[openib-general] [PATCH/RFC 1/2] IB: Return "maybe_missed_event" hint from ib_req_notify_cq()

[Roland Dreier]

    Pradeep> Is it possible that when one gets into the "rotting
    Pradeep> packet" case, the quota is at or close to 0 (on ehca). If
    Pradeep> in the cass it is 0 and netif_rx_reschedule() case wins
    Pradeep> (over netif_rx_schedule()) then it keeps spinning unable
    Pradeep> to process any packets since the undo parameter for
    Pradeep> netif_reschedule() is 0.

It is possible that the quota is close to 0, but I don't see how the
poll routine could spin with quota (the variable max) equal to 0.  If
max is 0, then the "while (max)" loop will never be entered, empty
will remain 0, and the poll routine will simply fall through and
return 1.  Do you agree with that summary?

We don't want the undo parameter of netif_rx_reschedule() to be
non-zero because when we go back to repoll, done is reset to 0.  So
there's no reason to increase the quota again.

I guess you could instrument how many iterations there are with a
small value of max, but I would assume it's self-limiting, since the
last few completions should appear fairly quickly.

 - R.