoCollect) {
CollectorData* data = sCollectorData.get();
if (data) {
MOZ_ASSERT(data->mCollector);
AUTO_PROFILER_LABEL("nsCycleCollector_shutdown", OTHER);
{
RefPtr<nsCycleCollector> collector = data->mCollector;
collector->Shutdown(aDoCollect);
data->mCollector = nullptr;
}
if (!data->mContext) {
delete data;
sCollectorData.set(nullptr);
}
}
}