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12 changes: 8 additions & 4 deletions libcpu/aarch64/common/atomic_aarch64.c
Original file line number Diff line number Diff line change
Expand Up @@ -90,7 +90,6 @@ rt_atomic_t rt_hw_atomic_flag_test_and_set(volatile rt_atomic_t *ptr)
rt_atomic_t rt_hw_atomic_compare_exchange_strong(volatile rt_atomic_t *ptr, rt_atomic_t *old, rt_atomic_t new)
{
rt_atomic_t tmp, oldval;

__asm__ volatile (
" prfm pstl1strm, %2\n"
"1: ldxr %0, %2\n"
Expand All @@ -99,10 +98,15 @@ rt_atomic_t rt_hw_atomic_compare_exchange_strong(volatile rt_atomic_t *ptr, rt_a
" stlxr %w1, %4, %2\n"
" cbnz %w1, 1b\n"
" dmb ish\n"
"2:"
" mov %w1, #1\n"
" b 3f\n"
"2: str %0, [%5]\n"
" mov %w1, #0\n"
"3:"
: "=&r" (oldval), "=&r" (tmp), "+Q" (*ptr)
: "Kr" (*old), "r" (new)
: "Kr" (*old), "r" (new), "r" (old)
: "memory");

return oldval == *old;
return tmp;
}