[openib-general] User Level Events - request for support

[Eitan Zahavi]

I would like to propose for gen2 stack to have a user level API supporting
registration for notifications on unaffiliated asynchronous events.

As an example in cases when the local IB port link goes down an SM that runs
on top of this port needs to be notified and start a sweep when the port is
back up. Missing such event, in user land, prevents the SM from knowing
about the change. 

Currently gen1 and gen2 OpenSM is not registered to get these events. The SM
will then fail to reconfigure the subnet in cases like:
1.	The SM cable connects to a switch and the user changes the switch
port the SM is connected to. In this case the SM might be in the middle of a
sweep and do not even notice (due to the short time the change takes) that
there was a change. Traps coming from the switch are forwarded to the old
port the SM was connected to and are dropped (as the port is down). As
OpenSM does not know there was any change in the subnet topology, it will
not perform a heavy sweep. 
2.	The switch connected to the SM is rebooted. If the reboot happens so
fast that it falls between two light sweeps, OpenSM will not be able to know
the switch was reset (as all SMPs are DR). 

Although one can write special case code to handle these cases, due to the
asynchronous nature of things there are many races that can not be resolved
without a simple "port up/down" event that the SM should register to.

Hope this provides enough reason behind my request for a user-level event
notification mechanism.

Eitan 


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