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strengthen some atomic operations for weak memory models

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This commit is contained in:
daan 2019-08-26 08:11:15 -07:00
parent 2159c22415
commit 5c7c106d62
4 changed files with 53 additions and 34 deletions
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18
src/alloc.c
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@ -118,22 +118,24 @@ static mi_decl_noinline void _mi_free_block_mt(mi_page_t* page, mi_block_t* bloc
mi_segment_t* segment = _mi_page_segment(page);
if (segment->page_kind==MI_PAGE_HUGE) {
// huge page segments are always abandoned and can be freed immediately
mi_assert_internal(segment->thread_id==0);
mi_assert_internal(segment->abandoned_next==NULL);
mi_assert_internal(mi_atomic_read_relaxed(&segment->thread_id)==0);
mi_assert_internal(mi_atomic_read_ptr_relaxed(mi_atomic_cast(void*,&segment->abandoned_next))==NULL);
// claim it and free
mi_block_set_next(page, block, page->free);
page->free = block;
page->used--;
mi_heap_t* heap = mi_get_default_heap();
segment->thread_id = heap->thread_id;
_mi_segment_page_free(page,true,&heap->tld->segments);
// paranoia: if this it the last reference, the cas should always succeed
if (mi_atomic_cas_strong(&segment->thread_id,heap->thread_id,0)) {
mi_block_set_next(page, block, page->free);
page->free = block;
page->used--;
_mi_segment_page_free(page,true,&heap->tld->segments);
}
return;
}
do {
tfree = page->thread_free;
use_delayed = (mi_tf_delayed(tfree) == MI_USE_DELAYED_FREE ||
(mi_tf_delayed(tfree) == MI_NO_DELAYED_FREE && page->used == page->thread_freed+1)
(mi_tf_delayed(tfree) == MI_NO_DELAYED_FREE && page->used == mi_atomic_read_relaxed(&page->thread_freed)+1) // data-race but ok, just optimizes early release of the page
);
if (mi_unlikely(use_delayed)) {
// unlikely: this only happens on the first concurrent free in a page that is in the full list