Jinoh Kang (@iamahuman) commented about dlls/ntdll/heap.c:
+ NtCurrentTeb()->HeapVirtualAffinity = affinity; + } + affinity %= ARRAY_SIZE(category->affinity_group); + + /* acquire a group, the thread will own it and no other thread can clear free bits. + * some other thread might still set the free bits if they are freeing blocks. + */ + if (!(group = heap_acquire_category_group( heap, flags, block_size, category ))) return NULL; + + /* serialize with heap_free_block_lfh: atomically set GROUP_FLAG_FREE when the free bits are all 0. */ + if (group_find_free_block( group, block_size, &block )) + InterlockedAnd( &group->free_bits, ~GROUP_FLAG_FREE ); + else + InterlockedCompareExchange( &group->free_bits, GROUP_FLAG_FREE, 0 ); + + /* if GROUP_FLAG_FREE was set, thread released its ownership. */ This comment is misleading since the current thread relinquishes ownership of the group in either case. Note that, in the current design, a thread does not own its affinity group; the group slot can be shared with arbitrary number of threads.
-- https://gitlab.winehq.org/wine/wine/-/merge_requests/1628#note_22836