From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932529AbcLHVJE (ORCPT ); Thu, 8 Dec 2016 16:09:04 -0500 Received: from mx2.suse.de ([195.135.220.15]:57511 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752254AbcLHVJC (ORCPT ); Thu, 8 Dec 2016 16:09:02 -0500 Date: Thu, 8 Dec 2016 22:08:59 +0100 From: "Luis R. Rodriguez" To: Kees Cook Cc: "Luis R. Rodriguez" , shuah@kernel.org, Jessica Yu , Rusty Russell , "Eric W. Biederman" , Dmitry Torokhov , Arnaldo Carvalho de Melo , Jonathan Corbet , martin.wilck@suse.com, Michal Marek , Petr Mladek , hare@suse.com, rwright@hpe.com, Jeff Mahoney , DSterba@suse.com, fdmanana@suse.com, neilb@suse.com, Guenter Roeck , rgoldwyn@suse.com, subashab@codeaurora.org, Heinrich Schuchardt , Aaron Tomlin , mbenes@suse.cz, "Paul E. McKenney" , Dan Williams , Josh Poimboeuf , "David S. Miller" , Ingo Molnar , Andrew Morton , Linus Torvalds , linux-kselftest@vger.kernel.org, "linux-doc@vger.kernel.org" , LKML Subject: Re: [RFC 04/10] kmod: provide wrappers for kmod_concurrent inc/dec Message-ID: <20161208210859.GZ1402@wotan.suse.de> References: <20161208184801.1689-1-mcgrof@kernel.org> <20161208194824.2532-1-mcgrof@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 08, 2016 at 12:29:42PM -0800, Kees Cook wrote: > On Thu, Dec 8, 2016 at 11:48 AM, Luis R. Rodriguez wrote: > > kmod_concurrent is used as an atomic counter for enabling > > the allowed limit of modprobe calls, provide wrappers for it > > to enable this to be expanded on more easily. This will be done > > later. > > > > Signed-off-by: Luis R. Rodriguez > > --- > > kernel/kmod.c | 27 +++++++++++++++++++++------ > > 1 file changed, 21 insertions(+), 6 deletions(-) > > > > diff --git a/kernel/kmod.c b/kernel/kmod.c > > index cb6f7ca7b8a5..049d7eabda38 100644 > > --- a/kernel/kmod.c > > +++ b/kernel/kmod.c > > @@ -44,6 +44,9 @@ > > #include > > > > extern int max_threads; > > + > > +static atomic_t kmod_concurrent = ATOMIC_INIT(0); > > + > > unsigned int max_modprobes; > > module_param(max_modprobes, uint, 0644); > > MODULE_PARM_DESC(max_modprobes, "Max number of allowed concurrent modprobes"); > > @@ -108,6 +111,20 @@ static int call_modprobe(char *module_name, int wait) > > return -ENOMEM; > > } > > > > +static int kmod_umh_threads_get(void) > > +{ > > + atomic_inc(&kmod_concurrent); > > + if (atomic_read(&kmod_concurrent) < max_modprobes) > > + return 0; > > + atomic_dec(&kmod_concurrent); > > + return -ENOMEM; > > +} > > + > > +static void kmod_umh_threads_put(void) > > +{ > > + atomic_dec(&kmod_concurrent); > > +} > > Can you use a kref here instead? We're trying to kill raw use of > atomic_t for reference counting... That's a much broader functional change than I was looking for, but I am up for it. Can you describe the benefit of using kref you expect or why this is an ongoing crusade? Since its a larger functional change how about doing this change later, and we can test impact with the tress test driver. In theory if there are benefits can't we add a test case to prove the gains? Luis