162306a36Sopenharmony_ciC MP+unlocklockonceonce+fencermbonceonce 262306a36Sopenharmony_ci 362306a36Sopenharmony_ci(* 462306a36Sopenharmony_ci * Result: Never 562306a36Sopenharmony_ci * 662306a36Sopenharmony_ci * If two locked critical sections execute on the same CPU, stores in the 762306a36Sopenharmony_ci * first must propagate to each CPU before stores in the second do, even if 862306a36Sopenharmony_ci * the critical sections are protected by different locks. 962306a36Sopenharmony_ci *) 1062306a36Sopenharmony_ci 1162306a36Sopenharmony_ci{} 1262306a36Sopenharmony_ci 1362306a36Sopenharmony_ciP0(spinlock_t *s, spinlock_t *t, int *x, int *y) 1462306a36Sopenharmony_ci{ 1562306a36Sopenharmony_ci spin_lock(s); 1662306a36Sopenharmony_ci WRITE_ONCE(*x, 1); 1762306a36Sopenharmony_ci spin_unlock(s); 1862306a36Sopenharmony_ci spin_lock(t); 1962306a36Sopenharmony_ci WRITE_ONCE(*y, 1); 2062306a36Sopenharmony_ci spin_unlock(t); 2162306a36Sopenharmony_ci} 2262306a36Sopenharmony_ci 2362306a36Sopenharmony_ciP1(int *x, int *y) 2462306a36Sopenharmony_ci{ 2562306a36Sopenharmony_ci int r1; 2662306a36Sopenharmony_ci int r2; 2762306a36Sopenharmony_ci 2862306a36Sopenharmony_ci r1 = READ_ONCE(*y); 2962306a36Sopenharmony_ci smp_rmb(); 3062306a36Sopenharmony_ci r2 = READ_ONCE(*x); 3162306a36Sopenharmony_ci} 3262306a36Sopenharmony_ci 3362306a36Sopenharmony_ciexists (1:r1=1 /\ 1:r2=0) 34