1C MP+fencewmbonceonce+fencermbonceonce 2 3(* 4 * Result: Never 5 * 6 * This litmus test demonstrates that smp_wmb() and smp_rmb() provide 7 * sufficient ordering for the message-passing pattern. However, it 8 * is usually better to use smp_store_release() and smp_load_acquire(). 9 *) 10 11{} 12 13P0(int *buf, int *flag) // Producer 14{ 15 WRITE_ONCE(*buf, 1); 16 smp_wmb(); 17 WRITE_ONCE(*flag, 1); 18} 19 20P1(int *buf, int *flag) // Consumer 21{ 22 int r0; 23 int r1; 24 25 r0 = READ_ONCE(*flag); 26 smp_rmb(); 27 r1 = READ_ONCE(*buf); 28} 29 30exists (1:r0=1 /\ 1:r1=0) (* Bad outcome. *) 31