[openib-general] is wc valid if ib_poll_cq() returns zero

[somenath]

Sean Hefty wrote:

> somenath wrote:
>
>> 1. if ib_poll_cq(cq, 1, &wc) returns zero, does wc contain a valid 
>> entry?
>
>
> no
>
>  * Poll a CQ for (possibly multiple) completions.  If the return value
>  * is < 0, an error occurred.  If the return value is >= 0, it is the
>  * number of completions returned.  If the return value is
>  * non-negative and strictly less than num_entries, then the CQ was
>  * emptied.
>
> - Sean


Thanks Sean!

As per the above definiton "no error" occurred since return value is 0..
And as per your clarification, wc doesn't contain a valid entry.

So  my next question:

2. why is the io completion routine called when ib_poll_cq() returns zero? 
does this kind of notification contain any information?
is there some error happening here? what are some possible problem areas?
any wild guess...?

anyone else seen this kind of stuff?

( I get send completion and recv completion both your 0 return value).

thanks, som.