From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S267786AbUBTGfp (ORCPT ); Fri, 20 Feb 2004 01:35:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S267788AbUBTGfp (ORCPT ); Fri, 20 Feb 2004 01:35:45 -0500 Received: from nwkea-mail-2.sun.com ([192.18.42.14]:2710 "EHLO nwkea-mail-2.sun.com") by vger.kernel.org with ESMTP id S267786AbUBTGfg (ORCPT ); Fri, 20 Feb 2004 01:35:36 -0500 Date: Thu, 19 Feb 2004 22:35:19 -0800 From: Tim Hockin To: Andrew Morton Cc: linux-kernel@vger.kernel.org, torvalds@osdl.org Subject: Re: PATCH: report NGROUPS_MAX via a sysctl (read-only) Message-ID: <20040220063519.GP9155@sun.com> Reply-To: thockin@sun.com References: <20040220023927.GN9155@sun.com> <20040219213028.42835364.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040219213028.42835364.akpm@osdl.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 19, 2004 at 09:30:28PM -0800, Andrew Morton wrote: > > Attached is a simple patch to expose NGROUPS_MAX via sysctl. > > Why does userspace actually care? You try to do an oversized setgroups(), > so you get an error? I am systematically tracking down apps that use it. glibc is almost free of it. sysconf() still uses it, but as long as the value compiled into glibc as NGROUPS_MAX is less-than-or-equal-to the current kernel's idea, it meets POSIX, right? If any one goes into their kernel source and lowers NGROUPS_MAX they might break things, but I guess that isn't too big of a worry. Some apps are still assuming that the value they get from sysconf() is the absolute max number of groups. Anyone with libc compiled against an older kernel will see 32, when they could have 64k. > And why does NGROUPS_MAX still exist, come to that? AFAICT the only thing Because Linus would not let me set it to INT_MAX. Something about "insanity" ;) As long as we can convince userspace apps to not trust sysconf() or NGROUPS_MAX constants, I guess we don't *need* it exposed. I guess that's a veto, then? -- Tim Hockin Sun Microsystems, Linux Software Engineering thockin@sun.com All opinions are my own, not Sun's