[Pvfs2-developers] BMI initial contact between new peers

[Scott Atchley]

Hi Sam,

> Hi Scott,
>
>> Since clients initiate all first contact with the servers, what is  
>> the
>> standard procedure? Send an unexpected message only or post a receive
>> and then send an unexpected message and wait for an expected send  
>> from
>> the server?
>
> The latter.
>
>> I am trying to determine whether a send or receive is posted first  
>> for a
>> new peer.
>
> The msgpairarray state machine in src/common/misc/msgpairarray.sm  
> is the
> engine for most of the request/response style unexpected messages from
> client to server.  The msgpairarray_post function first calls
> job_bmi_recv which posts the receive (calls BMI_post_recv), and then
> calls job_bmi_send_list, which basically translates to calling
> BMI_post_sendunexpected_list.

Then I need to have code in the recv function to create a new peer's  
state if it is the first contact. In Lustre, this only happens in the  
send function.

>> Also, can more than one BMI method be called at anyone time (e.g.
>> concurrent send and/or recvs)?
>
> Yes.  All the BMI calls are non-blocking, and we often post many
> receives and sends and let the test call drive completion of them.
>
> -sam

I should have have asked it a different way. Can multiple calls to  
the send function happen at the same time (i.e. is BMI threaded and  
make simultaneous calls to the send function or recv function or any  
combination of functions)? I am wondering about the potential for  
race conditions and when I need to protect against them.

Thanks,

Scott