[mirror_ubuntu-hirsute-kernel.git] / tools / memory-model / litmus-tests / MP+porevlocks.litmus

C MP+porevlocks

(*
 * Result: Never
 *
 * This litmus test demonstrates how lock acquisitions and releases can
 * stand in for smp_load_acquire() and smp_store_release(), respectively.
 * In other words, when holding a given lock (or indeed after releasing a
 * given lock), a CPU is not only guaranteed to see the accesses that other
 * CPUs made while previously holding that lock, it is also guaranteed to
 * see all prior accesses by those other CPUs.
 *)

{}

P0(int *x, int *y, spinlock_t *mylock)
{
	int r0;
	int r1;

	r0 = READ_ONCE(*y);
	spin_lock(mylock);
	r1 = READ_ONCE(*x);
	spin_unlock(mylock);
}

P1(int *x, int *y, spinlock_t *mylock)
{
	spin_lock(mylock);
	WRITE_ONCE(*x, 1);
	spin_unlock(mylock);
	WRITE_ONCE(*y, 1);
}

exists (0:r0=1 /\ 0:r1=0)
Commit	Line	Data
1c27b644 PM	1	C MP+porevlocks
1c27b644 PM	2
8f32543b PM	3	(*
	4	* Result: Never
	5	*
	6	* This litmus test demonstrates how lock acquisitions and releases can
	7	* stand in for smp_load_acquire() and smp_store_release(), respectively.
	8	* In other words, when holding a given lock (or indeed after releasing a
	9	* given lock), a CPU is not only guaranteed to see the accesses that other
	10	* CPUs made while previously holding that lock, it is also guaranteed to
	11	* see all prior accesses by those other CPUs.
	12	*)
	13
1c27b644 PM	14	{}
	15
	16	P0(int x, int y, spinlock_t *mylock)
	17	{
	18	int r0;
	19	int r1;
	20
	21	r0 = READ_ONCE(*y);
	22	spin_lock(mylock);
	23	r1 = READ_ONCE(*x);
	24	spin_unlock(mylock);
	25	}
	26
	27	P1(int x, int y, spinlock_t *mylock)
	28	{
	29	spin_lock(mylock);
	30	WRITE_ONCE(*x, 1);
	31	spin_unlock(mylock);
	32	WRITE_ONCE(*y, 1);
	33	}
	34
	35	exists (0:r0=1 /\ 0:r1=0)