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Diffstat (limited to 'js/src/gc/Sweeping.cpp')
| -rw-r--r-- | js/src/gc/Sweeping.cpp | 2383 |
1 files changed, 2383 insertions, 0 deletions
diff --git a/js/src/gc/Sweeping.cpp b/js/src/gc/Sweeping.cpp new file mode 100644 index 0000000000..80f4a20e74 --- /dev/null +++ b/js/src/gc/Sweeping.cpp @@ -0,0 +1,2383 @@ +/* -*- 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/. */ + +/* + * Implementation of GC sweeping. + * + * In the SpiderMonkey GC, 'sweeping' is used to mean two things: + * - updating data structures to remove pointers to dead GC things and updating + * pointers to moved GC things + * - finalizing dead GC things + * + * Furthermore, the GC carries out gray and weak marking after the start of the + * sweep phase. This is also implemented in this file. + */ + +#include "mozilla/Maybe.h" +#include "mozilla/ScopeExit.h" +#include "mozilla/TimeStamp.h" + +#include "builtin/FinalizationRegistryObject.h" +#include "builtin/WeakRefObject.h" +#include "debugger/DebugAPI.h" +#include "gc/AllocKind.h" +#include "gc/FinalizationObservers.h" +#include "gc/GCInternals.h" +#include "gc/GCLock.h" +#include "gc/GCProbes.h" +#include "gc/GCRuntime.h" +#include "gc/ParallelWork.h" +#include "gc/Statistics.h" +#include "gc/TraceKind.h" +#include "gc/WeakMap.h" +#include "gc/Zone.h" +#include "jit/JitRuntime.h" +#include "jit/JitZone.h" +#include "proxy/DeadObjectProxy.h" +#include "vm/BigIntType.h" +#include "vm/HelperThreads.h" +#include "vm/JSContext.h" +#include "vm/Time.h" +#include "vm/WrapperObject.h" + +#include "gc/PrivateIterators-inl.h" +#include "vm/GeckoProfiler-inl.h" +#include "vm/JSObject-inl.h" +#include "vm/PropMap-inl.h" +#include "vm/Shape-inl.h" +#include "vm/StringType-inl.h" + +using namespace js; +using namespace js::gc; + +using mozilla::TimeStamp; + +struct js::gc::FinalizePhase { + gcstats::PhaseKind statsPhase; + AllocKinds kinds; +}; + +/* + * Finalization order for objects swept incrementally on the main thread. + */ +static constexpr FinalizePhase ForegroundObjectFinalizePhase = { + gcstats::PhaseKind::FINALIZE_OBJECT, + {AllocKind::OBJECT0, AllocKind::OBJECT2, AllocKind::OBJECT4, + AllocKind::OBJECT8, AllocKind::OBJECT12, AllocKind::OBJECT16}}; + +/* + * Finalization order for GC things swept incrementally on the main thread. + */ +static constexpr FinalizePhase ForegroundNonObjectFinalizePhase = { + gcstats::PhaseKind::FINALIZE_NON_OBJECT, + {AllocKind::SCRIPT, AllocKind::JITCODE}}; + +/* + * Finalization order for GC things swept on the background thread. + */ +static constexpr FinalizePhase BackgroundFinalizePhases[] = { + {gcstats::PhaseKind::FINALIZE_OBJECT, + {AllocKind::FUNCTION, AllocKind::FUNCTION_EXTENDED, + AllocKind::OBJECT0_BACKGROUND, AllocKind::OBJECT2_BACKGROUND, + AllocKind::ARRAYBUFFER4, AllocKind::OBJECT4_BACKGROUND, + AllocKind::ARRAYBUFFER8, AllocKind::OBJECT8_BACKGROUND, + AllocKind::ARRAYBUFFER12, AllocKind::OBJECT12_BACKGROUND, + AllocKind::ARRAYBUFFER16, AllocKind::OBJECT16_BACKGROUND}}, + {gcstats::PhaseKind::FINALIZE_NON_OBJECT, + {AllocKind::SCOPE, AllocKind::REGEXP_SHARED, AllocKind::FAT_INLINE_STRING, + AllocKind::STRING, AllocKind::EXTERNAL_STRING, AllocKind::FAT_INLINE_ATOM, + AllocKind::ATOM, AllocKind::SYMBOL, AllocKind::BIGINT, AllocKind::SHAPE, + AllocKind::BASE_SHAPE, AllocKind::GETTER_SETTER, + AllocKind::COMPACT_PROP_MAP, AllocKind::NORMAL_PROP_MAP, + AllocKind::DICT_PROP_MAP}}}; + +template <typename T> +inline size_t Arena::finalize(JS::GCContext* gcx, AllocKind thingKind, + size_t thingSize) { + /* Enforce requirements on size of T. */ + MOZ_ASSERT(thingSize % CellAlignBytes == 0); + MOZ_ASSERT(thingSize >= MinCellSize); + MOZ_ASSERT(thingSize <= 255); + + MOZ_ASSERT(allocated()); + MOZ_ASSERT(thingKind == getAllocKind()); + MOZ_ASSERT(thingSize == getThingSize()); + MOZ_ASSERT(!onDelayedMarkingList_); + + uint_fast16_t firstThing = firstThingOffset(thingKind); + uint_fast16_t firstThingOrSuccessorOfLastMarkedThing = firstThing; + uint_fast16_t lastThing = ArenaSize - thingSize; + + FreeSpan newListHead; + FreeSpan* newListTail = &newListHead; + size_t nmarked = 0, nfinalized = 0; + + for (ArenaCellIterUnderFinalize cell(this); !cell.done(); cell.next()) { + T* t = cell.as<T>(); + if (TenuredThingIsMarkedAny(t)) { + uint_fast16_t thing = uintptr_t(t) & ArenaMask; + if (thing != firstThingOrSuccessorOfLastMarkedThing) { + // We just finished passing over one or more free things, + // so record a new FreeSpan. + newListTail->initBounds(firstThingOrSuccessorOfLastMarkedThing, + thing - thingSize, this); + newListTail = newListTail->nextSpanUnchecked(this); + } + firstThingOrSuccessorOfLastMarkedThing = thing + thingSize; + nmarked++; + } else { + t->finalize(gcx); + AlwaysPoison(t, JS_SWEPT_TENURED_PATTERN, thingSize, + MemCheckKind::MakeUndefined); + gcprobes::TenuredFinalize(t); + nfinalized++; + } + } + + if constexpr (std::is_same_v<T, JSObject>) { + if (isNewlyCreated_) { + zone->pretenuring.updateCellCountsInNewlyCreatedArenas( + nmarked + nfinalized, nmarked); + } + } + isNewlyCreated_ = 0; + + if (thingKind == AllocKind::STRING || + thingKind == AllocKind::FAT_INLINE_STRING) { + zone->markedStrings += nmarked; + zone->finalizedStrings += nfinalized; + } + + if (nmarked == 0) { + // Do nothing. The caller will update the arena appropriately. + MOZ_ASSERT(newListTail == &newListHead); + DebugOnlyPoison(data, JS_SWEPT_TENURED_PATTERN, sizeof(data), + MemCheckKind::MakeUndefined); + return nmarked; + } + + MOZ_ASSERT(firstThingOrSuccessorOfLastMarkedThing != firstThing); + uint_fast16_t lastMarkedThing = + firstThingOrSuccessorOfLastMarkedThing - thingSize; + if (lastThing == lastMarkedThing) { + // If the last thing was marked, we will have already set the bounds of + // the final span, and we just need to terminate the list. + newListTail->initAsEmpty(); + } else { + // Otherwise, end the list with a span that covers the final stretch of free + // things. + newListTail->initFinal(firstThingOrSuccessorOfLastMarkedThing, lastThing, + this); + } + + firstFreeSpan = newListHead; +#ifdef DEBUG + size_t nfree = numFreeThings(thingSize); + MOZ_ASSERT(nfree + nmarked == thingsPerArena(thingKind)); +#endif + return nmarked; +} + +// Finalize arenas from src list, releasing empty arenas if keepArenas wasn't +// specified and inserting the others into the appropriate destination size +// bins. +template <typename T> +static inline bool FinalizeTypedArenas(JS::GCContext* gcx, ArenaList& src, + SortedArenaList& dest, + AllocKind thingKind, + SliceBudget& budget) { + MOZ_ASSERT(gcx->isFinalizing()); + + size_t thingSize = Arena::thingSize(thingKind); + size_t thingsPerArena = Arena::thingsPerArena(thingKind); + size_t markCount = 0; + + auto updateMarkCount = mozilla::MakeScopeExit([&] { + GCRuntime* gc = &gcx->runtimeFromAnyThread()->gc; + gc->stats().addCount(gcstats::COUNT_CELLS_MARKED, markCount); + }); + + while (Arena* arena = src.takeFirstArena()) { + size_t nmarked = arena->finalize<T>(gcx, thingKind, thingSize); + size_t nfree = thingsPerArena - nmarked; + + markCount += nmarked; + + if (nmarked) { + dest.insertAt(arena, nfree); + } else { + arena->chunk()->recycleArena(arena, dest, thingsPerArena); + } + + budget.step(thingsPerArena); + if (budget.isOverBudget()) { + return false; + } + } + + return true; +} + +/* + * Finalize the list of areans. + */ +static bool FinalizeArenas(JS::GCContext* gcx, ArenaList& src, + SortedArenaList& dest, AllocKind thingKind, + SliceBudget& budget) { + switch (thingKind) { +#define EXPAND_CASE(allocKind, traceKind, type, sizedType, bgFinal, nursery, \ + compact) \ + case AllocKind::allocKind: \ + return FinalizeTypedArenas<type>(gcx, src, dest, thingKind, budget); + FOR_EACH_ALLOCKIND(EXPAND_CASE) +#undef EXPAND_CASE + + default: + MOZ_CRASH("Invalid alloc kind"); + } +} + +void GCRuntime::initBackgroundSweep(Zone* zone, JS::GCContext* gcx, + const FinalizePhase& phase) { + gcstats::AutoPhase ap(stats(), phase.statsPhase); + for (auto kind : phase.kinds) { + zone->arenas.initBackgroundSweep(kind); + } +} + +void ArenaLists::initBackgroundSweep(AllocKind thingKind) { + MOZ_ASSERT(IsBackgroundFinalized(thingKind)); + MOZ_ASSERT(concurrentUse(thingKind) == ConcurrentUse::None); + + if (!collectingArenaList(thingKind).isEmpty()) { + concurrentUse(thingKind) = ConcurrentUse::BackgroundFinalize; + } +} + +void GCRuntime::backgroundFinalize(JS::GCContext* gcx, Zone* zone, + AllocKind kind, Arena** empty) { + MOZ_ASSERT(empty); + + ArenaLists* lists = &zone->arenas; + ArenaList& arenas = lists->collectingArenaList(kind); + if (arenas.isEmpty()) { + MOZ_ASSERT(lists->concurrentUse(kind) == ArenaLists::ConcurrentUse::None); + return; + } + + SortedArenaList finalizedSorted(Arena::thingsPerArena(kind)); + + auto unlimited = SliceBudget::unlimited(); + FinalizeArenas(gcx, arenas, finalizedSorted, kind, unlimited); + MOZ_ASSERT(arenas.isEmpty()); + + finalizedSorted.extractEmpty(empty); + + // When marking begins, all arenas are moved from arenaLists to + // collectingArenaLists. When the mutator runs, new arenas are allocated in + // arenaLists. Now that finalization is complete, we want to merge these lists + // back together. + + // We must take the GC lock to be able to safely modify the ArenaList; + // however, this does not by itself make the changes visible to all threads, + // as not all threads take the GC lock to read the ArenaLists. + // That safety is provided by the ReleaseAcquire memory ordering of the + // background finalize state, which we explicitly set as the final step. + { + AutoLockGC lock(rt); + MOZ_ASSERT(lists->concurrentUse(kind) == + ArenaLists::ConcurrentUse::BackgroundFinalize); + lists->mergeFinalizedArenas(kind, finalizedSorted); + } + + lists->concurrentUse(kind) = ArenaLists::ConcurrentUse::None; +} + +// After finalizing arenas, merge the following to get the final state of an +// arena list: +// - arenas allocated during marking +// - arenas allocated during sweeping +// - finalized arenas +void ArenaLists::mergeFinalizedArenas(AllocKind kind, + SortedArenaList& finalizedArenas) { +#ifdef DEBUG + // Updating arena lists off-thread requires taking the GC lock because the + // main thread uses these when allocating. + if (IsBackgroundFinalized(kind)) { + runtimeFromAnyThread()->gc.assertCurrentThreadHasLockedGC(); + } +#endif + + ArenaList& arenas = arenaList(kind); + + ArenaList allocatedDuringCollection = std::move(arenas); + arenas = finalizedArenas.toArenaList(); + arenas.insertListWithCursorAtEnd(allocatedDuringCollection); + + collectingArenaList(kind).clear(); +} + +void ArenaLists::queueForegroundThingsForSweep() { + gcCompactPropMapArenasToUpdate = + collectingArenaList(AllocKind::COMPACT_PROP_MAP).head(); + gcNormalPropMapArenasToUpdate = + collectingArenaList(AllocKind::NORMAL_PROP_MAP).head(); +} + +void GCRuntime::sweepBackgroundThings(ZoneList& zones) { + if (zones.isEmpty()) { + return; + } + + JS::GCContext* gcx = TlsGCContext.get(); + MOZ_ASSERT(gcx->isFinalizing()); + + // Sweep zones in order. The atoms zone must be finalized last as other + // zones may have direct pointers into it. + while (!zones.isEmpty()) { + Zone* zone = zones.removeFront(); + MOZ_ASSERT(zone->isGCFinished()); + + TimeStamp startTime = TimeStamp::Now(); + + Arena* emptyArenas = zone->arenas.takeSweptEmptyArenas(); + + // We must finalize thing kinds in the order specified by + // BackgroundFinalizePhases. + for (auto phase : BackgroundFinalizePhases) { + for (auto kind : phase.kinds) { + backgroundFinalize(gcx, zone, kind, &emptyArenas); + } + } + + // Release any arenas that are now empty. + // + // Empty arenas are only released after everything has been finalized so + // that it's still possible to get a thing's zone after the thing has been + // finalized. The HeapPtr destructor depends on this, and this allows + // HeapPtrs between things of different alloc kind regardless of + // finalization order. + // + // Periodically drop and reaquire the GC lock every so often to avoid + // blocking the main thread from allocating chunks. + static const size_t LockReleasePeriod = 32; + + while (emptyArenas) { + AutoLockGC lock(this); + for (size_t i = 0; i < LockReleasePeriod && emptyArenas; i++) { + Arena* arena = emptyArenas; + emptyArenas = emptyArenas->next; + releaseArena(arena, lock); + } + } + + // Record time spent sweeping this zone. + TimeStamp endTime = TimeStamp::Now(); + zone->perZoneGCTime += endTime - startTime; + } +} + +void GCRuntime::assertBackgroundSweepingFinished() { +#ifdef DEBUG + { + AutoLockHelperThreadState lock; + MOZ_ASSERT(backgroundSweepZones.ref().isEmpty()); + } + + for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) { + for (auto kind : AllAllocKinds()) { + MOZ_ASSERT_IF(state() != State::Prepare && state() != State::Mark && + state() != State::Sweep, + zone->arenas.collectingArenaList(kind).isEmpty()); + MOZ_ASSERT(zone->arenas.doneBackgroundFinalize(kind)); + } + } +#endif +} + +void GCRuntime::queueZonesAndStartBackgroundSweep(ZoneList&& zones) { + { + AutoLockHelperThreadState lock; + MOZ_ASSERT(!requestSliceAfterBackgroundTask); + backgroundSweepZones.ref().appendList(std::move(zones)); + if (useBackgroundThreads) { + sweepTask.startOrRunIfIdle(lock); + } + } + if (!useBackgroundThreads) { + sweepTask.join(); + sweepTask.runFromMainThread(); + } +} + +BackgroundSweepTask::BackgroundSweepTask(GCRuntime* gc) + : GCParallelTask(gc, gcstats::PhaseKind::SWEEP, GCUse::Finalizing) {} + +void BackgroundSweepTask::run(AutoLockHelperThreadState& lock) { + gc->sweepFromBackgroundThread(lock); +} + +void GCRuntime::sweepFromBackgroundThread(AutoLockHelperThreadState& lock) { + do { + ZoneList zones; + zones.appendList(std::move(backgroundSweepZones.ref())); + + AutoUnlockHelperThreadState unlock(lock); + sweepBackgroundThings(zones); + + // The main thread may call queueZonesAndStartBackgroundSweep() while this + // is running so we must check there is no more work after releasing the + // lock. + } while (!backgroundSweepZones.ref().isEmpty()); + + maybeRequestGCAfterBackgroundTask(lock); +} + +void GCRuntime::waitBackgroundSweepEnd() { + sweepTask.join(); + if (state() != State::Sweep) { + assertBackgroundSweepingFinished(); + } +} + +void GCRuntime::startBackgroundFree() { + AutoLockHelperThreadState lock; + freeTask.startOrRunIfIdle(lock); +} + +BackgroundFreeTask::BackgroundFreeTask(GCRuntime* gc) + : GCParallelTask(gc, gcstats::PhaseKind::NONE) { + // This can occur outside GCs so doesn't have a stats phase. +} + +void BackgroundFreeTask::run(AutoLockHelperThreadState& lock) { + gc->freeFromBackgroundThread(lock); +} + +void GCRuntime::freeFromBackgroundThread(AutoLockHelperThreadState& lock) { + do { + LifoAlloc lifoBlocks(JSContext::TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE); + lifoBlocks.transferFrom(&lifoBlocksToFree.ref()); + + Nursery::BufferSet buffers; + std::swap(buffers, buffersToFreeAfterMinorGC.ref()); + + AutoUnlockHelperThreadState unlock(lock); + + lifoBlocks.freeAll(); + + JS::GCContext* gcx = TlsGCContext.get(); + for (Nursery::BufferSet::Range r = buffers.all(); !r.empty(); + r.popFront()) { + // Malloc memory associated with nursery objects is not tracked as these + // are assumed to be short lived. + gcx->freeUntracked(r.front()); + } + } while (!lifoBlocksToFree.ref().isEmpty() || + !buffersToFreeAfterMinorGC.ref().empty()); +} + +void GCRuntime::waitBackgroundFreeEnd() { freeTask.join(); } + +template <class ZoneIterT> +IncrementalProgress GCRuntime::markWeakReferences( + SliceBudget& incrementalBudget) { + MOZ_ASSERT(!marker().isWeakMarking()); + + gcstats::AutoPhase ap1(stats(), gcstats::PhaseKind::MARK_WEAK); + + auto unlimited = SliceBudget::unlimited(); + SliceBudget& budget = + marker().incrementalWeakMapMarkingEnabled ? incrementalBudget : unlimited; + + // Ensure we don't return to the mutator while we're still in weak marking + // mode. + auto leaveOnExit = + mozilla::MakeScopeExit([&] { marker().leaveWeakMarkingMode(); }); + + if (marker().enterWeakMarkingMode()) { + // If there was an 'enter-weak-marking-mode' token in the queue, then it + // and everything after it will still be in the queue so we can process + // them now. + while (processTestMarkQueue() == QueueYielded) { + }; + + // Do not rely on the information about not-yet-marked weak keys that have + // been collected by barriers. Clear out the gcEphemeronEdges entries and + // rebuild the full table. Note that this a cross-zone operation; delegate + // zone entries will be populated by map zone traversals, so everything + // needs to be cleared first, then populated. + if (!marker().incrementalWeakMapMarkingEnabled) { + for (ZoneIterT zone(this); !zone.done(); zone.next()) { + AutoEnterOOMUnsafeRegion oomUnsafe; + if (!zone->gcEphemeronEdges().clear()) { + oomUnsafe.crash("clearing weak keys when entering weak marking mode"); + } + } + } + + for (ZoneIterT zone(this); !zone.done(); zone.next()) { + if (zone->enterWeakMarkingMode(&marker(), budget) == NotFinished) { + return NotFinished; + } + } + } + + bool markedAny = true; + while (markedAny) { + if (!marker().markUntilBudgetExhausted(budget)) { + MOZ_ASSERT(marker().incrementalWeakMapMarkingEnabled); + return NotFinished; + } + + markedAny = false; + + if (!marker().isWeakMarking()) { + for (ZoneIterT zone(this); !zone.done(); zone.next()) { + markedAny |= WeakMapBase::markZoneIteratively(zone, &marker()); + } + } + + markedAny |= jit::JitRuntime::MarkJitcodeGlobalTableIteratively(&marker()); + } + + assertNoMarkingWork(); + + return Finished; +} + +IncrementalProgress GCRuntime::markWeakReferencesInCurrentGroup( + SliceBudget& budget) { + return markWeakReferences<SweepGroupZonesIter>(budget); +} + +template <class ZoneIterT> +IncrementalProgress GCRuntime::markGrayRoots(SliceBudget& budget, + gcstats::PhaseKind phase) { + MOZ_ASSERT(marker().markColor() == MarkColor::Gray); + + gcstats::AutoPhase ap(stats(), phase); + + AutoUpdateLiveCompartments updateLive(this); + marker().setRootMarkingMode(true); + auto guard = + mozilla::MakeScopeExit([this]() { marker().setRootMarkingMode(false); }); + + IncrementalProgress result = + traceEmbeddingGrayRoots(marker().tracer(), budget); + if (result == NotFinished) { + return NotFinished; + } + + Compartment::traceIncomingCrossCompartmentEdgesForZoneGC( + marker().tracer(), Compartment::GrayEdges); + + return Finished; +} + +IncrementalProgress GCRuntime::markAllWeakReferences() { + SliceBudget budget = SliceBudget::unlimited(); + return markWeakReferences<GCZonesIter>(budget); +} + +void GCRuntime::markAllGrayReferences(gcstats::PhaseKind phase) { + SliceBudget budget = SliceBudget::unlimited(); + markGrayRoots<GCZonesIter>(budget, phase); + drainMarkStack(); +} + +void GCRuntime::dropStringWrappers() { + /* + * String "wrappers" are dropped on GC because their presence would require + * us to sweep the wrappers in all compartments every time we sweep a + * compartment group. + */ + for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) { + zone->dropStringWrappersOnGC(); + } +} + +/* + * Group zones that must be swept at the same time. + * + * From the point of view of the mutator, groups of zones transition atomically + * from marking to sweeping. If compartment A has an edge to an unmarked object + * in compartment B, then we must not start sweeping A in a later slice than we + * start sweeping B. That's because a write barrier in A could lead to the + * unmarked object in B becoming marked. However, if we had already swept that + * object, we would be in trouble. + * + * If we consider these dependencies as a graph, then all the compartments in + * any strongly-connected component of this graph must start sweeping in the + * same slice. + * + * Tarjan's algorithm is used to calculate the components. + */ + +bool Compartment::findSweepGroupEdges() { + Zone* source = zone(); + for (WrappedObjectCompartmentEnum e(this); !e.empty(); e.popFront()) { + Compartment* targetComp = e.front(); + Zone* target = targetComp->zone(); + + if (!target->isGCMarking() || source->hasSweepGroupEdgeTo(target)) { + continue; + } + + for (ObjectWrapperEnum e(this, targetComp); !e.empty(); e.popFront()) { + JSObject* key = e.front().mutableKey(); + MOZ_ASSERT(key->zone() == target); + + // Add an edge to the wrapped object's zone to ensure that the wrapper + // zone is not still being marked when we start sweeping the wrapped zone. + // As an optimization, if the wrapped object is already marked black there + // is no danger of later marking and we can skip this. + if (key->isMarkedBlack()) { + continue; + } + + if (!source->addSweepGroupEdgeTo(target)) { + return false; + } + + // We don't need to consider any more wrappers for this target + // compartment since we already added an edge. + break; + } + } + + return true; +} + +bool Zone::findSweepGroupEdges(Zone* atomsZone) { + MOZ_ASSERT_IF(this != atomsZone, !isAtomsZone()); + +#ifdef DEBUG + if (FinalizationObservers* observers = finalizationObservers()) { + observers->checkTables(); + } +#endif + + // Any zone may have a pointer to an atom in the atoms zone, and these aren't + // in the cross compartment map. + if (atomsZone->wasGCStarted() && !addSweepGroupEdgeTo(atomsZone)) { + return false; + } + + for (CompartmentsInZoneIter comp(this); !comp.done(); comp.next()) { + if (!comp->findSweepGroupEdges()) { + return false; + } + } + + return WeakMapBase::findSweepGroupEdgesForZone(this); +} + +bool GCRuntime::addEdgesForMarkQueue() { +#ifdef DEBUG + // For testing only. + // + // Add edges between all objects mentioned in the test mark queue, since + // otherwise they will get marked in a different order than their sweep + // groups. Note that this is only done at the beginning of an incremental + // collection, so it is possible for objects to be added later that do not + // follow the sweep group ordering. These objects will wait until their sweep + // group comes up, or will be skipped if their sweep group is already past. + JS::Zone* prevZone = nullptr; + for (size_t i = 0; i < testMarkQueue.length(); i++) { + Value val = testMarkQueue[i].get(); + if (!val.isObject()) { + continue; + } + JSObject* obj = &val.toObject(); + JS::Zone* zone = obj->zone(); + if (!zone->isGCMarking()) { + continue; + } + if (prevZone && prevZone != zone) { + if (!prevZone->addSweepGroupEdgeTo(zone)) { + return false; + } + } + prevZone = zone; + } +#endif + return true; +} + +bool GCRuntime::findSweepGroupEdges() { + for (GCZonesIter zone(this); !zone.done(); zone.next()) { + if (!zone->findSweepGroupEdges(atomsZone())) { + return false; + } + } + + if (!addEdgesForMarkQueue()) { + return false; + } + + return DebugAPI::findSweepGroupEdges(rt); +} + +void GCRuntime::groupZonesForSweeping(JS::GCReason reason) { +#ifdef DEBUG + for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) { + MOZ_ASSERT(zone->gcSweepGroupEdges().empty()); + } +#endif + + JSContext* cx = rt->mainContextFromOwnThread(); + ZoneComponentFinder finder(cx); + if (!isIncremental || !findSweepGroupEdges()) { + finder.useOneComponent(); + } + + // Use one component for two-slice zeal modes. + if (useZeal && hasIncrementalTwoSliceZealMode()) { + finder.useOneComponent(); + } + + for (GCZonesIter zone(this); !zone.done(); zone.next()) { + MOZ_ASSERT(zone->isGCMarking()); + finder.addNode(zone); + } + sweepGroups = finder.getResultsList(); + currentSweepGroup = sweepGroups; + sweepGroupIndex = 1; + + for (GCZonesIter zone(this); !zone.done(); zone.next()) { + zone->clearSweepGroupEdges(); + } + +#ifdef DEBUG + unsigned idx = sweepGroupIndex; + for (Zone* head = currentSweepGroup; head; head = head->nextGroup()) { + for (Zone* zone = head; zone; zone = zone->nextNodeInGroup()) { + MOZ_ASSERT(zone->isGCMarking()); + zone->gcSweepGroupIndex = idx; + } + idx++; + } + + MOZ_ASSERT_IF(!isIncremental, !currentSweepGroup->nextGroup()); + for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) { + MOZ_ASSERT(zone->gcSweepGroupEdges().empty()); + } +#endif +} + +void GCRuntime::getNextSweepGroup() { + currentSweepGroup = currentSweepGroup->nextGroup(); + ++sweepGroupIndex; + if (!currentSweepGroup) { + abortSweepAfterCurrentGroup = false; + return; + } + + MOZ_ASSERT_IF(abortSweepAfterCurrentGroup, !isIncremental); + if (!isIncremental) { + ZoneComponentFinder::mergeGroups(currentSweepGroup); + } + + for (Zone* zone = currentSweepGroup; zone; zone = zone->nextNodeInGroup()) { + MOZ_ASSERT(zone->gcState() == zone->initialMarkingState()); + MOZ_ASSERT(!zone->isQueuedForBackgroundSweep()); + } + + if (abortSweepAfterCurrentGroup) { + markTask.join(); + + // Abort collection of subsequent sweep groups. + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + MOZ_ASSERT(!zone->gcNextGraphComponent); + zone->changeGCState(zone->initialMarkingState(), Zone::NoGC); + zone->arenas.unmarkPreMarkedFreeCells(); + zone->arenas.mergeArenasFromCollectingLists(); + zone->clearGCSliceThresholds(); + } + + for (SweepGroupCompartmentsIter comp(rt); !comp.done(); comp.next()) { + resetGrayList(comp); + } + + abortSweepAfterCurrentGroup = false; + currentSweepGroup = nullptr; + } +} + +/* + * Gray marking: + * + * At the end of collection, anything reachable from a gray root that has not + * otherwise been marked black must be marked gray. + * + * This means that when marking things gray we must not allow marking to leave + * the current compartment group, as that could result in things being marked + * gray when they might subsequently be marked black. To achieve this, when we + * find a cross compartment pointer we don't mark the referent but add it to a + * singly-linked list of incoming gray pointers that is stored with each + * compartment. + * + * The list head is stored in Compartment::gcIncomingGrayPointers and contains + * cross compartment wrapper objects. The next pointer is stored in the second + * extra slot of the cross compartment wrapper. + * + * The list is created during gray marking when one of the + * MarkCrossCompartmentXXX functions is called for a pointer that leaves the + * current compartent group. This calls DelayCrossCompartmentGrayMarking to + * push the referring object onto the list. + * + * The list is traversed and then unlinked in + * GCRuntime::markIncomingGrayCrossCompartmentPointers. + */ + +static bool IsGrayListObject(JSObject* obj) { + MOZ_ASSERT(obj); + return obj->is<CrossCompartmentWrapperObject>() && !IsDeadProxyObject(obj); +} + +/* static */ +unsigned ProxyObject::grayLinkReservedSlot(JSObject* obj) { + MOZ_ASSERT(IsGrayListObject(obj)); + return CrossCompartmentWrapperObject::GrayLinkReservedSlot; +} + +#ifdef DEBUG +static void AssertNotOnGrayList(JSObject* obj) { + MOZ_ASSERT_IF( + IsGrayListObject(obj), + GetProxyReservedSlot(obj, ProxyObject::grayLinkReservedSlot(obj)) + .isUndefined()); +} +#endif + +static void AssertNoWrappersInGrayList(JSRuntime* rt) { +#ifdef DEBUG + for (CompartmentsIter c(rt); !c.done(); c.next()) { + MOZ_ASSERT(!c->gcIncomingGrayPointers); + for (Compartment::ObjectWrapperEnum e(c); !e.empty(); e.popFront()) { + AssertNotOnGrayList(e.front().value().unbarrieredGet()); + } + } +#endif +} + +static JSObject* CrossCompartmentPointerReferent(JSObject* obj) { + MOZ_ASSERT(IsGrayListObject(obj)); + return &obj->as<ProxyObject>().private_().toObject(); +} + +static JSObject* NextIncomingCrossCompartmentPointer(JSObject* prev, + bool unlink) { + unsigned slot = ProxyObject::grayLinkReservedSlot(prev); + JSObject* next = GetProxyReservedSlot(prev, slot).toObjectOrNull(); + MOZ_ASSERT_IF(next, IsGrayListObject(next)); + + if (unlink) { + SetProxyReservedSlot(prev, slot, UndefinedValue()); + } + + return next; +} + +void js::gc::DelayCrossCompartmentGrayMarking(GCMarker* maybeMarker, + JSObject* src) { + MOZ_ASSERT_IF(!maybeMarker, !JS::RuntimeHeapIsBusy()); + MOZ_ASSERT(IsGrayListObject(src)); + MOZ_ASSERT(src->isMarkedGray()); + + AutoTouchingGrayThings tgt; + + mozilla::Maybe<AutoLockGC> lock; + if (maybeMarker && maybeMarker->isParallelMarking()) { + // Synchronize access to JSCompartment::gcIncomingGrayPointers. + // + // TODO: Instead of building this list we could scan all incoming CCWs and + // mark through gray ones when marking gray roots for a sweep group. + lock.emplace(maybeMarker->runtime()); + } + + /* Called from MarkCrossCompartmentXXX functions. */ + unsigned slot = ProxyObject::grayLinkReservedSlot(src); + JSObject* dest = CrossCompartmentPointerReferent(src); + Compartment* comp = dest->compartment(); + + if (GetProxyReservedSlot(src, slot).isUndefined()) { + SetProxyReservedSlot(src, slot, + ObjectOrNullValue(comp->gcIncomingGrayPointers)); + comp->gcIncomingGrayPointers = src; + } else { + MOZ_ASSERT(GetProxyReservedSlot(src, slot).isObjectOrNull()); + } + +#ifdef DEBUG + /* + * Assert that the object is in our list, also walking the list to check its + * integrity. + */ + JSObject* obj = comp->gcIncomingGrayPointers; + bool found = false; + while (obj) { + if (obj == src) { + found = true; + } + obj = NextIncomingCrossCompartmentPointer(obj, false); + } + MOZ_ASSERT(found); +#endif +} + +void GCRuntime::markIncomingGrayCrossCompartmentPointers() { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK_INCOMING_GRAY); + + for (SweepGroupCompartmentsIter c(rt); !c.done(); c.next()) { + MOZ_ASSERT(c->zone()->isGCMarkingBlackAndGray()); + MOZ_ASSERT_IF(c->gcIncomingGrayPointers, + IsGrayListObject(c->gcIncomingGrayPointers)); + + for (JSObject* src = c->gcIncomingGrayPointers; src; + src = NextIncomingCrossCompartmentPointer(src, true)) { + JSObject* dst = CrossCompartmentPointerReferent(src); + MOZ_ASSERT(dst->compartment() == c); + MOZ_ASSERT_IF(src->asTenured().isMarkedBlack(), + dst->asTenured().isMarkedBlack()); + + if (src->asTenured().isMarkedGray()) { + TraceManuallyBarrieredEdge(marker().tracer(), &dst, + "cross-compartment gray pointer"); + } + } + + c->gcIncomingGrayPointers = nullptr; + } +} + +static bool RemoveFromGrayList(JSObject* wrapper) { + AutoTouchingGrayThings tgt; + + if (!IsGrayListObject(wrapper)) { + return false; + } + + unsigned slot = ProxyObject::grayLinkReservedSlot(wrapper); + if (GetProxyReservedSlot(wrapper, slot).isUndefined()) { + return false; /* Not on our list. */ + } + + JSObject* tail = GetProxyReservedSlot(wrapper, slot).toObjectOrNull(); + SetProxyReservedSlot(wrapper, slot, UndefinedValue()); + + Compartment* comp = CrossCompartmentPointerReferent(wrapper)->compartment(); + JSObject* obj = comp->gcIncomingGrayPointers; + if (obj == wrapper) { + comp->gcIncomingGrayPointers = tail; + return true; + } + + while (obj) { + unsigned slot = ProxyObject::grayLinkReservedSlot(obj); + JSObject* next = GetProxyReservedSlot(obj, slot).toObjectOrNull(); + if (next == wrapper) { + js::detail::SetProxyReservedSlotUnchecked(obj, slot, + ObjectOrNullValue(tail)); + return true; + } + obj = next; + } + + MOZ_CRASH("object not found in gray link list"); +} + +void GCRuntime::resetGrayList(Compartment* comp) { + JSObject* src = comp->gcIncomingGrayPointers; + while (src) { + src = NextIncomingCrossCompartmentPointer(src, true); + } + comp->gcIncomingGrayPointers = nullptr; +} + +#ifdef DEBUG +static bool HasIncomingCrossCompartmentPointers(JSRuntime* rt) { + for (SweepGroupCompartmentsIter c(rt); !c.done(); c.next()) { + if (c->gcIncomingGrayPointers) { + return true; + } + } + + return false; +} +#endif + +void js::NotifyGCNukeWrapper(JSContext* cx, JSObject* wrapper) { + MOZ_ASSERT(IsCrossCompartmentWrapper(wrapper)); + + /* + * References to target of wrapper are being removed, we no longer have to + * remember to mark it. + */ + RemoveFromGrayList(wrapper); + + /* + * Clean up WeakRef maps which might include this wrapper. + */ + JSObject* target = UncheckedUnwrapWithoutExpose(wrapper); + if (target->is<WeakRefObject>()) { + WeakRefObject* weakRef = &target->as<WeakRefObject>(); + if (weakRef->target()) { + cx->runtime()->gc.nukeWeakRefWrapper(wrapper, weakRef); + } + } + + /* + * Clean up FinalizationRecord record objects which might be the target of + * this wrapper. + */ + if (target->is<FinalizationRecordObject>()) { + auto* record = &target->as<FinalizationRecordObject>(); + cx->runtime()->gc.nukeFinalizationRecordWrapper(wrapper, record); + } +} + +enum { + JS_GC_SWAP_OBJECT_A_REMOVED = 1 << 0, + JS_GC_SWAP_OBJECT_B_REMOVED = 1 << 1 +}; + +unsigned js::NotifyGCPreSwap(JSObject* a, JSObject* b) { + /* + * Two objects in the same compartment are about to have had their contents + * swapped. If either of them are in our gray pointer list, then we remove + * them from the lists, returning a bitset indicating what happened. + */ + return (RemoveFromGrayList(a) ? JS_GC_SWAP_OBJECT_A_REMOVED : 0) | + (RemoveFromGrayList(b) ? JS_GC_SWAP_OBJECT_B_REMOVED : 0); +} + +void js::NotifyGCPostSwap(JSObject* a, JSObject* b, unsigned removedFlags) { + /* + * Two objects in the same compartment have had their contents swapped. If + * either of them were in our gray pointer list, we re-add them again. + */ + if (removedFlags & JS_GC_SWAP_OBJECT_A_REMOVED) { + DelayCrossCompartmentGrayMarking(nullptr, b); + } + if (removedFlags & JS_GC_SWAP_OBJECT_B_REMOVED) { + DelayCrossCompartmentGrayMarking(nullptr, a); + } +} + +static inline void MaybeCheckWeakMapMarking(GCRuntime* gc) { +#if defined(JS_GC_ZEAL) || defined(DEBUG) + + bool shouldCheck; +# if defined(DEBUG) + shouldCheck = true; +# else + shouldCheck = gc->hasZealMode(ZealMode::CheckWeakMapMarking); +# endif + + if (shouldCheck) { + for (SweepGroupZonesIter zone(gc); !zone.done(); zone.next()) { + MOZ_RELEASE_ASSERT(WeakMapBase::checkMarkingForZone(zone)); + } + } + +#endif +} + +IncrementalProgress GCRuntime::beginMarkingSweepGroup(JS::GCContext* gcx, + SliceBudget& budget) { +#ifdef DEBUG + MOZ_ASSERT(!markOnBackgroundThreadDuringSweeping); + assertNoMarkingWork(); + for (auto& marker : markers) { + MOZ_ASSERT(marker->markColor() == MarkColor::Black); + } + MOZ_ASSERT(cellsToAssertNotGray.ref().empty()); +#endif + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK); + + // Change state of current group to MarkBlackAndGray to restrict gray marking + // to this group. Note that there may be pointers to the atoms zone, and these + // will be marked through, as they are not marked with + // TraceCrossCompartmentEdge. + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + zone->changeGCState(zone->initialMarkingState(), Zone::MarkBlackAndGray); + } + + AutoSetMarkColor setColorGray(marker(), MarkColor::Gray); + + // Mark incoming gray pointers from previously swept compartments. + markIncomingGrayCrossCompartmentPointers(); + + return Finished; +} + +IncrementalProgress GCRuntime::markGrayRootsInCurrentGroup( + JS::GCContext* gcx, SliceBudget& budget) { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK); + + AutoSetMarkColor setColorGray(marker(), MarkColor::Gray); + + return markGrayRoots<SweepGroupZonesIter>(budget, + gcstats::PhaseKind::MARK_GRAY); +} + +IncrementalProgress GCRuntime::markGray(JS::GCContext* gcx, + SliceBudget& budget) { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK); + + if (markUntilBudgetExhausted(budget, AllowParallelMarking) == NotFinished) { + return NotFinished; + } + + return Finished; +} + +IncrementalProgress GCRuntime::endMarkingSweepGroup(JS::GCContext* gcx, + SliceBudget& budget) { +#ifdef DEBUG + MOZ_ASSERT(!markOnBackgroundThreadDuringSweeping); + assertNoMarkingWork(); + for (auto& marker : markers) { + MOZ_ASSERT(marker->markColor() == MarkColor::Black); + } + MOZ_ASSERT(!HasIncomingCrossCompartmentPointers(rt)); +#endif + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK); + + if (markWeakReferencesInCurrentGroup(budget) == NotFinished) { + return NotFinished; + } + + AutoSetMarkColor setColorGray(marker(), MarkColor::Gray); + + // Mark transitively inside the current compartment group. + if (markWeakReferencesInCurrentGroup(budget) == NotFinished) { + return NotFinished; + } + + MOZ_ASSERT(marker().isDrained()); + + // We must not yield after this point before we start sweeping the group. + safeToYield = false; + + MaybeCheckWeakMapMarking(this); + + return Finished; +} + +// Causes the given WeakCache to be swept when run. +class ImmediateSweepWeakCacheTask : public GCParallelTask { + Zone* zone; + JS::detail::WeakCacheBase& cache; + + ImmediateSweepWeakCacheTask(const ImmediateSweepWeakCacheTask&) = delete; + + public: + ImmediateSweepWeakCacheTask(GCRuntime* gc, Zone* zone, + JS::detail::WeakCacheBase& wc) + : GCParallelTask(gc, gcstats::PhaseKind::SWEEP_WEAK_CACHES), + zone(zone), + cache(wc) {} + + ImmediateSweepWeakCacheTask(ImmediateSweepWeakCacheTask&& other) + : GCParallelTask(std::move(other)), + zone(other.zone), + cache(other.cache) {} + + void run(AutoLockHelperThreadState& lock) override { + AutoUnlockHelperThreadState unlock(lock); + AutoSetThreadIsSweeping threadIsSweeping(zone); + SweepingTracer trc(gc->rt); + cache.traceWeak(&trc, &gc->storeBuffer()); + } +}; + +void GCRuntime::updateAtomsBitmap() { + DenseBitmap marked; + if (atomMarking.computeBitmapFromChunkMarkBits(rt, marked)) { + for (GCZonesIter zone(this); !zone.done(); zone.next()) { + atomMarking.refineZoneBitmapForCollectedZone(zone, marked); + } + } else { + // Ignore OOM in computeBitmapFromChunkMarkBits. The + // refineZoneBitmapForCollectedZone call can only remove atoms from the + // zone bitmap, so it is conservative to just not call it. + } + + atomMarking.markAtomsUsedByUncollectedZones(rt); + + // For convenience sweep these tables non-incrementally as part of bitmap + // sweeping; they are likely to be much smaller than the main atoms table. + SweepingTracer trc(rt); + rt->symbolRegistry().traceWeak(&trc); +} + +void GCRuntime::sweepCCWrappers() { + SweepingTracer trc(rt); + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + zone->traceWeakCCWEdges(&trc); + } +} + +void GCRuntime::sweepRealmGlobals() { + SweepingTracer trc(rt); + for (SweepGroupRealmsIter r(this); !r.done(); r.next()) { + AutoSetThreadIsSweeping threadIsSweeping(r->zone()); + r->traceWeakGlobalEdge(&trc); + } +} + +void GCRuntime::sweepMisc() { + SweepingTracer trc(rt); + for (SweepGroupRealmsIter r(this); !r.done(); r.next()) { + AutoSetThreadIsSweeping threadIsSweeping(r->zone()); + r->traceWeakSavedStacks(&trc); + r->traceWeakRegExps(&trc); + } + for (SweepGroupCompartmentsIter c(this); !c.done(); c.next()) { + AutoSetThreadIsSweeping threadIsSweeping(c->zone()); + c->traceWeakNativeIterators(&trc); + } +} + +void GCRuntime::sweepCompressionTasks() { + JSRuntime* runtime = rt; + + // Attach finished compression tasks. + AutoLockHelperThreadState lock; + AttachFinishedCompressions(runtime, lock); + SweepPendingCompressions(lock); +} + +void GCRuntime::sweepWeakMaps() { + SweepingTracer trc(rt); + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + /* No need to look up any more weakmap keys from this sweep group. */ + AutoEnterOOMUnsafeRegion oomUnsafe; + if (!zone->gcEphemeronEdges().clear()) { + oomUnsafe.crash("clearing weak keys in beginSweepingSweepGroup()"); + } + + // Lock the storebuffer since this may access it when rehashing or resizing + // the tables. + AutoLockStoreBuffer lock(&storeBuffer()); + zone->sweepWeakMaps(&trc); + } +} + +void GCRuntime::sweepUniqueIds() { + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + AutoSetThreadIsSweeping threadIsSweeping(zone); + zone->sweepUniqueIds(); + } +} + +void JS::Zone::sweepUniqueIds() { + SweepingTracer trc(runtimeFromAnyThread()); + uniqueIds().traceWeak(&trc); +} + +/* static */ +bool UniqueIdGCPolicy::traceWeak(JSTracer* trc, Cell** keyp, uint64_t* valuep) { + // Since this is only ever used for sweeping, we can optimize it for that + // case. (Compacting GC updates this table manually when it moves a cell.) + MOZ_ASSERT(trc->kind() == JS::TracerKind::Sweeping); + return (*keyp)->isMarkedAny(); +} + +void GCRuntime::sweepFinalizationObserversOnMainThread() { + // This calls back into the browser which expects to be called from the main + // thread. + gcstats::AutoPhase ap1(stats(), gcstats::PhaseKind::SWEEP_COMPARTMENTS); + gcstats::AutoPhase ap2(stats(), + gcstats::PhaseKind::SWEEP_FINALIZATION_OBSERVERS); + SweepingTracer trc(rt); + AutoLockStoreBuffer lock(&storeBuffer()); + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + traceWeakFinalizationObserverEdges(&trc, zone); + } +} + +void GCRuntime::startTask(GCParallelTask& task, + AutoLockHelperThreadState& lock) { + if (!CanUseExtraThreads()) { + AutoUnlockHelperThreadState unlock(lock); + task.runFromMainThread(); + stats().recordParallelPhase(task.phaseKind, task.duration()); + return; + } + + task.startWithLockHeld(lock); +} + +void GCRuntime::joinTask(GCParallelTask& task, + AutoLockHelperThreadState& lock) { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::JOIN_PARALLEL_TASKS); + task.joinWithLockHeld(lock); +} + +void GCRuntime::sweepDebuggerOnMainThread(JS::GCContext* gcx) { + SweepingTracer trc(rt); + AutoLockStoreBuffer lock(&storeBuffer()); + + // Detach unreachable debuggers and global objects from each other. + // This can modify weakmaps and so must happen before weakmap sweeping. + DebugAPI::sweepAll(gcx); + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_COMPARTMENTS); + + // Sweep debug environment information. This performs lookups in the Zone's + // unique IDs table and so must not happen in parallel with sweeping that + // table. + { + gcstats::AutoPhase ap2(stats(), gcstats::PhaseKind::SWEEP_MISC); + for (SweepGroupRealmsIter r(rt); !r.done(); r.next()) { + r->traceWeakDebugEnvironmentEdges(&trc); + } + } +} + +void GCRuntime::sweepJitDataOnMainThread(JS::GCContext* gcx) { + SweepingTracer trc(rt); + { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_JIT_DATA); + + if (initialState != State::NotActive) { + // Cancel any active or pending off thread compilations. We also did + // this before marking (in DiscardJITCodeForGC) so this is a no-op + // for non-incremental GCs. + js::CancelOffThreadIonCompile(rt, JS::Zone::Sweep); + } + + // Bug 1071218: the following method has not yet been refactored to + // work on a single zone-group at once. + + // Sweep entries containing about-to-be-finalized JitCode and + // update relocated TypeSet::Types inside the JitcodeGlobalTable. + jit::JitRuntime::TraceWeakJitcodeGlobalTable(rt, &trc); + } + + if (initialState != State::NotActive) { + gcstats::AutoPhase apdc(stats(), gcstats::PhaseKind::SWEEP_DISCARD_CODE); + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + zone->discardJitCode(gcx); + } + } + + // JitZone/JitRealm must be swept *after* discarding JIT code, because + // Zone::discardJitCode might access CacheIRStubInfos deleted here. + { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_JIT_DATA); + + for (SweepGroupRealmsIter r(rt); !r.done(); r.next()) { + r->traceWeakEdgesInJitRealm(&trc); + } + + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + if (jit::JitZone* jitZone = zone->jitZone()) { + jitZone->traceWeak(&trc); + } + } + } +} + +using WeakCacheTaskVector = + mozilla::Vector<ImmediateSweepWeakCacheTask, 0, SystemAllocPolicy>; + +// Call a functor for all weak caches that need to be swept in the current +// sweep group. +template <typename Functor> +static inline bool IterateWeakCaches(JSRuntime* rt, Functor f) { + for (SweepGroupZonesIter zone(rt); !zone.done(); zone.next()) { + for (JS::detail::WeakCacheBase* cache : zone->weakCaches()) { + if (!f(cache, zone.get())) { + return false; + } + } + } + + for (JS::detail::WeakCacheBase* cache : rt->weakCaches()) { + if (!f(cache, nullptr)) { + return false; + } + } + + return true; +} + +static bool PrepareWeakCacheTasks(JSRuntime* rt, + WeakCacheTaskVector* immediateTasks) { + // Start incremental sweeping for caches that support it or add to a vector + // of sweep tasks to run on a helper thread. + + MOZ_ASSERT(immediateTasks->empty()); + + GCRuntime* gc = &rt->gc; + bool ok = + IterateWeakCaches(rt, [&](JS::detail::WeakCacheBase* cache, Zone* zone) { + if (cache->empty()) { + return true; + } + + // Caches that support incremental sweeping will be swept later. + if (zone && cache->setIncrementalBarrierTracer(&gc->sweepingTracer)) { + return true; + } + + return immediateTasks->emplaceBack(gc, zone, *cache); + }); + + if (!ok) { + immediateTasks->clearAndFree(); + } + + return ok; +} + +static void SweepAllWeakCachesOnMainThread(JSRuntime* rt) { + // If we ran out of memory, do all the work on the main thread. + gcstats::AutoPhase ap(rt->gc.stats(), gcstats::PhaseKind::SWEEP_WEAK_CACHES); + SweepingTracer trc(rt); + IterateWeakCaches(rt, [&](JS::detail::WeakCacheBase* cache, Zone* zone) { + if (cache->needsIncrementalBarrier()) { + cache->setIncrementalBarrierTracer(nullptr); + } + cache->traceWeak(&trc, &rt->gc.storeBuffer()); + return true; + }); +} + +void GCRuntime::sweepEmbeddingWeakPointers(JS::GCContext* gcx) { + using namespace gcstats; + + AutoLockStoreBuffer lock(&storeBuffer()); + + AutoPhase ap(stats(), PhaseKind::FINALIZE_START); + callFinalizeCallbacks(gcx, JSFINALIZE_GROUP_PREPARE); + { + AutoPhase ap2(stats(), PhaseKind::WEAK_ZONES_CALLBACK); + callWeakPointerZonesCallbacks(&sweepingTracer); + } + { + AutoPhase ap2(stats(), PhaseKind::WEAK_COMPARTMENT_CALLBACK); + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + for (CompartmentsInZoneIter comp(zone); !comp.done(); comp.next()) { + callWeakPointerCompartmentCallbacks(&sweepingTracer, comp); + } + } + } + callFinalizeCallbacks(gcx, JSFINALIZE_GROUP_START); +} + +IncrementalProgress GCRuntime::beginSweepingSweepGroup(JS::GCContext* gcx, + SliceBudget& budget) { + /* + * Begin sweeping the group of zones in currentSweepGroup, performing + * actions that must be done before yielding to caller. + */ + + using namespace gcstats; + + AutoSCC scc(stats(), sweepGroupIndex); + + bool sweepingAtoms = false; + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + /* Set the GC state to sweeping. */ + zone->changeGCState(Zone::MarkBlackAndGray, Zone::Sweep); + + /* Purge the ArenaLists before sweeping. */ + zone->arenas.checkSweepStateNotInUse(); + zone->arenas.unmarkPreMarkedFreeCells(); + zone->arenas.clearFreeLists(); + + if (zone->isAtomsZone()) { + sweepingAtoms = true; + } + } + +#ifdef DEBUG + for (auto cell : cellsToAssertNotGray.ref()) { + JS::AssertCellIsNotGray(cell); + } + cellsToAssertNotGray.ref().clearAndFree(); +#endif + + // Updating the atom marking bitmaps. This marks atoms referenced by + // uncollected zones so cannot be done in parallel with the other sweeping + // work below. + if (sweepingAtoms) { + AutoPhase ap(stats(), PhaseKind::UPDATE_ATOMS_BITMAP); + updateAtomsBitmap(); + } + +#ifdef JS_GC_ZEAL + validateIncrementalMarking(); +#endif + + AutoSetThreadIsSweeping threadIsSweeping; + + // This must happen before sweeping realm globals. + sweepDebuggerOnMainThread(gcx); + + // FinalizationRegistry sweeping touches weak maps and so must not run in + // parallel with that. This triggers a read barrier and can add marking work + // for zones that are still marking. Must happen before sweeping realm + // globals. + sweepFinalizationObserversOnMainThread(); + + // This must happen before updating embedding weak pointers. + sweepRealmGlobals(); + + sweepEmbeddingWeakPointers(gcx); + + { + AutoLockHelperThreadState lock; + + AutoPhase ap(stats(), PhaseKind::SWEEP_COMPARTMENTS); + + AutoRunParallelTask sweepCCWrappers(this, &GCRuntime::sweepCCWrappers, + PhaseKind::SWEEP_CC_WRAPPER, + GCUse::Sweeping, lock); + AutoRunParallelTask sweepMisc(this, &GCRuntime::sweepMisc, + PhaseKind::SWEEP_MISC, GCUse::Sweeping, lock); + AutoRunParallelTask sweepCompTasks(this, &GCRuntime::sweepCompressionTasks, + PhaseKind::SWEEP_COMPRESSION, + GCUse::Sweeping, lock); + AutoRunParallelTask sweepWeakMaps(this, &GCRuntime::sweepWeakMaps, + PhaseKind::SWEEP_WEAKMAPS, + GCUse::Sweeping, lock); + AutoRunParallelTask sweepUniqueIds(this, &GCRuntime::sweepUniqueIds, + PhaseKind::SWEEP_UNIQUEIDS, + GCUse::Sweeping, lock); + + WeakCacheTaskVector sweepCacheTasks; + bool canSweepWeakCachesOffThread = + PrepareWeakCacheTasks(rt, &sweepCacheTasks); + if (canSweepWeakCachesOffThread) { + weakCachesToSweep.ref().emplace(currentSweepGroup); + for (auto& task : sweepCacheTasks) { + startTask(task, lock); + } + } + + { + AutoUnlockHelperThreadState unlock(lock); + sweepJitDataOnMainThread(gcx); + + if (!canSweepWeakCachesOffThread) { + MOZ_ASSERT(sweepCacheTasks.empty()); + SweepAllWeakCachesOnMainThread(rt); + } + } + + for (auto& task : sweepCacheTasks) { + joinTask(task, lock); + } + } + + if (sweepingAtoms) { + startSweepingAtomsTable(); + } + + // Queue all GC things in all zones for sweeping, either on the foreground + // or on the background thread. + + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + for (const auto& phase : BackgroundFinalizePhases) { + initBackgroundSweep(zone, gcx, phase); + } + + zone->arenas.queueForegroundThingsForSweep(); + } + + MOZ_ASSERT(!sweepZone); + + safeToYield = true; + markOnBackgroundThreadDuringSweeping = CanUseExtraThreads(); + + return Finished; +} + +#ifdef JS_GC_ZEAL +bool GCRuntime::shouldYieldForZeal(ZealMode mode) { + bool yield = useZeal && hasZealMode(mode); + + // Only yield on the first sweep slice for this mode. + bool firstSweepSlice = initialState != State::Sweep; + if (mode == ZealMode::IncrementalMultipleSlices && !firstSweepSlice) { + yield = false; + } + + return yield; +} +#endif + +IncrementalProgress GCRuntime::endSweepingSweepGroup(JS::GCContext* gcx, + SliceBudget& budget) { + // This is to prevent a race between markTask checking the zone state and + // us changing it below. + if (joinBackgroundMarkTask() == NotFinished) { + return NotFinished; + } + + assertNoMarkingWork(); + + // Disable background marking during sweeping until we start sweeping the next + // zone group. + markOnBackgroundThreadDuringSweeping = false; + + { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::FINALIZE_END); + AutoLockStoreBuffer lock(&storeBuffer()); + callFinalizeCallbacks(gcx, JSFINALIZE_GROUP_END); + } + + /* Free LIFO blocks on a background thread if possible. */ + startBackgroundFree(); + + /* Update the GC state for zones we have swept. */ + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + if (jit::JitZone* jitZone = zone->jitZone()) { + // Clear out any small pools that we're hanging on to. + jitZone->execAlloc().purge(); + } + AutoLockGC lock(this); + zone->changeGCState(Zone::Sweep, Zone::Finished); + zone->arenas.unmarkPreMarkedFreeCells(); + zone->arenas.checkNoArenasToUpdate(); + zone->pretenuring.clearCellCountsInNewlyCreatedArenas(); + } + + /* + * Start background thread to sweep zones if required, sweeping any atoms + * zones last if present. + */ + ZoneList zones; + for (SweepGroupZonesIter zone(this); !zone.done(); zone.next()) { + if (zone->isAtomsZone()) { + zones.append(zone); + } else { + zones.prepend(zone); + } + } + + queueZonesAndStartBackgroundSweep(std::move(zones)); + + return Finished; +} + +IncrementalProgress GCRuntime::markDuringSweeping(JS::GCContext* gcx, + SliceBudget& budget) { + MOZ_ASSERT(markTask.isIdle()); + + if (markOnBackgroundThreadDuringSweeping) { + if (!marker().isDrained() || hasDelayedMarking()) { + AutoLockHelperThreadState lock; + MOZ_ASSERT(markTask.isIdle(lock)); + markTask.setBudget(budget); + markTask.startOrRunIfIdle(lock); + } + return Finished; // This means don't yield to the mutator here. + } + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::MARK); + return markUntilBudgetExhausted(budget, AllowParallelMarking); +} + +void GCRuntime::beginSweepPhase(JS::GCReason reason, AutoGCSession& session) { + /* + * Sweep phase. + * + * Finalize as we sweep, outside of lock but with RuntimeHeapIsBusy() + * true so that any attempt to allocate a GC-thing from a finalizer will + * fail, rather than nest badly and leave the unmarked newborn to be swept. + */ + + MOZ_ASSERT(!abortSweepAfterCurrentGroup); + MOZ_ASSERT(!markOnBackgroundThreadDuringSweeping); + +#ifdef DEBUG + releaseHeldRelocatedArenas(); + verifyAllChunks(); +#endif + +#ifdef JS_GC_ZEAL + computeNonIncrementalMarkingForValidation(session); +#endif + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP); + + AssertNoWrappersInGrayList(rt); + dropStringWrappers(); + + groupZonesForSweeping(reason); + + sweepActions->assertFinished(); +} + +bool GCRuntime::foregroundFinalize(JS::GCContext* gcx, Zone* zone, + AllocKind thingKind, + SliceBudget& sliceBudget, + SortedArenaList& sweepList) { + ArenaLists& lists = zone->arenas; + lists.checkNoArenasToUpdateForKind(thingKind); + + // Non-empty arenas are reused for use for new allocations as soon as the + // finalizers for that allocation kind have run. Empty arenas are only + // released when everything in the zone has been swept (see + // GCRuntime::sweepBackgroundThings for more details). + if (!FinalizeArenas(gcx, lists.collectingArenaList(thingKind), sweepList, + thingKind, sliceBudget)) { + // Copy the current contents of sweepList so that ArenaIter can find them. + lists.setIncrementalSweptArenas(thingKind, sweepList); + return false; + } + + sweepList.extractEmpty(&lists.savedEmptyArenas.ref()); + lists.mergeFinalizedArenas(thingKind, sweepList); + lists.clearIncrementalSweptArenas(); + + return true; +} + +BackgroundMarkTask::BackgroundMarkTask(GCRuntime* gc) + : GCParallelTask(gc, gcstats::PhaseKind::MARK, GCUse::Marking), + budget(SliceBudget::unlimited()) {} + +void js::gc::BackgroundMarkTask::run(AutoLockHelperThreadState& lock) { + AutoUnlockHelperThreadState unlock(lock); + + // Time reporting is handled separately for parallel tasks. + gc->sweepMarkResult = gc->markUntilBudgetExhausted( + this->budget, GCRuntime::SingleThreadedMarking, DontReportMarkTime); +} + +IncrementalProgress GCRuntime::joinBackgroundMarkTask() { + AutoLockHelperThreadState lock; + if (markTask.isIdle(lock)) { + return Finished; + } + + joinTask(markTask, lock); + + IncrementalProgress result = sweepMarkResult; + sweepMarkResult = Finished; + return result; +} + +template <typename T> +static void SweepThing(JS::GCContext* gcx, T* thing) { + if (!TenuredThingIsMarkedAny(thing)) { + thing->sweep(gcx); + } +} + +template <typename T> +static bool SweepArenaList(JS::GCContext* gcx, Arena** arenasToSweep, + SliceBudget& sliceBudget) { + while (Arena* arena = *arenasToSweep) { + MOZ_ASSERT(arena->zone->isGCSweeping()); + + for (ArenaCellIterUnderGC cell(arena); !cell.done(); cell.next()) { + SweepThing(gcx, cell.as<T>()); + } + + Arena* next = arena->next; + MOZ_ASSERT_IF(next, next->zone == arena->zone); + *arenasToSweep = next; + + AllocKind kind = MapTypeToAllocKind<T>::kind; + sliceBudget.step(Arena::thingsPerArena(kind)); + if (sliceBudget.isOverBudget()) { + return false; + } + } + + return true; +} + +void GCRuntime::startSweepingAtomsTable() { + auto& maybeAtoms = maybeAtomsToSweep.ref(); + MOZ_ASSERT(maybeAtoms.isNothing()); + + AtomsTable* atomsTable = rt->atomsForSweeping(); + if (!atomsTable) { + return; + } + + // Create secondary tables to hold new atoms added while we're sweeping the + // main tables incrementally. + if (!atomsTable->startIncrementalSweep(maybeAtoms)) { + SweepingTracer trc(rt); + atomsTable->traceWeak(&trc); + } +} + +IncrementalProgress GCRuntime::sweepAtomsTable(JS::GCContext* gcx, + SliceBudget& budget) { + if (!atomsZone()->isGCSweeping()) { + return Finished; + } + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_ATOMS_TABLE); + + auto& maybeAtoms = maybeAtomsToSweep.ref(); + if (!maybeAtoms) { + return Finished; + } + + if (!rt->atomsForSweeping()->sweepIncrementally(maybeAtoms.ref(), budget)) { + return NotFinished; + } + + maybeAtoms.reset(); + + return Finished; +} + +static size_t IncrementalSweepWeakCache(GCRuntime* gc, + const WeakCacheToSweep& item) { + AutoSetThreadIsSweeping threadIsSweeping(item.zone); + + JS::detail::WeakCacheBase* cache = item.cache; + MOZ_ASSERT(cache->needsIncrementalBarrier()); + + SweepingTracer trc(gc->rt); + size_t steps = cache->traceWeak(&trc, &gc->storeBuffer()); + cache->setIncrementalBarrierTracer(nullptr); + + return steps; +} + +WeakCacheSweepIterator::WeakCacheSweepIterator(JS::Zone* sweepGroup) + : sweepZone(sweepGroup), sweepCache(sweepZone->weakCaches().getFirst()) { + settle(); +} + +bool WeakCacheSweepIterator::done() const { return !sweepZone; } + +WeakCacheToSweep WeakCacheSweepIterator::get() const { + MOZ_ASSERT(!done()); + + return {sweepCache, sweepZone}; +} + +void WeakCacheSweepIterator::next() { + MOZ_ASSERT(!done()); + + sweepCache = sweepCache->getNext(); + settle(); +} + +void WeakCacheSweepIterator::settle() { + while (sweepZone) { + while (sweepCache && !sweepCache->needsIncrementalBarrier()) { + sweepCache = sweepCache->getNext(); + } + + if (sweepCache) { + break; + } + + sweepZone = sweepZone->nextNodeInGroup(); + if (sweepZone) { + sweepCache = sweepZone->weakCaches().getFirst(); + } + } + + MOZ_ASSERT((!sweepZone && !sweepCache) || + (sweepCache && sweepCache->needsIncrementalBarrier())); +} + +IncrementalProgress GCRuntime::sweepWeakCaches(JS::GCContext* gcx, + SliceBudget& budget) { + if (weakCachesToSweep.ref().isNothing()) { + return Finished; + } + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_COMPARTMENTS); + + WeakCacheSweepIterator& work = weakCachesToSweep.ref().ref(); + + AutoLockHelperThreadState lock; + + { + AutoRunParallelWork runWork(this, IncrementalSweepWeakCache, + gcstats::PhaseKind::SWEEP_WEAK_CACHES, + GCUse::Sweeping, work, budget, lock); + AutoUnlockHelperThreadState unlock(lock); + } + + if (work.done()) { + weakCachesToSweep.ref().reset(); + return Finished; + } + + return NotFinished; +} + +IncrementalProgress GCRuntime::finalizeAllocKind(JS::GCContext* gcx, + SliceBudget& budget) { + MOZ_ASSERT(sweepZone->isGCSweeping()); + + // Set the number of things per arena for this AllocKind. + size_t thingsPerArena = Arena::thingsPerArena(sweepAllocKind); + auto& sweepList = incrementalSweepList.ref(); + sweepList.setThingsPerArena(thingsPerArena); + + AutoSetThreadIsFinalizing threadIsFinalizing(gcx); + + if (!foregroundFinalize(gcx, sweepZone, sweepAllocKind, budget, sweepList)) { + return NotFinished; + } + + // Reset the slots of the sweep list that we used. + sweepList.reset(thingsPerArena); + + return Finished; +} + +IncrementalProgress GCRuntime::sweepPropMapTree(JS::GCContext* gcx, + SliceBudget& budget) { + // Remove dead SharedPropMaps from the tree. This happens incrementally on the + // main thread. PropMaps are finalized later on the a background thread. + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP_PROP_MAP); + + ArenaLists& al = sweepZone->arenas; + + if (!SweepArenaList<CompactPropMap>( + gcx, &al.gcCompactPropMapArenasToUpdate.ref(), budget)) { + return NotFinished; + } + if (!SweepArenaList<NormalPropMap>( + gcx, &al.gcNormalPropMapArenasToUpdate.ref(), budget)) { + return NotFinished; + } + + return Finished; +} + +// An iterator for a standard container that provides an STL-like begin()/end() +// interface. This iterator provides a done()/get()/next() style interface. +template <typename Container> +class ContainerIter { + using Iter = decltype(std::declval<const Container>().begin()); + using Elem = decltype(*std::declval<Iter>()); + + Iter iter; + const Iter end; + + public: + explicit ContainerIter(const Container& container) + : iter(container.begin()), end(container.end()) {} + + bool done() const { return iter == end; } + + Elem get() const { return *iter; } + + void next() { + MOZ_ASSERT(!done()); + ++iter; + } +}; + +// IncrementalIter is a template class that makes a normal iterator into one +// that can be used to perform incremental work by using external state that +// persists between instantiations. The state is only initialised on the first +// use and subsequent uses carry on from the previous state. +template <typename Iter> +struct IncrementalIter { + using State = mozilla::Maybe<Iter>; + using Elem = decltype(std::declval<Iter>().get()); + + private: + State& maybeIter; + + public: + template <typename... Args> + explicit IncrementalIter(State& maybeIter, Args&&... args) + : maybeIter(maybeIter) { + if (maybeIter.isNothing()) { + maybeIter.emplace(std::forward<Args>(args)...); + } + } + + ~IncrementalIter() { + if (done()) { + maybeIter.reset(); + } + } + + bool done() const { return maybeIter.ref().done(); } + + Elem get() const { return maybeIter.ref().get(); } + + void next() { maybeIter.ref().next(); } +}; + +// Iterate through the sweep groups created by +// GCRuntime::groupZonesForSweeping(). +class js::gc::SweepGroupsIter { + GCRuntime* gc; + + public: + explicit SweepGroupsIter(JSRuntime* rt) : gc(&rt->gc) { + MOZ_ASSERT(gc->currentSweepGroup); + } + + bool done() const { return !gc->currentSweepGroup; } + + Zone* get() const { return gc->currentSweepGroup; } + + void next() { + MOZ_ASSERT(!done()); + gc->getNextSweepGroup(); + } +}; + +namespace sweepaction { + +// Implementation of the SweepAction interface that calls a method on GCRuntime. +class SweepActionCall final : public SweepAction { + using Method = IncrementalProgress (GCRuntime::*)(JS::GCContext* gcx, + SliceBudget& budget); + + Method method; + + public: + explicit SweepActionCall(Method m) : method(m) {} + IncrementalProgress run(Args& args) override { + return (args.gc->*method)(args.gcx, args.budget); + } + void assertFinished() const override {} +}; + +// Implementation of the SweepAction interface that yields in a specified zeal +// mode. +class SweepActionMaybeYield final : public SweepAction { +#ifdef JS_GC_ZEAL + ZealMode mode; + bool isYielding; +#endif + + public: + explicit SweepActionMaybeYield(ZealMode mode) +#ifdef JS_GC_ZEAL + : mode(mode), + isYielding(false) +#endif + { + } + + IncrementalProgress run(Args& args) override { +#ifdef JS_GC_ZEAL + if (!isYielding && args.gc->shouldYieldForZeal(mode)) { + isYielding = true; + return NotFinished; + } + + isYielding = false; +#endif + return Finished; + } + + void assertFinished() const override { MOZ_ASSERT(!isYielding); } + + // These actions should be skipped if GC zeal is not configured. +#ifndef JS_GC_ZEAL + bool shouldSkip() override { return true; } +#endif +}; + +// Implementation of the SweepAction interface that calls a list of actions in +// sequence. +class SweepActionSequence final : public SweepAction { + using ActionVector = Vector<UniquePtr<SweepAction>, 0, SystemAllocPolicy>; + using Iter = IncrementalIter<ContainerIter<ActionVector>>; + + ActionVector actions; + typename Iter::State iterState; + + public: + bool init(UniquePtr<SweepAction>* acts, size_t count) { + for (size_t i = 0; i < count; i++) { + auto& action = acts[i]; + if (!action) { + return false; + } + if (action->shouldSkip()) { + continue; + } + if (!actions.emplaceBack(std::move(action))) { + return false; + } + } + return true; + } + + IncrementalProgress run(Args& args) override { + for (Iter iter(iterState, actions); !iter.done(); iter.next()) { + if (iter.get()->run(args) == NotFinished) { + return NotFinished; + } + } + return Finished; + } + + void assertFinished() const override { + MOZ_ASSERT(iterState.isNothing()); + for (const auto& action : actions) { + action->assertFinished(); + } + } +}; + +template <typename Iter, typename Init> +class SweepActionForEach final : public SweepAction { + using Elem = decltype(std::declval<Iter>().get()); + using IncrIter = IncrementalIter<Iter>; + + Init iterInit; + Elem* elemOut; + UniquePtr<SweepAction> action; + typename IncrIter::State iterState; + + public: + SweepActionForEach(const Init& init, Elem* maybeElemOut, + UniquePtr<SweepAction> action) + : iterInit(init), elemOut(maybeElemOut), action(std::move(action)) {} + + IncrementalProgress run(Args& args) override { + MOZ_ASSERT_IF(elemOut, *elemOut == Elem()); + auto clearElem = mozilla::MakeScopeExit([&] { setElem(Elem()); }); + for (IncrIter iter(iterState, iterInit); !iter.done(); iter.next()) { + setElem(iter.get()); + if (action->run(args) == NotFinished) { + return NotFinished; + } + } + return Finished; + } + + void assertFinished() const override { + MOZ_ASSERT(iterState.isNothing()); + MOZ_ASSERT_IF(elemOut, *elemOut == Elem()); + action->assertFinished(); + } + + private: + void setElem(const Elem& value) { + if (elemOut) { + *elemOut = value; + } + } +}; + +static UniquePtr<SweepAction> Call(IncrementalProgress (GCRuntime::*method)( + JS::GCContext* gcx, SliceBudget& budget)) { + return MakeUnique<SweepActionCall>(method); +} + +static UniquePtr<SweepAction> MaybeYield(ZealMode zealMode) { + return MakeUnique<SweepActionMaybeYield>(zealMode); +} + +template <typename... Rest> +static UniquePtr<SweepAction> Sequence(UniquePtr<SweepAction> first, + Rest... rest) { + UniquePtr<SweepAction> actions[] = {std::move(first), std::move(rest)...}; + auto seq = MakeUnique<SweepActionSequence>(); + if (!seq || !seq->init(actions, std::size(actions))) { + return nullptr; + } + + return UniquePtr<SweepAction>(std::move(seq)); +} + +static UniquePtr<SweepAction> RepeatForSweepGroup( + JSRuntime* rt, UniquePtr<SweepAction> action) { + if (!action) { + return nullptr; + } + + using Action = SweepActionForEach<SweepGroupsIter, JSRuntime*>; + return js::MakeUnique<Action>(rt, nullptr, std::move(action)); +} + +static UniquePtr<SweepAction> ForEachZoneInSweepGroup( + JSRuntime* rt, Zone** zoneOut, UniquePtr<SweepAction> action) { + if (!action) { + return nullptr; + } + + using Action = SweepActionForEach<SweepGroupZonesIter, JSRuntime*>; + return js::MakeUnique<Action>(rt, zoneOut, std::move(action)); +} + +static UniquePtr<SweepAction> ForEachAllocKind(AllocKinds kinds, + AllocKind* kindOut, + UniquePtr<SweepAction> action) { + if (!action) { + return nullptr; + } + + using Action = SweepActionForEach<ContainerIter<AllocKinds>, AllocKinds>; + return js::MakeUnique<Action>(kinds, kindOut, std::move(action)); +} + +} // namespace sweepaction + +bool GCRuntime::initSweepActions() { + using namespace sweepaction; + using sweepaction::Call; + + sweepActions.ref() = RepeatForSweepGroup( + rt, + Sequence( + Call(&GCRuntime::beginMarkingSweepGroup), + Call(&GCRuntime::markGrayRootsInCurrentGroup), + MaybeYield(ZealMode::YieldWhileGrayMarking), + Call(&GCRuntime::markGray), Call(&GCRuntime::endMarkingSweepGroup), + Call(&GCRuntime::beginSweepingSweepGroup), + MaybeYield(ZealMode::IncrementalMultipleSlices), + MaybeYield(ZealMode::YieldBeforeSweepingAtoms), + Call(&GCRuntime::sweepAtomsTable), + MaybeYield(ZealMode::YieldBeforeSweepingCaches), + Call(&GCRuntime::sweepWeakCaches), + ForEachZoneInSweepGroup( + rt, &sweepZone.ref(), + Sequence(MaybeYield(ZealMode::YieldBeforeSweepingObjects), + ForEachAllocKind(ForegroundObjectFinalizePhase.kinds, + &sweepAllocKind.ref(), + Call(&GCRuntime::finalizeAllocKind)), + MaybeYield(ZealMode::YieldBeforeSweepingNonObjects), + ForEachAllocKind(ForegroundNonObjectFinalizePhase.kinds, + &sweepAllocKind.ref(), + Call(&GCRuntime::finalizeAllocKind)), + MaybeYield(ZealMode::YieldBeforeSweepingPropMapTrees), + Call(&GCRuntime::sweepPropMapTree))), + Call(&GCRuntime::endSweepingSweepGroup))); + + return sweepActions != nullptr; +} + +IncrementalProgress GCRuntime::performSweepActions(SliceBudget& budget) { + AutoMajorGCProfilerEntry s(this); + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP); + + JS::GCContext* gcx = rt->gcContext(); + AutoSetThreadIsSweeping threadIsSweeping(gcx); + AutoPoisonFreedJitCode pjc(gcx); + + // Don't trigger pre-barriers when finalizing. + AutoDisableBarriers disableBarriers(this); + + // Drain the mark stack, possibly in a parallel task if we're in a part of + // sweeping that allows it. + // + // In the first sweep slice where we must not yield to the mutator until we've + // starting sweeping a sweep group but in that case the stack must be empty + // already. + +#ifdef DEBUG + MOZ_ASSERT(initialState <= State::Sweep); + if (initialState != State::Sweep) { + assertNoMarkingWork(); + } +#endif + + if (initialState == State::Sweep && + markDuringSweeping(gcx, budget) == NotFinished) { + return NotFinished; + } + + // Then continue running sweep actions. + + SweepAction::Args args{this, gcx, budget}; + IncrementalProgress sweepProgress = sweepActions->run(args); + IncrementalProgress markProgress = joinBackgroundMarkTask(); + + if (sweepProgress == Finished && markProgress == Finished) { + return Finished; + } + + MOZ_ASSERT(isIncremental); + return NotFinished; +} + +bool GCRuntime::allCCVisibleZonesWereCollected() { + // Calculate whether the gray marking state is now valid. + // + // The gray bits change from invalid to valid if we finished a full GC from + // the point of view of the cycle collector. We ignore the following: + // + // - Helper thread zones, as these are not reachable from the main heap. + // - The atoms zone, since strings and symbols are never marked gray. + // - Empty zones. + // + // These exceptions ensure that when the CC requests a full GC the gray mark + // state ends up valid even it we don't collect all of the zones. + + for (ZonesIter zone(this, SkipAtoms); !zone.done(); zone.next()) { + if (!zone->isCollecting() && !zone->arenas.arenaListsAreEmpty()) { + return false; + } + } + + return true; +} + +void GCRuntime::endSweepPhase(bool destroyingRuntime) { + MOZ_ASSERT(!markOnBackgroundThreadDuringSweeping); + + sweepActions->assertFinished(); + + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::SWEEP); + + MOZ_ASSERT_IF(destroyingRuntime, !useBackgroundThreads); + + { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::DESTROY); + + // Sweep shared script bytecode now all zones have been swept and finalizers + // for BaseScripts have released their references. + SweepScriptData(rt); + } + + { + gcstats::AutoPhase ap(stats(), gcstats::PhaseKind::FINALIZE_END); + AutoLockStoreBuffer lock(&storeBuffer()); + callFinalizeCallbacks(rt->gcContext(), JSFINALIZE_COLLECTION_END); + + if (allCCVisibleZonesWereCollected()) { + grayBitsValid = true; + } + } + + if (isIncremental) { + findDeadCompartments(); + } + +#ifdef JS_GC_ZEAL + finishMarkingValidation(); +#endif + +#ifdef DEBUG + for (ZonesIter zone(this, WithAtoms); !zone.done(); zone.next()) { + for (auto i : AllAllocKinds()) { + MOZ_ASSERT_IF(!IsBackgroundFinalized(i) || !useBackgroundThreads, + zone->arenas.collectingArenaList(i).isEmpty()); + } + } +#endif + + AssertNoWrappersInGrayList(rt); +} |