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1C Z6.0+pooncelock+pooncelock+pombonce2 3(*4 * Result: Sometimes5 *6 * This example demonstrates that a pair of accesses made by different7 * processes each while holding a given lock will not necessarily be8 * 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