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repair GC problem with 'atomic-interior / 'interior

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Some parts of the GC meant to traverse all objects on a page of
'atomic-interior or 'interior objects used "<" to detect the end of
the page, but "<=" was needed. As a result, things could sometimes go
wrong for the last object on a page for platform and size combinations
where the last object ends exactly at the end of the page.

This change consistenly computes the iteration end in a way that makes
both "<" and "<=" work.

Using MPFR bindings from the `math` library could trigger a problem
(but it's difficult to provoke the problem in a reasonably small
example --- difficult enough that I couldn't do it).
This commit is contained in:
Matthew Flatt 2019-08-30 12:14:14 -06:00
parent 65ce0cd468
commit 9fa6e9e25d
1 changed files with 21 additions and 18 deletions
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39
racket/src/racket/gc2/newgc.c
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@ -1246,6 +1246,8 @@ static inline int BTC_single_allocation_limit(NewGC *gc, size_t sizeb);
#define PAGE_START_VSS(page) ((void**) (((char *)((page)->addr)) + PREFIX_SIZE))
#define PAGE_END_VSS(page) ((void**) (((char *)((page)->addr)) + ((page)->size)))
#define MED_OBJHEAD_TO_OBJECT(ptr, page_size) ((void*) (((char *)MED_OBJHEAD((ptr), (page_size))) + OBJHEAD_SIZE));
#define MED_PAGE_START_PTR(p) PPTR(NUM((p)->addr) + PREFIX_SIZE)
#define MED_PAGE_END_PTR(p) PPTR(NUM((p)->addr) + APAGE_SIZE - ((p)->obj_size - 1))
#define BYTES_MULTIPLE_OF_WORD_TO_WORDS(sizeb) ((sizeb) >> gcLOG_WORD_SIZE)
@ -2116,8 +2118,8 @@ static void report_gen0_objects(NewGC *gc) {
for (i = 0; i < NUM_MED_PAGE_SIZES; i++) {
for (p = gc->med_pages[ty][i]; p; p = p->next) {
if (p->generation == AGE_GEN_0) {
void **start = PPTR(NUM(p->addr) + PREFIX_SIZE);
void **end = PPTR(NUM(p->addr) + APAGE_SIZE - p->obj_size);
void **start = MED_PAGE_START_PTR(p);
void **end = MED_PAGE_END_PTR(p);
while (start < end) {
objhead *info = (objhead *)start;
@ -4098,12 +4100,12 @@ static void mark_backpointers(NewGC *gc)
gc->memory_in_use -= gcWORDS_TO_BYTES(work->live_size);
} else {
/* medium page */
void **start = PPTR(NUM(work->addr) + PREFIX_SIZE);
void **end = PPTR(NUM(work->addr) + APAGE_SIZE - work->obj_size);
void **start = MED_PAGE_START_PTR(work);
void **end = MED_PAGE_END_PTR(work);
GC_ASSERT(work->size_class == SIZE_CLASS_MED_PAGE);
while (start <= end) {
while (start < end) {
objhead *info = (objhead *)start;
if (!info->dead) {
if (info->mark || work->non_dead_as_mark)
@ -4657,8 +4659,8 @@ static void repair_heap(NewGC *gc)
/* Don't clear `mark` flags, but do set `dead` flags,
so that the page will be treated correctly by
mark_backpointers. */
void **start = PPTR(NUM(page->addr) + PREFIX_SIZE);
void **end = PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size);
void **start = MED_PAGE_START_PTR(page);
void **end = MED_PAGE_END_PTR(page);
int live_count = 0;
while(start < end) {
objhead *info = (objhead *)start;
@ -4674,8 +4676,8 @@ static void repair_heap(NewGC *gc)
if ((page->generation == AGE_GEN_0) || gc->gc_full) {
if (!page->non_dead_as_mark) {
int live_size;
live_size = unmark_range(PPTR(NUM(page->addr) + PREFIX_SIZE),
PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size));
live_size = unmark_range(MED_PAGE_START_PTR(page),
MED_PAGE_END_PTR(page));
page->live_size = live_size;
} else {
need_fixup_now = page->back_pointers;
@ -4685,7 +4687,7 @@ static void repair_heap(NewGC *gc)
}
if (need_fixup_now)
repair_mixed_page(gc, page, PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size));
repair_mixed_page(gc, page, MED_PAGE_END_PTR(page));
memory_in_use += gcWORDS_TO_BYTES(page->live_size);
page->med_search_start = PREFIX_SIZE; /* start next block search at the beginning */
@ -4833,8 +4835,8 @@ static void incremental_repair_pages(NewGC *gc, int fuel)
PAGE_END_VSS(page));
} else {
GC_ASSERT(page->size_class == SIZE_CLASS_MED_PAGE);
live_size = unmark_range(PPTR(NUM(page->addr) + PREFIX_SIZE),
PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size));
live_size = unmark_range(MED_PAGE_START_PTR(page),
MED_PAGE_END_PTR(page));
}
gc->memory_in_use -= gcWORDS_TO_BYTES(page->live_size);
page->live_size = live_size;
@ -4999,6 +5001,7 @@ static void clean_up_heap(NewGC *gc)
if(next) work->next->prev = prev;
GCVERBOSEPAGE(gc, "Cleaning up MED NO MARKEDON", work);
check_mprotected_for_finished_incremental(gc, work);
gen1_free_mpage(pagemap, work);
--gc->num_gen1_pages;
} else {
@ -5204,7 +5207,7 @@ static void check_live_sizes(NewGC *gc)
for (i = 0; i < NUM_MED_PAGE_SIZES; i++) {
for (page = gc->med_pages[ty][i]; page; page = page->next) {
GC_ASSERT(page->live_size == get_live_size_range(PAGE_START_VSS(page),
PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size)));
MED_PAGE_END_PTR(page));
}
}
}
@ -6188,10 +6191,10 @@ void GC_dump_with_traces(int flags,
for (ty = 0; ty < MED_PAGE_TYPES; ty++) {
for (i = 0; i < NUM_MED_PAGE_SIZES; i++) {
for (page = gc->med_pages[ty][i]; page; page = page->next) {
void **start = PPTR(NUM(page->addr) + PREFIX_SIZE);
void **end = PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size);
void **start = MED_PAGE_START_PTR(page);
void **end = MED_PAGE_END_PTR(page);
while(start <= end) {
while(start < end) {
objhead *info = (objhead *)start;
if (!info->dead) {
if (info->type == PAGE_TAGGED) {
@ -6327,8 +6330,8 @@ void GC_dump_with_traces(int flags,
if (gc->med_pages[ty][i]) {
intptr_t count = 0, page_count = 0;
for (page = gc->med_pages[ty][i]; page; page = page->next) {
void **start = PPTR(NUM(page->addr) + PREFIX_SIZE);
void **end = PPTR(NUM(page->addr) + APAGE_SIZE - page->obj_size);
void **start = MED_PAGE_START_PTR(page);
void **end = MED_PAGE_END_PTR(page);
page_count++;