1C Z6.0+pooncelock+pooncelock+pombonce 2 3(* 4 * Result: Sometimes 5 * 6 * This example demonstrates that a pair of accesses made by different 7 * processes each while holding a given lock will not necessarily be 8 * seen as ordered by a third process not holding that lock. 9 *) 10 11{} 12 13P0(int *x, int *y, spinlock_t *mylock) 14{ 15 spin_lock(mylock); 16 WRITE_ONCE(*x, 1); 17 WRITE_ONCE(*y, 1); 18 spin_unlock(mylock); 19} 20 21P1(int *y, int *z, spinlock_t *mylock) 22{ 23 int r0; 24 25 spin_lock(mylock); 26 r0 = READ_ONCE(*y); 27 WRITE_ONCE(*z, 1); 28 spin_unlock(mylock); 29} 30 31P2(int *x, int *z) 32{ 33 int r1; 34 35 WRITE_ONCE(*z, 2); 36 smp_mb(); 37 r1 = READ_ONCE(*x); 38} 39 40exists (1:r0=1 /\ z=2 /\ 2:r1=0) 41