[dpdk-dev] [PATCH 1/6] ring: change head and tail to pointer-width size

[Bruce Richardson]

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