Re: [PATCH rdma-core RESEND] providers/rxe: Replace '%' with '&' in check_qp_queue_full()

["yangx.jy@fujitsu.com" <yangx.jy@fujitsu.com>]

On 2022/1/11 18:47, Leon Romanovsky wrote:
> On Tue, Jan 11, 2022 at 09:19:46AM +0000, yangx.jy@fujitsu.com wrote:
>> On 2022/1/11 14:11, Leon Romanovsky wrote:
>>> On Tue, Jan 11, 2022 at 10:24:04AM +0800, Xiao Yang wrote:
>>>> The expression "cons == ((qp->cur_index + 1) % q->index_mask)" mistakenly
>>>> assumes the queue is full when the number of entires is equal to "maximum - 1"
>>>> (maximum is correct).
>>>>
>>>> For example:
>>>> If cons and qp->cur_index are 0 and q->index_mask is 1, check_qp_queue_full()
>>>> reports ENOSPC.
>>>>
>>>> Fixes: 1a894ca10105 ("Providers/rxe: Implement ibv_create_qp_ex verb")
>>>> Signed-off-by: Xiao Yang<yangx.jy@fujitsu.com>
>>>> ---
>>>>    providers/rxe/rxe_queue.h | 2 +-
>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/providers/rxe/rxe_queue.h b/providers/rxe/rxe_queue.h
>>>> index 6de8140c..708e76ac 100644
>>>> --- a/providers/rxe/rxe_queue.h
>>>> +++ b/providers/rxe/rxe_queue.h
>>>> @@ -205,7 +205,7 @@ static inline int check_qp_queue_full(struct rxe_qp *qp)
>>>>    	if (qp->err)
>>>>    		goto err;
>>>>
>>>> -	if (cons == ((qp->cur_index + 1) % q->index_mask))
>>>> +	if (cons == ((qp->cur_index + 1)&   q->index_mask))
>>> Please reuse queue_full().
>> Hi Leon,
>>
>> qp->cur_index and qp->err are introduced for new ibv_wr_* APIs and I am
>> not sure if check_qp_queue_full() can be replaced with queue_full().
>>
>> Bob, do you have any suggestion?
>
> diff --git a/providers/rxe/rxe_queue.h b/providers/rxe/rxe_queue.h
> index 6de8140c..83eb4a5f 100644
> --- a/providers/rxe/rxe_queue.h
> +++ b/providers/rxe/rxe_queue.h
> @@ -198,14 +198,11 @@ static inline void advance_qp_cur_index(struct rxe_qp *qp)
>   static inline int check_qp_queue_full(struct rxe_qp *qp)
>   {
>          struct rxe_queue_buf *q = qp->sq.queue;
> -       uint32_t cons;
> -
> -       cons = atomic_load_explicit(consumer(q), memory_order_acquire);
>
>          if (qp->err)
>                  goto err;
>
> -       if (cons == ((qp->cur_index + 1) % q->index_mask))
> +       if (queue_full(q))
>                  qp->err = ENOSPC;
>   err:
>          return qp->err;
> (END)
>
Hi Leon,

This change using q->producer_index makes qp->cur_index unused.
According to commit 1a894ca10105, qp->cur_index and related functions 
(advance_qp_cur_index() , check_qp_queue_full()) are introduced for 
ibv_wr_* APIs on purpose.
I am not sure if we can replace qp->cur_index with q->producer_index 
directly. I think we need Bob to confirm it.
By the way, could we just fix the issue here?

Best Regards,
Xiao Yang
>> Best Regards,
>> Xiao Yang
>>> Thanks
>>>
>>>>    		qp->err = ENOSPC;
>>>>    err:
>>>>    	return qp->err;
>>>> -- 
>>>> 2.25.1
>>>>
>>>>
>>>>