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Unified Diff: src/heap/marking.h

Issue 2857713002: [heap] Make non-atomic markbit operations consistent with atomic ones. (Closed)
Patch Set: fix overlap check Created 3 years, 7 months ago
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Index: src/heap/marking.h
diff --git a/src/heap/marking.h b/src/heap/marking.h
index b20a4d86f149bb7012d648563e47b90613c9fd5b..ab98a124bc4c77c63f4815b93453a088aad8fae6 100644
--- a/src/heap/marking.h
+++ b/src/heap/marking.h
@@ -38,12 +38,16 @@ class MarkBit {
}
}
+ // The function returns true if it succeeded to
+ // transition the bit from 0 to 1.
template <AccessMode mode = NON_ATOMIC>
inline bool Set();
template <AccessMode mode = NON_ATOMIC>
inline bool Get();
+ // The function returns true if it succeeded to
+ // transition the bit from 1 to 0.
template <AccessMode mode = NON_ATOMIC>
inline bool Clear();
@@ -57,8 +61,9 @@ class MarkBit {
template <>
inline bool MarkBit::Set<MarkBit::NON_ATOMIC>() {
- *cell_ |= mask_;
- return true;
+ base::Atomic32 old_value = *cell_;
+ *cell_ = old_value | mask_;
+ return (old_value & mask_) == 0;
}
template <>
@@ -86,8 +91,9 @@ inline bool MarkBit::Get<MarkBit::ATOMIC>() {
template <>
inline bool MarkBit::Clear<MarkBit::NON_ATOMIC>() {
- *cell_ &= ~mask_;
- return true;
+ base::Atomic32 old_value = *cell_;
+ *cell_ = old_value & ~mask_;
+ return (old_value & mask_) == mask_;
}
template <>
@@ -412,24 +418,17 @@ class Marking : public AllStatic {
template <MarkBit::AccessMode mode = MarkBit::NON_ATOMIC>
INLINE(static bool WhiteToGrey(MarkBit markbit)) {
- DCHECK(mode == MarkBit::ATOMIC || IsWhite(markbit));
return markbit.Set<mode>();
}
- // Warning: this method is not safe in general in concurrent scenarios.
- // If you know that nobody else will change the bits on the given location
- // then you may use it.
template <MarkBit::AccessMode mode = MarkBit::NON_ATOMIC>
- INLINE(static void WhiteToBlack(MarkBit markbit)) {
- DCHECK(mode == MarkBit::ATOMIC || IsWhite(markbit));
- markbit.Set<mode>();
- markbit.Next().Set<mode>();
+ INLINE(static bool WhiteToBlack(MarkBit markbit)) {
+ return markbit.Set<mode>() && markbit.Next().Set<mode>();
}
template <MarkBit::AccessMode mode = MarkBit::NON_ATOMIC>
INLINE(static bool GreyToBlack(MarkBit markbit)) {
- DCHECK(mode == MarkBit::ATOMIC || IsGrey(markbit));
- return markbit.Next().Set<mode>();
+ return markbit.Get<mode>() && markbit.Next().Set<mode>();
}
enum ObjectColor {
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