[Caml-list] Thread and sockets

[David Mentre <David.Mentre@inria.fr>]

Hello,

I'm building a Caml client/server program using posix threads and
sockets. Right now, I have 3 threads:

 1. normal thread for user computation

 2. a thread doing a blocking call to Unix.accept to setup new
    connections

 3. a thread doing a blocking call to Thread.select (with infinite
    timeout) to get messages on opened connections

I've observed that my design is bad and I have several race
conditions. Worse problems are when I open and close connections. For
example, if thread (3) is blocked and a new connection is opened by
thread (2), thread (3) won't read new messages. I have similar problems
when sockets are closed. How to do it properly?

I think I should open a dedicated thread for each new socket [1].
However I don't know how to stop a thread waiting inside a blocking
call. What happens if the remote part close the socket where a thread is
doing a select (or a read). Does this thread get an exception?

I also don't know how to stop cleanly thread (2). Should another thread
close the socket where thread (2) is doing an Unix.accept on?

I would accept with pleasure any advice on this subjet.

Best regards,
david

[1] At first, I did not choose this design to avoid creating zillions of
    new posix (i.e. kernel, on Linux) threads.
-- 
 David.Mentre@inria.fr
 Opinions expressed here are only mine.
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