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potential fix for low address allocations, issue #1087

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daanx 2025-05-13 14:41:40 -07:00
parent a92f86dc73
commit ad0764272a
1 changed files with 19 additions and 10 deletions
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29
src/page-map.c
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@ -218,10 +218,14 @@ bool _mi_page_map_init(void) {
if (!mi_page_map_memid.initially_committed) {
_mi_os_commit(&_mi_page_map[0], os_page_size, NULL); // commit first part of the map
}
_mi_page_map[0] = (mi_page_t**)((uint8_t*)_mi_page_map + page_map_size); // we reserved 2 sub maps at the end already
_mi_page_map[0] = (mi_page_t**)((uint8_t*)_mi_page_map + page_map_size); // we reserved a submap part at the end already
if (!mi_page_map_memid.initially_committed) {
_mi_os_commit(_mi_page_map[0], os_page_size, NULL); // only first OS page
}
if (!mi_page_map_memid.initially_zero) { // initialize first addresses with NULL
_mi_memzero_aligned(_mi_page_map[0], os_page_size);
}
mi_assert_internal(_mi_ptr_page(NULL)==NULL);
return true;
}
@ -271,19 +275,24 @@ static mi_page_t** mi_page_map_ensure_committed(size_t idx) {
static mi_page_t** mi_page_map_ensure_at(size_t idx) {
mi_page_t** sub = mi_page_map_ensure_committed(idx);
if mi_unlikely(sub == NULL) {
if mi_unlikely(sub == NULL || idx == 0 /* low addresses */) {
// sub map not yet allocated, alloc now
mi_memid_t memid;
sub = (mi_page_t**)_mi_os_alloc(MI_PAGE_MAP_SUB_COUNT * sizeof(mi_page_t*), &memid);
mi_page_t** expect = NULL;
if (!mi_atomic_cas_ptr_strong_acq_rel(mi_page_t*, ((_Atomic(mi_page_t**)*)&_mi_page_map[idx]), &expect, sub)) {
// another thread already allocated it.. free and continue
_mi_os_free(sub, MI_PAGE_MAP_SUB_COUNT * sizeof(mi_page_t*), memid);
sub = expect;
mi_assert_internal(sub!=NULL);
}
mi_page_t** expect = sub;
const size_t submap_size = MI_PAGE_MAP_SUB_COUNT * sizeof(mi_page_t*);
sub = (mi_page_t**)_mi_os_alloc(submap_size, &memid);
if (sub == NULL) {
_mi_error_message(EFAULT, "internal error: unable to extend the page map\n");
return NULL;
}
if (!memid.initially_zero) {
_mi_memzero_aligned(sub, submap_size);
}
if (!mi_atomic_cas_ptr_strong_acq_rel(mi_page_t*, ((_Atomic(mi_page_t**)*)&_mi_page_map[idx]), &expect, sub)) {
// another thread already allocated it.. free and continue
_mi_os_free(sub, submap_size, memid);
sub = expect;
mi_assert_internal(sub!=NULL);
}
}
return sub;