Messages in this thread | | | Date | Thu, 19 Feb 2004 22:47:52 -0800 | From | Andrew Morton <> | Subject | Re: PATCH: report NGROUPS_MAX via a sysctl (read-only) |
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Tim Hockin <thockin@sun.com> wrote: > > 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.
OK, well certainly fishing the number out of the currently-running kernel is the one sure way of getting it right.
> > 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" ;)
Is 64k enough?
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