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Fix failed assertion due to racy memory access

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While calculating the number of stashed pointers, multiple variables
potentially modified by a concurrent thread were used for the
calculation.  This led to some inconsistencies, correctly detected by
the assertions.  The change eliminates some possible inconsistencies by
using unmodified variables and only once a concurrently modified one.
The assertions are omitted for the cases where we acknowledge potential
inconsistencies too.
This commit is contained in:
Alex Lapenkou
2022-02-14 17:57:14 -08:00
committed by Alexander Lapenkov
parent 063d134aeb
commit ca709c3139
2 changed files with 63 additions and 18 deletions
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6
src/cache_bin.c
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@@ -83,8 +83,10 @@ cache_bin_init(cache_bin_t *bin, cache_bin_info_t *info, void *alloc,
bin->low_bits_low_water = (uint16_t)(uintptr_t)bin->stack_head;
bin->low_bits_full = (uint16_t)(uintptr_t)full_position;
bin->low_bits_empty = (uint16_t)(uintptr_t)empty_position;
assert(cache_bin_diff(bin, bin->low_bits_full,
(uint16_t)(uintptr_t) bin->stack_head) == bin_stack_size);
cache_bin_sz_t free_spots = cache_bin_diff(bin,
bin->low_bits_full, (uint16_t)(uintptr_t)bin->stack_head,
/* racy */ false);
assert(free_spots == bin_stack_size);
assert(cache_bin_ncached_get_local(bin, info) == 0);
assert(cache_bin_empty_position_get(bin) == empty_position);