Re: Re: Re: Re: [PATCH for-next] RDMA/siw: fix SQ/RQ drain logic to support ib_drain_qp

[Krishnamraju Eraparaju <krishna2@chelsio.com>]

On Thursday, October 10/03/19, 2019 at 14:03:05 +0000, Bernard Metzler wrote:
> There are other reasons why the generic
> __ib_drain_sq() may fail. A CQ overflow is one
> such candidate. Failures are not handled by the ULP,
> since calling a void function.
The function description of ib_drain_qp() says:
 * The caller must:
 *
 * ensure there is room in the CQ(s), SQ, and RQ for drain work requests
 * and completions.
 *
 * allocate the CQs using ib_alloc_cq().
 *
 * ensure that there are no other contexts that are posting WRs
 * concurrently.
 * Otherwise the drain is not guaranteed.
 */


So, it looks like ULP has to check for available CQs before calling
ib_drain_xx(). 
> 
> At the other hand, we know that if we have reached
> ERROR state, the QP will never escape back to become
> full functional; ERROR is the QP's final state.
> 
> So we could do an extra check if we cannot get
> the state lock - if we are already in ERROR. And
> if yes, complete immediately there as well.
> 
> I can change the patch accordingly. Makes sense?
Yes, I think addressing this would make the fix complete.

Thanks,
Krishna.