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tenfourfox/xpcom/base/CycleCollectedJSRuntime.cpp

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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/. */
// We're dividing JS objects into 3 categories:
//
// 1. "real" roots, held by the JS engine itself or rooted through the root
// and lock JS APIs. Roots from this category are considered black in the
// cycle collector, any cycle they participate in is uncollectable.
//
// 2. certain roots held by C++ objects that are guaranteed to be alive.
// Roots from this category are considered black in the cycle collector,
// and any cycle they participate in is uncollectable. These roots are
// traced from TraceNativeBlackRoots.
//
// 3. all other roots held by C++ objects that participate in cycle
// collection, held by us (see TraceNativeGrayRoots). Roots from this
// category are considered grey in the cycle collector; whether or not
// they are collected depends on the objects that hold them.
//
// Note that if a root is in multiple categories the fact that it is in
// category 1 or 2 that takes precedence, so it will be considered black.
//
// During garbage collection we switch to an additional mark color (gray)
// when tracing inside TraceNativeGrayRoots. This allows us to walk those
// roots later on and add all objects reachable only from them to the
// cycle collector.
//
// Phases:
//
// 1. marking of the roots in category 1 by having the JS GC do its marking
// 2. marking of the roots in category 2 by having the JS GC call us back
// (via JS_SetExtraGCRootsTracer) and running TraceNativeBlackRoots
// 3. marking of the roots in category 3 by TraceNativeGrayRoots using an
// additional color (gray).
// 4. end of GC, GC can sweep its heap
//
// At some later point, when the cycle collector runs:
//
// 5. walk gray objects and add them to the cycle collector, cycle collect
//
// JS objects that are part of cycles the cycle collector breaks will be
// collected by the next JS GC.
//
// If WantAllTraces() is false the cycle collector will not traverse roots
// from category 1 or any JS objects held by them. Any JS objects they hold
// will already be marked by the JS GC and will thus be colored black
// themselves. Any C++ objects they hold will have a missing (untraversed)
// edge from the JS object to the C++ object and so it will be marked black
// too. This decreases the number of objects that the cycle collector has to
// deal with.
// To improve debugging, if WantAllTraces() is true all JS objects are
// traversed.
#include "mozilla/CycleCollectedJSRuntime.h"
#include <algorithm>
#include "mozilla/ArrayUtils.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Snprintf.h"
#include "mozilla/DebuggerOnGCRunnable.h"
#include "mozilla/dom/DOMJSClass.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/ScriptSettings.h"
#include "jsprf.h"
#include "js/Debug.h"
#include "nsContentUtils.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollector.h"
#include "nsDOMJSUtils.h"
#include "nsJSUtils.h"
#ifdef MOZ_CRASHREPORTER
#include "nsExceptionHandler.h"
#endif
#include "nsIException.h"
#include "nsThread.h"
#include "nsThreadUtils.h"
#include "xpcpublic.h"
using namespace mozilla;
using namespace mozilla::dom;
namespace mozilla {
struct DeferredFinalizeFunctionHolder
{
DeferredFinalizeFunction run;
void* data;
};
class IncrementalFinalizeRunnable : public nsRunnable
{
typedef nsAutoTArray<DeferredFinalizeFunctionHolder, 16> DeferredFinalizeArray;
typedef CycleCollectedJSRuntime::DeferredFinalizerTable DeferredFinalizerTable;
CycleCollectedJSRuntime* mRuntime;
DeferredFinalizeArray mDeferredFinalizeFunctions;
uint32_t mFinalizeFunctionToRun;
bool mReleasing;
static const PRTime SliceMillis = 5; /* ms */
public:
IncrementalFinalizeRunnable(CycleCollectedJSRuntime* aRt,
DeferredFinalizerTable& aFinalizerTable);
virtual ~IncrementalFinalizeRunnable();
void ReleaseNow(bool aLimited);
NS_DECL_NSIRUNNABLE
};
} // namespace mozilla
struct NoteWeakMapChildrenTracer : public JS::CallbackTracer
{
NoteWeakMapChildrenTracer(JSRuntime* aRt,
nsCycleCollectionNoteRootCallback& aCb)
: JS::CallbackTracer(aRt), mCb(aCb), mTracedAny(false), mMap(nullptr),
mKey(nullptr), mKeyDelegate(nullptr)
{
}
void onChild(const JS::GCCellPtr& aThing) override;
nsCycleCollectionNoteRootCallback& mCb;
bool mTracedAny;
JSObject* mMap;
JS::GCCellPtr mKey;
JSObject* mKeyDelegate;
};
void
NoteWeakMapChildrenTracer::onChild(const JS::GCCellPtr& aThing)
{
if (aThing.is<JSString>()) {
return;
}
if (!JS::GCThingIsMarkedGray(aThing) && !mCb.WantAllTraces()) {
return;
}
if (AddToCCKind(aThing.kind())) {
mCb.NoteWeakMapping(mMap, mKey, mKeyDelegate, aThing);
mTracedAny = true;
} else {
JS::TraceChildren(this, aThing);
}
}
struct NoteWeakMapsTracer : public js::WeakMapTracer
{
NoteWeakMapsTracer(JSRuntime* aRt, nsCycleCollectionNoteRootCallback& aCccb)
: js::WeakMapTracer(aRt), mCb(aCccb), mChildTracer(aRt, aCccb)
{
}
void trace(JSObject* aMap, JS::GCCellPtr aKey, JS::GCCellPtr aValue) override;
nsCycleCollectionNoteRootCallback& mCb;
NoteWeakMapChildrenTracer mChildTracer;
};
void
NoteWeakMapsTracer::trace(JSObject* aMap, JS::GCCellPtr aKey,
JS::GCCellPtr aValue)
{
// If nothing that could be held alive by this entry is marked gray, return.
if ((!aKey || !JS::GCThingIsMarkedGray(aKey)) &&
MOZ_LIKELY(!mCb.WantAllTraces())) {
if (!aValue || !JS::GCThingIsMarkedGray(aValue) || aValue.is<JSString>()) {
return;
}
}
// The cycle collector can only properly reason about weak maps if it can
// reason about the liveness of their keys, which in turn requires that
// the key can be represented in the cycle collector graph. All existing
// uses of weak maps use either objects or scripts as keys, which are okay.
MOZ_ASSERT(AddToCCKind(aKey.kind()));
// As an emergency fallback for non-debug builds, if the key is not
// representable in the cycle collector graph, we treat it as marked. This
// can cause leaks, but is preferable to ignoring the binding, which could
// cause the cycle collector to free live objects.
if (!AddToCCKind(aKey.kind())) {
aKey = nullptr;
}
JSObject* kdelegate = nullptr;
if (aKey.is<JSObject>()) {
kdelegate = js::GetWeakmapKeyDelegate(&aKey.as<JSObject>());
}
if (AddToCCKind(aValue.kind())) {
mCb.NoteWeakMapping(aMap, aKey, kdelegate, aValue);
} else {
mChildTracer.mTracedAny = false;
mChildTracer.mMap = aMap;
mChildTracer.mKey = aKey;
mChildTracer.mKeyDelegate = kdelegate;
if (aValue.is<JSString>()) {
JS::TraceChildren(&mChildTracer, aValue);
}
// The delegate could hold alive the key, so report something to the CC
// if we haven't already.
if (!mChildTracer.mTracedAny &&
aKey && JS::GCThingIsMarkedGray(aKey) && kdelegate) {
mCb.NoteWeakMapping(aMap, aKey, kdelegate, nullptr);
}
}
}
// This is based on the logic in FixWeakMappingGrayBitsTracer::trace.
struct FixWeakMappingGrayBitsTracer : public js::WeakMapTracer
{
explicit FixWeakMappingGrayBitsTracer(JSRuntime* aRt)
: js::WeakMapTracer(aRt)
{
}
void
FixAll()
{
do {
mAnyMarked = false;
js::TraceWeakMaps(this);
} while (mAnyMarked);
}
void trace(JSObject* aMap, JS::GCCellPtr aKey, JS::GCCellPtr aValue) override
{
// If nothing that could be held alive by this entry is marked gray, return.
bool delegateMightNeedMarking = aKey && JS::GCThingIsMarkedGray(aKey);
bool valueMightNeedMarking = aValue && JS::GCThingIsMarkedGray(aValue) &&
aValue.kind() != JS::TraceKind::String;
if (!delegateMightNeedMarking && !valueMightNeedMarking) {
return;
}
if (!AddToCCKind(aKey.kind())) {
aKey = nullptr;
}
if (delegateMightNeedMarking && aKey.is<JSObject>()) {
JSObject* kdelegate = js::GetWeakmapKeyDelegate(&aKey.as<JSObject>());
if (kdelegate && !JS::ObjectIsMarkedGray(kdelegate)) {
if (JS::UnmarkGrayGCThingRecursively(aKey)) {
mAnyMarked = true;
}
}
}
if (aValue && JS::GCThingIsMarkedGray(aValue) &&
(!aKey || !JS::GCThingIsMarkedGray(aKey)) &&
(!aMap || !JS::ObjectIsMarkedGray(aMap)) &&
aValue.kind() != JS::TraceKind::Shape) {
if (JS::UnmarkGrayGCThingRecursively(aValue)) {
mAnyMarked = true;
}
}
}
bool mAnyMarked;
};
static void
CheckParticipatesInCycleCollection(JS::GCCellPtr aThing, const char* aName,
void* aClosure)
{
bool* cycleCollectionEnabled = static_cast<bool*>(aClosure);
if (*cycleCollectionEnabled) {
return;
}
if (AddToCCKind(aThing.kind()) && JS::GCThingIsMarkedGray(aThing)) {
*cycleCollectionEnabled = true;
}
}
NS_IMETHODIMP
JSGCThingParticipant::Traverse(void* aPtr,
nsCycleCollectionTraversalCallback& aCb)
{
auto runtime = reinterpret_cast<CycleCollectedJSRuntime*>(
reinterpret_cast<char*>(this) - offsetof(CycleCollectedJSRuntime,
mGCThingCycleCollectorGlobal));
JS::GCCellPtr cellPtr(aPtr, js::GCThingTraceKind(aPtr));
runtime->TraverseGCThing(CycleCollectedJSRuntime::TRAVERSE_FULL, cellPtr, aCb);
return NS_OK;
}
// NB: This is only used to initialize the participant in
// CycleCollectedJSRuntime. It should never be used directly.
static JSGCThingParticipant sGCThingCycleCollectorGlobal;
NS_IMETHODIMP
JSZoneParticipant::Traverse(void* aPtr, nsCycleCollectionTraversalCallback& aCb)
{
auto runtime = reinterpret_cast<CycleCollectedJSRuntime*>(
reinterpret_cast<char*>(this) - offsetof(CycleCollectedJSRuntime,
mJSZoneCycleCollectorGlobal));
MOZ_ASSERT(!aCb.WantAllTraces());
JS::Zone* zone = static_cast<JS::Zone*>(aPtr);
runtime->TraverseZone(zone, aCb);
return NS_OK;
}
struct TraversalTracer : public JS::CallbackTracer
{
TraversalTracer(JSRuntime* aRt, nsCycleCollectionTraversalCallback& aCb)
: JS::CallbackTracer(aRt, DoNotTraceWeakMaps), mCb(aCb)
{
}
void onChild(const JS::GCCellPtr& aThing) override;
nsCycleCollectionTraversalCallback& mCb;
};
void
TraversalTracer::onChild(const JS::GCCellPtr& aThing)
{
// Don't traverse non-gray objects, unless we want all traces.
if (!JS::GCThingIsMarkedGray(aThing) && !mCb.WantAllTraces()) {
return;
}
/*
* This function needs to be careful to avoid stack overflow. Normally, when
* AddToCCKind is true, the recursion terminates immediately as we just add
* |thing| to the CC graph. So overflow is only possible when there are long
* or cyclic chains of non-AddToCCKind GC things. Places where this can occur
* use special APIs to handle such chains iteratively.
*/
if (AddToCCKind(aThing.kind())) {
if (MOZ_UNLIKELY(mCb.WantDebugInfo())) {
char buffer[200];
getTracingEdgeName(buffer, sizeof(buffer));
mCb.NoteNextEdgeName(buffer);
}
if (aThing.is<JSObject>()) {
mCb.NoteJSObject(&aThing.as<JSObject>());
} else {
mCb.NoteJSScript(&aThing.as<JSScript>());
}
} else if (aThing.is<js::Shape>()) {
// The maximum depth of traversal when tracing a Shape is unbounded, due to
// the parent pointers on the shape.
JS_TraceShapeCycleCollectorChildren(this, aThing);
} else if (aThing.is<js::ObjectGroup>()) {
// The maximum depth of traversal when tracing an ObjectGroup is unbounded,
// due to information attached to the groups which can lead other groups to
// be traced.
JS_TraceObjectGroupCycleCollectorChildren(this, aThing);
} else if (!aThing.is<JSString>()) {
JS::TraceChildren(this, aThing);
}
}
static void
NoteJSChildGrayWrapperShim(void* aData, JS::GCCellPtr aThing)
{
TraversalTracer* trc = static_cast<TraversalTracer*>(aData);
trc->onChild(aThing);
}
/*
* The cycle collection participant for a Zone is intended to produce the same
* results as if all of the gray GCthings in a zone were merged into a single node,
* except for self-edges. This avoids the overhead of representing all of the GCthings in
* the zone in the cycle collector graph, which should be much faster if many of
* the GCthings in the zone are gray.
*
* Zone merging should not always be used, because it is a conservative
* approximation of the true cycle collector graph that can incorrectly identify some
* garbage objects as being live. For instance, consider two cycles that pass through a
* zone, where one is garbage and the other is live. If we merge the entire
* zone, the cycle collector will think that both are alive.
*
* We don't have to worry about losing track of a garbage cycle, because any such garbage
* cycle incorrectly identified as live must contain at least one C++ to JS edge, and
* XPConnect will always add the C++ object to the CC graph. (This is in contrast to pure
* C++ garbage cycles, which must always be properly identified, because we clear the
* purple buffer during every CC, which may contain the last reference to a garbage
* cycle.)
*/
// NB: This is only used to initialize the participant in
// CycleCollectedJSRuntime. It should never be used directly.
static const JSZoneParticipant sJSZoneCycleCollectorGlobal;
CycleCollectedJSRuntime::CycleCollectedJSRuntime(JSRuntime* aParentRuntime,
uint32_t aMaxBytes,
uint32_t aMaxNurseryBytes)
: mGCThingCycleCollectorGlobal(sGCThingCycleCollectorGlobal)
, mJSZoneCycleCollectorGlobal(sJSZoneCycleCollectorGlobal)
, mJSRuntime(nullptr)
, mPrevGCSliceCallback(nullptr)
, mJSHolders(256)
, mDoingStableStates(false)
, mOutOfMemoryState(OOMState::OK)
, mLargeAllocationFailureState(OOMState::OK)
{
nsCOMPtr<nsIThread> thread = do_GetCurrentThread();
mOwningThread = thread.forget().downcast<nsThread>().take();
MOZ_RELEASE_ASSERT(mOwningThread);
mOwningThread->SetScriptObserver(this);
// The main thread has a base recursion depth of 0, workers of 1.
mBaseRecursionDepth = RecursionDepth();
mozilla::dom::InitScriptSettings();
mJSRuntime = JS_NewRuntime(aMaxBytes, aMaxNurseryBytes, aParentRuntime);
if (!mJSRuntime) {
MOZ_CRASH();
}
if (!JS_AddExtraGCRootsTracer(mJSRuntime, TraceBlackJS, this)) {
MOZ_CRASH();
}
JS_SetGrayGCRootsTracer(mJSRuntime, TraceGrayJS, this);
JS_SetGCCallback(mJSRuntime, GCCallback, this);
mPrevGCSliceCallback = JS::SetGCSliceCallback(mJSRuntime, GCSliceCallback);
JS::SetOutOfMemoryCallback(mJSRuntime, OutOfMemoryCallback, this);
JS::SetLargeAllocationFailureCallback(mJSRuntime,
LargeAllocationFailureCallback, this);
JS_SetContextCallback(mJSRuntime, ContextCallback, this);
JS_SetDestroyZoneCallback(mJSRuntime, XPCStringConvert::FreeZoneCache);
JS_SetSweepZoneCallback(mJSRuntime, XPCStringConvert::ClearZoneCache);
static js::DOMCallbacks DOMcallbacks = {
InstanceClassHasProtoAtDepth
};
SetDOMCallbacks(mJSRuntime, &DOMcallbacks);
JS::dbg::SetDebuggerMallocSizeOf(mJSRuntime, moz_malloc_size_of);
nsCycleCollector_registerJSRuntime(this);
}
CycleCollectedJSRuntime::~CycleCollectedJSRuntime()
{
MOZ_ASSERT(mJSRuntime);
MOZ_ASSERT(!mDeferredFinalizerTable.Count());
// Last chance to process any events.
ProcessMetastableStateQueue(mBaseRecursionDepth);
MOZ_ASSERT(mMetastableStateEvents.IsEmpty());
ProcessStableStateQueue();
MOZ_ASSERT(mStableStateEvents.IsEmpty());
// Clear mPendingException first, since it might be cycle collected.
mPendingException = nullptr;
JS_DestroyRuntime(mJSRuntime);
mJSRuntime = nullptr;
nsCycleCollector_forgetJSRuntime();
mozilla::dom::DestroyScriptSettings();
mOwningThread->SetScriptObserver(nullptr);
NS_RELEASE(mOwningThread);
}
size_t
CycleCollectedJSRuntime::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const
{
size_t n = 0;
// We're deliberately not measuring anything hanging off the entries in
// mJSHolders.
n += mJSHolders.ShallowSizeOfExcludingThis(aMallocSizeOf);
return n;
}
void
CycleCollectedJSRuntime::UnmarkSkippableJSHolders()
{
for (auto iter = mJSHolders.Iter(); !iter.Done(); iter.Next()) {
void* holder = iter.Key();
nsScriptObjectTracer*& tracer = iter.Data();
tracer->CanSkip(holder, true);
}
}
void
CycleCollectedJSRuntime::DescribeGCThing(bool aIsMarked, JS::GCCellPtr aThing,
nsCycleCollectionTraversalCallback& aCb) const
{
if (!aCb.WantDebugInfo()) {
aCb.DescribeGCedNode(aIsMarked, "JS Object");
return;
}
char name[72];
uint64_t compartmentAddress = 0;
if (aThing.is<JSObject>()) {
JSObject* obj = &aThing.as<JSObject>();
compartmentAddress = (uint64_t)js::GetObjectCompartment(obj);
const js::Class* clasp = js::GetObjectClass(obj);
// Give the subclass a chance to do something
if (DescribeCustomObjects(obj, clasp, name)) {
// Nothing else to do!
} else if (js::IsFunctionObject(obj)) {
JSFunction* fun = JS_GetObjectFunction(obj);
JSString* str = JS_GetFunctionDisplayId(fun);
if (str) {
JSFlatString* flat = JS_ASSERT_STRING_IS_FLAT(str);
nsAutoString chars;
AssignJSFlatString(chars, flat);
NS_ConvertUTF16toUTF8 fname(chars);
snprintf_literal(name, "JS Object (Function - %s)", fname.get());
} else {
snprintf_literal(name, "JS Object (Function)");
}
} else {
snprintf_literal(name, "JS Object (%s)", clasp->name);
}
} else {
snprintf_literal(name, "JS %s", JS::GCTraceKindToAscii(aThing.kind()));
}
// Disable printing global for objects while we figure out ObjShrink fallout.
aCb.DescribeGCedNode(aIsMarked, name, compartmentAddress);
}
void
CycleCollectedJSRuntime::NoteGCThingJSChildren(JS::GCCellPtr aThing,
nsCycleCollectionTraversalCallback& aCb) const
{
MOZ_ASSERT(mJSRuntime);
TraversalTracer trc(mJSRuntime, aCb);
JS::TraceChildren(&trc, aThing);
}
void
CycleCollectedJSRuntime::NoteGCThingXPCOMChildren(const js::Class* aClasp,
JSObject* aObj,
nsCycleCollectionTraversalCallback& aCb) const
{
MOZ_ASSERT(aClasp);
MOZ_ASSERT(aClasp == js::GetObjectClass(aObj));
if (NoteCustomGCThingXPCOMChildren(aClasp, aObj, aCb)) {
// Nothing else to do!
return;
}
// XXX This test does seem fragile, we should probably whitelist classes
// that do hold a strong reference, but that might not be possible.
else if (aClasp->flags & JSCLASS_HAS_PRIVATE &&
aClasp->flags & JSCLASS_PRIVATE_IS_NSISUPPORTS) {
NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "js::GetObjectPrivate(obj)");
aCb.NoteXPCOMChild(static_cast<nsISupports*>(js::GetObjectPrivate(aObj)));
} else {
const DOMJSClass* domClass = GetDOMClass(aObj);
if (domClass) {
NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "UnwrapDOMObject(obj)");
// It's possible that our object is an unforgeable holder object, in
// which case it doesn't actually have a C++ DOM object associated with
// it. Use UnwrapPossiblyNotInitializedDOMObject, which produces null in
// that case, since NoteXPCOMChild/NoteNativeChild are null-safe.
if (domClass->mDOMObjectIsISupports) {
aCb.NoteXPCOMChild(UnwrapPossiblyNotInitializedDOMObject<nsISupports>(aObj));
} else if (domClass->mParticipant) {
aCb.NoteNativeChild(UnwrapPossiblyNotInitializedDOMObject<void>(aObj),
domClass->mParticipant);
}
}
}
}
void
CycleCollectedJSRuntime::TraverseGCThing(TraverseSelect aTs, JS::GCCellPtr aThing,
nsCycleCollectionTraversalCallback& aCb)
{
bool isMarkedGray = JS::GCThingIsMarkedGray(aThing);
if (aTs == TRAVERSE_FULL) {
DescribeGCThing(!isMarkedGray, aThing, aCb);
}
// If this object is alive, then all of its children are alive. For JS objects,
// the black-gray invariant ensures the children are also marked black. For C++
// objects, the ref count from this object will keep them alive. Thus we don't
// need to trace our children, unless we are debugging using WantAllTraces.
if (!isMarkedGray && !aCb.WantAllTraces()) {
return;
}
if (aTs == TRAVERSE_FULL) {
NoteGCThingJSChildren(aThing, aCb);
}
if (aThing.is<JSObject>()) {
JSObject* obj = &aThing.as<JSObject>();
NoteGCThingXPCOMChildren(js::GetObjectClass(obj), obj, aCb);
}
}
struct TraverseObjectShimClosure
{
nsCycleCollectionTraversalCallback& cb;
CycleCollectedJSRuntime* self;
};
void
CycleCollectedJSRuntime::TraverseZone(JS::Zone* aZone,
nsCycleCollectionTraversalCallback& aCb)
{
/*
* We treat the zone as being gray. We handle non-gray GCthings in the
* zone by not reporting their children to the CC. The black-gray invariant
* ensures that any JS children will also be non-gray, and thus don't need to be
* added to the graph. For C++ children, not representing the edge from the
* non-gray JS GCthings to the C++ object will keep the child alive.
*
* We don't allow zone merging in a WantAllTraces CC, because then these
* assumptions don't hold.
*/
aCb.DescribeGCedNode(false, "JS Zone");
/*
* Every JS child of everything in the zone is either in the zone
* or is a cross-compartment wrapper. In the former case, we don't need to
* represent these edges in the CC graph because JS objects are not ref counted.
* In the latter case, the JS engine keeps a map of these wrappers, which we
* iterate over. Edges between compartments in the same zone will add
* unnecessary loop edges to the graph (bug 842137).
*/
TraversalTracer trc(mJSRuntime, aCb);
js::VisitGrayWrapperTargets(aZone, NoteJSChildGrayWrapperShim, &trc);
/*
* To find C++ children of things in the zone, we scan every JS Object in
* the zone. Only JS Objects can have C++ children.
*/
TraverseObjectShimClosure closure = { aCb, this };
js::IterateGrayObjects(aZone, TraverseObjectShim, &closure);
}
/* static */ void
CycleCollectedJSRuntime::TraverseObjectShim(void* aData, JS::GCCellPtr aThing)
{
TraverseObjectShimClosure* closure =
static_cast<TraverseObjectShimClosure*>(aData);
MOZ_ASSERT(aThing.is<JSObject>());
closure->self->TraverseGCThing(CycleCollectedJSRuntime::TRAVERSE_CPP,
aThing, closure->cb);
}
void
CycleCollectedJSRuntime::TraverseNativeRoots(nsCycleCollectionNoteRootCallback& aCb)
{
// NB: This is here just to preserve the existing XPConnect order. I doubt it
// would hurt to do this after the JS holders.
TraverseAdditionalNativeRoots(aCb);
for (auto iter = mJSHolders.Iter(); !iter.Done(); iter.Next()) {
void* holder = iter.Key();
nsScriptObjectTracer*& tracer = iter.Data();
bool noteRoot = false;
if (MOZ_UNLIKELY(aCb.WantAllTraces())) {
noteRoot = true;
} else {
tracer->Trace(holder,
TraceCallbackFunc(CheckParticipatesInCycleCollection),
&noteRoot);
}
if (noteRoot) {
aCb.NoteNativeRoot(holder, tracer);
}
}
}
/* static */ void
CycleCollectedJSRuntime::TraceBlackJS(JSTracer* aTracer, void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
self->TraceNativeBlackRoots(aTracer);
}
/* static */ void
CycleCollectedJSRuntime::TraceGrayJS(JSTracer* aTracer, void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
// Mark these roots as gray so the CC can walk them later.
self->TraceNativeGrayRoots(aTracer);
}
/* static */ void
CycleCollectedJSRuntime::GCCallback(JSRuntime* aRuntime,
JSGCStatus aStatus,
void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(aRuntime == self->Runtime());
self->OnGC(aStatus);
}
/* static */ void
CycleCollectedJSRuntime::GCSliceCallback(JSRuntime* aRuntime,
JS::GCProgress aProgress,
const JS::GCDescription& aDesc)
{
CycleCollectedJSRuntime* self = CycleCollectedJSRuntime::Get();
MOZ_ASSERT(self->Runtime() == aRuntime);
if (aProgress == JS::GC_CYCLE_END) {
JS::gcreason::Reason reason = aDesc.reason_;
NS_WARN_IF(NS_FAILED(DebuggerOnGCRunnable::Enqueue(aRuntime, aDesc)) &&
reason != JS::gcreason::SHUTDOWN_CC &&
reason != JS::gcreason::DESTROY_RUNTIME &&
reason != JS::gcreason::XPCONNECT_SHUTDOWN);
}
if (self->mPrevGCSliceCallback) {
self->mPrevGCSliceCallback(aRuntime, aProgress, aDesc);
}
}
/* static */ void
CycleCollectedJSRuntime::OutOfMemoryCallback(JSContext* aContext,
void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(JS_GetRuntime(aContext) == self->Runtime());
self->OnOutOfMemory();
}
/* static */ void
CycleCollectedJSRuntime::LargeAllocationFailureCallback(void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
self->OnLargeAllocationFailure();
}
/* static */ bool
CycleCollectedJSRuntime::ContextCallback(JSContext* aContext,
unsigned aOperation,
void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(JS_GetRuntime(aContext) == self->Runtime());
return self->CustomContextCallback(aContext, aOperation);
}
struct JsGcTracer : public TraceCallbacks
{
virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallValueTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallIdTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallObjectTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallTenuredObjectTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallStringTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallScriptTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName,
void* aClosure) const override
{
JS_CallFunctionTracer(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
};
void
mozilla::TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer)
{
nsXPCOMCycleCollectionParticipant* participant = nullptr;
CallQueryInterface(aHolder, &participant);
participant->Trace(aHolder, JsGcTracer(), aTracer);
}
void
CycleCollectedJSRuntime::TraceNativeGrayRoots(JSTracer* aTracer)
{
// NB: This is here just to preserve the existing XPConnect order. I doubt it
// would hurt to do this after the JS holders.
TraceAdditionalNativeGrayRoots(aTracer);
for (auto iter = mJSHolders.Iter(); !iter.Done(); iter.Next()) {
void* holder = iter.Key();
nsScriptObjectTracer*& tracer = iter.Data();
tracer->Trace(holder, JsGcTracer(), aTracer);
}
}
void
CycleCollectedJSRuntime::AddJSHolder(void* aHolder, nsScriptObjectTracer* aTracer)
{
mJSHolders.Put(aHolder, aTracer);
}
struct ClearJSHolder : TraceCallbacks
{
virtual void Trace(JS::Heap<JS::Value>* aPtr, const char*, void*) const override
{
aPtr->setUndefined();
}
virtual void Trace(JS::Heap<jsid>* aPtr, const char*, void*) const override
{
*aPtr = JSID_VOID;
}
virtual void Trace(JS::Heap<JSObject*>* aPtr, const char*, void*) const override
{
*aPtr = nullptr;
}
virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char*, void*) const override
{
*aPtr = nullptr;
}
virtual void Trace(JS::Heap<JSString*>* aPtr, const char*, void*) const override
{
*aPtr = nullptr;
}
virtual void Trace(JS::Heap<JSScript*>* aPtr, const char*, void*) const override
{
*aPtr = nullptr;
}
virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char*, void*) const override
{
*aPtr = nullptr;
}
};
void
CycleCollectedJSRuntime::RemoveJSHolder(void* aHolder)
{
nsScriptObjectTracer* tracer = mJSHolders.Get(aHolder);
if (!tracer) {
return;
}
tracer->Trace(aHolder, ClearJSHolder(), nullptr);
mJSHolders.Remove(aHolder);
}
#ifdef DEBUG
bool
CycleCollectedJSRuntime::IsJSHolder(void* aHolder)
{
return mJSHolders.Get(aHolder, nullptr);
}
static void
AssertNoGcThing(JS::GCCellPtr aGCThing, const char* aName, void* aClosure)
{
MOZ_ASSERT(!aGCThing);
}
void
CycleCollectedJSRuntime::AssertNoObjectsToTrace(void* aPossibleJSHolder)
{
nsScriptObjectTracer* tracer = mJSHolders.Get(aPossibleJSHolder);
if (tracer) {
tracer->Trace(aPossibleJSHolder, TraceCallbackFunc(AssertNoGcThing), nullptr);
}
}
#endif
already_AddRefed<nsIException>
CycleCollectedJSRuntime::GetPendingException() const
{
nsCOMPtr<nsIException> out = mPendingException;
return out.forget();
}
void
CycleCollectedJSRuntime::SetPendingException(nsIException* aException)
{
mPendingException = aException;
}
std::queue<nsCOMPtr<nsIRunnable>>&
CycleCollectedJSRuntime::GetPromiseMicroTaskQueue()
{
return mPromiseMicroTaskQueue;
}
nsCycleCollectionParticipant*
CycleCollectedJSRuntime::GCThingParticipant()
{
return &mGCThingCycleCollectorGlobal;
}
nsCycleCollectionParticipant*
CycleCollectedJSRuntime::ZoneParticipant()
{
return &mJSZoneCycleCollectorGlobal;
}
nsresult
CycleCollectedJSRuntime::TraverseRoots(nsCycleCollectionNoteRootCallback& aCb)
{
TraverseNativeRoots(aCb);
NoteWeakMapsTracer trc(mJSRuntime, aCb);
js::TraceWeakMaps(&trc);
return NS_OK;
}
/*
* Return true if there exists a JSContext with a default global whose current
* inner is gray. The intent is to look for JS Object windows. We don't merge
* system compartments, so we don't use them to trigger merging CCs.
*/
bool
CycleCollectedJSRuntime::UsefulToMergeZones() const
{
if (!NS_IsMainThread()) {
return false;
}
JSContext* iter = nullptr;
JSContext* cx;
JSAutoRequest ar(nsContentUtils::GetSafeJSContext());
while ((cx = JS_ContextIterator(mJSRuntime, &iter))) {
// Skip anything without an nsIScriptContext.
nsIScriptContext* scx = GetScriptContextFromJSContext(cx);
JS::RootedObject obj(cx, scx ? scx->GetWindowProxyPreserveColor() : nullptr);
if (!obj) {
continue;
}
MOZ_ASSERT(js::IsWindowProxy(obj));
// Grab the global from the WindowProxy.
obj = js::ToWindowIfWindowProxy(obj);
MOZ_ASSERT(JS_IsGlobalObject(obj));
if (JS::ObjectIsMarkedGray(obj) &&
!js::IsSystemCompartment(js::GetObjectCompartment(obj))) {
return true;
}
}
return false;
}
void
CycleCollectedJSRuntime::FixWeakMappingGrayBits() const
{
MOZ_ASSERT(!JS::IsIncrementalGCInProgress(mJSRuntime),
"Don't call FixWeakMappingGrayBits during a GC.");
FixWeakMappingGrayBitsTracer fixer(mJSRuntime);
fixer.FixAll();
}
bool
CycleCollectedJSRuntime::AreGCGrayBitsValid() const
{
return js::AreGCGrayBitsValid(mJSRuntime);
}
void
CycleCollectedJSRuntime::GarbageCollect(uint32_t aReason) const
{
MOZ_ASSERT(aReason < JS::gcreason::NUM_REASONS);
JS::gcreason::Reason gcreason = static_cast<JS::gcreason::Reason>(aReason);
JS::PrepareForFullGC(mJSRuntime);
JS::GCForReason(mJSRuntime, GC_NORMAL, gcreason);
}
void
CycleCollectedJSRuntime::DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
DeferredFinalizeFunction aFunc,
void* aThing)
{
void* thingArray = nullptr;
bool hadThingArray = mDeferredFinalizerTable.Get(aFunc, &thingArray);
thingArray = aAppendFunc(thingArray, aThing);
if (!hadThingArray) {
mDeferredFinalizerTable.Put(aFunc, thingArray);
}
}
void
CycleCollectedJSRuntime::DeferredFinalize(nsISupports* aSupports)
{
typedef DeferredFinalizerImpl<nsISupports> Impl;
DeferredFinalize(Impl::AppendDeferredFinalizePointer, Impl::DeferredFinalize,
aSupports);
}
void
CycleCollectedJSRuntime::DumpJSHeap(FILE* aFile)
{
js::DumpHeap(Runtime(), aFile, js::CollectNurseryBeforeDump);
}
void
CycleCollectedJSRuntime::ProcessStableStateQueue()
{
MOZ_RELEASE_ASSERT(!mDoingStableStates);
mDoingStableStates = true;
for (uint32_t i = 0; i < mStableStateEvents.Length(); ++i) {
nsCOMPtr<nsIRunnable> event = mStableStateEvents[i].forget();
event->Run();
}
mStableStateEvents.Clear();
mDoingStableStates = false;
}
void
CycleCollectedJSRuntime::ProcessMetastableStateQueue(uint32_t aRecursionDepth)
{
MOZ_RELEASE_ASSERT(!mDoingStableStates);
mDoingStableStates = true;
nsTArray<RunInMetastableStateData> localQueue = Move(mMetastableStateEvents);
for (uint32_t i = 0; i < localQueue.Length(); ++i)
{
RunInMetastableStateData& data = localQueue[i];
if (data.mRecursionDepth != aRecursionDepth) {
continue;
}
{
nsCOMPtr<nsIRunnable> runnable = data.mRunnable.forget();
runnable->Run();
}
localQueue.RemoveElementAt(i--);
}
// If the queue has events in it now, they were added from something we called,
// so they belong at the end of the queue.
localQueue.AppendElements(mMetastableStateEvents);
localQueue.SwapElements(mMetastableStateEvents);
mDoingStableStates = false;
}
void
CycleCollectedJSRuntime::AfterProcessTask(uint32_t aRecursionDepth)
{
// See HTML 6.1.4.2 Processing model
// Execute any events that were waiting for a microtask to complete.
// This is not (yet) in the spec.
ProcessMetastableStateQueue(aRecursionDepth);
// Step 4.1: Execute microtasks.
if (NS_IsMainThread()) {
nsContentUtils::PerformMainThreadMicroTaskCheckpoint();
}
Promise::PerformMicroTaskCheckpoint();
// Step 4.2 Execute any events that were waiting for a stable state.
ProcessStableStateQueue();
}
void
CycleCollectedJSRuntime::AfterProcessMicrotask()
{
AfterProcessMicrotask(RecursionDepth());
}
void
CycleCollectedJSRuntime::AfterProcessMicrotask(uint32_t aRecursionDepth)
{
// Between microtasks, execute any events that were waiting for a microtask
// to complete.
ProcessMetastableStateQueue(aRecursionDepth);
}
uint32_t
CycleCollectedJSRuntime::RecursionDepth()
{
return mOwningThread->RecursionDepth();
}
void
CycleCollectedJSRuntime::RunInStableState(already_AddRefed<nsIRunnable>&& aRunnable)
{
MOZ_ASSERT(mJSRuntime);
mStableStateEvents.AppendElement(Move(aRunnable));
}
void
CycleCollectedJSRuntime::RunInMetastableState(already_AddRefed<nsIRunnable>&& aRunnable)
{
RunInMetastableStateData data;
data.mRunnable = aRunnable;
MOZ_ASSERT(mOwningThread);
data.mRecursionDepth = RecursionDepth();
// There must be an event running to get here.
#ifndef MOZ_WIDGET_COCOA
MOZ_ASSERT(data.mRecursionDepth > mBaseRecursionDepth);
#endif
mMetastableStateEvents.AppendElement(Move(data));
}
IncrementalFinalizeRunnable::IncrementalFinalizeRunnable(CycleCollectedJSRuntime* aRt,
DeferredFinalizerTable& aFinalizers)
: mRuntime(aRt)
, mFinalizeFunctionToRun(0)
, mReleasing(false)
{
for (auto iter = aFinalizers.Iter(); !iter.Done(); iter.Next()) {
DeferredFinalizeFunction& function = iter.Key();
void*& data = iter.Data();
DeferredFinalizeFunctionHolder* holder =
mDeferredFinalizeFunctions.AppendElement();
holder->run = function;
holder->data = data;
iter.Remove();
}
}
IncrementalFinalizeRunnable::~IncrementalFinalizeRunnable()
{
MOZ_ASSERT(this != mRuntime->mFinalizeRunnable);
}
void
IncrementalFinalizeRunnable::ReleaseNow(bool aLimited)
{
if (mReleasing) {
NS_WARNING("Re-entering ReleaseNow");
return;
}
{
mozilla::AutoRestore<bool> ar(mReleasing);
mReleasing = true;
MOZ_ASSERT(mDeferredFinalizeFunctions.Length() != 0,
"We should have at least ReleaseSliceNow to run");
MOZ_ASSERT(mFinalizeFunctionToRun < mDeferredFinalizeFunctions.Length(),
"No more finalizers to run?");
TimeDuration sliceTime = TimeDuration::FromMilliseconds(SliceMillis);
TimeStamp started = TimeStamp::Now();
bool timeout = false;
do {
const DeferredFinalizeFunctionHolder& function =
mDeferredFinalizeFunctions[mFinalizeFunctionToRun];
if (aLimited) {
bool done = false;
while (!timeout && !done) {
/*
* We don't want to read the clock too often, so we try to
* release slices of 100 items.
*/
done = function.run(100, function.data);
timeout = TimeStamp::Now() - started >= sliceTime;
}
if (done) {
++mFinalizeFunctionToRun;
}
if (timeout) {
break;
}
} else {
while (!function.run(UINT32_MAX, function.data));
++mFinalizeFunctionToRun;
}
} while (mFinalizeFunctionToRun < mDeferredFinalizeFunctions.Length());
}
if (mFinalizeFunctionToRun == mDeferredFinalizeFunctions.Length()) {
MOZ_ASSERT(mRuntime->mFinalizeRunnable == this);
mDeferredFinalizeFunctions.Clear();
// NB: This may delete this!
mRuntime->mFinalizeRunnable = nullptr;
}
}
NS_IMETHODIMP
IncrementalFinalizeRunnable::Run()
{
if (mRuntime->mFinalizeRunnable != this) {
/* These items were already processed synchronously in JSGC_END. */
MOZ_ASSERT(!mDeferredFinalizeFunctions.Length());
return NS_OK;
}
#if(0)
TimeStamp start = TimeStamp::Now();
#endif
ReleaseNow(true);
if (mDeferredFinalizeFunctions.Length()) {
nsresult rv = NS_DispatchToCurrentThread(this);
if (NS_FAILED(rv)) {
ReleaseNow(false);
}
}
#if(0)
uint32_t duration = (uint32_t)((TimeStamp::Now() - start).ToMilliseconds());
#endif
return NS_OK;
}
void
CycleCollectedJSRuntime::FinalizeDeferredThings(DeferredFinalizeType aType)
{
/*
* If the previous GC created a runnable to finalize objects
* incrementally, and if it hasn't finished yet, finish it now. We
* don't want these to build up. We also don't want to allow any
* existing incremental finalize runnables to run after a
* non-incremental GC, since they are often used to detect leaks.
*/
if (mFinalizeRunnable) {
mFinalizeRunnable->ReleaseNow(false);
if (mFinalizeRunnable) {
// If we re-entered ReleaseNow, we couldn't delete mFinalizeRunnable and
// we need to just continue processing it.
return;
}
}
if (mDeferredFinalizerTable.Count() == 0) {
return;
}
mFinalizeRunnable = new IncrementalFinalizeRunnable(this,
mDeferredFinalizerTable);
// Everything should be gone now.
MOZ_ASSERT(mDeferredFinalizerTable.Count() == 0);
if (aType == FinalizeIncrementally) {
NS_DispatchToCurrentThread(mFinalizeRunnable);
} else {
mFinalizeRunnable->ReleaseNow(false);
MOZ_ASSERT(!mFinalizeRunnable);
}
}
void
CycleCollectedJSRuntime::AnnotateAndSetOutOfMemory(OOMState* aStatePtr,
OOMState aNewState)
{
*aStatePtr = aNewState;
#ifdef MOZ_CRASHREPORTER
CrashReporter::AnnotateCrashReport(aStatePtr == &mOutOfMemoryState
? NS_LITERAL_CSTRING("JSOutOfMemory")
: NS_LITERAL_CSTRING("JSLargeAllocationFailure"),
aNewState == OOMState::Reporting
? NS_LITERAL_CSTRING("Reporting")
: aNewState == OOMState::Reported
? NS_LITERAL_CSTRING("Reported")
: NS_LITERAL_CSTRING("Recovered"));
#endif
}
void
CycleCollectedJSRuntime::OnGC(JSGCStatus aStatus)
{
switch (aStatus) {
case JSGC_BEGIN:
nsCycleCollector_prepareForGarbageCollection();
mZonesWaitingForGC.Clear();
break;
case JSGC_END: {
#ifdef MOZ_CRASHREPORTER
if (mOutOfMemoryState == OOMState::Reported) {
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Recovered);
}
if (mLargeAllocationFailureState == OOMState::Reported) {
AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, OOMState::Recovered);
}
#endif
// Do any deferred finalization of native objects.
FinalizeDeferredThings(JS::WasIncrementalGC(mJSRuntime) ? FinalizeIncrementally :
FinalizeNow);
break;
}
default:
MOZ_CRASH();
}
CustomGCCallback(aStatus);
}
void
CycleCollectedJSRuntime::OnOutOfMemory()
{
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reporting);
CustomOutOfMemoryCallback();
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reported);
}
void
CycleCollectedJSRuntime::OnLargeAllocationFailure()
{
AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, OOMState::Reporting);
CustomLargeAllocationFailureCallback();
AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, OOMState::Reported);
}
void
CycleCollectedJSRuntime::PrepareWaitingZonesForGC()
{
if (mZonesWaitingForGC.Count() == 0) {
JS::PrepareForFullGC(Runtime());
} else {
for (auto iter = mZonesWaitingForGC.Iter(); !iter.Done(); iter.Next()) {
JS::PrepareZoneForGC(iter.Get()->GetKey());
}
mZonesWaitingForGC.Clear();
}
}
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