[ECOS] HTTP server and multiple threads

[Hans Hübner <hans dot huebner at junger-audio dot com>]

Hi,

I am currently developing a C++ http server for eCos.  Even though it is a new 
development, I'm looking at the built in http server for inspiration.

I have a question regarding its thread handling and select():  The builtin 
http server can be built with multiple threads so that more than one request 
can be served at the same time.  This is implemented by first opening the 
server socket, setting the local address and calling listen().  Then, a number 
of threads is started, each with cug_httpd_server() as the thread function. 
In cyg_httpd_server, each of the worker threads calls select() for the server 
socket (only), calls accept if the server socket is ready and then starts 
cyg_httpd_process() on the given file descriptor in order to actually process 
the request.

This sequence of operations, even though looking consistent and elegent, seems 
kind of unsual to me:  Are multiple threads allowed to select on the same set 
of file descriptors?  If so, is there any guarantee that only one of the 
selects will actually return once a file descriptor becomes ready?  Is this an 
eCos speciality, or is this common among multi threaded systems supplying 
select() and friends?

Thanks for shading some light - I've grown up with 16 bit Unix and select, let 
alone multi threading, never made it into my natural understanding of the API 
:)

-Hans

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