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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* 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 gc_GCInternals_h
#define gc_GCInternals_h
#include "mozilla/ArrayUtils.h"
#include "mozilla/Maybe.h"
#include "mozilla/PodOperations.h"
#include "jscntxt.h"
#include "gc/Zone.h"
#include "vm/HelperThreads.h"
#include "vm/Runtime.h"
namespace js {
namespace gc {
void FinishGC(JSContext* cx);
/*
* This class should be used by any code that needs to exclusive access to the
* heap in order to trace through it...
*/
class MOZ_RAII AutoTraceSession
{
public:
explicit AutoTraceSession(JSRuntime* rt, JS::HeapState state = JS::HeapState::Tracing);
~AutoTraceSession();
// Threads with an exclusive context can hit refillFreeList while holding
// the exclusive access lock. To avoid deadlocking when we try to acquire
// this lock during GC and the other thread is waiting, make sure we hold
// the exclusive access lock during GC sessions.
AutoLockForExclusiveAccess lock;
protected:
JSRuntime* runtime;
private:
AutoTraceSession(const AutoTraceSession&) = delete;
void operator=(const AutoTraceSession&) = delete;
JS::HeapState prevState;
AutoSPSEntry pseudoFrame;
};
class MOZ_RAII AutoPrepareForTracing
{
mozilla::Maybe<AutoTraceSession> session_;
public:
AutoPrepareForTracing(JSContext* cx, ZoneSelector selector);
AutoTraceSession& session() { return session_.ref(); }
};
AbortReason
IsIncrementalGCUnsafe(JSRuntime* rt);
#ifdef JS_GC_ZEAL
class MOZ_RAII AutoStopVerifyingBarriers
{
GCRuntime* gc;
bool restartPreVerifier;
public:
AutoStopVerifyingBarriers(JSRuntime* rt, bool isShutdown)
: gc(&rt->gc)
{
if (gc->isVerifyPreBarriersEnabled()) {
gc->endVerifyPreBarriers();
restartPreVerifier = !isShutdown;
} else {
restartPreVerifier = false;
}
}
~AutoStopVerifyingBarriers() {
// Nasty special case: verification runs a minor GC, which *may* nest
// inside of an outer minor GC. This is not allowed by the
// gc::Statistics phase tree. So we pause the "real" GC, if in fact one
// is in progress.
gcstats::Phase outer = gc->stats.currentPhase();
if (outer != gcstats::PHASE_NONE)
gc->stats.endPhase(outer);
MOZ_ASSERT((gc->stats.currentPhase() == gcstats::PHASE_NONE) ||
(gc->stats.currentPhase() == gcstats::PHASE_GC_BEGIN) ||
(gc->stats.currentPhase() == gcstats::PHASE_GC_END));
if (restartPreVerifier)
gc->startVerifyPreBarriers();
if (outer != gcstats::PHASE_NONE)
gc->stats.beginPhase(outer);
}
};
#else
struct MOZ_RAII AutoStopVerifyingBarriers
{
AutoStopVerifyingBarriers(JSRuntime*, bool) {}
};
#endif /* JS_GC_ZEAL */
#ifdef JSGC_HASH_TABLE_CHECKS
void CheckHashTablesAfterMovingGC(JSRuntime* rt);
void CheckHeapAfterGC(JSRuntime* rt);
#endif
struct MovingTracer : JS::CallbackTracer
{
explicit MovingTracer(JSRuntime* rt) : CallbackTracer(rt, TraceWeakMapKeysValues) {}
void onObjectEdge(JSObject** objp) override;
void onShapeEdge(Shape** shapep) override;
void onStringEdge(JSString** stringp) override;
void onScriptEdge(JSScript** scriptp) override;
void onLazyScriptEdge(LazyScript** lazyp) override;
void onBaseShapeEdge(BaseShape** basep) override;
void onScopeEdge(Scope** basep) override;
void onChild(const JS::GCCellPtr& thing) override {
MOZ_ASSERT(!RelocationOverlay::isCellForwarded(thing.asCell()));
}
#ifdef DEBUG
TracerKind getTracerKind() const override { return TracerKind::Moving; }
#endif
};
// Structure for counting how many times objects in a particular group have
// been tenured during a minor collection.
struct TenureCount
{
ObjectGroup* group;
int count;
};
// Keep rough track of how many times we tenure objects in particular groups
// during minor collections, using a fixed size hash for efficiency at the cost
// of potential collisions.
struct TenureCountCache
{
static const size_t EntryShift = 4;
static const size_t EntryCount = 1 << EntryShift;
TenureCount entries[EntryCount];
TenureCountCache() { mozilla::PodZero(this); }
HashNumber hash(ObjectGroup* group) {
#if JS_BITS_PER_WORD == 32
static const size_t ZeroBits = 3;
#else
static const size_t ZeroBits = 4;
#endif
uintptr_t word = uintptr_t(group);
MOZ_ASSERT((word & ((1 << ZeroBits) - 1)) == 0);
word >>= ZeroBits;
return HashNumber((word >> EntryShift) ^ word);
}
TenureCount& findEntry(ObjectGroup* group) {
return entries[hash(group) % EntryCount];
}
};
} /* namespace gc */
} /* namespace js */
#endif /* gc_GCInternals_h */
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