svn commit: r244154 - head/bin/ps

[Konstantin Belousov]

On Fri, Dec 14, 2012 at 10:42:47PM +0100, Pawel Jakub Dawidek wrote:
> On Fri, Dec 14, 2012 at 11:52:15AM -0500, John Baldwin wrote:
> > On Thursday, December 13, 2012 6:12:44 am Pawel Jakub Dawidek wrote:
> > > On Wed, Dec 12, 2012 at 11:06:52PM +0200, Konstantin Belousov wrote:
> > > > On Wed, Dec 12, 2012 at 03:45:04PM +0000, Pawel Jakub Dawidek wrote:
> > > > > Author: pjd
> > > > > Date: Wed Dec 12 15:45:03 2012
> > > > > New Revision: 244154
> > > > > URL: http://svnweb.freebsd.org/changeset/base/244154
> > > > > 
> > > > > Log:
> > > > >   Use kern.max_pid sysctl to obtain maximum PID number instead of using local
> > > > >   define.
> > > > It is pid_max, not max_pid.
> > > > 
> > > > But the change is wrong. The kern.pid_max only limits newly allocated pids,
> > > > it does not magically moves existing pids, which are out of range, to the
> > > > limited region. See the corresponding commit log for the description.
> > > > It was added to make it easier to run FreeBSD 1.x binaries on the modern
> > > > kernels.
> > > 
> > > I saw CTLFLAG_TUN on the sysctl and assumed it is read-only...
> > > How about defining BSD_PID_MAX in sys/proc.h, which would be visible by
> > > userland as well and setting PID_MAX to BSD_PID_MAX?
> > > 
> > > This would also help bsnmpd.
> > > 
> > > 	http://people.freebsd.org/~pjd/patches/PID_MAX.patch
> > 
> > This doesn't help your actual use case though where you want to boot a kernel
> > with a different PID_MAX.  I would much rather our tools learn such constants
> > from the kernel via sysctl than have them compiled in.  So, I would add a new
> > sysctl which exports the true PID_MAX constant (and is read-only and never
> > changes) and use that in ps, etc.
> 
> In that case I'd prefer to make existing kern.pid_max sysctl read-only
> and make it loader tunable. I don't expect there are many users of this
> sysctl...
> 
No, I described you the purpose of the sysctl. Requiring reboot just for
running the old binaries is not useful. Please do not break it.
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