From owner-freebsd-hackers  Sun Jan 28 10:38: 9 2001
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From: Luigi Rizzo <rizzo@aciri.org>
Message-Id: <200101281837.f0SIbGI24332@iguana.aciri.org>
Subject: Re: [kernel patch] fcntl(...) to close many descriptors
In-Reply-To: <01012820234100.00214@dades.chilali.net> from mouss at "Jan 28, 2001  8: 9:53 pm"
To: usebsd@free.fr (mouss)
Date: Sun, 28 Jan 2001 10:37:16 -0800 (PST)
Cc: drosih@rpi.edu, hackers@FreeBSD.ORG,
	wollman@khavrinen.lcs.mit.edu
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> I agree that breaking coherence is bad, though I find fcntl is the kind of
> functions to use when you don't have a more specific one:)

do we have (or could we design) a generic mechanism for machine-specific
syscalls which are not available on all OS ?

basically i am thinking of something like

	generic_syscall("fdcloseall", ....);

In this way it would be clear what the non-portable pieces of code
are, and the mechanism would be extensible with no changes to
libraries and syscalls. You could even have dynamically-loaded
modules implementing new "syscalls".

	cheers
	luigi

> then I'd propose
> 	int fdcloseall(int start);
> 
> (I remember having seen some closeall() function in M$ windows
> I think there is such function in M$ windows, so while I didn't sell my soul to
> Bill, I don't see enough reason to choose a new one (that said, I'm not sure of
> the syntax and use there...).
> 
> Note that unlike fcntl() change, this requires adding a syscall, and remaking
> libc. 
> 
> I'm gonna work on this (and put in the optimization idea suggested by Matt).
> 
> regards,
> mouss
> 
> 
> On Sat, 27 Jan 2001, Garance A Drosihn wrote:
> >  
> > [snip]
> >     void closeallfds(int start);
> > 
> > While I understand that defining a new routine is more work
> > than just adding a parameter to an existing routine, I do
> > think it is more appropriate to have that new routine than
> > to use fcntl for this.  The description for fcntl says the
> > first parameter is:
> >       a descriptor to be operated on by 'cmd' as
> >       described below.
> > For the proposed F_CLOSEM command, it does not operate on the
> > GIVEN fd, it operates on a whole bunch of OTHER fd's.  This
> > means that a program which calls fcntl with a cmd-argument
> > which is different than the programmer thinks is being passed
> > could cause some pretty painful-to-debug errors in sections of
> > the program which have nothing to do with the section that has
> > the bug.
> > [snip]
> 
> 
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