From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750892AbaEAWvS (ORCPT ); Thu, 1 May 2014 18:51:18 -0400 Received: from static.92.5.9.176.clients.your-server.de ([176.9.5.92]:38846 "EHLO mail.hallyn.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750749AbaEAWvR (ORCPT ); Thu, 1 May 2014 18:51:17 -0400 Date: Fri, 2 May 2014 00:51:16 +0200 From: "Serge E. Hallyn" To: Richard Guy Briggs Cc: linux-audit@redhat.com, linux-kernel@vger.kernel.org, containers@lists.linux-foundation.org, serge.hallyn@ubuntu.com, eparis@redhat.com, sgrubb@redhat.com, ebiederm@xmission.com Subject: Re: [PATCH 1/2] namespaces: give each namespace a serial number Message-ID: <20140501225116.GB25669@mail.hallyn.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Richard Guy Briggs (rgb@redhat.com): Most of this looks reasonable, but I'm curious about something, > +/** > + * ns_serial - compute a serial number for the namespace > + * > + * Compute a serial number for the namespace to uniquely identify it in > + * audit records. > + */ > +unsigned int ns_serial(void) > +{ > + static DEFINE_SPINLOCK(serial_lock); > + static unsigned int serial = 4; /* reserved for IPC, UTS, user, PID */ > + > + unsigned long flags; > + unsigned int ret; > + > + spin_lock_irqsave(&serial_lock, flags); > + do { > + ret = ++serial; > + } while (unlikely(!ret)); Why exactly are you doing this? Surely if serial is going to wrap around we've got a bigger problem than just wanting go bump one more time? > + spin_unlock_irqrestore(&serial_lock, flags); > + > + return ret; > +}