On Mon, 13 Feb 2017, Paul E. McKenney wrote: > On Mon, Feb 13, 2017 at 08:14:23PM +0100, Tobias Klausmann wrote: > > Hi! > > > > On Mon, 13 Feb 2017, Paul E. McKenney wrote: > > > On Mon, Feb 13, 2017 at 01:53:27PM -0500, bob smith wrote: > > > > On 2/13/17 1:39 PM, Paul E. McKenney wrote: > > > > > 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: > > > > > 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); No, please, not this. It should be: r1 = READ_ONCE(*x1); That is, the auto/C-LB-LRW+OB-Ov.litmus test. > WRITE_ONCE(*u0, r1); > } > > exists > (0:r1=1 /\ 1:r1=1) Alan -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
