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

[somenath]

Sean Hefty wrote:

> somenath wrote:
>
>> 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...?
>
>
> Can you clarify what's happening?  Are you calling ib_poll_cq() from 
> your ib_comp_handler() and not finding a completion?
>
> - Sean

That's right Sean. I establish a RC connection and pre-post a buffer of 
size 4K in one side,
and try to send 4K packet from the other side. each side gets a 
completion event when ib_poll_cq()
rets zero.

ib_recv_comp_hanlder(cq, arg) {
    struct ib_wc wc;

  ib_req_notify_cq(cq, IB_CQ_NEXT_COMP); //i check for errors, there is 
no error;
 
  count = ib_poll_cq(cq, 1, &wc);
  // here I find count = 0
}

same happens to send_comp_handler too..

so, everytime I get a cq notification, I get a zero entry (send and recv 
completion
event occurs on respective nodes).

thanks, som.