atomic_add_return_relaxed
KCSAN_EXPECT_READ_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
KCSAN_EXPECT_WRITE_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
KCSAN_EXPECT_RW_BARRIER(atomic_add_return_relaxed(1, &dummy), false);
atomic_add_return_relaxed(first, mapped) < ENTIRELY_MAPPED)
nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped);
return atomic_add_return_relaxed(i, v);