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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/. */
+
+#ifndef mozilla_CycleCollectedJSRuntime_h
+#define mozilla_CycleCollectedJSRuntime_h
+
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/DeferredFinalize.h"
+#include "mozilla/HashTable.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/SegmentedVector.h"
+#include "jsapi.h"
+#include "jsfriendapi.h"
+#include "js/TypeDecls.h"
+
+#include "nsCycleCollectionParticipant.h"
+#include "nsTHashMap.h"
+#include "nsHashKeys.h"
+#include "nsStringFwd.h"
+#include "nsTHashSet.h"
+
+class nsCycleCollectionNoteRootCallback;
+class nsIException;
+class nsWrapperCache;
+
+namespace mozilla {
+
+class JSGCThingParticipant : public nsCycleCollectionParticipant {
+ public:
+ constexpr JSGCThingParticipant() : nsCycleCollectionParticipant(false) {}
+
+ NS_IMETHOD_(void) Root(void*) override {
+ MOZ_ASSERT(false, "Don't call Root on GC things");
+ }
+
+ NS_IMETHOD_(void) Unlink(void*) override {
+ MOZ_ASSERT(false, "Don't call Unlink on GC things, as they may be dead");
+ }
+
+ NS_IMETHOD_(void) Unroot(void*) override {
+ MOZ_ASSERT(false, "Don't call Unroot on GC things, as they may be dead");
+ }
+
+ NS_IMETHOD_(void) DeleteCycleCollectable(void* aPtr) override {
+ MOZ_ASSERT(false, "Can't directly delete a cycle collectable GC thing");
+ }
+
+ NS_IMETHOD TraverseNative(void* aPtr,
+ nsCycleCollectionTraversalCallback& aCb) override;
+
+ NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(JSGCThingParticipant)
+};
+
+class JSZoneParticipant : public nsCycleCollectionParticipant {
+ public:
+ constexpr JSZoneParticipant() : nsCycleCollectionParticipant(false) {}
+
+ NS_IMETHOD_(void) Root(void*) override {
+ MOZ_ASSERT(false, "Don't call Root on GC things");
+ }
+
+ NS_IMETHOD_(void) Unlink(void*) override {
+ MOZ_ASSERT(false, "Don't call Unlink on GC things, as they may be dead");
+ }
+
+ NS_IMETHOD_(void) Unroot(void*) override {
+ MOZ_ASSERT(false, "Don't call Unroot on GC things, as they may be dead");
+ }
+
+ NS_IMETHOD_(void) DeleteCycleCollectable(void*) override {
+ MOZ_ASSERT(false, "Can't directly delete a cycle collectable GC thing");
+ }
+
+ NS_IMETHOD TraverseNative(void* aPtr,
+ nsCycleCollectionTraversalCallback& aCb) override;
+
+ NS_DECL_CYCLE_COLLECTION_CLASS_NAME_METHOD(JSZoneParticipant)
+};
+
+class IncrementalFinalizeRunnable;
+
+// A map from JS holders to tracer objects, where the values are stored in
+// SegmentedVector to speed up iteration.
+class JSHolderMap {
+ public:
+ enum WhichHolders { AllHolders, HoldersRequiredForGrayMarking };
+
+ class Iter;
+
+ JSHolderMap();
+ ~JSHolderMap() { MOZ_RELEASE_ASSERT(!mHasIterator); }
+
+ bool Has(void* aHolder) const;
+ nsScriptObjectTracer* Get(void* aHolder) const;
+ nsScriptObjectTracer* Extract(void* aHolder);
+ void Put(void* aHolder, nsScriptObjectTracer* aTracer, JS::Zone* aZone);
+
+ size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
+
+ private:
+ struct Entry {
+ void* mHolder;
+ nsScriptObjectTracer* mTracer;
+#ifdef DEBUG
+ JS::Zone* mZone;
+#endif
+
+ Entry();
+ Entry(void* aHolder, nsScriptObjectTracer* aTracer, JS::Zone* aZone);
+ };
+
+ using EntryMap = mozilla::HashMap<void*, Entry*, DefaultHasher<void*>,
+ InfallibleAllocPolicy>;
+
+ using EntryVector = SegmentedVector<Entry, 256, InfallibleAllocPolicy>;
+
+ using EntryVectorMap =
+ mozilla::HashMap<JS::Zone*, UniquePtr<EntryVector>,
+ DefaultHasher<JS::Zone*>, InfallibleAllocPolicy>;
+
+ class EntryVectorIter;
+
+ bool RemoveEntry(EntryVector& aJSHolders, Entry* aEntry);
+
+ // A map from a holder pointer to a pointer to an entry in a vector.
+ EntryMap mJSHolderMap;
+
+ // A vector of holders not associated with a particular zone or that can
+ // contain pointers to GC things in more than one zone.
+ EntryVector mAnyZoneJSHolders;
+
+ // A map from a zone to a vector of holders that only contain pointers to GC
+ // things in that zone.
+ //
+ // Currently this will only contain wrapper cache wrappers since these are the
+ // only holders to pass a zone parameter through to AddJSHolder.
+ EntryVectorMap mPerZoneJSHolders;
+
+ // Iterators can mutate the element vectors by removing stale elements. Allow
+ // at most one to exist at a time.
+ bool mHasIterator = false;
+};
+
+// An iterator over an EntryVector that skips over removed entries and removes
+// them from the map.
+class JSHolderMap::EntryVectorIter {
+ public:
+ EntryVectorIter(JSHolderMap& aMap, EntryVector& aVector)
+ : mHolderMap(aMap), mVector(aVector), mIter(aVector.Iter()) {
+ Settle();
+ }
+
+ const EntryVector& Vector() const { return mVector; }
+
+ bool Done() const { return mIter.Done(); }
+ const Entry& Get() const { return mIter.Get(); }
+ void Next() {
+ mIter.Next();
+ Settle();
+ }
+
+ operator const Entry*() const { return &Get(); }
+ const Entry* operator->() const { return &Get(); }
+
+ private:
+ void Settle();
+ friend class JSHolderMap::Iter;
+
+ JSHolderMap& mHolderMap;
+ EntryVector& mVector;
+ EntryVector::IterImpl mIter;
+};
+
+class JSHolderMap::Iter {
+ public:
+ explicit Iter(JSHolderMap& aMap, WhichHolders aWhich = AllHolders);
+
+ ~Iter() {
+ MOZ_RELEASE_ASSERT(mHolderMap.mHasIterator);
+ mHolderMap.mHasIterator = false;
+ }
+
+ bool Done() const { return mIter.Done(); }
+ const Entry& Get() const { return mIter.Get(); }
+ void Next() {
+ mIter.Next();
+ Settle();
+ }
+
+ // If the holders have been removed from the map while the iterator is live,
+ // then the iterator may point to a removed entry. Update the iterator to make
+ // sure it points to a valid entry or is done.
+ void UpdateForRemovals();
+
+ operator const Entry*() const { return &Get(); }
+ const Entry* operator->() const { return &Get(); }
+
+ JS::Zone* Zone() const { return mZone; }
+
+ private:
+ void Settle();
+
+ JSHolderMap& mHolderMap;
+ Vector<JS::Zone*, 1, InfallibleAllocPolicy> mZones;
+ JS::Zone* mZone = nullptr;
+ EntryVectorIter mIter;
+};
+
+class CycleCollectedJSRuntime {
+ friend class JSGCThingParticipant;
+ friend class JSZoneParticipant;
+ friend class IncrementalFinalizeRunnable;
+ friend class CycleCollectedJSContext;
+
+ protected:
+ CycleCollectedJSRuntime(JSContext* aMainContext);
+ virtual ~CycleCollectedJSRuntime();
+
+ virtual void Shutdown(JSContext* cx);
+
+ size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
+ void UnmarkSkippableJSHolders();
+
+ virtual void TraverseAdditionalNativeRoots(
+ nsCycleCollectionNoteRootCallback& aCb) {}
+ virtual void TraceAdditionalNativeGrayRoots(JSTracer* aTracer) {}
+
+ virtual void CustomGCCallback(JSGCStatus aStatus) {}
+ virtual void CustomOutOfMemoryCallback() {}
+
+ CycleCollectedJSContext* GetContext() { return mContext; }
+
+ private:
+ void DescribeGCThing(bool aIsMarked, JS::GCCellPtr aThing,
+ nsCycleCollectionTraversalCallback& aCb) const;
+
+ virtual bool DescribeCustomObjects(JSObject* aObject, const JSClass* aClasp,
+ char (&aName)[72]) const {
+ return false; // We did nothing.
+ }
+
+ void NoteGCThingJSChildren(JS::GCCellPtr aThing,
+ nsCycleCollectionTraversalCallback& aCb) const;
+
+ void NoteGCThingXPCOMChildren(const JSClass* aClasp, JSObject* aObj,
+ nsCycleCollectionTraversalCallback& aCb) const;
+
+ virtual bool NoteCustomGCThingXPCOMChildren(
+ const JSClass* aClasp, JSObject* aObj,
+ nsCycleCollectionTraversalCallback& aCb) const {
+ return false; // We did nothing.
+ }
+
+ enum TraverseSelect { TRAVERSE_CPP, TRAVERSE_FULL };
+
+ void TraverseGCThing(TraverseSelect aTs, JS::GCCellPtr aThing,
+ nsCycleCollectionTraversalCallback& aCb);
+
+ void TraverseZone(JS::Zone* aZone, nsCycleCollectionTraversalCallback& aCb);
+
+ static void TraverseObjectShim(void* aData, JS::GCCellPtr aThing,
+ const JS::AutoRequireNoGC& nogc);
+
+ void TraverseNativeRoots(nsCycleCollectionNoteRootCallback& aCb);
+
+ static void TraceBlackJS(JSTracer* aTracer, void* aData);
+
+ // Trace gray JS roots until budget is exceeded and return whether we
+ // finished.
+ static bool TraceGrayJS(JSTracer* aTracer, js::SliceBudget& budget,
+ void* aData);
+
+ static void GCCallback(JSContext* aContext, JSGCStatus aStatus,
+ JS::GCReason aReason, void* aData);
+ static void GCSliceCallback(JSContext* aContext, JS::GCProgress aProgress,
+ const JS::GCDescription& aDesc);
+ static void GCNurseryCollectionCallback(JSContext* aContext,
+ JS::GCNurseryProgress aProgress,
+ JS::GCReason aReason, void* data);
+ static void OutOfMemoryCallback(JSContext* aContext, void* aData);
+
+ static bool ContextCallback(JSContext* aCx, unsigned aOperation, void* aData);
+
+ static void* BeforeWaitCallback(uint8_t* aMemory);
+ static void AfterWaitCallback(void* aCookie);
+
+ virtual void TraceNativeBlackRoots(JSTracer* aTracer){};
+
+#ifdef NS_BUILD_REFCNT_LOGGING
+ void TraceAllNativeGrayRoots(JSTracer* aTracer);
+#endif
+
+ bool TraceNativeGrayRoots(JSTracer* aTracer, JSHolderMap::WhichHolders aWhich,
+ js::SliceBudget& aBudget);
+ bool TraceJSHolders(JSTracer* aTracer, JSHolderMap::Iter& aIter,
+ js::SliceBudget& aBudget);
+
+ public:
+ enum DeferredFinalizeType {
+ // Never finalize immediately, because it would be unsafe.
+ FinalizeLater,
+ // Finalize later if we can, but it is okay to do it immediately.
+ FinalizeIncrementally,
+ // Finalize immediately, for shutdown or testing purposes.
+ FinalizeNow,
+ };
+
+ void FinalizeDeferredThings(DeferredFinalizeType aType);
+
+ virtual void PrepareForForgetSkippable() = 0;
+ virtual void BeginCycleCollectionCallback(mozilla::CCReason aReason) = 0;
+ virtual void EndCycleCollectionCallback(CycleCollectorResults& aResults) = 0;
+ virtual void DispatchDeferredDeletion(bool aContinuation,
+ bool aPurge = false) = 0;
+
+ // Two conditions, JSOutOfMemory and JSLargeAllocationFailure, are noted in
+ // crash reports. Here are the values that can appear in the reports:
+ enum class OOMState : uint32_t {
+ // The condition has never happened. No entry appears in the crash report.
+ OK,
+
+ // We are currently reporting the given condition.
+ //
+ // Suppose a crash report contains "JSLargeAllocationFailure:
+ // Reporting". This means we crashed while executing memory-pressure
+ // observers, trying to shake loose some memory. The large allocation in
+ // question did not return null: it is still on the stack. Had we not
+ // crashed, it would have been retried.
+ Reporting,
+
+ // The condition has been reported since the last GC.
+ //
+ // If a crash report contains "JSOutOfMemory: Reported", that means a small
+ // allocation failed, and then we crashed, probably due to buggy
+ // error-handling code that ran after allocation returned null.
+ //
+ // This contrasts with "Reporting" which means that no error-handling code
+ // had executed yet.
+ Reported,
+
+ // The condition has happened, but a GC cycle ended since then.
+ //
+ // GC is taken as a proxy for "we've been banging on the heap a good bit
+ // now and haven't crashed; the OOM was probably handled correctly".
+ Recovered
+ };
+
+ const char* OOMStateToString(const OOMState aOomState) const;
+
+ // Returns true if OOM was reported and a new successful GC cycle hasn't
+ // occurred since.
+ bool OOMReported();
+
+ void SetLargeAllocationFailure(OOMState aNewState);
+
+ void AnnotateAndSetOutOfMemory(OOMState* aStatePtr, OOMState aNewState);
+ void OnGC(JSContext* aContext, JSGCStatus aStatus, JS::GCReason aReason);
+ void OnOutOfMemory();
+ void OnLargeAllocationFailure();
+
+ JSRuntime* Runtime() { return mJSRuntime; }
+ const JSRuntime* Runtime() const { return mJSRuntime; }
+
+ bool HasPendingIdleGCTask() const {
+ // Idle GC task associates with JSRuntime.
+ MOZ_ASSERT_IF(mHasPendingIdleGCTask, Runtime());
+ return mHasPendingIdleGCTask;
+ }
+ void SetPendingIdleGCTask() {
+ // Idle GC task associates with JSRuntime.
+ MOZ_ASSERT(Runtime());
+ mHasPendingIdleGCTask = true;
+ }
+ void ClearPendingIdleGCTask() { mHasPendingIdleGCTask = false; }
+
+ void RunIdleTimeGCTask() {
+ if (HasPendingIdleGCTask()) {
+ JS::MaybeRunNurseryCollection(Runtime(),
+ JS::GCReason::EAGER_NURSERY_COLLECTION);
+ ClearPendingIdleGCTask();
+ }
+ }
+
+ bool IsIdleGCTaskNeeded() {
+ return !HasPendingIdleGCTask() && Runtime() &&
+ JS::WantEagerMinorGC(Runtime()) != JS::GCReason::NO_REASON;
+ }
+
+ public:
+ void AddJSHolder(void* aHolder, nsScriptObjectTracer* aTracer,
+ JS::Zone* aZone);
+ void RemoveJSHolder(void* aHolder);
+#ifdef DEBUG
+ void AssertNoObjectsToTrace(void* aPossibleJSHolder);
+#endif
+
+ nsCycleCollectionParticipant* GCThingParticipant();
+ nsCycleCollectionParticipant* ZoneParticipant();
+
+ nsresult TraverseRoots(nsCycleCollectionNoteRootCallback& aCb);
+ virtual bool UsefulToMergeZones() const;
+ void FixWeakMappingGrayBits() const;
+ void CheckGrayBits() const;
+ bool AreGCGrayBitsValid() const;
+ void GarbageCollect(JS::GCOptions options, JS::GCReason aReason) const;
+
+ // This needs to be an nsWrapperCache, not a JSObject, because we need to know
+ // when our object gets moved. But we can't trace it (and hence update our
+ // storage), because we do not want to keep it alive. nsWrapperCache handles
+ // this for us via its "object moved" handling.
+ void NurseryWrapperAdded(nsWrapperCache* aCache);
+ void JSObjectsTenured();
+
+ void DeferredFinalize(DeferredFinalizeAppendFunction aAppendFunc,
+ DeferredFinalizeFunction aFunc, void* aThing);
+ void DeferredFinalize(nsISupports* aSupports);
+
+ void DumpJSHeap(FILE* aFile);
+
+ // Add aZone to the set of zones waiting for a GC.
+ void AddZoneWaitingForGC(JS::Zone* aZone) {
+ mZonesWaitingForGC.Insert(aZone);
+ }
+
+ static void OnZoneDestroyed(JS::GCContext* aGcx, JS::Zone* aZone);
+
+ // Prepare any zones for GC that have been passed to AddZoneWaitingForGC()
+ // since the last GC or since the last call to PrepareWaitingZonesForGC(),
+ // whichever was most recent. If there were no such zones, prepare for a
+ // full GC.
+ void PrepareWaitingZonesForGC();
+
+ // Get the current thread's CycleCollectedJSRuntime. Returns null if there
+ // isn't one.
+ static CycleCollectedJSRuntime* Get();
+
+ void SetContext(CycleCollectedJSContext* aContext);
+
+#ifdef NIGHTLY_BUILD
+ bool GetRecentDevError(JSContext* aContext,
+ JS::MutableHandle<JS::Value> aError);
+ void ClearRecentDevError();
+#endif // defined(NIGHTLY_BUILD)
+
+ private:
+ CycleCollectedJSContext* mContext;
+
+ JSGCThingParticipant mGCThingCycleCollectorGlobal;
+
+ JSZoneParticipant mJSZoneCycleCollectorGlobal;
+
+ JSRuntime* mJSRuntime;
+ bool mHasPendingIdleGCTask;
+
+ JS::GCSliceCallback mPrevGCSliceCallback;
+
+ mozilla::TimeStamp mLatestNurseryCollectionStart;
+
+ JSHolderMap mJSHolders;
+ Maybe<JSHolderMap::Iter> mHolderIter;
+
+ using DeferredFinalizerTable = nsTHashMap<DeferredFinalizeFunction, void*>;
+ DeferredFinalizerTable mDeferredFinalizerTable;
+
+ RefPtr<IncrementalFinalizeRunnable> mFinalizeRunnable;
+
+ OOMState mOutOfMemoryState;
+ OOMState mLargeAllocationFailureState;
+
+ static const size_t kSegmentSize = 512;
+ SegmentedVector<nsWrapperCache*, kSegmentSize, InfallibleAllocPolicy>
+ mNurseryObjects;
+
+ nsTHashSet<JS::Zone*> mZonesWaitingForGC;
+
+ struct EnvironmentPreparer : public js::ScriptEnvironmentPreparer {
+ void invoke(JS::Handle<JSObject*> global, Closure& closure) override;
+ };
+ EnvironmentPreparer mEnvironmentPreparer;
+
+#ifdef DEBUG
+ bool mShutdownCalled;
+#endif
+
+#ifdef NIGHTLY_BUILD
+ // Implementation of the error interceptor.
+ // Built on nightly only to avoid any possible performance impact on release
+
+ struct ErrorInterceptor final : public JSErrorInterceptor {
+ virtual void interceptError(JSContext* cx,
+ JS::Handle<JS::Value> exn) override;
+ void Shutdown(JSRuntime* rt);
+
+ // Copy of the details of the exception.
+ // We store this rather than the exception itself to avoid dealing with
+ // complicated garbage-collection scenarios, e.g. a JSContext being killed
+ // while we still hold onto an exception thrown from it.
+ struct ErrorDetails {
+ nsString mFilename;
+ nsString mMessage;
+ nsString mStack;
+ JSExnType mType;
+ uint32_t mLine;
+ uint32_t mColumn;
+ };
+
+ // If we have encountered at least one developer error,
+ // the first error we have encountered. Otherwise, or
+ // if we have reset since the latest error, `None`.
+ Maybe<ErrorDetails> mThrownError;
+ };
+ ErrorInterceptor mErrorInterceptor;
+
+#endif // defined(NIGHTLY_BUILD)
+};
+
+void TraceScriptHolder(nsISupports* aHolder, JSTracer* aTracer);
+
+} // namespace mozilla
+
+#endif // mozilla_CycleCollectedJSRuntime_h