1C MP+polockmbonce+poacquiresilsil 2 3(* 4 * Result: Never 5 * 6 * Do spinlocks combined with smp_mb__after_spinlock() provide order 7 * to outside observers using spin_is_locked() to sense the lock-held 8 * state, ordered by acquire? Note that when the first spin_is_locked() 9 * returns false and the second true, we know that the smp_load_acquire() 10 * executed before the lock was acquired (loosely speaking). 11 *) 12 13{} 14 15P0(spinlock_t *lo, int *x) // Producer 16{ 17 spin_lock(lo); 18 smp_mb__after_spinlock(); 19 WRITE_ONCE(*x, 1); 20 spin_unlock(lo); 21} 22 23P1(spinlock_t *lo, int *x) // Consumer 24{ 25 int r1; 26 int r2; 27 int r3; 28 29 r1 = smp_load_acquire(x); 30 r2 = spin_is_locked(lo); 31 r3 = spin_is_locked(lo); 32} 33 34exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *) 35