162306a36Sopenharmony_ciC Z6.0+pooncelock+pooncelock+pombonce 262306a36Sopenharmony_ci 362306a36Sopenharmony_ci(* 462306a36Sopenharmony_ci * Result: Sometimes 562306a36Sopenharmony_ci * 662306a36Sopenharmony_ci * This example demonstrates that a pair of accesses made by different 762306a36Sopenharmony_ci * processes each while holding a given lock will not necessarily be 862306a36Sopenharmony_ci * seen as ordered by a third process not holding that lock. 962306a36Sopenharmony_ci *) 1062306a36Sopenharmony_ci 1162306a36Sopenharmony_ci{} 1262306a36Sopenharmony_ci 1362306a36Sopenharmony_ciP0(int *x, int *y, spinlock_t *mylock) 1462306a36Sopenharmony_ci{ 1562306a36Sopenharmony_ci spin_lock(mylock); 1662306a36Sopenharmony_ci WRITE_ONCE(*x, 1); 1762306a36Sopenharmony_ci WRITE_ONCE(*y, 1); 1862306a36Sopenharmony_ci spin_unlock(mylock); 1962306a36Sopenharmony_ci} 2062306a36Sopenharmony_ci 2162306a36Sopenharmony_ciP1(int *y, int *z, spinlock_t *mylock) 2262306a36Sopenharmony_ci{ 2362306a36Sopenharmony_ci int r0; 2462306a36Sopenharmony_ci 2562306a36Sopenharmony_ci spin_lock(mylock); 2662306a36Sopenharmony_ci r0 = READ_ONCE(*y); 2762306a36Sopenharmony_ci WRITE_ONCE(*z, 1); 2862306a36Sopenharmony_ci spin_unlock(mylock); 2962306a36Sopenharmony_ci} 3062306a36Sopenharmony_ci 3162306a36Sopenharmony_ciP2(int *x, int *z) 3262306a36Sopenharmony_ci{ 3362306a36Sopenharmony_ci int r1; 3462306a36Sopenharmony_ci 3562306a36Sopenharmony_ci WRITE_ONCE(*z, 2); 3662306a36Sopenharmony_ci smp_mb(); 3762306a36Sopenharmony_ci r1 = READ_ONCE(*x); 3862306a36Sopenharmony_ci} 3962306a36Sopenharmony_ci 4062306a36Sopenharmony_ciexists (1:r0=1 /\ z=2 /\ 2:r1=0) 41