From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752361Ab1HPUKt (ORCPT ); Tue, 16 Aug 2011 16:10:49 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:59029 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844Ab1HPUKr (ORCPT ); Tue, 16 Aug 2011 16:10:47 -0400 Date: Tue, 16 Aug 2011 13:10:10 -0700 From: Andrew Morton To: Kay Sievers Cc: linux-kernel@vger.kernel.org, Lennart Poettering Subject: Re: [PATCH] prctl: add PR_{SET,GET}_CHILD_REAPER to allow simple process supervision Message-Id: <20110816131010.7a6e9a99.akpm@linux-foundation.org> In-Reply-To: <1311897706.16657.2.camel@mop> References: <1311897706.16657.2.camel@mop> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 29 Jul 2011 02:01:44 +0200 Kay Sievers wrote: > From: Lennart Poettering > Subject: prctl: add PR_{SET,GET}_CHILD_REAPER to allow simple process supervision > > Userspace service managers/supervisors need to track their started > services. Many services daemonize by double-forking and get implicitely > re-parented to PID 1. The process manager will no longer be able to > receive the SIGCHLD signals for them. > > With this prctl, a service manager can mark itself as a sort of > 'sub-init' process, able to stay as the parent process for all processes > created by the started services. All SIGCHLD signals will be delivered > to the service manager. > > As a side effect, the relevant parent PID information does not get lost > by a double-fork, which results in a more elaborate process tree and 'ps' > output. > > This is orthogonal to PID namespaces. PID namespaces are isolated > from each other, while a service management process usually requires > the serices to live in the same namespace, to be able to talk to each > other. > > Users of this will be the systemd per-user instance, which provides > init-like functionality for the user's login session and D-Bus, which > activates bus services on on-demand. Both will need init-like capabilities > to be able to properly keep track of the services they start. > Interesting patch. I can't immediately see any nasty effects from it.. Did you consider using the existing taskstats capability for this? The comment block over find_new_reaper() is now incomplete. Please update it? prctl(2) has a manpage. What's the plan for updating it?