[Boost-users] inter thread communication with message queues

Subject: [Boost-users] inter thread communication with message queues
From: Kenneth Adam Miller (kennethadammiller_at_[hidden])
Date: 2014-01-24 10:05:46

I was reading about message queues with respect to inter thread
communication, and I have a specific use case that I want to describe. It's
rather complex, so I want to be careful that I design it so that there are
no race conditions.

Pool A is a buffer (of type 1) handle manager, that feeds buffer handles
into thread set 1, and receives old handles from thread set 2. There is
only one thread running pool A.

Thread set 1 is a set of N threads that fill up buffers of type 1 with
regular data. It pushes full buffers to thread set 2.

Thread set 2 is a set of M threads that compress buffers of type 1 into
data buffers of type 2. Once the buffer of type 1 has be used up, it is
cleared and sent back to Pool A. It pulls fresh data buffers of type 2 from
Pool B, and sends freshly filled compressed buffers to Pool C.

Pool C does something with the buffer, clears it and hands it to Pool B.

Can this be done safely using an implementation like what I see here:
http://www.justsoftwaresolutions.co.uk/threading/implementing-a-thread-safe-queue-using-condition-variables.html
?

Note 1: -= denotes a 1-to-N connect and =- a N-to-1 connect

RR = Request reply relationship

   +--------------------------------------------------------------------+
   |                                                                    |
   v                                                                    |
 Pool A     RR   Thread Set 1         Router X                          |
PULL-PUSH --==> PULL-read-PUSH ==--> PULL-PUSH --==> PULL Thread Set 2 PUSH
                                                         \            /
                                                          +-compress-+
                                      Pool B      RR     /            \
                                     PULL-PUSH --==> PULL              PUSH
                                      ^                                 ||
                                      |                                 ||
                                      +----------- PUSH-write-PULL <--==++
                                                      Pool C

Questions: how do I have a separate thread poll on multiple shared message
queues? Like, I have a thread pool that both receives requests for buffer
handles and that receives old buffer handles to recycle.