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Use atomics when sweeping

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Otherwise, there is a race with concurrent marking, though possibly just
during the ragged stop.
This commit is contained in:
Andy Wingo 2022-05-01 16:23:10 +02:00
parent 2a68dadf22
commit f51e969730
1 changed files with 6 additions and 6 deletions
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12
mark-sweep.h
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@ -660,27 +660,27 @@ static size_t mark_space_live_object_granules(uint8_t *metadata) {
return n + 1; return n + 1;
} }
// FIXME: use atomics
static int sweep_byte(uint8_t *loc, uintptr_t sweep_mask) { static int sweep_byte(uint8_t *loc, uintptr_t sweep_mask) {
uint8_t metadata = *loc; uint8_t metadata = atomic_load_explicit(loc, memory_order_relaxed);
// If the metadata byte is nonzero, that means either a young, dead, // If the metadata byte is nonzero, that means either a young, dead,
// survived, or marked object. If it's live (young, survived, or // survived, or marked object. If it's live (young, survived, or
// marked), we found the next mark. Otherwise it's dead and we clear // marked), we found the next mark. Otherwise it's dead and we clear
// the byte. // the byte. If we see an END, that means an end of a dead object;
// clear it.
if (metadata) { if (metadata) {
if (metadata & sweep_mask) if (metadata & sweep_mask)
return 1; return 1;
*loc = 0; atomic_store_explicit(loc, 0, memory_order_relaxed);
} }
return 0; return 0;
} }
static int sweep_word(uintptr_t *loc, uintptr_t sweep_mask) { static int sweep_word(uintptr_t *loc, uintptr_t sweep_mask) {
uintptr_t metadata = *loc; uintptr_t metadata = atomic_load_explicit(loc, memory_order_relaxed);
if (metadata) { if (metadata) {
if (metadata & sweep_mask) if (metadata & sweep_mask)
return 1; return 1;
*loc = 0; atomic_store_explicit(loc, 0, memory_order_relaxed);
} }
return 0; return 0;
} }