AuroraMiddleware/v8
1
0
Fork 0
Code Issues 2 Pull Requests Releases Wiki Activity

cppgc: Check ephemerons for unset key

Browse Source 
Ephemerons are based around WeakMember which may just be null at the
time the pair is considered for liveness. Bail out of marking for null
keys, as they write barrier would anyways make the value strong when
marking the key.

Bug: chromium:1056170
Change-Id: If8775a370824b88fc67fa479a0c0893985fbf5f4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2692571
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72714}
This commit is contained in:
Michael Lippautz 2021-02-12 16:57:42 +01:00 committed by Commit Bot
parent 0df0d7ab67
commit 695a449032
3 changed files with 35 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/cppgc/ephemeron-pair.h
View File

@ -5,6 +5,7 @@
#ifndef INCLUDE_CPPGC_EPHEMERON_PAIR_H_
#define INCLUDE_CPPGC_EPHEMERON_PAIR_H_
#include "cppgc/liveness-broker.h"
#include "cppgc/member.h"
namespace cppgc {
@ -18,6 +19,10 @@ struct EphemeronPair {
EphemeronPair(K* k, V* v) : key(k), value(v) {}
WeakMember<K> key;
Member<V> value;
void ClearValueIfKeyIsDead(const LivenessBroker& broker) {
if (!broker.IsHeapObjectAlive(key)) value = nullptr;
}
};
} // namespace cppgc

5
include/cppgc/visitor.h
View File

@ -152,6 +152,9 @@ class V8_EXPORT Visitor {
template <typename K, typename V>
void Trace(const EphemeronPair<K, V>& ephemeron_pair) {
TraceEphemeron(ephemeron_pair.key, &ephemeron_pair.value);
RegisterWeakCallbackMethod<EphemeronPair<K, V>,
&EphemeronPair<K, V>::ClearValueIfKeyIsDead>(
&ephemeron_pair);
}
/**
@ -163,6 +166,8 @@ class V8_EXPORT Visitor {
*/
template <typename K, typename V>
void TraceEphemeron(const WeakMember<K>& key, const V* value) {
const K* k = key.GetRawAtomic();
if (!k) return;
TraceDescriptor value_desc = TraceTrait<V>::GetTraceDescriptor(value);
if (!value_desc.base_object_payload) return;
VisitEphemeron(key, value_desc);

25
test/unittests/heap/cppgc/ephemeron-pair-unittest.cc
View File

@ -26,6 +26,10 @@ class EphemeronHolder : public GarbageCollected<GCed> {
EphemeronHolder(GCed* key, GCed* value) : ephemeron_pair_(key, value) {}
void Trace(cppgc::Visitor* visitor) const { visitor->Trace(ephemeron_pair_); }
const EphemeronPair<GCed, GCed>& ephemeron_pair() const {
return ephemeron_pair_;
}
private:
EphemeronPair<GCed, GCed> ephemeron_pair_;
};
@ -143,5 +147,26 @@ TEST_F(EphemeronPairTest, EmptyValue) {
FinishMarking();
}
TEST_F(EphemeronPairTest, EmptyKey) {
GCed* value = MakeGarbageCollected<GCed>(GetAllocationHandle());
Persistent<EphemeronHolderTraceEphemeron> holder =
MakeGarbageCollected<EphemeronHolderTraceEphemeron>(GetAllocationHandle(),
nullptr, value);
InitializeMarker(*Heap::From(GetHeap()), GetPlatformHandle().get());
FinishMarking();
// Key is not alive and value should thus not be held alive.
EXPECT_FALSE(HeapObjectHeader::FromPayload(value).IsMarked());
}
using EphemeronPairGCTest = testing::TestWithHeap;
TEST_F(EphemeronPairGCTest, EphemeronPairValueIsCleared) {
GCed* value = MakeGarbageCollected<GCed>(GetAllocationHandle());
Persistent<EphemeronHolder> holder = MakeGarbageCollected<EphemeronHolder>(
GetAllocationHandle(), nullptr, value);
PreciseGC();
EXPECT_EQ(nullptr, holder->ephemeron_pair().value.Get());
}
} // namespace internal
} // namespace cppgc