atomic_fetch_add_relaxed
int old = atomic_fetch_add_relaxed(i, &r->refs);
KCSAN_EXPECT_READ_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
KCSAN_EXPECT_WRITE_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
KCSAN_EXPECT_RW_BARRIER(atomic_fetch_add_relaxed(1, &dummy), false);
return atomic_fetch_add_relaxed(i, v);