Re: [PATCH net-next 05/12] ptr_ring: disallow lockless __ptr_ring_full

[Jason Wang]

On 2018å01æ29æ 12:41, Michael S. Tsirkin wrote:
> On Mon, Jan 29, 2018 at 11:36:09AM +0800, Jason Wang wrote:
> > On 2018å01æ26æ 10:46, Michael S. Tsirkin wrote:
> > > > On 2018å01æ26æ 07:36, Michael S. Tsirkin wrote:
> > > > > Similar to bcecb4bbf88a ("net: ptr_ring: otherwise safe empty checks can
> > > > > overrun array bounds") a lockless use of __ptr_ring_full might
> > > > > cause an out of bounds access.
> > > > >
> > > > > We can fix this, but it's easier to just disallow lockless
> > > > > __ptr_ring_full for now.
> > > > It looks to me that just fix this is better than disallow through doc (which
> > > > is easily to be ignored ...).
> > > >
> > > > Thanks
> > > lockless is tricky, and I'd rather not sprinkle READ/WRITE_ONCE where
> > > they aren't necessary.
> > The problem is then API looks a little bit strange. Lockless were only
> > allowed to be done at __ptr_ring_empty() but not __ptr_ring_full().
> >
> > Thanks
> So __ptr_ring_empty doesn't really work lockless. It merely does not crash.
> I don't believe we can do anything to remove the need to read the
> docs unless people use the safe non __ variants.

Ok, then I will ack the series.

Thanks