Date: Wed, 19 Jun 1996 14:04:20 GMT From: James Raynard <fqueries@jraynard.demon.co.uk> To: af@biomath.jussieu.fr Cc: freebsd-questions@freebsd.org Subject: Re: Max first parameter of a Select call? Message-ID: <199606191404.OAA20852@jraynard.demon.co.uk> In-Reply-To: <199606190804.AA28032@iaka.biomath.jussieu.fr> (message from Alain FAUCONNET on Wed, 19 Jun 1996 09:04:52 %2B0100 (GMT%2B0100))
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> > How do you get the 'select' call in FreeBSD to be happy with something
> > greater than 256 as a first parameter?
> > Anything above this seems to give a "Select error 22 - invalid argument"
> >
>
> Not a reply, just a followup: this "feature" seems to have a lot of
> interesting side effects on my machine (2.1-STABLE pre-earthquake).
> When I set user resources limits to hard limits ("unlimit" C-shell
> command) and the max file descriptors goes >> 256, sudo no longer
> works ("Password:" prompt exits immediately), fvwm sets system load at
> 1.0 permanently. I have ktraced fvwm and actually saw that select
> returning an error. Everything goes back to normal when I set max fd
> <= 256.
Hmm. As I understand the select() man page, a user program can
increase FD_SETSIZE above the value specified in <sys/types.h>, which
just happens to be 256, but not above the value compiled into the
kernel.
However, <sys/types.h> is a copy of the types.h used in compiling the
kernel, which is where the kernel picks up its value of FD_SETSIZE
from. So a user program can never safely use FD_SETSIZE > 256 without
a kernel re-compile first!
Perhaps we need a FD_SETSIZE option in the kernel config file? (I have
a vague memory of seeing one once, but there's no record of it in my
CVS tree).
--
James Raynard, Edinburgh, Scotland
james@jraynard.demon.co.uk
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