tools/memory-model/litmus-tests/Z6.0+pooncelock+pooncelock+pombonce.litmus


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C Z6.0+pooncelock+pooncelock+pombonce

(*
 * Result: Sometimes
 *
 * This example demonstrates that a pair of accesses made by different
 * processes each while holding a given lock will not necessarily be
 * seen as ordered by a third process not holding that lock.
 *)

{}

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

P1(int *y, int *z, spinlock_t *mylock)
{
	int r0;

	spin_lock(mylock);
	r0 = READ_ONCE(*y);
	WRITE_ONCE(*z, 1);
	spin_unlock(mylock);
}

P2(int *x, int *z)
{
	int r1;

	WRITE_ONCE(*z, 2);
	smp_mb();
	r1 = READ_ONCE(*x);
}

exists (1:r0=1 /\ z=2 /\ 2:r1=0)