From: Tim Hockin <thockin@hockin.org>
To: Glen Turner <glen.turner@aarnet.edu.au>
Cc: linux-kernel@vger.kernel.org
Subject: Re: PATCH: report NGROUPS_MAX via a sysctl (read-only)
Date: Tue, 24 Feb 2004 17:14:51 -0800 [thread overview]
Message-ID: <20040225011451.GA29101@hockin.org> (raw)
In-Reply-To: <1077670767.24730.51.camel@andromache>
On Wed, Feb 25, 2004 at 11:29:27AM +1030, Glen Turner wrote:
> The mere existence of the value means it can be used correctly
> in application code for sanity checking.
Andrew seems to have picked it up for -mm. I sent a patch to glibc-bugs (is
that the right place? any libc folk?) to use the new sysctl in
sysconf(_SC_NGROUPS_MAX). So if/when all those releases converge, you
should be able to get the kernel's idea of NGROUPS_MAX from
sysconf(_SC_NGROUPS_MAX);
> Returning INT_MAX for NGROUPS_MAX isn't wrong, but you
> then can't blame user space for making inefficient choices
> if the kernel limit is actually smaller.
Well, if the kernel HAS no limit, then NGROUPS_MAX really is INT_MAX. There
are not many legit uses I can think of for userspace to actually care about
NGROUPS_MAX. Just the current number of groups, which is easily gotten via
setgroups().
Now that the sysctl is in, it's a very tiny patch to make ngroups_max
actually raisable/ by sysctl, though it is debatable whether it is useful AT
ALL, and dubious whether it is safe to lower that value after any apps are
running.
--
Tim Hockin
thockin@hockin.org
Soon anyone who's not on the World Wide Web will qualify for a government
subsidy for the home-pageless.
next prev parent reply other threads:[~2004-02-25 1:15 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-20 2:39 PATCH: report NGROUPS_MAX via a sysctl (read-only) Tim Hockin
2004-02-20 5:30 ` Andrew Morton
2004-02-20 6:35 ` Tim Hockin
2004-02-20 6:47 ` Andrew Morton
2004-02-20 7:10 ` Tim Hockin
2004-02-25 0:59 ` Glen Turner
2004-02-25 1:14 ` Tim Hockin [this message]
2004-02-25 7:32 ` Ulrich Drepper
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