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Rebuild ring buffer pointers after injecting events

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The ring buffer pointers are no longer valid as we may have displaced
events around. The pointers of the affected region are reconstructed by
reading the events again, following their size.
This commit is contained in:
Rodrigo Arias 2024-09-06 14:56:13 +02:00
parent 49149e452c
commit e5448af6d8
2 changed files with 35 additions and 9 deletions
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4
CHANGELOG.md
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@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Enable -Wconversion and -Wsign-conversion. - Enable -Wconversion and -Wsign-conversion.
### Fixed
- Fix bug in ovnisort when injecting events in a previously modified section.
## [1.10.0] - 2024-07-26 ## [1.10.0] - 2024-07-26
### Changed ### Changed

40
src/emu/ovnisort.c
View File

@ -75,11 +75,10 @@ ring_add(struct ring *r, struct ovni_ev *ev)
} }
static void static void
ring_check(struct ring *r, long long from) ring_check(struct ring *r, long long start)
{ {
uint64_t last_clock = 0; uint64_t last_clock = 0;
long long start = from != -1 ? from : r->head; for (long long i = start; i != r->tail; i = (i + 1) % r->size) {
for (long long i = start; i != r->tail; i = i + 1 >= r->size ? 0 : i + 1) {
uint64_t clock = r->ev[i]->header.clock; uint64_t clock = r->ev[i]->header.clock;
if (clock < last_clock) { if (clock < last_clock) {
die("ring not sorted at i=%lld, last_clock=%"PRIu64" clock=%"PRIu64 , die("ring not sorted at i=%lld, last_clock=%"PRIu64" clock=%"PRIu64 ,
@ -281,6 +280,32 @@ write_stream(int fd, void *base, void *dst, const void *src, size_t size)
} }
} }
static void
rebuild_ring(struct ring *r, long long start, struct ovni_ev *first, struct ovni_ev *last)
{
long long nbad = 0;
long long n = 0;
struct ovni_ev *ev = first;
for (long long i = start; i != r->tail; i = i + 1 >= r->size ? 0 : i + 1) {
n++;
if (ev != r->ev[i])
nbad++;
if (ev >= last)
die("exceeding last pointer");
r->ev[i] = ev;
size_t size = ovni_ev_size(ev);
ev = (struct ovni_ev *) (((uint8_t *) ev) + size);
}
if (ev != last)
die("inconsistency: ev != last");
dbg("rebuilt ring with %lld / %lld misplaced events", nbad, n);
}
static int static int
execute_sort_plan(struct sortplan *sp) execute_sort_plan(struct sortplan *sp)
{ {
@ -322,6 +347,9 @@ execute_sort_plan(struct sortplan *sp)
free(buf); free(buf);
/* Pointers from the ring buffer are invalid now, rebuild them */
rebuild_ring(sp->r, dirty, first, sp->next);
/* Invariant: The ring buffer is always sorted here. Check from the /* Invariant: The ring buffer is always sorted here. Check from the
* dirty position onwards, so we avoid scanning all events. */ * dirty position onwards, so we avoid scanning all events. */
ring_check(sp->r, dirty); ring_check(sp->r, dirty);
@ -386,12 +414,6 @@ stream_winsort(struct stream *stream, struct ring *r)
} }
} }
/* FIXME: After executing a sort plan, we may have pointers that
* now point to garbage, as the events have moved. We can test
* this by first sorting a given region so that it displaces the
* offsets of the end marker, and then injecting events that are
* inside the first unsorted region. Hopefully, trying to access
* the clock of the end marker will now read garbage. */
ring_add(r, ev); ring_add(r, ev);
} }