1C Z6.0+pooncelock+poonceLock+pombonce 2 3(* 4 * Result: Never 5 * 6 * This litmus test demonstrates how smp_mb__after_spinlock() may be 7 * used to ensure that accesses in different critical sections for a 8 * given lock running on different CPUs are nevertheless seen in order 9 * by CPUs not holding that lock. 10 *) 11 12{} 13 14P0(int *x, int *y, spinlock_t *mylock) 15{ 16 spin_lock(mylock); 17 WRITE_ONCE(*x, 1); 18 WRITE_ONCE(*y, 1); 19 spin_unlock(mylock); 20} 21 22P1(int *y, int *z, spinlock_t *mylock) 23{ 24 int r0; 25 26 spin_lock(mylock); 27 smp_mb__after_spinlock(); 28 r0 = READ_ONCE(*y); 29 WRITE_ONCE(*z, 1); 30 spin_unlock(mylock); 31} 32 33P2(int *x, int *z) 34{ 35 int r1; 36 37 WRITE_ONCE(*z, 2); 38 smp_mb(); 39 r1 = READ_ONCE(*x); 40} 41 42exists (1:r0=1 /\ z=2 /\ 2:r1=0) 43