18c2ecf20Sopenharmony_ciC MP+polockonce+poacquiresilsil 28c2ecf20Sopenharmony_ci 38c2ecf20Sopenharmony_ci(* 48c2ecf20Sopenharmony_ci * Result: Sometimes 58c2ecf20Sopenharmony_ci * 68c2ecf20Sopenharmony_ci * Do spinlocks provide order to outside observers using spin_is_locked() 78c2ecf20Sopenharmony_ci * to sense the lock-held state, ordered by acquire? Note that when the 88c2ecf20Sopenharmony_ci * first spin_is_locked() returns false and the second true, we know that 98c2ecf20Sopenharmony_ci * the smp_load_acquire() executed before the lock was acquired (loosely 108c2ecf20Sopenharmony_ci * speaking). 118c2ecf20Sopenharmony_ci *) 128c2ecf20Sopenharmony_ci 138c2ecf20Sopenharmony_ci{ 148c2ecf20Sopenharmony_ci} 158c2ecf20Sopenharmony_ci 168c2ecf20Sopenharmony_ciP0(spinlock_t *lo, int *x) 178c2ecf20Sopenharmony_ci{ 188c2ecf20Sopenharmony_ci spin_lock(lo); 198c2ecf20Sopenharmony_ci WRITE_ONCE(*x, 1); 208c2ecf20Sopenharmony_ci spin_unlock(lo); 218c2ecf20Sopenharmony_ci} 228c2ecf20Sopenharmony_ci 238c2ecf20Sopenharmony_ciP1(spinlock_t *lo, int *x) 248c2ecf20Sopenharmony_ci{ 258c2ecf20Sopenharmony_ci int r1; 268c2ecf20Sopenharmony_ci int r2; 278c2ecf20Sopenharmony_ci int r3; 288c2ecf20Sopenharmony_ci 298c2ecf20Sopenharmony_ci r1 = smp_load_acquire(x); 308c2ecf20Sopenharmony_ci r2 = spin_is_locked(lo); 318c2ecf20Sopenharmony_ci r3 = spin_is_locked(lo); 328c2ecf20Sopenharmony_ci} 338c2ecf20Sopenharmony_ci 348c2ecf20Sopenharmony_ciexists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) 35