From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751801AbdJCVyB (ORCPT ); Tue, 3 Oct 2017 17:54:01 -0400 Received: from mail-wr0-f182.google.com ([209.85.128.182]:46499 "EHLO mail-wr0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751548AbdJCVxw (ORCPT ); Tue, 3 Oct 2017 17:53:52 -0400 X-Google-Smtp-Source: AOwi7QCzR8yPucIeYAc4jky3eX0wSiM0AmC63mPAOpxjC/m7rKubT9e7Ri0kGH0R1TEwWGv4WPIAnA== Date: Wed, 4 Oct 2017 00:53:49 +0300 From: Alexey Dobriyan To: Oleg Nesterov Cc: akpm@linux-foundation.org, ebiederm@xmission.com, keescook@chromium.org, mm-commits@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: + pid-delete-reserved_pids.patch added to -mm tree Message-ID: <20171003215349.GA7023@avx2> References: <59d2c819.FeJw+478bpKqle6W%akpm@linux-foundation.org> <20171003155314.GA9929@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171003155314.GA9929@redhat.com> User-Agent: Mutt/1.7.2 (2016-11-26) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 03, 2017 at 05:53:15PM +0200, Oleg Nesterov wrote: > On 10/02, Andrew Morton wrote: > > > > From: Alexey Dobriyan > > Subject: pid: delete RESERVED_PIDS > > > > RESERVED_PIDS had a noble goal: to protect root from PID exhaustion since > > at least ~2.5.40 > > I am just curious, where did you find the change which documents this goal? Now that you asked, I'm not exactly sure. :-( Please don't tell it is for some kind of stupid userspace which assumed low numbers are kernel threads. > > except it never did that because there was no capability > > or uid checks. > > > > Allow small pids to be allocated after rollover, there is nothing sacred > > about them. > > > > Resource exhaustion should be handled by rlimits and/or kernel memory > > accounting. > > I won't argue, but I always thought that the only purpose of RESERVED_PIDS > is to make the system/kernek daemons started at boot time more "visible" in > /usr/bin/ps output. They will be first in line naturally: kthreadd + init execute first and rarely exit.