How to deal with backlog messages in crypto driver

Hi All ,


As per my understanding backlogs are used when crypto hardware
processing a request ,then multiple incoming requests comes to serve .
A queue/backlog is created to enqueue the request .Please let me know
if my understanding is incorrect.

EX:
M4,M3,M2,M1 ----> H(M0)

Here H(M0) under processing, M1 - M4 request comes when M0 is under
processing so M1-M4 are backlogged.

I am unable to understand how backlog messaging works in Linux kernel
crypto subsystem,Please can some one help me to understand following.


#1: In open source I can find references like below

         backlog = crypto_get_backlog(&dd->queue);
         async_req = crypto_dequeue_request(&dd->queue);

         if (backlog)
                 backlog->complete(backlog, -EINPROGRESS); // Not
really sure what does this call for?


Here When does this backlogged message gets processed?

Note:from http://www.mail-archive.com/linux-crypto%40vger.kernel.org/msg12206.html
,I can understand that backlogged messages need not to be resubmitted.

Please can some one help me to understand how/when to make use of
backlog technique in linux kernel crypto subsystem.

BR,
Srisowj