> -----Original Message-----
> From: Richardson, Bruce
> Sent: Friday, January 11, 2019 5:59 AM
> To: Burakov, Anatoly <anatoly.bura...@intel.com>
> Cc: Eads, Gage <gage.e...@intel.com>; dev@dpdk.org;
> olivier.m...@6wind.com; arybche...@solarflare.com; Ananyev, Konstantin
> <konstantin.anan...@intel.com>
> Subject: Re: [dpdk-dev] [PATCH 1/6] ring: change head and tail to
> pointer-width
> size
>
> On Fri, Jan 11, 2019 at 11:30:24AM +0000, Burakov, Anatoly wrote:
> > On 11-Jan-19 10:58 AM, Bruce Richardson wrote:
> > > On Fri, Jan 11, 2019 at 10:40:19AM +0000, Burakov, Anatoly wrote:
> > > > <...>
> > > >
> > > > > + * Copyright(c) 2016-2019 Intel Corporation
> > > > > */
> > > > > /**
> > > > > @@ -88,7 +88,7 @@ rte_event_ring_enqueue_burst(struct
> rte_event_ring *r,
> > > > > const struct rte_event *events,
> > > > > unsigned int n, uint16_t *free_space)
> > > > > {
> > > > > - uint32_t prod_head, prod_next;
> > > > > + uintptr_t prod_head, prod_next;
> > > >
> > > > I would also question the use of uinptr_t. I think semnatically,
> > > > size_t is more appropriate.
> > > >
> > > Yes, it would, but I believe in this case they want to use the
> > > largest size of (unsigned)int where there exists an atomic for
> > > manipulating 2 of them simultaneously. [The largest size is to
> > > minimize any chance of an ABA issue occuring]. Therefore we need
> > > 32-bit values on 32-bit and 64-bit on 64, and I suspect the best way
> > > to guarantee this is to use pointer-sized values. If size_t is
> > > guaranteed across all OS's to have the same size as uintptr_t it could
> > > also be
> used, though.
> > >
> > > /Bruce
> > >
> >
> > Technically, size_t and uintptr_t are not guaranteed to match. In
> > practice, they won't match only on architectures that DPDK doesn't
> > intend to run on (such as 16-bit segmented archs, where size_t would
> > be 16-bit but uinptr_t would be 32-bit).
> >
> > In all the rest of DPDK code, we use size_t for this kind of thing.
> >
>
> Ok.
> If we do use size_t, I think we also need to add a compile-time check into the
> build too, to error out if sizeof(size_t) != sizeof(uintptr_t).
Ok, I wasn't aware of the precedent of using size_t for this purpose. I'll
change it and look into adding a static assert.
Thanks,
Gage
