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gecko/xpcom/base/nsCycleCollector.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is mozilla.org code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2006
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
*
* Alternatively, the contents of this file may be used under the terms of
* either of the GNU General Public License Version 2 or later (the "GPL"),
* or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
//
// This file implements a garbage-cycle collector based on the paper
//
// Concurrent Cycle Collection in Reference Counted Systems
// Bacon & Rajan (2001), ECOOP 2001 / Springer LNCS vol 2072
//
// We are not using the concurrent or acyclic cases of that paper; so
// the green, red and orange colors are not used.
//
// The collector is based on tracking pointers of four colors:
//
// Black nodes are definitely live. If we ever determine a node is
// black, it's ok to forget about, drop from our records.
//
// White nodes are definitely garbage cycles. Once we finish with our
// scanning, we unlink all the white nodes and expect that by
// unlinking them they will self-destruct (since a garbage cycle is
// only keeping itself alive with internal links, by definition).
//
// Grey nodes are being scanned. Nodes that turn grey will turn
// either black if we determine that they're live, or white if we
// determine that they're a garbage cycle. After the main collection
// algorithm there should be no grey nodes.
//
// Purple nodes are *candidates* for being scanned. They are nodes we
// haven't begun scanning yet because they're not old enough, or we're
// still partway through the algorithm.
//
// XPCOM objects participating in garbage-cycle collection are obliged
// to inform us when they ought to turn purple; that is, when their
// refcount transitions from N+1 -> N, for nonzero N. Furthermore we
// require that *after* an XPCOM object has informed us of turning
// purple, they will tell us when they either transition back to being
// black (incremented refcount) or are ultimately deleted.
// Safety:
//
// An XPCOM object is either scan-safe or scan-unsafe, purple-safe or
// purple-unsafe.
//
// An object is scan-safe if:
//
// - It can be QI'ed to |nsCycleCollectionParticipant|, though this
// operation loses ISupports identity (like nsIClassInfo).
// - The operation |traverse| on the resulting
// nsCycleCollectionParticipant does not cause *any* refcount
// adjustment to occur (no AddRef / Release calls).
//
// An object is purple-safe if it satisfies the following properties:
//
// - The object is scan-safe.
// - If the object calls |nsCycleCollector::suspect(this)|,
// it will eventually call |nsCycleCollector::forget(this)|,
// exactly once per call to |suspect|, before being destroyed.
//
// When we receive a pointer |ptr| via
// |nsCycleCollector::suspect(ptr)|, we assume it is purple-safe. We
// can check the scan-safety, but have no way to ensure the
// purple-safety; objects must obey, or else the entire system falls
// apart. Don't involve an object in this scheme if you can't
// guarantee its purple-safety.
//
// When we have a scannable set of purple nodes ready, we begin
// our walks. During the walks, the nodes we |traverse| should only
// feed us more scan-safe nodes, and should not adjust the refcounts
// of those nodes.
//
// We do not |AddRef| or |Release| any objects during scanning. We
// rely on purple-safety of the roots that call |suspect| and
// |forget| to hold, such that we will forget about a purple pointer
// before it is destroyed. The pointers that are merely scan-safe,
// we hold only for the duration of scanning, and there should be no
// objects released from the scan-safe set during the scan (there
// should be no threads involved).
//
// We *do* call |AddRef| and |Release| on every white object, on
// either side of the calls to |Unlink|. This keeps the set of white
// objects alive during the unlinking.
//
#ifndef __MINGW32__
#ifdef WIN32
#include <crtdbg.h>
#include <errno.h>
#endif
#endif
#include "nsCycleCollectionParticipant.h"
#include "nsIProgrammingLanguage.h"
#include "nsBaseHashtable.h"
#include "nsHashKeys.h"
#include "nsDeque.h"
#include "nsCycleCollector.h"
#include "nsThreadUtils.h"
#include "prenv.h"
#include "prprf.h"
#include "plstr.h"
#include "prtime.h"
#include "nsPrintfCString.h"
#include "nsTArray.h"
#include <stdio.h>
#ifdef WIN32
#include <io.h>
#include <process.h>
#endif
#define DEFAULT_SHUTDOWN_COLLECTIONS 5
#ifdef DEBUG_CC
#define SHUTDOWN_COLLECTIONS(params) params.mShutdownCollections
#else
#define SHUTDOWN_COLLECTIONS(params) DEFAULT_SHUTDOWN_COLLECTIONS
#endif
// Various parameters of this collector can be tuned using environment
// variables.
struct nsCycleCollectorParams
{
PRBool mDoNothing;
#ifdef DEBUG_CC
PRBool mReportStats;
PRBool mHookMalloc;
PRBool mDrawGraphs;
PRBool mFaultIsFatal;
PRBool mLogPointers;
PRUint32 mShutdownCollections;
#endif
PRUint32 mScanDelay;
nsCycleCollectorParams() :
#ifdef DEBUG_CC
mDoNothing (PR_GetEnv("XPCOM_CC_DO_NOTHING") != NULL),
mReportStats (PR_GetEnv("XPCOM_CC_REPORT_STATS") != NULL),
mHookMalloc (PR_GetEnv("XPCOM_CC_HOOK_MALLOC") != NULL),
mDrawGraphs (PR_GetEnv("XPCOM_CC_DRAW_GRAPHS") != NULL),
mFaultIsFatal (PR_GetEnv("XPCOM_CC_FAULT_IS_FATAL") != NULL),
mLogPointers (PR_GetEnv("XPCOM_CC_LOG_POINTERS") != NULL),
mShutdownCollections(DEFAULT_SHUTDOWN_COLLECTIONS),
#else
mDoNothing (PR_FALSE),
#endif
// The default number of collections to "age" candidate
// pointers in the purple buffer before we decide that any
// garbage cycle they're in has stabilized and we want to
// consider scanning it.
//
// Making this number smaller causes:
// - More time to be spent in the collector (bad)
// - Less delay between forming garbage and collecting it (good)
mScanDelay(10)
{
#ifdef DEBUG_CC
char *s = PR_GetEnv("XPCOM_CC_SCAN_DELAY");
if (s)
PR_sscanf(s, "%d", &mScanDelay);
s = PR_GetEnv("XPCOM_CC_SHUTDOWN_COLLECTIONS");
if (s)
PR_sscanf(s, "%d", &mShutdownCollections);
#endif
}
};
#ifdef DEBUG_CC
// Various operations involving the collector are recorded in a
// statistics table. These are for diagnostics.
struct nsCycleCollectorStats
{
PRUint32 mFailedQI;
PRUint32 mSuccessfulQI;
PRUint32 mVisitedNode;
PRUint32 mVisitedJSNode;
PRUint32 mWalkedGraph;
PRUint32 mCollectedBytes;
PRUint32 mFreeCalls;
PRUint32 mFreedBytes;
PRUint32 mSetColorGrey;
PRUint32 mSetColorBlack;
PRUint32 mSetColorWhite;
PRUint32 mFailedUnlink;
PRUint32 mCollectedNode;
PRUint32 mBumpGeneration;
PRUint32 mZeroGeneration;
PRUint32 mSuspectNode;
PRUint32 mSpills;
PRUint32 mForgetNode;
PRUint32 mFreedWhilePurple;
PRUint32 mCollection;
nsCycleCollectorStats()
{
memset(this, 0, sizeof(nsCycleCollectorStats));
}
void Dump()
{
fprintf(stderr, "\f\n");
#define DUMP(entry) fprintf(stderr, "%30.30s: %-20.20d\n", #entry, entry)
DUMP(mFailedQI);
DUMP(mSuccessfulQI);
DUMP(mVisitedNode);
DUMP(mVisitedJSNode);
DUMP(mWalkedGraph);
DUMP(mCollectedBytes);
DUMP(mFreeCalls);
DUMP(mFreedBytes);
DUMP(mSetColorGrey);
DUMP(mSetColorBlack);
DUMP(mSetColorWhite);
DUMP(mFailedUnlink);
DUMP(mCollectedNode);
DUMP(mBumpGeneration);
DUMP(mZeroGeneration);
DUMP(mSuspectNode);
DUMP(mSpills);
DUMP(mForgetNode);
DUMP(mFreedWhilePurple);
DUMP(mCollection);
#undef DUMP
}
};
#endif
static void
ToParticipant(nsISupports *s, nsCycleCollectionParticipant **cp);
#ifdef DEBUG_CC
static PRBool
nsCycleCollector_shouldSuppress(nsISupports *s);
#endif
////////////////////////////////////////////////////////////////////////
// Base types
////////////////////////////////////////////////////////////////////////
enum NodeColor { black, white, grey };
// This structure should be kept as small as possible; we may expect
// a million of them to be allocated and touched repeatedly during
// each cycle collection.
struct PtrInfo
: public PLDHashEntryStub
{
PRUint32 mColor : 2;
PRUint32 mInternalRefs : 30;
// FIXME: mLang expands back to a full word when bug 368774 lands.
PRUint32 mLang : 2;
PRUint32 mRefCount : 30;
#ifdef DEBUG_CC
size_t mBytes;
const char *mName;
#endif
};
PR_STATIC_CALLBACK(PRBool)
InitPtrInfo(PLDHashTable *table, PLDHashEntryHdr *entry, const void *key)
{
PtrInfo* pi = (PtrInfo*)entry;
pi->key = key;
pi->mColor = black;
pi->mInternalRefs = 0;
pi->mLang = nsIProgrammingLanguage::CPLUSPLUS;
pi->mRefCount = 0;
#ifdef DEBUG_CC
pi->mBytes = 0;
pi->mName = nsnull;
#endif
return PR_TRUE;
}
static PLDHashTableOps GCTableOps = {
PL_DHashAllocTable,
PL_DHashFreeTable,
PL_DHashVoidPtrKeyStub,
PL_DHashMatchEntryStub,
PL_DHashMoveEntryStub,
PL_DHashClearEntryStub,
PL_DHashFinalizeStub,
InitPtrInfo
};
struct GCTable
{
PLDHashTable mTab;
GCTable()
{
Init();
}
~GCTable()
{
if (mTab.ops)
PL_DHashTableFinish(&mTab);
}
void Init()
{
if (!PL_DHashTableInit(&mTab, &GCTableOps, nsnull, sizeof(PtrInfo),
32768))
mTab.ops = nsnull;
}
void Clear()
{
if (!mTab.ops || mTab.entryCount > 0) {
if (mTab.ops)
PL_DHashTableFinish(&mTab);
Init();
}
}
PtrInfo *Lookup(void *key)
{
if (!mTab.ops)
return nsnull;
PLDHashEntryHdr *entry =
PL_DHashTableOperate(&mTab, key, PL_DHASH_LOOKUP);
return PL_DHASH_ENTRY_IS_BUSY(entry) ? (PtrInfo*)entry : nsnull;
}
PtrInfo *Add(void *key)
{
if (!mTab.ops)
return nsnull;
return (PtrInfo*)PL_DHashTableOperate(&mTab, key, PL_DHASH_ADD);
}
void Enumerate(PLDHashEnumerator etor, void *arg)
{
if (mTab.ops)
PL_DHashTableEnumerate(&mTab, etor, arg);
}
};
// XXX Would be nice to have an nsHashSet<KeyType> API that has
// Add/Remove/Has rather than PutEntry/RemoveEntry/GetEntry.
typedef nsTHashtable<nsVoidPtrHashKey> PointerSet;
typedef nsBaseHashtable<nsVoidPtrHashKey, PRUint32, PRUint32>
PointerSetWithGeneration;
static void
Fault(const char *msg, const void *ptr);
struct nsPurpleBuffer
{
#define ASSOCIATIVITY 2
#define INDEX_LOW_BIT 6
#define N_INDEX_BITS 13
#define N_ENTRIES (1 << N_INDEX_BITS)
#define N_POINTERS (N_ENTRIES * ASSOCIATIVITY)
#define TOTAL_BYTES (N_POINTERS * PR_BYTES_PER_WORD)
#define INDEX_MASK PR_BITMASK(N_INDEX_BITS)
#define POINTER_INDEX(P) ((((PRUword)P) >> INDEX_LOW_BIT) & (INDEX_MASK))
#if (INDEX_LOW_BIT + N_INDEX_BITS > (8 * PR_BYTES_PER_WORD))
#error "index bit overflow"
#endif
// This class serves as a generational wrapper around a pldhash
// table: a subset of generation zero lives in mCache, the
// remainder spill into the mBackingStore hashtable. The idea is
// to get a higher hit rate and greater locality of reference for
// generation zero, in which the vast majority of suspect/forget
// calls annihilate one another.
nsCycleCollectorParams &mParams;
#ifdef DEBUG_CC
nsCycleCollectorStats &mStats;
#endif
void* mCache[N_POINTERS];
PRUint32 mCurrGen;
PointerSetWithGeneration mBackingStore;
nsDeque *mTransferBuffer;
#ifdef DEBUG_CC
nsPurpleBuffer(nsCycleCollectorParams &params,
nsCycleCollectorStats &stats)
: mParams(params),
mStats(stats),
mTransferBuffer(nsnull)
{
Init();
}
#else
nsPurpleBuffer(nsCycleCollectorParams &params)
: mParams(params),
mTransferBuffer(nsnull)
{
Init();
}
#endif
~nsPurpleBuffer()
{
memset(mCache, 0, sizeof(mCache));
mBackingStore.Clear();
}
void Init()
{
memset(mCache, 0, sizeof(mCache));
mBackingStore.Init();
}
void BumpGeneration();
void SelectAgedPointers(nsDeque *transferBuffer);
PRBool Exists(void *p)
{
PRUint32 idx = POINTER_INDEX(p);
for (PRUint32 i = 0; i < ASSOCIATIVITY; ++i) {
if (mCache[idx+i] == p)
return PR_TRUE;
}
PRUint32 gen;
return mBackingStore.Get(p, &gen);
}
void Put(void *p)
{
PRUint32 idx = POINTER_INDEX(p);
for (PRUint32 i = 0; i < ASSOCIATIVITY; ++i) {
if (!mCache[idx+i]) {
mCache[idx+i] = p;
return;
}
}
#ifdef DEBUG_CC
mStats.mSpills++;
#endif
SpillOne(p);
}
void Remove(void *p)
{
PRUint32 idx = POINTER_INDEX(p);
for (PRUint32 i = 0; i < ASSOCIATIVITY; ++i) {
if (mCache[idx+i] == p) {
mCache[idx+i] = (void*)0;
return;
}
}
mBackingStore.Remove(p);
}
void SpillOne(void* &p)
{
mBackingStore.Put(p, mCurrGen);
p = (void*)0;
}
void SpillAll()
{
for (PRUint32 i = 0; i < N_POINTERS; ++i) {
if (mCache[i]) {
SpillOne(mCache[i]);
}
}
}
};
static PR_CALLBACK PLDHashOperator
zeroGenerationCallback(const void* ptr,
PRUint32& generation,
void* userArg)
{
#ifdef DEBUG_CC
nsPurpleBuffer *purp = NS_STATIC_CAST(nsPurpleBuffer*, userArg);
purp->mStats.mZeroGeneration++;
#endif
generation = 0;
return PL_DHASH_NEXT;
}
void nsPurpleBuffer::BumpGeneration()
{
SpillAll();
if (mCurrGen == 0xffffffff) {
mBackingStore.Enumerate(zeroGenerationCallback, this);
mCurrGen = 0;
} else {
++mCurrGen;
}
#ifdef DEBUG_CC
mStats.mBumpGeneration++;
#endif
}
static inline PRBool
SufficientlyAged(PRUint32 generation, nsPurpleBuffer *p)
{
return generation + p->mParams.mScanDelay < p->mCurrGen;
}
static PR_CALLBACK PLDHashOperator
ageSelectionCallback(const void* ptr,
PRUint32& generation,
void* userArg)
{
nsPurpleBuffer *purp = NS_STATIC_CAST(nsPurpleBuffer*, userArg);
if (SufficientlyAged(generation, purp)) {
nsISupports *root = NS_STATIC_CAST(nsISupports *,
NS_CONST_CAST(void*, ptr));
purp->mTransferBuffer->Push(root);
}
return PL_DHASH_NEXT;
}
void
nsPurpleBuffer::SelectAgedPointers(nsDeque *transferBuffer)
{
mTransferBuffer = transferBuffer;
mBackingStore.Enumerate(ageSelectionCallback, this);
mTransferBuffer = nsnull;
}
////////////////////////////////////////////////////////////////////////
// Implement the LanguageRuntime interface for C++/XPCOM
////////////////////////////////////////////////////////////////////////
struct nsCycleCollectionXPCOMRuntime :
public nsCycleCollectionLanguageRuntime
{
nsresult BeginCycleCollection()
{
return NS_OK;
}
nsresult Traverse(void *p, nsCycleCollectionTraversalCallback &cb)
{
nsresult rv;
nsISupports *s = NS_STATIC_CAST(nsISupports *, p);
nsCycleCollectionParticipant *cp;
ToParticipant(s, &cp);
if (!cp) {
Fault("walking wrong type of pointer", s);
return NS_ERROR_FAILURE;
}
rv = cp->Traverse(s, cb);
if (NS_FAILED(rv)) {
Fault("XPCOM pointer traversal failed", s);
return NS_ERROR_FAILURE;
}
return NS_OK;
}
nsresult Root(const nsDeque &nodes)
{
for (PRInt32 i = 0; i < nodes.GetSize(); ++i) {
void *p = nodes.ObjectAt(i);
nsISupports *s = NS_STATIC_CAST(nsISupports *, p);
NS_ADDREF(s);
}
return NS_OK;
}
nsresult Unlink(const nsDeque &nodes)
{
nsresult rv;
for (PRInt32 i = 0; i < nodes.GetSize(); ++i) {
void *p = nodes.ObjectAt(i);
nsISupports *s = NS_STATIC_CAST(nsISupports *, p);
nsCycleCollectionParticipant *cp;
ToParticipant(s, &cp);
if (!cp) {
Fault("unlinking wrong kind of pointer", s);
return NS_ERROR_FAILURE;
}
rv = cp->Unlink(s);
if (NS_FAILED(rv)) {
Fault("failed unlink", s);
return NS_ERROR_FAILURE;
}
}
return NS_OK;
}
nsresult Unroot(const nsDeque &nodes)
{
for (PRInt32 i = 0; i < nodes.GetSize(); ++i) {
void *p = nodes.ObjectAt(i);
nsISupports *s = NS_STATIC_CAST(nsISupports *, p);
NS_RELEASE(s);
}
return NS_OK;
}
nsresult FinishCycleCollection()
{
return NS_OK;
}
};
struct nsCycleCollector
{
PRBool mCollectionInProgress;
PRBool mScanInProgress;
GCTable mGraph;
nsCycleCollectionLanguageRuntime *mRuntimes[nsIProgrammingLanguage::MAX+1];
nsCycleCollectionXPCOMRuntime mXPCOMRuntime;
// The set of buffers |mBufs| serves a variety of purposes; mostly
// involving the transfer of pointers from a hashtable iterator
// routine to some outer logic that might also need to mutate the
// hashtable. In some contexts, only buffer 0 is used (as a
// set-of-all-pointers); in other contexts, one buffer is used
// per-language (as a set-of-pointers-in-language-N).
nsDeque mBufs[nsIProgrammingLanguage::MAX + 1];
nsCycleCollectorParams mParams;
nsPurpleBuffer mPurpleBuf;
void RegisterRuntime(PRUint32 langID,
nsCycleCollectionLanguageRuntime *rt);
void ForgetRuntime(PRUint32 langID);
void CollectPurple(); // XXXldb Should this be called SelectPurple?
void MarkRoots();
void ScanRoots();
void CollectWhite();
nsCycleCollector();
~nsCycleCollector();
void Suspect(nsISupports *n, PRBool current = PR_FALSE);
void Forget(nsISupports *n);
void Allocated(void *n, size_t sz);
void Freed(void *n);
void Collect(PRUint32 aTryCollections = 1);
void Shutdown();
#ifdef DEBUG_CC
nsCycleCollectorStats mStats;
FILE *mPtrLog;
void MaybeDrawGraphs();
void ExplainLiveExpectedGarbage();
void ShouldBeFreed(nsISupports *n);
void WasFreed(nsISupports *n);
PointerSet mExpectedGarbage;
#endif
};
class GraphWalker :
public nsCycleCollectionTraversalCallback
{
private:
nsDeque mQueue;
PtrInfo *mCurrPi;
protected:
GCTable &mGraph;
nsCycleCollectionLanguageRuntime **mRuntimes;
public:
GraphWalker(GCTable & tab,
nsCycleCollectionLanguageRuntime **runtimes) :
mQueue(nsnull),
mCurrPi(nsnull),
mGraph(tab),
mRuntimes(runtimes)
{}
virtual ~GraphWalker()
{}
void Walk(void *s0);
// nsCycleCollectionTraversalCallback methods.
#ifdef DEBUG_CC
void DescribeNode(size_t refCount, size_t objSz, const char *objName);
#else
void DescribeNode(size_t refCount);
#endif
void NoteXPCOMChild(nsISupports *child);
void NoteScriptChild(PRUint32 langID, void *child);
// Provided by concrete walker subtypes.
virtual PRBool ShouldVisitNode(PtrInfo const *pi) = 0;
virtual void VisitNode(PtrInfo *pi, size_t refcount) = 0;
virtual void NoteChild(PtrInfo *childpi) = 0;
};
////////////////////////////////////////////////////////////////////////
// The static collector object
////////////////////////////////////////////////////////////////////////
static nsCycleCollector *sCollector = nsnull;
////////////////////////////////////////////////////////////////////////
// Utility functions
////////////////////////////////////////////////////////////////////////
#ifdef DEBUG_CC
struct safetyCallback :
public nsCycleCollectionTraversalCallback
{
// This is just a dummy interface to feed to children when we're
// called, to force potential segfaults to happen early, so gdb
// can give us an informative stack trace. If we don't use it, the
// collector runs faster but segfaults happen after pointers have
// been queued and dequeued, at which point their owner is
// obscure.
void DescribeNode(size_t refCount, size_t objSz, const char *objName) {}
void NoteXPCOMChild(nsISupports *child) {}
void NoteScriptChild(PRUint32 langID, void *child) {}
};
static safetyCallback sSafetyCallback;
#endif
static void
Fault(const char *msg, const void *ptr=nsnull)
{
#ifdef DEBUG_CC
// This should be nearly impossible, but just in case.
if (!sCollector)
return;
if (sCollector->mParams.mFaultIsFatal) {
if (ptr)
printf("Fatal fault in cycle collector: %s (ptr: %p)\n", msg, ptr);
else
printf("Fatal fault in cycle collector: %s\n", msg);
exit(1);
}
#endif
NS_NOTREACHED(nsPrintfCString(256,
"Fault in cycle collector: %s (ptr: %p)\n",
msg, ptr).get());
// When faults are not fatal, we assume we're running in a
// production environment and we therefore want to disable the
// collector on a fault. This will unfortunately cause the browser
// to leak pretty fast wherever creates cyclical garbage, but it's
// probably a better user experience than crashing. Besides, we
// *should* never hit a fault.
sCollector->mParams.mDoNothing = PR_TRUE;
}
void
#ifdef DEBUG_CC
GraphWalker::DescribeNode(size_t refCount, size_t objSz, const char *objName)
#else
GraphWalker::DescribeNode(size_t refCount)
#endif
{
if (refCount == 0)
Fault("zero refcount", mCurrPi->key);
#ifdef DEBUG_CC
mCurrPi->mBytes = objSz;
mCurrPi->mName = objName;
#endif
this->VisitNode(mCurrPi, refCount);
#ifdef DEBUG_CC
sCollector->mStats.mVisitedNode++;
if (mCurrPi->mLang == nsIProgrammingLanguage::JAVASCRIPT)
sCollector->mStats.mVisitedJSNode++;
#endif
}
static nsISupports *
canonicalize(nsISupports *in)
{
nsCOMPtr<nsISupports> child;
in->QueryInterface(NS_GET_IID(nsCycleCollectionISupports),
getter_AddRefs(child));
return child.get();
}
void
GraphWalker::NoteXPCOMChild(nsISupports *child)
{
if (!child)
return;
child = canonicalize(child);
PRBool scanSafe = nsCycleCollector_isScanSafe(child);
#ifdef DEBUG_CC
scanSafe &= !nsCycleCollector_shouldSuppress(child);
#endif
if (scanSafe) {
PtrInfo *childPi = mGraph.Add(child);
if (!childPi)
return;
this->NoteChild(childPi);
#ifdef DEBUG_CC
mRuntimes[nsIProgrammingLanguage::CPLUSPLUS]->Traverse(child, sSafetyCallback);
#endif
mQueue.Push(child);
}
}
void
GraphWalker::NoteScriptChild(PRUint32 langID, void *child)
{
if (!child)
return;
if (langID > nsIProgrammingLanguage::MAX || !mRuntimes[langID]) {
Fault("traversing pointer for unregistered language", child);
return;
}
PtrInfo *childPi = mGraph.Add(child);
if (!childPi)
return;
childPi->mLang = langID;
this->NoteChild(childPi);
#ifdef DEBUG_CC
mRuntimes[langID]->Traverse(child, sSafetyCallback);
#endif
mQueue.Push(child);
}
void
GraphWalker::Walk(void *s0)
{
mQueue.Empty();
mQueue.Push(s0);
while (mQueue.GetSize() > 0) {
void *ptr = mQueue.Pop();
mCurrPi = mGraph.Lookup(ptr);
if (!mCurrPi) {
Fault("unknown pointer", ptr);
continue;
}
#ifdef DEBUG_CC
if (mCurrPi->mLang > nsIProgrammingLanguage::MAX ) {
Fault("unknown language during walk");
continue;
}
if (!mRuntimes[mCurrPi->mLang]) {
Fault("script pointer for unregistered language");
continue;
}
#endif
if (this->ShouldVisitNode(mCurrPi)) {
nsresult rv = mRuntimes[mCurrPi->mLang]->Traverse(ptr, *this);
if (NS_FAILED(rv)) {
Fault("script pointer traversal failed", ptr);
}
}
}
#ifdef DEBUG_CC
sCollector->mStats.mWalkedGraph++;
#endif
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |MarkRoots| routine.
////////////////////////////////////////////////////////////////////////
struct MarkGreyWalker : public GraphWalker
{
MarkGreyWalker(GCTable &tab,
nsCycleCollectionLanguageRuntime **runtimes)
: GraphWalker(tab, runtimes)
{}
PRBool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor != grey;
}
void VisitNode(PtrInfo *pi, size_t refcount)
{
pi->mColor = grey;
pi->mRefCount = refcount;
#ifdef DEBUG_CC
sCollector->mStats.mSetColorGrey++;
#endif
}
void NoteChild(PtrInfo *childpi)
{
childpi->mInternalRefs++;
}
};
void
nsCycleCollector::CollectPurple()
{
mPurpleBuf.SelectAgedPointers(&mBufs[0]);
}
void
nsCycleCollector::MarkRoots()
{
int i;
for (i = 0; i < mBufs[0].GetSize(); ++i) {
nsISupports *s = NS_STATIC_CAST(nsISupports *, mBufs[0].ObjectAt(i));
s = canonicalize(s);
mGraph.Add(s);
MarkGreyWalker(mGraph, mRuntimes).Walk(s);
}
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |ScanRoots| routine.
////////////////////////////////////////////////////////////////////////
struct ScanBlackWalker : public GraphWalker
{
ScanBlackWalker(GCTable &tab,
nsCycleCollectionLanguageRuntime **runtimes)
: GraphWalker(tab, runtimes)
{}
PRBool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor != black;
}
void VisitNode(PtrInfo *pi, size_t refcount)
{
pi->mColor = black;
#ifdef DEBUG_CC
sCollector->mStats.mSetColorBlack++;
#endif
}
void NoteChild(PtrInfo *childpi) {}
};
struct scanWalker : public GraphWalker
{
scanWalker(GCTable &tab,
nsCycleCollectionLanguageRuntime **runtimes)
: GraphWalker(tab, runtimes)
{}
PRBool ShouldVisitNode(PtrInfo const *pi)
{
return pi->mColor == grey;
}
void VisitNode(PtrInfo *pi, size_t refcount)
{
if (pi->mColor != grey)
Fault("scanning non-grey node", pi->key);
if (pi->mInternalRefs > refcount)
Fault("traversed refs exceed refcount", pi->key);
if (pi->mInternalRefs == refcount) {
pi->mColor = white;
#ifdef DEBUG_CC
sCollector->mStats.mSetColorWhite++;
#endif
} else {
ScanBlackWalker(mGraph, mRuntimes).Walk(NS_CONST_CAST(void*,
pi->key));
NS_ASSERTION(pi->mColor == black,
"Why didn't ScanBlackWalker make pi black?");
}
}
void NoteChild(PtrInfo *childpi) {}
};
#ifdef DEBUG_CC
PR_STATIC_CALLBACK(PLDHashOperator)
NoGreyCallback(PLDHashTable *table, PLDHashEntryHdr *hdr, PRUint32 number,
void *arg)
{
PtrInfo *pinfo = (PtrInfo *) hdr;
if (pinfo->mColor == grey)
Fault("valid grey node after scanning", pinfo->key);
return PL_DHASH_NEXT;
}
#endif
void
nsCycleCollector::ScanRoots()
{
int i;
for (i = 0; i < mBufs[0].GetSize(); ++i) {
nsISupports *s = NS_STATIC_CAST(nsISupports *, mBufs[0].ObjectAt(i));
s = canonicalize(s);
scanWalker(mGraph, mRuntimes).Walk(s);
}
#ifdef DEBUG_CC
// Sanity check: scan should have colored all grey nodes black or
// white. So we ensure we have no grey nodes at this point.
mGraph.Enumerate(NoGreyCallback, this);
#endif
}
////////////////////////////////////////////////////////////////////////
// Bacon & Rajan's |CollectWhite| routine, somewhat modified.
////////////////////////////////////////////////////////////////////////
PR_STATIC_CALLBACK(PLDHashOperator)
FindWhiteCallback(PLDHashTable *table, PLDHashEntryHdr *hdr, PRUint32 number,
void *arg)
{
nsCycleCollector *collector = NS_STATIC_CAST(nsCycleCollector*, arg);
PtrInfo *pinfo = (PtrInfo *) hdr;
void *p = NS_CONST_CAST(void*, pinfo->key);
NS_ASSERTION(pinfo->mLang == nsIProgrammingLanguage::CPLUSPLUS ||
!collector->mPurpleBuf.Exists(p),
"Need to remove non-CPLUSPLUS objects from purple buffer!");
if (pinfo->mColor == white) {
if (pinfo->mLang > nsIProgrammingLanguage::MAX)
Fault("White node has bad language ID", p);
else
collector->mBufs[pinfo->mLang].Push(p);
if (pinfo->mLang == nsIProgrammingLanguage::CPLUSPLUS) {
nsISupports* s = NS_STATIC_CAST(nsISupports*, p);
collector->Forget(s);
}
}
else if (pinfo->mLang == nsIProgrammingLanguage::CPLUSPLUS) {
nsISupports* s = NS_STATIC_CAST(nsISupports*, p);
nsCycleCollectionParticipant* cp;
CallQueryInterface(s, &cp);
if (cp)
cp->UnmarkPurple(s);
collector->Forget(s);
}
return PL_DHASH_NEXT;
}
void
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.
PRUint32 i;
nsresult rv;
for (i = 0; i < nsIProgrammingLanguage::MAX+1; ++i)
mBufs[i].Empty();
#if defined(DEBUG_CC) && !defined(__MINGW32__) && defined(WIN32)
struct _CrtMemState ms1, ms2;
_CrtMemCheckpoint(&ms1);
#endif
mGraph.Enumerate(FindWhiteCallback, this);
for (i = 0; i < nsIProgrammingLanguage::MAX+1; ++i) {
if (mRuntimes[i] &&
mBufs[i].GetSize() > 0) {
rv = mRuntimes[i]->Root(mBufs[i]);
if (NS_FAILED(rv))
Fault("Failed root call while unlinking");
}
}
for (i = 0; i < nsIProgrammingLanguage::MAX+1; ++i) {
if (mRuntimes[i] &&
mBufs[i].GetSize() > 0) {
rv = mRuntimes[i]->Unlink(mBufs[i]);
if (NS_FAILED(rv)) {
Fault("Failed unlink call while unlinking");
#ifdef DEBUG_CC
mStats.mFailedUnlink++;
#endif
} else {
#ifdef DEBUG_CC
mStats.mCollectedNode += mBufs[i].GetSize();
#endif
}
}
}
for (i = 0; i < nsIProgrammingLanguage::MAX+1; ++i) {
if (mRuntimes[i] &&
mBufs[i].GetSize() > 0) {
rv = mRuntimes[i]->Unroot(mBufs[i]);
if (NS_FAILED(rv))
Fault("Failed unroot call while unlinking");
}
}
for (i = 0; i < nsIProgrammingLanguage::MAX+1; ++i)
mBufs[i].Empty();
#if defined(DEBUG_CC) && !defined(__MINGW32__) && defined(WIN32)
_CrtMemCheckpoint(&ms2);
if (ms2.lTotalCount < ms1.lTotalCount)
mStats.mFreedBytes += (ms1.lTotalCount - ms2.lTotalCount);
#endif
}
#ifdef DEBUG_CC
////////////////////////////////////////////////////////////////////////
// Extra book-keeping functions.
////////////////////////////////////////////////////////////////////////
struct graphVizWalker : public GraphWalker
{
// We can't just use _popen here because graphviz-for-windows
// doesn't set up its stdin stream properly, sigh.
PointerSet mVisited;
const void *mParent;
FILE *mStream;
graphVizWalker(GCTable &tab,
nsCycleCollectionLanguageRuntime **runtimes)
: GraphWalker(tab, runtimes),
mParent(nsnull),
mStream(nsnull)
{
#ifdef WIN32
mStream = fopen("c:\\cycle-graph.dot", "w+");
#else
mStream = popen("dotty -", "w");
#endif
mVisited.Init();
fprintf(mStream,
"digraph collection {\n"
"rankdir=LR\n"
"node [fontname=fixed, fontsize=10, style=filled, shape=box]\n"
);
}
~graphVizWalker()
{
fprintf(mStream, "\n}\n");
#ifdef WIN32
fclose(mStream);
// Even dotty doesn't work terribly well on windows, since
// they execute lefty asynchronously. So we'll just run
// lefty ourselves.
_spawnlp(_P_WAIT,
"lefty",
"lefty",
"-e",
"\"load('dotty.lefty');"
"dotty.simple('c:\\cycle-graph.dot');\"",
NULL);
unlink("c:\\cycle-graph.dot");
#else
pclose(mStream);
#endif
}
PRBool ShouldVisitNode(PtrInfo const *pi)
{
return ! mVisited.GetEntry(pi->key);
}
void VisitNode(PtrInfo *pi, size_t refcount)
{
const void *p = pi->key;
mVisited.PutEntry(p);
mParent = p;
fprintf(mStream,
"n%p [label=\"%s\\n%p\\n%u/%u refs found\", "
"fillcolor=%s, fontcolor=%s]\n",
p,
pi->mName,
p,
pi->mInternalRefs, pi->mRefCount,
(pi->mColor == black ? "black" : "white"),
(pi->mColor == black ? "white" : "black"));
}
void NoteChild(PtrInfo *childpi)
{
fprintf(mStream, "n%p -> n%p\n", mParent, childpi->key);
}
};
////////////////////////////////////////////////////////////////////////
// Memory-hooking stuff
// When debugging wild pointers, it sometimes helps to hook malloc and
// free. This stuff is disabled unless you set an environment variable.
////////////////////////////////////////////////////////////////////////
static PRBool hookedMalloc = PR_FALSE;
#ifdef __GLIBC__
#include <malloc.h>
static void* (*old_memalign_hook)(size_t, size_t, const void *);
static void* (*old_realloc_hook)(void *, size_t, const void *);
static void* (*old_malloc_hook)(size_t, const void *);
static void (*old_free_hook)(void *, const void *);
static void* my_memalign_hook(size_t, size_t, const void *);
static void* my_realloc_hook(void *, size_t, const void *);
static void* my_malloc_hook(size_t, const void *);
static void my_free_hook(void *, const void *);
static inline void
install_old_hooks()
{
__memalign_hook = old_memalign_hook;
__realloc_hook = old_realloc_hook;
__malloc_hook = old_malloc_hook;
__free_hook = old_free_hook;
}
static inline void
save_old_hooks()
{
// Glibc docs recommend re-saving old hooks on
// return from recursive calls. Strangely when
// we do this, we find ourselves in infinite
// recursion.
// old_memalign_hook = __memalign_hook;
// old_realloc_hook = __realloc_hook;
// old_malloc_hook = __malloc_hook;
// old_free_hook = __free_hook;
}
static inline void
install_new_hooks()
{
__memalign_hook = my_memalign_hook;
__realloc_hook = my_realloc_hook;
__malloc_hook = my_malloc_hook;
__free_hook = my_free_hook;
}
static void*
my_realloc_hook(void *ptr, size_t size, const void *caller)
{
void *result;
install_old_hooks();
result = realloc(ptr, size);
save_old_hooks();
if (sCollector) {
sCollector->Freed(ptr);
sCollector->Allocated(result, size);
}
install_new_hooks();
return result;
}
static void*
my_memalign_hook(size_t size, size_t alignment, const void *caller)
{
void *result;
install_old_hooks();
result = memalign(size, alignment);
save_old_hooks();
if (sCollector)
sCollector->Allocated(result, size);
install_new_hooks();
return result;
}
static void
my_free_hook (void *ptr, const void *caller)
{
install_old_hooks();
free(ptr);
save_old_hooks();
if (sCollector)
sCollector->Freed(ptr);
install_new_hooks();
}
static void*
my_malloc_hook (size_t size, const void *caller)
{
void *result;
install_old_hooks();
result = malloc (size);
save_old_hooks();
if (sCollector)
sCollector->Allocated(result, size);
install_new_hooks();
return result;
}
static void
InitMemHook(void)
{
if (!hookedMalloc) {
save_old_hooks();
install_new_hooks();
hookedMalloc = PR_TRUE;
}
}
#elif defined(WIN32)
#ifndef __MINGW32__
static int
AllocHook(int allocType, void *userData, size_t size, int
blockType, long requestNumber, const unsigned char *filename, int
lineNumber)
{
if (allocType == _HOOK_FREE)
sCollector->Freed(userData);
return 1;
}
static void InitMemHook(void)
{
if (!hookedMalloc) {
_CrtSetAllocHook (AllocHook);
hookedMalloc = PR_TRUE;
}
}
#endif // __MINGW32__
#elif 0 // defined(XP_MACOSX)
#include <malloc/malloc.h>
static void (*old_free)(struct _malloc_zone_t *zone, void *ptr);
static void
freehook(struct _malloc_zone_t *zone, void *ptr)
{
if (sCollector)
sCollector->Freed(ptr);
old_free(zone, ptr);
}
static void
InitMemHook(void)
{
if (!hookedMalloc) {
malloc_zone_t *default_zone = malloc_default_zone();
old_free = default_zone->free;
default_zone->free = freehook;
hookedMalloc = PR_TRUE;
}
}
#else
static void
InitMemHook(void)
{
}
#endif // GLIBC / WIN32 / OSX
#endif // DEBUG_CC
////////////////////////////////////////////////////////////////////////
// Collector implementation
////////////////////////////////////////////////////////////////////////
nsCycleCollector::nsCycleCollector() :
mCollectionInProgress(PR_FALSE),
mScanInProgress(PR_FALSE),
#ifdef DEBUG_CC
mPurpleBuf(mParams, mStats),
mPtrLog(nsnull)
#else
mPurpleBuf(mParams)
#endif
{
#ifdef DEBUG_CC
mExpectedGarbage.Init();
#endif
memset(mRuntimes, 0, sizeof(mRuntimes));
mRuntimes[nsIProgrammingLanguage::CPLUSPLUS] = &mXPCOMRuntime;
}
nsCycleCollector::~nsCycleCollector()
{
mGraph.Clear();
for (PRUint32 i = 0; i < nsIProgrammingLanguage::MAX+1; ++i) {
mRuntimes[i] = NULL;
}
}
void
nsCycleCollector::RegisterRuntime(PRUint32 langID,
nsCycleCollectionLanguageRuntime *rt)
{
if (mParams.mDoNothing)
return;
if (langID > nsIProgrammingLanguage::MAX)
Fault("unknown language runtime in registration");
if (mRuntimes[langID])
Fault("multiple registrations of language runtime", rt);
mRuntimes[langID] = rt;
}
void
nsCycleCollector::ForgetRuntime(PRUint32 langID)
{
if (mParams.mDoNothing)
return;
if (langID > nsIProgrammingLanguage::MAX)
Fault("unknown language runtime in deregistration");
if (! mRuntimes[langID])
Fault("forgetting non-registered language runtime");
mRuntimes[langID] = nsnull;
}
#ifdef DEBUG_CC
static PR_CALLBACK PLDHashOperator
FindAnyWhiteCallback(PLDHashTable *table, PLDHashEntryHdr *hdr, PRUint32 number,
void *arg)
{
PtrInfo *pinfo = (PtrInfo *) hdr;
if (pinfo->mColor == white) {
*NS_STATIC_CAST(PRBool*, arg) = PR_TRUE;
return PL_DHASH_STOP;
}
return PL_DHASH_NEXT;
}
void
nsCycleCollector::MaybeDrawGraphs()
{
if (mParams.mDrawGraphs) {
// We draw graphs only if there were any white nodes.
PRBool anyWhites = PR_FALSE;
mGraph.Enumerate(FindAnyWhiteCallback, &anyWhites);
if (anyWhites) {
graphVizWalker gw(mGraph, mRuntimes);
while (mBufs[0].GetSize() > 0) {
nsISupports *s = NS_STATIC_CAST(nsISupports *, mBufs[0].Pop());
s = canonicalize(s);
gw.Walk(s);
}
}
}
}
class Suppressor :
public nsCycleCollectionTraversalCallback
{
protected:
static char *sSuppressionList;
static PRBool sInitialized;
PRBool mSuppressThisNode;
public:
Suppressor()
{
}
PRBool shouldSuppress(nsISupports *s)
{
if (!sInitialized) {
sSuppressionList = PR_GetEnv("XPCOM_CC_SUPPRESS");
sInitialized = PR_TRUE;
}
if (sSuppressionList == nsnull) {
mSuppressThisNode = PR_FALSE;
} else {
nsresult rv;
nsCOMPtr<nsCycleCollectionParticipant> cp = do_QueryInterface(s, &rv);
if (NS_FAILED(rv)) {
Fault("checking suppression on wrong type of pointer", s);
return PR_TRUE;
}
cp->Traverse(s, *this);
}
return mSuppressThisNode;
}
void DescribeNode(size_t refCount, size_t objSz, const char *objName)
{
mSuppressThisNode = (PL_strstr(sSuppressionList, objName) != nsnull);
}
void NoteXPCOMChild(nsISupports *child) {}
void NoteScriptChild(PRUint32 langID, void *child) {}
};
char *Suppressor::sSuppressionList = nsnull;
PRBool Suppressor::sInitialized = PR_FALSE;
static PRBool
nsCycleCollector_shouldSuppress(nsISupports *s)
{
Suppressor supp;
return supp.shouldSuppress(s);
}
#endif
void
nsCycleCollector::Suspect(nsISupports *n, PRBool current)
{
// Re-entering ::Suspect during collection used to be a fault, but
// we are canonicalizing nsISupports pointers using QI, so we will
// see some spurious refcount traffic here.
if (mScanInProgress)
return;
NS_ASSERTION(nsCycleCollector_isScanSafe(n),
"suspected a non-scansafe pointer");
NS_ASSERTION(NS_IsMainThread(), "trying to suspect from non-main thread");
if (mParams.mDoNothing)
return;
#ifdef DEBUG_CC
mStats.mSuspectNode++;
if (nsCycleCollector_shouldSuppress(n))
return;
#ifndef __MINGW32__
if (mParams.mHookMalloc)
InitMemHook();
#endif
if (mParams.mLogPointers) {
if (!mPtrLog)
mPtrLog = fopen("pointer_log", "w");
fprintf(mPtrLog, "S %p\n", NS_STATIC_CAST(void*, n));
}
#endif
if (current)
mBufs[0].Push(n);
else
mPurpleBuf.Put(n);
}
void
nsCycleCollector::Forget(nsISupports *n)
{
// Re-entering ::Forget during collection used to be a fault, but
// we are canonicalizing nsISupports pointers using QI, so we will
// see some spurious refcount traffic here.
if (mScanInProgress)
return;
NS_ASSERTION(NS_IsMainThread(), "trying to forget from non-main thread");
if (mParams.mDoNothing)
return;
#ifdef DEBUG_CC
mStats.mForgetNode++;
#ifndef __MINGW32__
if (mParams.mHookMalloc)
InitMemHook();
#endif
if (mParams.mLogPointers) {
if (!mPtrLog)
mPtrLog = fopen("pointer_log", "w");
fprintf(mPtrLog, "F %p\n", NS_STATIC_CAST(void*, n));
}
#endif
mPurpleBuf.Remove(n);
}
#ifdef DEBUG_CC
void
nsCycleCollector::Allocated(void *n, size_t sz)
{
}
void
nsCycleCollector::Freed(void *n)
{
mStats.mFreeCalls++;
if (!n) {
// Ignore null pointers coming through
return;
}
if (mPurpleBuf.Exists(n)) {
mStats.mForgetNode++;
mStats.mFreedWhilePurple++;
Fault("freed while purple", n);
mPurpleBuf.Remove(n);
if (mParams.mLogPointers) {
if (!mPtrLog)
mPtrLog = fopen("pointer_log", "w");
fprintf(mPtrLog, "R %p\n", n);
}
}
}
#endif
void
nsCycleCollector::Collect(PRUint32 aTryCollections)
{
#if defined(DEBUG_CC) && !defined(__MINGW32__)
if (!mParams.mDoNothing && mParams.mHookMalloc)
InitMemHook();
#endif
#ifdef COLLECT_TIME_DEBUG
printf("cc: Starting nsCycleCollector::Collect(%d)\n", aTryCollections);
PRTime start = PR_Now(), now;
#endif
while (aTryCollections > 0) {
// This triggers a JS GC. Our caller assumes we always trigger at
// least one JS GC -- they rely on this fact to avoid redundant JS
// GC calls -- so it's essential that we actually execute this
// step!
//
// It is also essential to empty mBufs[0] here because starting up
// collection in language runtimes may force some "current" suspects
// into mBufs[0].
mBufs[0].Empty();
#ifdef COLLECT_TIME_DEBUG
now = PR_Now();
#endif
for (PRUint32 i = 0; i <= nsIProgrammingLanguage::MAX; ++i) {
if (mRuntimes[i])
mRuntimes[i]->BeginCycleCollection();
}
#ifdef COLLECT_TIME_DEBUG
printf("cc: mRuntimes[*]->BeginCycleCollection() took %lldms\n",
(PR_Now() - now) / PR_USEC_PER_MSEC);
#endif
if (mParams.mDoNothing) {
aTryCollections = 0;
} else {
#ifdef COLLECT_TIME_DEBUG
now = PR_Now();
#endif
CollectPurple();
#ifdef COLLECT_TIME_DEBUG
printf("cc: CollectPurple() took %lldms\n",
(PR_Now() - now) / PR_USEC_PER_MSEC);
#endif
if (mBufs[0].GetSize() == 0) {
aTryCollections = 0;
} else {
if (mCollectionInProgress)
Fault("re-entered collection");
mCollectionInProgress = PR_TRUE;
mScanInProgress = PR_TRUE;
mGraph.Clear();
// The main Bacon & Rajan collection algorithm.
#ifdef COLLECT_TIME_DEBUG
now = PR_Now();
#endif
MarkRoots();
#ifdef COLLECT_TIME_DEBUG
{
PRTime then = PR_Now();
printf("cc: MarkRoots() took %lldms\n",
(then - now) / PR_USEC_PER_MSEC);
now = then;
}
#endif
ScanRoots();
#ifdef COLLECT_TIME_DEBUG
printf("cc: ScanRoots() took %lldms\n",
(PR_Now() - now) / PR_USEC_PER_MSEC);
#endif
#ifdef DEBUG_CC
MaybeDrawGraphs();
#endif
mScanInProgress = PR_FALSE;
#ifdef COLLECT_TIME_DEBUG
now = PR_Now();
#endif
CollectWhite();
#ifdef COLLECT_TIME_DEBUG
printf("cc: CollectWhite() took %lldms\n",
(PR_Now() - now) / PR_USEC_PER_MSEC);
#endif
// Some additional book-keeping.
mGraph.Clear();
--aTryCollections;
}
mPurpleBuf.BumpGeneration();
#ifdef DEBUG_CC
mStats.mCollection++;
if (mParams.mReportStats)
mStats.Dump();
#endif
mCollectionInProgress = PR_FALSE;
}
for (PRUint32 i = 0; i <= nsIProgrammingLanguage::MAX; ++i) {
if (mRuntimes[i])
mRuntimes[i]->FinishCycleCollection();
}
}
#ifdef COLLECT_TIME_DEBUG
printf("cc: Collect() took %lldms\n",
(PR_Now() - start) / PR_USEC_PER_MSEC);
#endif
}
void
nsCycleCollector::Shutdown()
{
// Here we want to run a final collection on everything we've seen
// buffered, irrespective of age; then permanently disable
// the collector because the program is shutting down.
mPurpleBuf.BumpGeneration();
mParams.mScanDelay = 0;
Collect(SHUTDOWN_COLLECTIONS(mParams));
#ifdef DEBUG_CC
CollectPurple();
if (mBufs[0].GetSize() != 0) {
printf("Might have been able to release more cycles if the cycle collector would "
"run once more at shutdown.\n");
}
ExplainLiveExpectedGarbage();
#endif
mParams.mDoNothing = PR_TRUE;
}
#ifdef DEBUG_CC
PR_STATIC_CALLBACK(PLDHashOperator)
AddExpectedGarbage(nsVoidPtrHashKey *p, void *arg)
{
nsCycleCollector *c = NS_STATIC_CAST(nsCycleCollector*, arg);
c->mBufs[0].Push(NS_CONST_CAST(void*, p->GetKey()));
return PL_DHASH_NEXT;
}
struct explainWalker : public GraphWalker
{
explainWalker(GCTable &tab,
nsCycleCollectionLanguageRuntime **runtimes)
: GraphWalker(tab, runtimes)
{}
PRBool ShouldVisitNode(PtrInfo const *pi)
{
// We set them back to gray as we explain problems.
return pi->mColor != grey;
}
void VisitNode(PtrInfo *pi, size_t refcount)
{
if (pi->mColor == grey)
Fault("scanning grey node", pi->key);
if (pi->mColor == white) {
printf("nsCycleCollector: %s %p was not collected due to\n"
" missing call to suspect or failure to unlink\n",
pi->mName, pi->key);
}
if (pi->mInternalRefs != refcount) {
// Note that the external references may have been external
// to a different node in the cycle collection that just
// happened, if that different node was purple and then
// black.
printf("nsCycleCollector: %s %p was not collected due to %d\n"
" external references\n",
pi->mName, pi->key, refcount - pi->mInternalRefs);
}
pi->mColor = grey;
}
void NoteChild(PtrInfo *childpi) {}
};
void
nsCycleCollector::ExplainLiveExpectedGarbage()
{
if (mScanInProgress || mCollectionInProgress)
Fault("can't explain expected garbage during collection itself");
if (mParams.mDoNothing) {
printf("nsCycleCollector: not explaining expected garbage since\n"
" cycle collection disabled\n");
return;
}
for (PRUint32 i = 0; i <= nsIProgrammingLanguage::MAX; ++i) {
if (mRuntimes[i])
mRuntimes[i]->BeginCycleCollection();
}
mCollectionInProgress = PR_TRUE;
mScanInProgress = PR_TRUE;
mGraph.Clear();
mBufs[0].Empty();
// Instead of filling mBufs[0] from the purple buffer, we fill it
// from the list of nodes we were expected to collect.
mExpectedGarbage.EnumerateEntries(&AddExpectedGarbage, this);
MarkRoots();
ScanRoots();
mScanInProgress = PR_FALSE;
for (int i = 0; i < mBufs[0].GetSize(); ++i) {
nsISupports *s = NS_STATIC_CAST(nsISupports *, mBufs[0].ObjectAt(i));
s = canonicalize(s);
explainWalker(mGraph, mRuntimes).Walk(s);
}
mGraph.Clear();
mCollectionInProgress = PR_FALSE;
for (PRUint32 i = 0; i <= nsIProgrammingLanguage::MAX; ++i) {
if (mRuntimes[i])
mRuntimes[i]->FinishCycleCollection();
}
}
void
nsCycleCollector::ShouldBeFreed(nsISupports *n)
{
mExpectedGarbage.PutEntry(n);
}
void
nsCycleCollector::WasFreed(nsISupports *n)
{
mExpectedGarbage.RemoveEntry(n);
}
#endif
////////////////////////////////////////////////////////////////////////
// Module public API (exported in nsCycleCollector.h)
// Just functions that redirect into the singleton, once it's built.
////////////////////////////////////////////////////////////////////////
void
nsCycleCollector_registerRuntime(PRUint32 langID,
nsCycleCollectionLanguageRuntime *rt)
{
if (sCollector)
sCollector->RegisterRuntime(langID, rt);
}
void
nsCycleCollector_forgetRuntime(PRUint32 langID)
{
if (sCollector)
sCollector->ForgetRuntime(langID);
}
void
nsCycleCollector_suspect(nsISupports *n)
{
if (sCollector)
sCollector->Suspect(n);
}
void
nsCycleCollector_suspectCurrent(nsISupports *n)
{
if (sCollector)
sCollector->Suspect(n, PR_TRUE);
}
void
nsCycleCollector_forget(nsISupports *n)
{
if (sCollector)
sCollector->Forget(n);
}
void
nsCycleCollector_collect()
{
if (sCollector)
sCollector->Collect();
}
nsresult
nsCycleCollector_startup()
{
NS_ASSERTION(!sCollector, "Forgot to call nsCycleCollector_shutdown?");
sCollector = new nsCycleCollector();
return sCollector ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
}
void
nsCycleCollector_shutdown()
{
if (sCollector) {
sCollector->Shutdown();
delete sCollector;
sCollector = nsnull;
}
}
#ifdef DEBUG
void
nsCycleCollector_DEBUG_shouldBeFreed(nsISupports *n)
{
#ifdef DEBUG_CC
if (sCollector)
sCollector->ShouldBeFreed(n);
#endif
}
void
nsCycleCollector_DEBUG_wasFreed(nsISupports *n)
{
#ifdef DEBUG_CC
if (sCollector)
sCollector->WasFreed(n);
#endif
}
#endif
PRBool
nsCycleCollector_isScanSafe(nsISupports *s)
{
if (!s)
return PR_FALSE;
nsCycleCollectionParticipant *cp;
ToParticipant(s, &cp);
return cp != nsnull;
}
static void
ToParticipant(nsISupports *s, nsCycleCollectionParticipant **cp)
{
// We use QI to move from an nsISupports to an
// nsCycleCollectionParticipant, which is a per-class singleton helper
// object that implements traversal and unlinking logic for the nsISupports
// in question.
CallQueryInterface(s, cp);
#ifdef DEBUG_CC
if (cp)
++sCollector->mStats.mSuccessfulQI;
else
++sCollector->mStats.mFailedQI;
#endif
}
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