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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
// TraceNativeGrayRootsInCollectingZones 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 <utility>
#include "js/Debug.h"
#include "js/friend/DumpFunctions.h" // js::DumpHeap
#include "js/GCAPI.h"
#include "js/HeapAPI.h"
#include "js/Object.h" // JS::GetClass, JS::GetCompartment, JS::GetPrivate
#include "js/Warnings.h" // JS::SetWarningReporter
#include "jsfriendapi.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/AutoRestore.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/DebuggerOnGCRunnable.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/ProfilerLabels.h"
#include "mozilla/ProfilerMarkers.h"
#include "mozilla/Sprintf.h"
#include "mozilla/Telemetry.h"
#include "mozilla/TimelineConsumers.h"
#include "mozilla/TimelineMarker.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/AutoEntryScript.h"
#include "mozilla/dom/DOMJSClass.h"
#include "mozilla/dom/JSExecutionManager.h"
#include "mozilla/dom/ProfileTimelineMarkerBinding.h"
#include "mozilla/dom/Promise.h"
#include "mozilla/dom/PromiseBinding.h"
#include "mozilla/dom/PromiseDebugging.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsContentUtils.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollector.h"
#include "nsDOMJSUtils.h"
#include "nsExceptionHandler.h"
#include "nsJSUtils.h"
#include "nsStringBuffer.h"
#include "nsWrapperCache.h"
#if defined(XP_MACOSX)
# include "nsMacUtilsImpl.h"
#endif
#include "nsThread.h"
#include "nsThreadUtils.h"
#include "xpcpublic.h"
#ifdef NIGHTLY_BUILD
// For performance reasons, we make the JS Dev Error Interceptor a Nightly-only
// feature.
# define MOZ_JS_DEV_ERROR_INTERCEPTOR = 1
#endif // NIGHTLY_BUILD
using namespace mozilla;
using namespace mozilla::dom;
namespace mozilla {
struct DeferredFinalizeFunctionHolder {
DeferredFinalizeFunction run;
void* data;
};
class IncrementalFinalizeRunnable : public DiscardableRunnable {
typedef AutoTArray<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, JS::TracerKind::Callback,
JS::IdTraceAction::CanSkip),
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 (JS::IsCCTraceKind(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(JS::IsCCTraceKind(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 (!JS::IsCCTraceKind(aKey.kind())) {
aKey = nullptr;
}
JSObject* kdelegate = nullptr;
if (aKey.is<JSObject>()) {
kdelegate = js::UncheckedUnwrapWithoutExpose(&aKey.as<JSObject>());
}
if (JS::IsCCTraceKind(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);
}
}
}
// Report whether the key or value of a weak mapping entry are gray but need to
// be marked black.
static void ShouldWeakMappingEntryBeBlack(JSObject* aMap, JS::GCCellPtr aKey,
JS::GCCellPtr aValue,
bool* aKeyShouldBeBlack,
bool* aValueShouldBeBlack) {
*aKeyShouldBeBlack = false;
*aValueShouldBeBlack = false;
// If nothing that could be held alive by this entry is marked gray, return.
bool keyMightNeedMarking = aKey && JS::GCThingIsMarkedGray(aKey);
bool valueMightNeedMarking = aValue && JS::GCThingIsMarkedGray(aValue) &&
aValue.kind() != JS::TraceKind::String;
if (!keyMightNeedMarking && !valueMightNeedMarking) {
return;
}
if (!JS::IsCCTraceKind(aKey.kind())) {
aKey = nullptr;
}
if (keyMightNeedMarking && aKey.is<JSObject>()) {
JSObject* kdelegate =
js::UncheckedUnwrapWithoutExpose(&aKey.as<JSObject>());
if (kdelegate && !JS::ObjectIsMarkedGray(kdelegate) &&
(!aMap || !JS::ObjectIsMarkedGray(aMap))) {
*aKeyShouldBeBlack = true;
}
}
if (aValue && JS::GCThingIsMarkedGray(aValue) &&
(!aKey || !JS::GCThingIsMarkedGray(aKey)) &&
(!aMap || !JS::ObjectIsMarkedGray(aMap)) &&
aValue.kind() != JS::TraceKind::Shape) {
*aValueShouldBeBlack = true;
}
}
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 {
bool keyShouldBeBlack;
bool valueShouldBeBlack;
ShouldWeakMappingEntryBeBlack(aMap, aKey, aValue, &keyShouldBeBlack,
&valueShouldBeBlack);
if (keyShouldBeBlack && JS::UnmarkGrayGCThingRecursively(aKey)) {
mAnyMarked = true;
}
if (valueShouldBeBlack && JS::UnmarkGrayGCThingRecursively(aValue)) {
mAnyMarked = true;
}
}
MOZ_INIT_OUTSIDE_CTOR bool mAnyMarked;
};
#ifdef DEBUG
// Check whether weak maps are marked correctly according to the logic above.
struct CheckWeakMappingGrayBitsTracer : public js::WeakMapTracer {
explicit CheckWeakMappingGrayBitsTracer(JSRuntime* aRt)
: js::WeakMapTracer(aRt), mFailed(false) {}
static bool Check(JSRuntime* aRt) {
CheckWeakMappingGrayBitsTracer tracer(aRt);
js::TraceWeakMaps(&tracer);
return !tracer.mFailed;
}
void trace(JSObject* aMap, JS::GCCellPtr aKey,
JS::GCCellPtr aValue) override {
bool keyShouldBeBlack;
bool valueShouldBeBlack;
ShouldWeakMappingEntryBeBlack(aMap, aKey, aValue, &keyShouldBeBlack,
&valueShouldBeBlack);
if (keyShouldBeBlack) {
fprintf(stderr, "Weak mapping key %p of map %p should be black\n",
aKey.asCell(), aMap);
mFailed = true;
}
if (valueShouldBeBlack) {
fprintf(stderr, "Weak mapping value %p of map %p should be black\n",
aValue.asCell(), aMap);
mFailed = true;
}
}
bool mFailed;
};
#endif // DEBUG
static void CheckParticipatesInCycleCollection(JS::GCCellPtr aThing,
const char* aName,
void* aClosure) {
bool* cycleCollectionEnabled = static_cast<bool*>(aClosure);
if (*cycleCollectionEnabled) {
return;
}
if (JS::IsCCTraceKind(aThing.kind()) && JS::GCThingIsMarkedGray(aThing)) {
*cycleCollectionEnabled = true;
}
}
NS_IMETHODIMP
JSGCThingParticipant::TraverseNative(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::TraverseNative(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, JS::TracerKind::Callback,
JS::TraceOptions(JS::WeakMapTraceAction::Skip,
JS::WeakEdgeTraceAction::Trace,
JS::IdTraceAction::CanSkip)),
mCb(aCb) {}
void onChild(const JS::GCCellPtr& aThing) override;
nsCycleCollectionTraversalCallback& mCb;
};
void TraversalTracer::onChild(const JS::GCCellPtr& aThing) {
// Checking strings and symbols for being gray is rather slow, and we don't
// need either of them for the cycle collector.
if (aThing.is<JSString>() || aThing.is<JS::Symbol>()) {
return;
}
// 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
* IsCCTraceKind 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-IsCCTraceKind GC things. Places where this can
* occur use special APIs to handle such chains iteratively.
*/
if (JS::IsCCTraceKind(aThing.kind())) {
if (MOZ_UNLIKELY(mCb.WantDebugInfo())) {
char buffer[200];
context().getEdgeName(buffer, sizeof(buffer));
mCb.NoteNextEdgeName(buffer);
}
mCb.NoteJSChild(aThing);
return;
}
// Allow re-use of this tracer inside trace callback.
JS::AutoClearTracingContext actc(this);
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 {
JS::TraceChildren(this, 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;
static void JSObjectsTenuredCb(JSContext* aContext, void* aData) {
static_cast<CycleCollectedJSRuntime*>(aData)->JSObjectsTenured();
}
static void MozCrashWarningReporter(JSContext*, JSErrorReport*) {
MOZ_CRASH("Why is someone touching JSAPI without an AutoJSAPI?");
}
JSHolderMap::Entry::Entry() : Entry(nullptr, nullptr, nullptr) {}
JSHolderMap::Entry::Entry(void* aHolder, nsScriptObjectTracer* aTracer,
JS::Zone* aZone)
: mHolder(aHolder),
mTracer(aTracer)
#ifdef DEBUG
,
mZone(aZone)
#endif
{
}
JSHolderMap::JSHolderMap() : mJSHolderMap(256) {}
template <typename F>
inline void JSHolderMap::ForEach(F&& f, WhichHolders aWhich) {
// Multi-zone JS holders must always be considered.
ForEach(mAnyZoneJSHolders, f, nullptr);
for (auto i = mPerZoneJSHolders.modIter(); !i.done(); i.next()) {
if (aWhich == HoldersInCollectingZones &&
!JS::ZoneIsCollecting(i.get().key())) {
continue;
}
EntryVector* holders = i.get().value().get();
ForEach(*holders, f, i.get().key());
if (holders->IsEmpty()) {
i.remove();
}
}
}
template <typename F>
inline void JSHolderMap::ForEach(EntryVector& aJSHolders, const F& f,
JS::Zone* aZone) {
for (auto iter = aJSHolders.Iter(); !iter.Done(); iter.Next()) {
Entry* entry = &iter.Get();
// If the entry has been cleared, remove it and shrink the vector.
if (!entry->mHolder && !RemoveEntry(aJSHolders, entry)) {
break; // Removed the last entry.
}
MOZ_ASSERT_IF(aZone, entry->mZone == aZone);
f(entry->mHolder, entry->mTracer, aZone);
}
}
bool JSHolderMap::RemoveEntry(EntryVector& aJSHolders, Entry* aEntry) {
MOZ_ASSERT(aEntry);
MOZ_ASSERT(!aEntry->mHolder);
// Remove all dead entries from the end of the vector.
while (!aJSHolders.GetLast().mHolder && &aJSHolders.GetLast() != aEntry) {
aJSHolders.PopLast();
}
// Swap the element we want to remove with the last one and update the hash
// table.
Entry* lastEntry = &aJSHolders.GetLast();
if (aEntry != lastEntry) {
MOZ_ASSERT(lastEntry->mHolder);
*aEntry = *lastEntry;
MOZ_ASSERT(mJSHolderMap.has(aEntry->mHolder));
MOZ_ALWAYS_TRUE(mJSHolderMap.put(aEntry->mHolder, aEntry));
}
aJSHolders.PopLast();
// Return whether aEntry is still in the vector.
return aEntry != lastEntry;
}
inline bool JSHolderMap::Has(void* aHolder) const {
return mJSHolderMap.has(aHolder);
}
inline nsScriptObjectTracer* JSHolderMap::Get(void* aHolder) const {
auto ptr = mJSHolderMap.lookup(aHolder);
if (!ptr) {
return nullptr;
}
Entry* entry = ptr->value();
MOZ_ASSERT(entry->mHolder == aHolder);
return entry->mTracer;
}
inline nsScriptObjectTracer* JSHolderMap::Extract(void* aHolder) {
MOZ_ASSERT(aHolder);
auto ptr = mJSHolderMap.lookup(aHolder);
if (!ptr) {
return nullptr;
}
Entry* entry = ptr->value();
MOZ_ASSERT(entry->mHolder == aHolder);
nsScriptObjectTracer* tracer = entry->mTracer;
// Clear the entry's contents. It will be removed during the next iteration.
*entry = Entry();
mJSHolderMap.remove(ptr);
return tracer;
}
inline void JSHolderMap::Put(void* aHolder, nsScriptObjectTracer* aTracer,
JS::Zone* aZone) {
MOZ_ASSERT(aHolder);
MOZ_ASSERT(aTracer);
// Don't associate multi-zone holders with a zone, even if one is supplied.
if (aTracer->IsMultiZoneJSHolder()) {
aZone = nullptr;
}
auto ptr = mJSHolderMap.lookupForAdd(aHolder);
if (ptr) {
Entry* entry = ptr->value();
#ifdef DEBUG
MOZ_ASSERT(entry->mHolder == aHolder);
MOZ_ASSERT(entry->mTracer == aTracer,
"Don't call HoldJSObjects in superclass ctors");
if (aZone) {
if (entry->mZone) {
MOZ_ASSERT(entry->mZone == aZone);
} else {
entry->mZone = aZone;
}
}
#endif
entry->mTracer = aTracer;
return;
}
EntryVector* vector = &mAnyZoneJSHolders;
if (aZone) {
auto ptr = mPerZoneJSHolders.lookupForAdd(aZone);
if (!ptr) {
MOZ_ALWAYS_TRUE(
mPerZoneJSHolders.add(ptr, aZone, MakeUnique<EntryVector>()));
}
vector = ptr->value().get();
}
vector->InfallibleAppend(Entry{aHolder, aTracer, aZone});
MOZ_ALWAYS_TRUE(mJSHolderMap.add(ptr, aHolder, &vector->GetLast()));
}
size_t JSHolderMap::SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const {
size_t n = 0;
// We're deliberately not measuring anything hanging off the entries in
// mJSHolders.
n += mJSHolderMap.shallowSizeOfExcludingThis(aMallocSizeOf);
n += mAnyZoneJSHolders.SizeOfExcludingThis(aMallocSizeOf);
n += mPerZoneJSHolders.shallowSizeOfExcludingThis(aMallocSizeOf);
for (auto i = mPerZoneJSHolders.iter(); !i.done(); i.next()) {
n += i.get().value()->SizeOfExcludingThis(aMallocSizeOf);
}
return n;
}
CycleCollectedJSRuntime::CycleCollectedJSRuntime(JSContext* aCx)
: mContext(nullptr),
mGCThingCycleCollectorGlobal(sGCThingCycleCollectorGlobal),
mJSZoneCycleCollectorGlobal(sJSZoneCycleCollectorGlobal),
mJSRuntime(JS_GetRuntime(aCx)),
mHasPendingIdleGCTask(false),
mPrevGCSliceCallback(nullptr),
mPrevGCNurseryCollectionCallback(nullptr),
mOutOfMemoryState(OOMState::OK),
mLargeAllocationFailureState(OOMState::OK)
#ifdef DEBUG
,
mShutdownCalled(false)
#endif
{
MOZ_COUNT_CTOR(CycleCollectedJSRuntime);
MOZ_ASSERT(aCx);
MOZ_ASSERT(mJSRuntime);
#if defined(XP_MACOSX)
if (!XRE_IsParentProcess()) {
nsMacUtilsImpl::EnableTCSMIfAvailable();
}
#endif
if (!JS_AddExtraGCRootsTracer(aCx, TraceBlackJS, this)) {
MOZ_CRASH("JS_AddExtraGCRootsTracer failed");
}
JS_SetGrayGCRootsTracer(aCx, TraceGrayJS, this);
JS_SetGCCallback(aCx, GCCallback, this);
mPrevGCSliceCallback = JS::SetGCSliceCallback(aCx, GCSliceCallback);
if (NS_IsMainThread()) {
// We would like to support all threads here, but the way timeline consumers
// are set up currently, you can either add a marker for one specific
// docshell, or for every consumer globally. We would like to add a marker
// for every consumer observing anything on this thread, but that is not
// currently possible. For now, add global markers only when we are on the
// main thread, since the UI for this tracing data only displays data
// relevant to the main-thread.
mPrevGCNurseryCollectionCallback =
JS::SetGCNurseryCollectionCallback(aCx, GCNurseryCollectionCallback);
}
JS_SetObjectsTenuredCallback(aCx, JSObjectsTenuredCb, this);
JS::SetOutOfMemoryCallback(aCx, OutOfMemoryCallback, this);
JS::SetWaitCallback(mJSRuntime, BeforeWaitCallback, AfterWaitCallback,
sizeof(dom::AutoYieldJSThreadExecution));
JS::SetWarningReporter(aCx, MozCrashWarningReporter);
js::AutoEnterOOMUnsafeRegion::setAnnotateOOMAllocationSizeCallback(
CrashReporter::AnnotateOOMAllocationSize);
static js::DOMCallbacks DOMcallbacks = {InstanceClassHasProtoAtDepth};
SetDOMCallbacks(aCx, &DOMcallbacks);
js::SetScriptEnvironmentPreparer(aCx, &mEnvironmentPreparer);
JS::dbg::SetDebuggerMallocSizeOf(aCx, moz_malloc_size_of);
#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
JS_SetErrorInterceptorCallback(mJSRuntime, &mErrorInterceptor);
#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
JS_SetDestroyZoneCallback(aCx, OnZoneDestroyed);
}
#ifdef NS_BUILD_REFCNT_LOGGING
class JSLeakTracer : public JS::CallbackTracer {
public:
explicit JSLeakTracer(JSRuntime* aRuntime)
: JS::CallbackTracer(aRuntime, JS::TracerKind::Callback,
JS::WeakMapTraceAction::TraceKeysAndValues) {}
private:
void onChild(const JS::GCCellPtr& thing) override {
const char* kindName = JS::GCTraceKindToAscii(thing.kind());
size_t size = JS::GCTraceKindSize(thing.kind());
MOZ_LOG_CTOR(thing.asCell(), kindName, size);
}
};
#endif
void CycleCollectedJSRuntime::Shutdown(JSContext* cx) {
#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
mErrorInterceptor.Shutdown(mJSRuntime);
#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
// There should not be any roots left to trace at this point. Ensure any that
// remain are flagged as leaks.
#ifdef NS_BUILD_REFCNT_LOGGING
JSLeakTracer tracer(Runtime());
TraceNativeBlackRoots(&tracer);
TraceNativeGrayRoots(&tracer, JSHolderMap::AllHolders);
#endif
#ifdef DEBUG
mShutdownCalled = true;
#endif
JS_SetDestroyZoneCallback(cx, nullptr);
}
CycleCollectedJSRuntime::~CycleCollectedJSRuntime() {
MOZ_COUNT_DTOR(CycleCollectedJSRuntime);
MOZ_ASSERT(!mDeferredFinalizerTable.Count());
MOZ_ASSERT(!mFinalizeRunnable);
MOZ_ASSERT(mShutdownCalled);
}
void CycleCollectedJSRuntime::SetContext(CycleCollectedJSContext* aContext) {
MOZ_ASSERT(!mContext || !aContext, "Don't replace the context!");
mContext = aContext;
}
size_t CycleCollectedJSRuntime::SizeOfExcludingThis(
MallocSizeOf aMallocSizeOf) const {
return mJSHolders.SizeOfExcludingThis(aMallocSizeOf);
}
void CycleCollectedJSRuntime::UnmarkSkippableJSHolders() {
mJSHolders.ForEach([](void* holder, nsScriptObjectTracer* tracer,
JS::Zone* zone) { 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::GetCompartment(obj);
const JSClass* clasp = JS::GetClass(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) {
JSLinearString* linear = JS_ASSERT_STRING_IS_LINEAR(str);
nsAutoString chars;
AssignJSLinearString(chars, linear);
NS_ConvertUTF16toUTF8 fname(chars);
SprintfLiteral(name, "JS Object (Function - %s)", fname.get());
} else {
SprintfLiteral(name, "JS Object (Function)");
}
} else {
SprintfLiteral(name, "JS Object (%s)", clasp->name);
}
} else {
SprintfLiteral(name, "%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 {
TraversalTracer trc(mJSRuntime, aCb);
JS::TraceChildren(&trc, aThing);
}
void CycleCollectedJSRuntime::NoteGCThingXPCOMChildren(
const JSClass* aClasp, JSObject* aObj,
nsCycleCollectionTraversalCallback& aCb) const {
MOZ_ASSERT(aClasp);
MOZ_ASSERT(aClasp == JS::GetClass(aObj));
JS::Rooted<JSObject*> obj(RootingCx(), aObj);
if (NoteCustomGCThingXPCOMChildren(aClasp, obj, 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.
if (aClasp->flags & JSCLASS_HAS_PRIVATE &&
aClasp->flags & JSCLASS_PRIVATE_IS_NSISUPPORTS) {
NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(aCb, "JS::GetPrivate(obj)");
aCb.NoteXPCOMChild(static_cast<nsISupports*>(JS::GetPrivate(obj)));
return;
}
const DOMJSClass* domClass = GetDOMClass(aClasp);
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>(obj));
} else if (domClass->mParticipant) {
aCb.NoteNativeChild(UnwrapPossiblyNotInitializedDOMObject<void>(obj),
domClass->mParticipant);
}
return;
}
if (IsRemoteObjectProxy(obj)) {
auto handler =
static_cast<const RemoteObjectProxyBase*>(js::GetProxyHandler(obj));
return handler->NoteChildren(obj, aCb);
}
JS::Value value = js::MaybeGetScriptPrivate(obj);
if (!value.isUndefined()) {
aCb.NoteXPCOMChild(static_cast<nsISupports*>(value.toPrivate()));
}
}
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::GetClass(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::TraceGrayWrapperTargets(&trc, aZone);
/*
* 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, const JS::AutoRequireNoGC& nogc) {
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);
mJSHolders.ForEach(
[&aCb](void* holder, nsScriptObjectTracer* tracer, JS::Zone* zone) {
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, JSHolderMap::HoldersInCollectingZones);
}
/* static */
void CycleCollectedJSRuntime::GCCallback(JSContext* aContext,
JSGCStatus aStatus,
JS::GCReason aReason, void* aData) {
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Runtime() == self);
self->OnGC(aContext, aStatus, aReason);
}
/* static */
void CycleCollectedJSRuntime::GCSliceCallback(JSContext* aContext,
JS::GCProgress aProgress,
const JS::GCDescription& aDesc) {
CycleCollectedJSRuntime* self = CycleCollectedJSRuntime::Get();
MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext);
#ifdef MOZ_GECKO_PROFILER
if (profiler_thread_is_being_profiled()) {
if (aProgress == JS::GC_CYCLE_END) {
struct GCMajorMarker {
static constexpr mozilla::Span<const char> MarkerTypeName() {
return mozilla::MakeStringSpan("GCMajor");
}
static void StreamJSONMarkerData(
mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
const mozilla::ProfilerString8View& aTimingJSON) {
if (aTimingJSON.Length() != 0) {
aWriter.SplicedJSONProperty("timings", aTimingJSON);
} else {
aWriter.NullProperty("timings");
}
}
static mozilla::MarkerSchema MarkerTypeDisplay() {
using MS = mozilla::MarkerSchema;
MS schema{MS::Location::markerChart, MS::Location::markerTable,
MS::Location::timelineMemory};
schema.AddStaticLabelValue(
"Description",
"Summary data for an entire major GC, encompassing a set of "
"incremental slices. The main thread is not blocked for the "
"entire major GC interval, only for the individual slices.");
// No display instructions here, there is special handling in the
// front-end.
return schema;
}
};
profiler_add_marker("GCMajor", baseprofiler::category::GCCC,
MarkerTiming::Interval(aDesc.startTime(aContext),
aDesc.endTime(aContext)),
GCMajorMarker{},
ProfilerString8View::WrapNullTerminatedString(
aDesc.formatJSONProfiler(aContext).get()));
} else if (aProgress == JS::GC_SLICE_END) {
struct GCSliceMarker {
static constexpr mozilla::Span<const char> MarkerTypeName() {
return mozilla::MakeStringSpan("GCSlice");
}
static void StreamJSONMarkerData(
mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
const mozilla::ProfilerString8View& aTimingJSON) {
if (aTimingJSON.Length() != 0) {
aWriter.SplicedJSONProperty("timings", aTimingJSON);
} else {
aWriter.NullProperty("timings");
}
}
static mozilla::MarkerSchema MarkerTypeDisplay() {
using MS = mozilla::MarkerSchema;
MS schema{MS::Location::markerChart, MS::Location::markerTable,
MS::Location::timelineMemory};
schema.AddStaticLabelValue(
"Description",
"One slice of an incremental garbage collection (GC). The main "
"thread is blocked during this time.");
// No display instructions here, there is special handling in the
// front-end.
return schema;
}
};
profiler_add_marker("GCSlice", baseprofiler::category::GCCC,
MarkerTiming::Interval(aDesc.lastSliceStart(aContext),
aDesc.lastSliceEnd(aContext)),
GCSliceMarker{},
ProfilerString8View::WrapNullTerminatedString(
aDesc.sliceToJSONProfiler(aContext).get()));
}
}
#endif
if (aProgress == JS::GC_CYCLE_END &&
JS::dbg::FireOnGarbageCollectionHookRequired(aContext)) {
JS::GCReason reason = aDesc.reason_;
Unused << NS_WARN_IF(
NS_FAILED(DebuggerOnGCRunnable::Enqueue(aContext, aDesc)) &&
reason != JS::GCReason::SHUTDOWN_CC &&
reason != JS::GCReason::DESTROY_RUNTIME &&
reason != JS::GCReason::XPCONNECT_SHUTDOWN);
}
if (self->mPrevGCSliceCallback) {
self->mPrevGCSliceCallback(aContext, aProgress, aDesc);
}
}
class MinorGCMarker : public TimelineMarker {
private:
JS::GCReason mReason;
public:
MinorGCMarker(MarkerTracingType aTracingType, JS::GCReason aReason)
: TimelineMarker("MinorGC", aTracingType, MarkerStackRequest::NO_STACK),
mReason(aReason) {
MOZ_ASSERT(aTracingType == MarkerTracingType::START ||
aTracingType == MarkerTracingType::END);
}
MinorGCMarker(JS::GCNurseryProgress aProgress, JS::GCReason aReason)
: TimelineMarker(
"MinorGC",
aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_START
? MarkerTracingType::START
: MarkerTracingType::END,
MarkerStackRequest::NO_STACK),
mReason(aReason) {}
virtual void AddDetails(JSContext* aCx,
dom::ProfileTimelineMarker& aMarker) override {
TimelineMarker::AddDetails(aCx, aMarker);
if (GetTracingType() == MarkerTracingType::START) {
auto reason = JS::ExplainGCReason(mReason);
aMarker.mCauseName.Construct(NS_ConvertUTF8toUTF16(reason));
}
}
virtual UniquePtr<AbstractTimelineMarker> Clone() override {
auto clone = MakeUnique<MinorGCMarker>(GetTracingType(), mReason);
clone->SetCustomTime(GetTime());
return UniquePtr<AbstractTimelineMarker>(std::move(clone));
}
};
/* static */
void CycleCollectedJSRuntime::GCNurseryCollectionCallback(
JSContext* aContext, JS::GCNurseryProgress aProgress,
JS::GCReason aReason) {
CycleCollectedJSRuntime* self = CycleCollectedJSRuntime::Get();
MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext);
MOZ_ASSERT(NS_IsMainThread());
RefPtr<TimelineConsumers> timelines = TimelineConsumers::Get();
if (timelines && !timelines->IsEmpty()) {
UniquePtr<AbstractTimelineMarker> abstractMarker(
MakeUnique<MinorGCMarker>(aProgress, aReason));
timelines->AddMarkerForAllObservedDocShells(abstractMarker);
}
if (aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_START) {
self->mLatestNurseryCollectionStart = TimeStamp::Now();
}
#ifdef MOZ_GECKO_PROFILER
else if (aProgress == JS::GCNurseryProgress::GC_NURSERY_COLLECTION_END &&
profiler_thread_is_being_profiled()) {
struct GCMinorMarker {
static constexpr mozilla::Span<const char> MarkerTypeName() {
return mozilla::MakeStringSpan("GCMinor");
}
static void StreamJSONMarkerData(
mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
const mozilla::ProfilerString8View& aTimingJSON) {
if (aTimingJSON.Length() != 0) {
aWriter.SplicedJSONProperty("nursery", aTimingJSON);
} else {
aWriter.NullProperty("nursery");
}
}
static mozilla::MarkerSchema MarkerTypeDisplay() {
using MS = mozilla::MarkerSchema;
MS schema{MS::Location::markerChart, MS::Location::markerTable,
MS::Location::timelineMemory};
schema.AddStaticLabelValue(
"Description",
"A minor GC (aka nursery collection) to clear out the buffer used "
"for recent allocations and move surviving data to the tenured "
"(long-lived) heap.");
// No display instructions here, there is special handling in the
// front-end.
return schema;
}
};
profiler_add_marker(
"GCMinor", baseprofiler::category::GCCC,
MarkerTiming::IntervalUntilNowFrom(self->mLatestNurseryCollectionStart),
GCMinorMarker{},
ProfilerString8View::WrapNullTerminatedString(
JS::MinorGcToJSON(aContext).get()));
}
#endif
if (self->mPrevGCNurseryCollectionCallback) {
self->mPrevGCNurseryCollectionCallback(aContext, aProgress, aReason);
}
}
/* static */
void CycleCollectedJSRuntime::OutOfMemoryCallback(JSContext* aContext,
void* aData) {
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Runtime() == self);
self->OnOutOfMemory();
}
/* static */
void* CycleCollectedJSRuntime::BeforeWaitCallback(uint8_t* aMemory) {
MOZ_ASSERT(aMemory);
// aMemory is stack allocated memory to contain our RAII object. This allows
// for us to avoid allocations on the heap during this callback.
return new (aMemory) dom::AutoYieldJSThreadExecution;
}
/* static */
void CycleCollectedJSRuntime::AfterWaitCallback(void* aCookie) {
MOZ_ASSERT(aCookie);
static_cast<dom::AutoYieldJSThreadExecution*>(aCookie)
->~AutoYieldJSThreadExecution();
}
struct JsGcTracer : public TraceCallbacks {
virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(nsWrapperCache* aPtr, const char* aName,
void* aClosure) const override {
aPtr->TraceWrapper(static_cast<JSTracer*>(aClosure), aName);
}
virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName,
void* aClosure) const override {
JS::TraceEdge(static_cast<JSTracer*>(aClosure), aPtr, aName);
}
};
void mozilla::TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer) {
nsXPCOMCycleCollectionParticipant* participant = nullptr;
CallQueryInterface(aHolder, &participant);
participant->Trace(aHolder, JsGcTracer(), aTracer);
}
#if defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION) || defined(DEBUG)
# define CHECK_SINGLE_ZONE_JS_HOLDERS
#endif
#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS
// A tracer that checks that a JS holder only holds JS GC things in a single
// JS::Zone.
struct CheckZoneTracer : public TraceCallbacks {
const char* mClassName;
mutable JS::Zone* mZone;
explicit CheckZoneTracer(const char* aClassName, JS::Zone* aZone = nullptr)
: mClassName(aClassName), mZone(aZone) {}
void checkZone(JS::Zone* aZone, const char* aName) const {
if (!mZone) {
mZone = aZone;
return;
}
if (aZone == mZone) {
return;
}
// Most JS holders only contain pointers to GC things in a single zone. In
// the future this will allow us to improve GC performance by only tracing
// holders in zones that are being collected.
//
// If you added a holder that has pointers into multiple zones please try to
// remedy this. Some options are:
//
// - wrap all JS GC things into the same compartment
// - split GC thing pointers between separate cycle collected objects
//
// If all else fails, flag the class as containing pointers into multiple
// zones by using NS_IMPL_CYCLE_COLLECTION_MULTI_ZONE_JSHOLDER_CLASS.
MOZ_CRASH_UNSAFE_PRINTF(
"JS holder %s contains pointers to GC things in more than one zone ("
"found in %s)\n",
mClassName, aName);
}
virtual void Trace(JS::Heap<JS::Value>* aPtr, const char* aName,
void* aClosure) const override {
JS::Value value = aPtr->unbarrieredGet();
if (value.isGCThing()) {
checkZone(JS::GetGCThingZone(value.toGCCellPtr()), aName);
}
}
virtual void Trace(JS::Heap<jsid>* aPtr, const char* aName,
void* aClosure) const override {
jsid id = aPtr->unbarrieredGet();
if (id.isGCThing()) {
checkZone(JS::GetTenuredGCThingZone(id.toGCCellPtr()), aName);
}
}
virtual void Trace(JS::Heap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override {
JSObject* obj = aPtr->unbarrieredGet();
if (obj) {
checkZone(js::GetObjectZoneFromAnyThread(obj), aName);
}
}
virtual void Trace(nsWrapperCache* aPtr, const char* aName,
void* aClosure) const override {
JSObject* obj = aPtr->GetWrapperPreserveColor();
if (obj) {
checkZone(js::GetObjectZoneFromAnyThread(obj), aName);
}
}
virtual void Trace(JS::TenuredHeap<JSObject*>* aPtr, const char* aName,
void* aClosure) const override {
JSObject* obj = aPtr->unbarrieredGetPtr();
if (obj) {
checkZone(js::GetObjectZoneFromAnyThread(obj), aName);
}
}
virtual void Trace(JS::Heap<JSString*>* aPtr, const char* aName,
void* aClosure) const override {
JSString* str = aPtr->unbarrieredGet();
if (str) {
checkZone(JS::GetStringZone(str), aName);
}
}
virtual void Trace(JS::Heap<JSScript*>* aPtr, const char* aName,
void* aClosure) const override {
JSScript* script = aPtr->unbarrieredGet();
if (script) {
checkZone(JS::GetTenuredGCThingZone(JS::GCCellPtr(script)), aName);
}
}
virtual void Trace(JS::Heap<JSFunction*>* aPtr, const char* aName,
void* aClosure) const override {
JSFunction* fun = aPtr->unbarrieredGet();
if (fun) {
checkZone(js::GetObjectZoneFromAnyThread(JS_GetFunctionObject(fun)),
aName);
}
}
};
static inline void CheckHolderIsSingleZone(
void* aHolder, nsCycleCollectionParticipant* aParticipant,
JS::Zone* aZone) {
CheckZoneTracer tracer(aParticipant->ClassName(), aZone);
aParticipant->Trace(aHolder, tracer, nullptr);
}
#endif
static inline bool ShouldCheckSingleZoneHolders() {
#if defined(DEBUG)
return true;
#elif defined(NIGHTLY_BUILD) || defined(MOZ_DEV_EDITION)
// Don't check every time to avoid performance impact.
return rand() % 256 == 0;
#else
return false;
#endif
}
void CycleCollectedJSRuntime::TraceNativeGrayRoots(
JSTracer* aTracer, JSHolderMap::WhichHolders aWhich) {
// 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);
bool checkSingleZoneHolders = ShouldCheckSingleZoneHolders();
mJSHolders.ForEach(
[aTracer, checkSingleZoneHolders](
void* holder, nsScriptObjectTracer* tracer, JS::Zone* zone) {
#ifdef CHECK_SINGLE_ZONE_JS_HOLDERS
if (checkSingleZoneHolders && !tracer->IsMultiZoneJSHolder()) {
CheckHolderIsSingleZone(holder, tracer, zone);
}
#else
Unused << checkSingleZoneHolders;
#endif
tracer->Trace(holder, JsGcTracer(), aTracer);
},
aWhich);
}
void CycleCollectedJSRuntime::AddJSHolder(void* aHolder,
nsScriptObjectTracer* aTracer,
JS::Zone* aZone) {
mJSHolders.Put(aHolder, aTracer, aZone);
}
struct ClearJSHolder : public 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(nsWrapperCache* aPtr, const char* aName,
void* aClosure) const override {
aPtr->ClearWrapper();
}
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.Extract(aHolder);
if (tracer) {
// Bug 1531951: The analysis can't see through the virtual call but we know
// that the ClearJSHolder tracer will never GC.
JS::AutoSuppressGCAnalysis nogc;
tracer->Trace(aHolder, ClearJSHolder(), nullptr);
}
}
#ifdef DEBUG
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
nsCycleCollectionParticipant* CycleCollectedJSRuntime::GCThingParticipant() {
return &mGCThingCycleCollectorGlobal;
}
nsCycleCollectionParticipant* CycleCollectedJSRuntime::ZoneParticipant() {
return &mJSZoneCycleCollectorGlobal;
}
nsresult CycleCollectedJSRuntime::TraverseRoots(
nsCycleCollectionNoteRootCallback& aCb) {
TraverseNativeRoots(aCb);
NoteWeakMapsTracer trc(mJSRuntime, aCb);
js::TraceWeakMaps(&trc);