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gecko-dev/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/CycleCollectedJSContext.h"
#include "mozilla/Move.h"
#include "mozilla/MemoryReporting.h"
#include "mozilla/Sprintf.h"
#include "mozilla/Telemetry.h"
#include "mozilla/TimelineConsumers.h"
#include "mozilla/TimelineMarker.h"
#include "mozilla/Unused.h"
#include "mozilla/DebuggerOnGCRunnable.h"
#include "mozilla/dom/DOMJSClass.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 "jsprf.h"
#include "js/Debug.h"
#include "js/GCAPI.h"
#include "nsContentUtils.h"
#include "nsCycleCollectionNoteRootCallback.h"
#include "nsCycleCollectionParticipant.h"
#include "nsCycleCollector.h"
#include "nsDOMJSUtils.h"
#include "nsExceptionHandler.h"
#include "nsJSUtils.h"
#include "nsWrapperCache.h"
#include "nsStringBuffer.h"
#include "GeckoProfiler.h"
#ifdef MOZ_GECKO_PROFILER
#include "ProfilerMarkerPayload.h"
#endif
#include "nsIException.h"
#include "nsIPlatformInfo.h"
#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 CancelableRunnable
{
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), 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);
}
}
}
// 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 (!AddToCCKind(aKey.kind())) {
aKey = nullptr;
}
if (keyMightNeedMarking && aKey.is<JSObject>()) {
JSObject* kdelegate = js::GetWeakmapKeyDelegate(&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 (AddToCCKind(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, 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);
}
mCb.NoteJSChild(aThing);
} 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;
static
void JSObjectsTenuredCb(JSContext* aContext, void* aData)
{
static_cast<CycleCollectedJSRuntime*>(aData)->JSObjectsTenured();
}
bool
mozilla::GetBuildId(JS::BuildIdCharVector* aBuildID)
{
nsCOMPtr<nsIPlatformInfo> info = do_GetService("@mozilla.org/xre/app-info;1");
if (!info) {
return false;
}
nsCString buildID;
nsresult rv = info->GetPlatformBuildID(buildID);
NS_ENSURE_SUCCESS(rv, false);
if (!aBuildID->resize(buildID.Length())) {
return false;
}
for (size_t i = 0; i < buildID.Length(); i++) {
(*aBuildID)[i] = buildID[i];
}
return true;
}
static void
MozCrashWarningReporter(JSContext*, JSErrorReport*)
{
MOZ_CRASH("Why is someone touching JSAPI without an AutoJSAPI?");
}
CycleCollectedJSRuntime::CycleCollectedJSRuntime(JSContext* aCx)
: mGCThingCycleCollectorGlobal(sGCThingCycleCollectorGlobal)
, mJSZoneCycleCollectorGlobal(sJSZoneCycleCollectorGlobal)
, mJSRuntime(JS_GetRuntime(aCx))
, mHasPendingIdleGCTask(false)
, mPrevGCSliceCallback(nullptr)
, mPrevGCNurseryCollectionCallback(nullptr)
, mJSHolderMap(256)
, mOutOfMemoryState(OOMState::OK)
, mLargeAllocationFailureState(OOMState::OK)
#ifdef DEBUG
, mShutdownCalled(false)
#endif
{
MOZ_COUNT_CTOR(CycleCollectedJSRuntime);
MOZ_ASSERT(aCx);
MOZ_ASSERT(mJSRuntime);
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_SetExternalStringSizeofCallback(aCx, SizeofExternalStringCallback);
JS::SetBuildIdOp(aCx, GetBuildId);
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
}
void
CycleCollectedJSRuntime::Shutdown(JSContext* cx)
{
#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
mErrorInterceptor.Shutdown(mJSRuntime);
#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
JS_RemoveExtraGCRootsTracer(cx, TraceBlackJS, this);
JS_RemoveExtraGCRootsTracer(cx, TraceGrayJS, this);
#ifdef DEBUG
mShutdownCalled = true;
#endif
}
CycleCollectedJSRuntime::~CycleCollectedJSRuntime()
{
MOZ_COUNT_DTOR(CycleCollectedJSRuntime);
MOZ_ASSERT(!mDeferredFinalizerTable.Count());
MOZ_ASSERT(mShutdownCalled);
}
void
CycleCollectedJSRuntime::AddContext(CycleCollectedJSContext* aContext)
{
mContexts.insertBack(aContext);
}
void
CycleCollectedJSRuntime::RemoveContext(CycleCollectedJSContext* aContext)
{
aContext->removeFrom(mContexts);
}
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.SizeOfExcludingThis(aMallocSizeOf);
n += mJSHolderMap.ShallowSizeOfExcludingThis(aMallocSizeOf);
return n;
}
void
CycleCollectedJSRuntime::UnmarkSkippableJSHolders()
{
for (auto iter = mJSHolders.Iter(); !iter.Done(); iter.Next()) {
void* holder = iter.Get().mHolder;
nsScriptObjectTracer* tracer = iter.Get().mTracer;
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);
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, "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
{
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.Get().mHolder;
nsScriptObjectTracer* tracer = iter.Get().mTracer;
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(JSContext* aContext,
JSGCStatus aStatus,
void* aData)
{
CycleCollectedJSRuntime* self = static_cast<CycleCollectedJSRuntime*>(aData);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Context() == aContext);
MOZ_ASSERT(CycleCollectedJSContext::Get()->Runtime() == self);
self->OnGC(aContext, aStatus);
}
/* 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_is_active()) {
if (aProgress == JS::GC_CYCLE_END) {
profiler_add_marker(
"GCMajor",
MakeUnique<GCMajorMarkerPayload>(aDesc.startTime(aContext),
aDesc.endTime(aContext),
aDesc.summaryToJSON(aContext)));
} else if (aProgress == JS::GC_SLICE_END) {
profiler_add_marker(
"GCSlice",
MakeUnique<GCSliceMarkerPayload>(aDesc.lastSliceStart(aContext),
aDesc.lastSliceEnd(aContext),
aDesc.sliceToJSON(aContext)));
}
}
#endif
if (aProgress == JS::GC_CYCLE_END &&
JS::dbg::FireOnGarbageCollectionHookRequired(aContext)) {
JS::gcreason::Reason 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::Reason mReason;
public:
MinorGCMarker(MarkerTracingType aTracingType,
JS::gcreason::Reason aReason)
: TimelineMarker("MinorGC",
aTracingType,
MarkerStackRequest::NO_STACK)
, mReason(aReason)
{
MOZ_ASSERT(aTracingType == MarkerTracingType::START ||
aTracingType == MarkerTracingType::END);
}
MinorGCMarker(JS::GCNurseryProgress aProgress,
JS::gcreason::Reason 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::gcreason::ExplainReason(mReason);
aMarker.mCauseName.Construct(NS_ConvertUTF8toUTF16(reason));
}
}
virtual UniquePtr<AbstractTimelineMarker>
Clone() override
{
auto clone = MakeUnique<MinorGCMarker>(GetTracingType(), mReason);
clone->SetCustomTime(GetTime());
return UniquePtr<AbstractTimelineMarker>(Move(clone));
}
};
/* static */ void
CycleCollectedJSRuntime::GCNurseryCollectionCallback(JSContext* aContext,
JS::GCNurseryProgress aProgress,
JS::gcreason::Reason 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_is_active())
{
profiler_add_marker(
"GCMinor",
MakeUnique<GCMinorMarkerPayload>(self->mLatestNurseryCollectionStart,
TimeStamp::Now(),
JS::MinorGcToJSON(aContext)));
}
#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 */ size_t
CycleCollectedJSRuntime::SizeofExternalStringCallback(JSString* aStr,
MallocSizeOf aMallocSizeOf)
{
// We promised the JS engine we would not GC. Enforce that:
JS::AutoCheckCannotGC autoCannotGC;
if (!XPCStringConvert::IsDOMString(aStr)) {
// Might be a literal or something we don't understand. Just claim 0.
return 0;
}
const char16_t* chars = JS_GetTwoByteExternalStringChars(aStr);
const nsStringBuffer* buf = nsStringBuffer::FromData((void*)chars);
// We want sizeof including this, because the entire string buffer is owned by
// the external string. But only report here if we're unshared; if we're
// shared then we don't know who really owns this data.
return buf->SizeOfIncludingThisIfUnshared(aMallocSizeOf);
}
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(JSObject** aPtr, const char* aName,
void* aClosure) const override
{
js::UnsafeTraceManuallyBarrieredEdge(static_cast<JSTracer*>(aClosure), aPtr, 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);
}
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.Get().mHolder;
nsScriptObjectTracer* tracer = iter.Get().mTracer;
tracer->Trace(holder, JsGcTracer(), aTracer);
}
}
void
CycleCollectedJSRuntime::AddJSHolder(void* aHolder, nsScriptObjectTracer* aTracer)
{
auto entry = mJSHolderMap.LookupForAdd(aHolder);
if (entry) {
JSHolderInfo* info = entry.Data();
MOZ_ASSERT(info->mHolder == aHolder);
info->mTracer = aTracer;
return;
}
mJSHolders.InfallibleAppend(JSHolderInfo {aHolder, aTracer});
entry.OrInsert([&] {return &mJSHolders.GetLast();});
}
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(JSObject** aPtr, const char* aName,
void* aClosure) 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)
{
auto entry = mJSHolderMap.Lookup(aHolder);
if (entry) {
JSHolderInfo* info = entry.Data();
MOZ_ASSERT(info->mHolder == aHolder);
info->mTracer->Trace(aHolder, ClearJSHolder(), nullptr);
JSHolderInfo* lastInfo = &mJSHolders.GetLast();
bool updateLast = (info != lastInfo);
if (updateLast) {
*info = *lastInfo;
}
mJSHolders.PopLast();
entry.Remove();
if (updateLast) {
// We have to do this after removing the entry above to ensure that we
// don't trip over the hashtable generation number assertion.
mJSHolderMap.Put(info->mHolder, info);
}
}
}
#ifdef DEBUG
bool
CycleCollectedJSRuntime::IsJSHolder(void* aHolder)
{
return mJSHolderMap.Get(aHolder, nullptr);
}
static void
AssertNoGcThing(JS::GCCellPtr aGCThing, const char* aName, void* aClosure)
{
MOZ_ASSERT(!aGCThing);
}
void
CycleCollectedJSRuntime::AssertNoObjectsToTrace(void* aPossibleJSHolder)
{
JSHolderInfo* info = nullptr;
if (!mJSHolderMap.Get(aPossibleJSHolder, &info)) {
return;
}
MOZ_ASSERT(info->mHolder == aPossibleJSHolder);
info->mTracer->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);
return NS_OK;
}
bool
CycleCollectedJSRuntime::UsefulToMergeZones() const
{
return false;
}
void
CycleCollectedJSRuntime::FixWeakMappingGrayBits() const
{
MOZ_ASSERT(!JS::IsIncrementalGCInProgress(mJSRuntime),
"Don't call FixWeakMappingGrayBits during a GC.");
FixWeakMappingGrayBitsTracer fixer(mJSRuntime);
fixer.FixAll();
}
void
CycleCollectedJSRuntime::CheckGrayBits() const
{
MOZ_ASSERT(!JS::IsIncrementalGCInProgress(mJSRuntime),
"Don't call CheckGrayBits during a GC.");
#ifndef ANDROID
// Bug 1346874 - The gray state check is expensive. Android tests are already
// slow enough that this check can easily push them over the threshold to a
// timeout.
MOZ_ASSERT(js::CheckGrayMarkingState(mJSRuntime));
MOZ_ASSERT(CheckWeakMappingGrayBitsTracer::Check(mJSRuntime));
#endif
}
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);
JSContext* cx = CycleCollectedJSContext::Get()->Context();
JS::PrepareForFullGC(cx);
JS::GCForReason(cx, GC_NORMAL, gcreason);
}
void
CycleCollectedJSRuntime::JSObjectsTenured()
{
for (auto iter = mNurseryObjects.Iter(); !iter.Done(); iter.Next()) {
nsWrapperCache* cache = iter.Get();
JSObject* wrapper = cache->GetWrapperMaybeDead();
MOZ_DIAGNOSTIC_ASSERT(wrapper);
if (!JS::ObjectIsTenured(wrapper)) {
MOZ_ASSERT(!cache->PreservingWrapper());
const JSClass* jsClass = js::GetObjectJSClass(wrapper);
jsClass->doFinalize(nullptr, wrapper);
}
}
#ifdef DEBUG
for (auto iter = mPreservedNurseryObjects.Iter(); !iter.Done(); iter.Next()) {
MOZ_ASSERT(JS::ObjectIsTenured(iter.Get().get()));
}
#endif
mNurseryObjects.Clear();
mPreservedNurseryObjects.Clear();
}
void
CycleCollectedJSRuntime::NurseryWrapperAdded(nsWrapperCache* aCache)
{
MOZ_ASSERT(aCache);
MOZ_ASSERT(aCache->GetWrapperMaybeDead());
MOZ_ASSERT(!JS::ObjectIsTenured(aCache->GetWrapperMaybeDead()));
mNurseryObjects.InfallibleAppend(aCache);
}
void
CycleCollectedJSRuntime::NurseryWrapperPreserved(JSObject* aWrapper)
{
mPreservedNurseryObjects.InfallibleAppend(
JS::PersistentRooted<JSObject*>(mJSRuntime, aWrapper));
}
void
CycleCollectedJSRuntime::DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
DeferredFinalizeFunction aFunc,
void* aThing)
{
if (auto entry = mDeferredFinalizerTable.LookupForAdd(aFunc)) {
aAppendFunc(entry.Data(), aThing);
} else {
entry.OrInsert(
[aAppendFunc, aThing] () { return aAppendFunc(nullptr, aThing); });
}
}
void
CycleCollectedJSRuntime::DeferredFinalize(nsISupports* aSupports)
{
typedef DeferredFinalizerImpl<nsISupports> Impl;
DeferredFinalize(Impl::AppendDeferredFinalizePointer, Impl::DeferredFinalize,
aSupports);
}
void
CycleCollectedJSRuntime::DumpJSHeap(FILE* aFile)
{
JSContext* cx = CycleCollectedJSContext::Get()->Context();
js::DumpHeap(cx, aFile, js::CollectNurseryBeforeDump);
}
IncrementalFinalizeRunnable::IncrementalFinalizeRunnable(CycleCollectedJSRuntime* aRt,
DeferredFinalizerTable& aFinalizers)
: CancelableRunnable("IncrementalFinalizeRunnable")
, 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;
}
TimeStamp start = TimeStamp::Now();
ReleaseNow(true);
if (mDeferredFinalizeFunctions.Length()) {
nsresult rv = NS_DispatchToCurrentThread(this);
if (NS_FAILED(rv)) {
ReleaseNow(false);
}
}
uint32_t duration = (uint32_t)((TimeStamp::Now() - start).ToMilliseconds());
Telemetry::Accumulate(Telemetry::DEFERRED_FINALIZE_ASYNC, duration);
return NS_OK;
}
void
CycleCollectedJSRuntime::FinalizeDeferredThings(CycleCollectedJSContext::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 == CycleCollectedJSContext::FinalizeIncrementally) {
NS_IdleDispatchToCurrentThread(do_AddRef(mFinalizeRunnable), 2500);
} else {
mFinalizeRunnable->ReleaseNow(false);
MOZ_ASSERT(!mFinalizeRunnable);
}
}
void
CycleCollectedJSRuntime::AnnotateAndSetOutOfMemory(OOMState* aStatePtr,
OOMState aNewState)
{
*aStatePtr = aNewState;
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"));
}
void
CycleCollectedJSRuntime::OnGC(JSContext* aContext,
JSGCStatus aStatus)
{
switch (aStatus) {
case JSGC_BEGIN:
nsCycleCollector_prepareForGarbageCollection();
mZonesWaitingForGC.Clear();
break;
case JSGC_END: {
if (mOutOfMemoryState == OOMState::Reported) {
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Recovered);
}
if (mLargeAllocationFailureState == OOMState::Reported) {
AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, OOMState::Recovered);
}
// Do any deferred finalization of native objects. Normally we do this
// incrementally for an incremental GC, and immediately for a
// non-incremental GC, on the basis that the type of GC reflects how
// urgently resources should be destroyed. However under some circumstances
// (such as in js::InternalCallOrConstruct) we can end up running a
// non-incremental GC when there is a pending exception, and the finalizers
// are not set up to handle that. In that case, just run them later, after
// we've returned to the event loop.
bool finalizeIncrementally = JS::WasIncrementalGC(mJSRuntime) || JS_IsExceptionPending(aContext);
FinalizeDeferredThings(finalizeIncrementally
? CycleCollectedJSContext::FinalizeIncrementally
: CycleCollectedJSContext::FinalizeNow);
break;
}
default:
MOZ_CRASH();
}
CustomGCCallback(aStatus);
}
void
CycleCollectedJSRuntime::OnOutOfMemory()
{
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reporting);
CustomOutOfMemoryCallback();
AnnotateAndSetOutOfMemory(&mOutOfMemoryState, OOMState::Reported);
}
void
CycleCollectedJSRuntime::SetLargeAllocationFailure(OOMState aNewState)
{
AnnotateAndSetOutOfMemory(&mLargeAllocationFailureState, aNewState);
}
void
CycleCollectedJSRuntime::PrepareWaitingZonesForGC()
{
JSContext* cx = CycleCollectedJSContext::Get()->Context();
if (mZonesWaitingForGC.Count() == 0) {
JS::PrepareForFullGC(cx);
} else {
for (auto iter = mZonesWaitingForGC.Iter(); !iter.Done(); iter.Next()) {
JS::PrepareZoneForGC(iter.Get()->GetKey());
}
mZonesWaitingForGC.Clear();
}
}
void
CycleCollectedJSRuntime::EnvironmentPreparer::invoke(JS::HandleObject scope,
js::ScriptEnvironmentPreparer::Closure& closure)
{
nsIGlobalObject* global = xpc::NativeGlobal(scope);
// Not much we can do if we simply don't have a usable global here...
NS_ENSURE_TRUE_VOID(global && global->GetGlobalJSObject());
AutoEntryScript aes(global, "JS-engine-initiated execution");
MOZ_ASSERT(!JS_IsExceptionPending(aes.cx()));
DebugOnly<bool> ok = closure(aes.cx());
MOZ_ASSERT_IF(ok, !JS_IsExceptionPending(aes.cx()));
// The AutoEntryScript will check for JS_IsExceptionPending on the
// JSContext and report it as needed as it comes off the stack.
}
/* static */ CycleCollectedJSRuntime*
CycleCollectedJSRuntime::Get()
{
auto context = CycleCollectedJSContext::Get();
if (context) {
return context->Runtime();
}
return nullptr;
}
#ifdef MOZ_JS_DEV_ERROR_INTERCEPTOR
namespace js {
extern void DumpValue(const JS::Value& val);
}
void
CycleCollectedJSRuntime::ErrorInterceptor::Shutdown(JSRuntime* rt)
{
JS_SetErrorInterceptorCallback(rt, nullptr);
mThrownError.reset();
}
/* virtual */ void
CycleCollectedJSRuntime::ErrorInterceptor::interceptError(JSContext* cx, const JS::Value& exn)
{
if (mThrownError) {
// We already have an error, we don't need anything more.
return;
}
if (!nsContentUtils::ThreadsafeIsSystemCaller(cx)) {
// We are only interested in chrome code.
return;
}
const auto type = JS_GetErrorType(exn);
if (!type) {
// This is not one of the primitive error types.
return;
}
switch (*type) {
case JSExnType::JSEXN_REFERENCEERR:
case JSExnType::JSEXN_SYNTAXERR:
case JSExnType::JSEXN_TYPEERR:
break;
default:
// Not one of the errors we are interested in.
return;
}
// Now copy the details of the exception locally.
// While copying the details of an exception could be expensive, in most runs,
// this will be done at most once during the execution of the process, so the
// total cost should be reasonable.
JS::RootedValue value(cx, exn);
ErrorDetails details;
details.mType = *type;
// If `exn` isn't an exception object, `ExtractErrorValues` could end up calling
// `toString()`, which could in turn end up throwing an error. While this should
// work, we want to avoid that complex use case.
// Fortunately, we have already checked above that `exn` is an exception object,
// so nothing such should happen.
nsContentUtils::ExtractErrorValues(cx, value, details.mFilename, &details.mLine, &details.mColumn, details.mMessage);
nsAutoCString stack;
JS::UniqueChars buf = JS::FormatStackDump(cx, nullptr, /* showArgs = */ false, /* showLocals = */ false, /* showThisProps = */ false);
stack.Append(buf.get());
CopyUTF8toUTF16(buf.get(), details.mStack);
mThrownError.emplace(Move(details));
}
void
CycleCollectedJSRuntime::ClearRecentDevError()
{
mErrorInterceptor.mThrownError.reset();
}
bool
CycleCollectedJSRuntime::GetRecentDevError(JSContext*cx, JS::MutableHandle<JS::Value> error)
{
if (!mErrorInterceptor.mThrownError) {
return true;
}
// Create a copy of the exception.
JS::RootedObject obj(cx, JS_NewPlainObject(cx));
if (!obj) {
return false;
}
JS::RootedValue message(cx);
JS::RootedValue filename(cx);
JS::RootedValue stack(cx);
if (!ToJSValue(cx, mErrorInterceptor.mThrownError->mMessage, &message) ||
!ToJSValue(cx, mErrorInterceptor.mThrownError->mFilename, &filename) ||
!ToJSValue(cx, mErrorInterceptor.mThrownError->mStack, &stack)) {
return false;
}
// Build the object.
const auto FLAGS = JSPROP_READONLY | JSPROP_ENUMERATE | JSPROP_PERMANENT;
if (!JS_DefineProperty(cx, obj, "message", message, FLAGS) ||
!JS_DefineProperty(cx, obj, "fileName", filename, FLAGS) ||
!JS_DefineProperty(cx, obj, "lineNumber", mErrorInterceptor.mThrownError->mLine, FLAGS) ||
!JS_DefineProperty(cx, obj, "stack", stack, FLAGS)) {
return false;
}
// Pass the result.
error.setObject(*obj);
return true;
}
#endif // MOZ_JS_DEV_ERROR_INTERCEPTOR
#undef MOZ_JS_DEV_ERROR_INTERCEPTOR
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