On Thu, Jun 21, 2018 at 08:04:22PM +0200, Peter Zijlstra wrote:
> On Thu, Jun 21, 2018 at 01:27:12PM -0400, Alan Stern wrote:
> > More than one kernel developer has expressed the opinion that the LKMM
> > should enforce ordering of writes by release-acquire chains and by
> > locking. In other words, given the following code:
> >
> > WRITE_ONCE(x, 1);
> > spin_unlock(&s):
> > spin_lock(&s);
> > WRITE_ONCE(y, 1);
> >
> > or the following:
> >
> > smp_store_release(&x, 1);
> > r1 = smp_load_acquire(&x); // r1 = 1
> > WRITE_ONCE(y, 1);
> >
> > the stores to x and y should be propagated in order to all other CPUs,
> > even though those other CPUs might not access the lock s or be part of
> > the release-acquire chain. In terms of the memory model, this means
> > that rel-rf-acq-po should be part of the cumul-fence relation.
> >
> > All the architectures supported by the Linux kernel (including RISC-V)
> > do behave this way, albeit for varying reasons. Therefore this patch
> > changes the model in accordance with the developers' wishes.
> >
> > Signed-off-by: Alan Stern <st...@rowland.harvard.edu>
>
> Thanks for that Alan!
>
> Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
I queued both, with Peter's ack on the second, thank you both!
(Peter, if you meant to ack both, please let me know.)
Thanx, Paul
