171b7ff5eSAndrea ParriC MP+fencewmbonceonce+fencermbonceonce 271b7ff5eSAndrea Parri 371b7ff5eSAndrea Parri(* 471b7ff5eSAndrea Parri * Result: Never 571b7ff5eSAndrea Parri * 671b7ff5eSAndrea Parri * This litmus test demonstrates that smp_wmb() and smp_rmb() provide 771b7ff5eSAndrea Parri * sufficient ordering for the message-passing pattern. However, it 871b7ff5eSAndrea Parri * is usually better to use smp_store_release() and smp_load_acquire(). 971b7ff5eSAndrea Parri *) 1071b7ff5eSAndrea Parri 11*5c587f9bSAkira Yokosawa{} 1271b7ff5eSAndrea Parri 13b6ff3084SPaul E. McKenneyP0(int *buf, int *flag) // Producer 1471b7ff5eSAndrea Parri{ 15acc4bdc5SPaul E. McKenney WRITE_ONCE(*buf, 1); 1671b7ff5eSAndrea Parri smp_wmb(); 17acc4bdc5SPaul E. McKenney WRITE_ONCE(*flag, 1); 1871b7ff5eSAndrea Parri} 1971b7ff5eSAndrea Parri 20b6ff3084SPaul E. McKenneyP1(int *buf, int *flag) // Consumer 2171b7ff5eSAndrea Parri{ 2271b7ff5eSAndrea Parri int r0; 2371b7ff5eSAndrea Parri int r1; 2471b7ff5eSAndrea Parri 25acc4bdc5SPaul E. McKenney r0 = READ_ONCE(*flag); 2671b7ff5eSAndrea Parri smp_rmb(); 27acc4bdc5SPaul E. McKenney r1 = READ_ONCE(*buf); 2871b7ff5eSAndrea Parri} 2971b7ff5eSAndrea Parri 30b6ff3084SPaul E. McKenneyexists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *) 31