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C MP+polockonce+poacquiresilsil
(*
* Result: Sometimes
*
* Do spinlocks provide order to outside observers using spin_is_locked()
* to sense the lock-held state, ordered by acquire? Note that when the
* first spin_is_locked() returns false and the second true, we know that
* the smp_load_acquire() executed before the lock was acquired (loosely
* speaking).
*)
{}
P0(spinlock_t *lo, int *x) // Producer
{
spin_lock(lo);
WRITE_ONCE(*x, 1);
spin_unlock(lo);
}
P1(spinlock_t *lo, int *x) // Consumer
{
int r1;
int r2;
int r3;
r1 = smp_load_acquire(x);
r2 = spin_is_locked(lo);
r3 = spin_is_locked(lo);
}
exists (1:r1=1 /\ 1:r2=0 /\ 1:r3=1) (* Bad outcome. *)
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