[dpdk-dev] [PATCH v5 7/9] ring: introduce peek style API

[Ananyev, Konstantin]

> 
> > > diff --git a/lib/librte_ring/rte_ring_generic.h
> > > b/lib/librte_ring/rte_ring_generic.h
> > > index 953cdbbd5..9f5fdf13b 100644
> > > --- a/lib/librte_ring/rte_ring_generic.h
> > > +++ b/lib/librte_ring/rte_ring_generic.h
> > Changes in this file are not required as we agreed to implement only C11 for new features.
> 
> Right, will remove.

Actually no, spoke too early before thinking properly
We do need these functions in rte_ring_generic.h for SP/SC _start_/_finish_.
Konstantin

> 
> >
> > > @@ -10,6 +10,54 @@
> > >  #ifndef _RTE_RING_GENERIC_H_
> > >  #define _RTE_RING_GENERIC_H_
> > >
> > > +/**
> > > + * @internal get current tail value.
> > > + * This function should be used only for single thread producer/consumer.
> > > + * Check that user didn't request to move tail above the head.
> > > + * In that situation:
> > > + * - return zero, that will cause abort any pending changes and
> > > + *   return head to its previous position.
> > > + * - throw an assert in debug mode.
> > > + */
> > > +static __rte_always_inline uint32_t
> > > +__rte_ring_st_get_tail(struct rte_ring_headtail *ht, uint32_t *tail,
> > > +	uint32_t num)
> > > +{
> > > +	uint32_t h, n, t;
> > > +
> > > +	h = ht->head;
> > > +	t = ht->tail;
> > > +	n = h - t;
> > > +
> > > +	RTE_ASSERT(n >= num);
> > > +	num = (n >= num) ? num : 0;
> > > +
> > > +	*tail = h;
> > > +	return num;
> > > +}
> > > +
> > > +/**
> > > + * @internal set new values for head and tail.
> > > + * This function should be used only for single thread producer/consumer.
> > > + * Should be used only in conjunction with __rte_ring_st_get_tail.
> > > + */
> > > +static __rte_always_inline void
> > > +__rte_ring_st_set_head_tail(struct rte_ring_headtail *ht, uint32_t tail,
> > > +	uint32_t num, uint32_t enqueue)
> > > +{
> > > +	uint32_t pos;
> > > +
> > > +	pos = tail + num;
> > > +
> > > +	if (enqueue)
> > > +		rte_smp_wmb();
> > > +	else
> > > +		rte_smp_rmb();
> > > +
> > > +	ht->head = pos;
> > > +	ht->tail = pos;
> > > +}
> > > +
> > >  static __rte_always_inline void
> > >  update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
> > >  		uint32_t single, uint32_t enqueue)
> > > diff --git a/lib/librte_ring/rte_ring_peek.h b/lib/librte_ring/rte_ring_peek.h
> > > new file mode 100644 index 000000000..2d06888b6
> > > --- /dev/null