Test MP-unlock-lock

C MP-unlock-lock

{}

P0(int *x, int *y, spinlock_t *s)
{
 spin_lock(s);
 WRITE_ONCE(*x, 1);
 spin_unlock(s);
 spin_lock(s);
 WRITE_ONCE(*y, 1);
 spin_unlock(s);
}

P1(int *x, int *y)
{
 int r0;
 int r1;

 r0 = READ_ONCE(*y);
 smp_rmb();
 r1 = READ_ONCE(*x);
}

Observed
    1:r1=0; 1:r0=1;