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nofl: Use atomics to prevent races in parallel marker

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This commit is contained in:
Andy Wingo 2025-07-04 15:01:51 +02:00
parent 60d6b9dcbf
commit d34dd9a644
1 changed files with 13 additions and 21 deletions
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34
src/nofl-space.h
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@ -1617,31 +1617,23 @@ nofl_space_should_evacuate(struct nofl_space *space, uint8_t metadata_byte,
}
static inline int
nofl_space_set_mark_relaxed(struct nofl_space *space, uint8_t *metadata,
uint8_t byte) {
nofl_space_set_mark(struct nofl_space *space, uint8_t *metadata,
uint8_t byte) {
uint8_t mask = NOFL_METADATA_BYTE_MARK_MASK;
atomic_store_explicit(metadata,
(byte & ~mask) | space->current_mark,
memory_order_relaxed);
return 1;
}
static inline int
nofl_space_set_mark(struct nofl_space *space, uint8_t *metadata, uint8_t byte) {
uint8_t mask = NOFL_METADATA_BYTE_MARK_MASK;
atomic_store_explicit(metadata,
(byte & ~mask) | space->current_mark,
memory_order_release);
return 1;
byte = (byte & ~mask) | space->current_mark;
uint8_t prev = atomic_exchange_explicit(metadata, byte, memory_order_relaxed);
return byte != prev;
}
static inline int
nofl_space_set_nonempty_mark(struct nofl_space *space, uint8_t *metadata,
uint8_t byte, struct gc_ref ref) {
// FIXME: Check that relaxed atomics are actually worth it.
nofl_space_set_mark_relaxed(space, metadata, byte);
nofl_block_set_mark(gc_ref_value(ref));
return 1;
if (nofl_space_set_mark(space, metadata, byte)) {
nofl_block_set_mark(gc_ref_value(ref));
return 1;
}
return 0;
}
static inline void
@ -1775,7 +1767,7 @@ nofl_space_evacuate_or_mark_object(struct nofl_space *space,
struct gc_ref old_ref,
struct nofl_allocator *evacuate) {
uint8_t *metadata = nofl_metadata_byte_for_object(old_ref);
uint8_t byte = *metadata;
uint8_t byte = atomic_load_explicit(metadata, memory_order_acquire);
if (nofl_metadata_byte_has_mark(byte, space->current_mark))
return 0;
@ -1790,7 +1782,7 @@ static inline int
nofl_space_mark_object(struct nofl_space *space, struct gc_ref ref,
struct nofl_allocator *evacuate) {
uint8_t *metadata = nofl_metadata_byte_for_object(ref);
uint8_t byte = *metadata;
uint8_t byte = atomic_load_explicit(metadata, memory_order_acquire);
if (nofl_metadata_byte_has_mark(byte, space->current_mark))
return 0;
@ -1833,7 +1825,7 @@ nofl_space_forward_or_mark_if_traced(struct nofl_space *space,
struct gc_edge edge,
struct gc_ref ref) {
uint8_t *metadata = nofl_metadata_byte_for_object(ref);
uint8_t byte = *metadata;
uint8_t byte = atomic_load_explicit(metadata, memory_order_acquire);
if (nofl_metadata_byte_has_mark(byte, space->current_mark))
return 1;