18c2ecf20Sopenharmony_ciC Z6.0+pooncelock+pooncelock+pombonce 28c2ecf20Sopenharmony_ci 38c2ecf20Sopenharmony_ci(* 48c2ecf20Sopenharmony_ci * Result: Sometimes 58c2ecf20Sopenharmony_ci * 68c2ecf20Sopenharmony_ci * This example demonstrates that a pair of accesses made by different 78c2ecf20Sopenharmony_ci * processes each while holding a given lock will not necessarily be 88c2ecf20Sopenharmony_ci * seen as ordered by a third process not holding that lock. 98c2ecf20Sopenharmony_ci *) 108c2ecf20Sopenharmony_ci 118c2ecf20Sopenharmony_ci{} 128c2ecf20Sopenharmony_ci 138c2ecf20Sopenharmony_ciP0(int *x, int *y, spinlock_t *mylock) 148c2ecf20Sopenharmony_ci{ 158c2ecf20Sopenharmony_ci spin_lock(mylock); 168c2ecf20Sopenharmony_ci WRITE_ONCE(*x, 1); 178c2ecf20Sopenharmony_ci WRITE_ONCE(*y, 1); 188c2ecf20Sopenharmony_ci spin_unlock(mylock); 198c2ecf20Sopenharmony_ci} 208c2ecf20Sopenharmony_ci 218c2ecf20Sopenharmony_ciP1(int *y, int *z, spinlock_t *mylock) 228c2ecf20Sopenharmony_ci{ 238c2ecf20Sopenharmony_ci int r0; 248c2ecf20Sopenharmony_ci 258c2ecf20Sopenharmony_ci spin_lock(mylock); 268c2ecf20Sopenharmony_ci r0 = READ_ONCE(*y); 278c2ecf20Sopenharmony_ci WRITE_ONCE(*z, 1); 288c2ecf20Sopenharmony_ci spin_unlock(mylock); 298c2ecf20Sopenharmony_ci} 308c2ecf20Sopenharmony_ci 318c2ecf20Sopenharmony_ciP2(int *x, int *z) 328c2ecf20Sopenharmony_ci{ 338c2ecf20Sopenharmony_ci int r1; 348c2ecf20Sopenharmony_ci 358c2ecf20Sopenharmony_ci WRITE_ONCE(*z, 2); 368c2ecf20Sopenharmony_ci smp_mb(); 378c2ecf20Sopenharmony_ci r1 = READ_ONCE(*x); 388c2ecf20Sopenharmony_ci} 398c2ecf20Sopenharmony_ci 408c2ecf20Sopenharmony_ciexists (1:r0=1 /\ z=2 /\ 2:r1=0) 41