On Mon, Feb 13, 2017 at 08:14:23PM +0100, Tobias Klausmann wrote:

Hi! 

On Mon, 13 Feb 2017, Paul E. McKenney wrote:

quoted

On Mon, Feb 13, 2017 at 01:53:27PM -0500, bob smith wrote:

quoted

On 2/13/17 1:39 PM, Paul E. McKenney wrote:

quoted

can real DEC Alpha hardware end up with both instances of "r1"
having the value 1?

I thought this question reminded me of something, so I found this:

quoted

https://www.kernel.org/doc/Documentation/memory-barriers.txt

and I pasted in the content - David Howells is one of the authors and
maybe that is why the question sort of reminded me.

Maybe someone has an update but this is what was said then.

Well, thank you for pointing me to this, but my question was intended to
check whether or not the words I helped to write in memory-barriers.txt
are in fact accurate.  So if you have an SMP DEC Alpha system that you
could provide remote access to, that would be very helpful!

I have a 4-cpu ES40. Send me a test program and I'll gladly run
it for you.

Andrea, could you please convert the litmus test below and send it to
Tobias?

							Thanx, Paul

------------------------------------------------------------------------

C auto/C-LB-LRW+OB-Dv
(*
 * Result: Never
 * 
 *)
{
}

P0(int *u0, int *x1)
{
	r1 = READ_ONCE(*u0);
	smp_mb();
	WRITE_ONCE(*x1, 1);
}


P1(int *u0, int *x1)
{
	r1 = rcu_dereference(*x1);
	WRITE_ONCE(*u0, r1);
}

exists
(0:r1=1 /\ 1:r1=1)