Re: Problem with RDMA device removal architecture

[Steve Wise <swise-7bPotxP6k4+P2YhJcF5u+vpXobYPEAuW@public.gmane.org>]

Steve Wise wrote:
>
>> But to Roland's point, how will we ummap resources?
>> If an application won't respond to device removal event and clean up 
>> properly,
>> perhaps it is "okay" to let it crash.  Alternatively, what about a
>> RDMA_CM_EVENT_DEVICE_REMOVAL_PENDING and RDMA_CM_EVENT_DEVICE_REMOVED 
>> scheme.
>> Post the first event to allow good applications to clean up.  The 
>> second event
>> to notify apps that the device is "gone".  After the second event, we 
>> can then
>> get violent and shoot to kill?
>>   
>
> You probably don't need the two events as you can detect when the apps 
> free up these resources anyway.   So your proposal boils down to:  
> post the DEVICE_REMOVAL/ DEVICE_FATAL events, and wait some amount of 
> time.  After said timeout, you fire a SIGBUS at each process still 
> owning resources for the device in question.
>
> Roland, is that terrible in your opinion?
>
>

Actually, we don't need to deliver the signal at all.   Just continue 
with the device removal after the timeout. The mapped resources would 
get unmapped, I guess, and then accessing them would cause a fault in 
the process. 

So we try and wait for well behaved apps, but we don't hang the device 
removal forever...

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