[openib-general] agent_mad_send

Thu Oct 28 05:22:36 PDT 2004

The reason for this is that for special QPs the driver insert the AV to the
packet and not the HW.
In regular QP the HW reads the AV only when is actually doing the send and
thus you have to wait 
and not destroy the AV till the send completes.

Tziporet

-----Original Message-----
From: Roland Dreier [mailto:roland at topspin.com]
Sent: Wednesday, October 27, 2004 6:18 AM
To: Sean Hefty
Cc: openib-general at openib.org
Subject: Re: [openib-general] agent_mad_send

    Sean> In agent_mad_send, a call is made to create an address
    Sean> handle.  Immediately after calling ib_post_send_mad, the
    Sean> address handle is destroyed.  I think that we want to wait
    Sean> until the send is completed before destroying the address
    Sean> handle, and require this of all callers of ib_post_send_mad.

Yes, that's correct.  Because of a quirk in the way Mellanox HCA's
implement special QPs, it's actually OK to destroy the AH immediately
after posting the send, but for an ordinary QP this will lead to some
bizarre problems.

 - R.
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