static void __init futex_detect_cmpxchg(void)
{
#ifndef CONFIG_HAVE_FUTEX_CMPXCHG
	u32 curval;

	/*
	 * This will fail and we want it. Some arch implementations do
	 * runtime detection of the futex_atomic_cmpxchg_inatomic()
	 * functionality. We want to know that before we call in any
	 * of the complex code paths. Also we want to prevent
	 * registration of robust lists in that case. NULL is
	 * guaranteed to fault and we get -EFAULT on functional
	 * implementation, the non-functional ones will return
	 * -ENOSYS.
	 */
	if (cmpxchg_futex_value_locked(&curval, NULL, 0, 0) == -EFAULT)
		futex_cmpxchg_enabled = 1;
#endif
}
Unknown