Re: When is it safe to release connection resources?

[Flavio Baronti <f.baronti-ngIpsMLAhaq41k5uCYKmRQ@public.gmane.org>]

So in order to safely call ibv_destroy_cq, I should call ibv_ack_cq_events *after* ibv_poll_cq? The example on the man 
page for ibv_get_cq_event calls it before, is it an error?

Flavio

Il 1/2/2012 17:39 PM, Hefty, Sean ha scritto:
>> If I understood correctly, when ibv_get_cq_event returns, it holds some sort
>> of lock over the completion queue, which is
>
> ibv_get_cq_event will increment a reference count on the CQ that it is returning.
>
>> released when I call ibv_req_notify_cq. This lock is checked also in
>
> You decrement the count with ibv_ack_cq_events.  ibv_req_notify_cq is used to arm the cq, so that a completion generates an interrupt and a new event.
>
>> ibv_destroy_cq, so that:
>> 1) When ibv_destroy_cq returns, I am certain that there is no thread running
>> somewhere between ibv_get_cq_event and
>> ibv_req_notify_cq
>
> ibv_destroy_cq will block until all outstanding references on the cq have been released.  The intent is to protect the user from ibv_get_cq_event from returning a reference to a cq that is being destroyed from another thread, which could result in a crash in the user's code.
>
>> 2) When ibv_destroy_cq returns, I am certain that ibv_get_cq_event will not
>> return the destroyed cq any more.
>
> correct
>
> - Sean
>

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