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 spinlock_t mylock; 13 int x; 14 int y; 15 int z; 16} 17 18P0(int *x, int *y, spinlock_t *mylock) 19{ 20 spin_lock(mylock); 21 WRITE_ONCE(*x, 1); 22 WRITE_ONCE(*y, 1); 23 spin_unlock(mylock); 24} 25 26P1(int *y, int *z, spinlock_t *mylock) 27{ 28 int r0; 29 30 spin_lock(mylock); 31 r0 = READ_ONCE(*y); 32 WRITE_ONCE(*z, 1); 33 spin_unlock(mylock); 34} 35 36P2(int *x, int *z) 37{ 38 int r1; 39 40 WRITE_ONCE(*z, 2); 41 smp_mb(); 42 r1 = READ_ONCE(*x); 43} 44 45exists (1:r0=1 /\ z=2 /\ 2:r1=0) 46