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Found a race condition where the LOH flag on a segment is set too late. #54839

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Merged
PeterSolMS merged 1 commit into from
Jun 29, 2021
Merged

Found a race condition where the LOH flag on a segment is set too late. #54839

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29 changes: 26 additions & 3 deletions src/coreclr/gc/gc.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5674,9 +5674,17 @@ heap_segment* gc_heap::get_segment_for_uoh (int gen_number, size_t size
#ifdef MULTIPLE_HEAPS
heap_segment_heap (res) = hp;
#endif //MULTIPLE_HEAPS
res->flags |= (gen_number == poh_generation) ?
heap_segment_flags_poh :
heap_segment_flags_loh;

size_t flags = (gen_number == poh_generation) ?
heap_segment_flags_poh :
heap_segment_flags_loh;

#ifdef USE_REGIONS
// in the regions case, flags are set by get_new_region
assert ((res->flags & (heap_segment_flags_loh | heap_segment_flags_poh)) == flags);
#else //USE_REGIONS
res->flags |= flags;
#endif //USE_REGIONS

FIRE_EVENT(GCCreateSegment_V1,
heap_segment_mem(res),
Expand Down Expand Up @@ -28284,6 +28292,21 @@ heap_segment* gc_heap::get_new_region (int gen_number, size_t size)

if (new_region)
{
switch (gen_number)
{
default:
assert ((new_region->flags & (heap_segment_flags_loh | heap_segment_flags_poh)) == 0);
break;

case loh_generation:
new_region->flags |= heap_segment_flags_loh;
break;

case poh_generation:
new_region->flags |= heap_segment_flags_poh;
break;
}

generation* gen = generation_of (gen_number);
heap_segment_next (generation_tail_region (gen)) = new_region;
generation_tail_region (gen) = new_region;
Expand Down