Re: [dpdk-dev] [PATCH] eventdev: fix incorrect MP/MC tail updates in rte_event_ring

["Van Haaren, Harry" <harry.van.haaren@intel.com>]

> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Mattias Rönnblom
> Sent: Wednesday, March 28, 2018 10:17 AM
> To: dev@dpdk.org
> Cc: Mattias Rönnblom <hofors@lysator.liu.se>
> Subject: [dpdk-dev] [PATCH] eventdev: fix incorrect MP/MC tail updates in
> rte_event_ring
> 
> rte_event_ring enqueue and dequeue tail updates were hardcoded for a
> SC/SP configuration.
> 
> Signed-off-by: Mattias Rönnblom <hofors@lysator.liu.se>
> ---

Hi Mattias,


Thanks for your patch, a few notes;

1)
You can CC the maintainer of a section - the event rings falls under
the eventdev library, and Jerin Jacob is the maintainer.


2)
In DPDK we note patches that are "Fixes",
so we can track what commit they fix. Fixes patches are
also often candidates for backporting.

Details on getting the fixes line here:
https://dpdk.org/doc/guides/contributing/patches.html#commit-messages-body

For this patch, the following is the fixline:

Fixes: dc39e2f359b5 ("eventdev: add ring structure for events")
Cc: bruce.richardson@intel.com


>  lib/librte_eventdev/rte_event_ring.h | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_eventdev/rte_event_ring.h
> b/lib/librte_eventdev/rte_event_ring.h
> index 29d4228..07b4559 100644
> --- a/lib/librte_eventdev/rte_event_ring.h
> +++ b/lib/librte_eventdev/rte_event_ring.h
> @@ -99,7 +99,7 @@ rte_event_ring_enqueue_burst(struct rte_event_ring *r,
> 
>  	ENQUEUE_PTRS(&r->r, &r[1], prod_head, events, n, struct rte_event);
> 
> -	update_tail(&r->r.prod, prod_head, prod_next, 1, 1);
> +	update_tail(&r->r.prod, prod_head, prod_next, 1, r->r.prod.single);
>  end:
>  	if (free_space != NULL)
>  		*free_space = free_entries - n;
> @@ -140,7 +140,7 @@ rte_event_ring_dequeue_burst(struct rte_event_ring *r,
> 
>  	DEQUEUE_PTRS(&r->r, &r[1], cons_head, events, n, struct rte_event);
> 
> -	update_tail(&r->r.cons, cons_head, cons_next, 1, 0);
> +	update_tail(&r->r.cons, cons_head, cons_next, 1, r->r.cons.single);


The signature of update_tail() is as follows:

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)

It seems to be that the 2nd last parameter sets the single/multi producer?

The value that has been changed in this patch is the enqueue or dequeue parameter, which changes the type of memory barrier that is used..


Please review this code, and you can post a V2 of the patch in reply to this one (see contrib guidelines above for details).


Regards, -Harry