From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933023Ab3GWN4e (ORCPT ); Tue, 23 Jul 2013 09:56:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:17583 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932520Ab3GWN4d (ORCPT ); Tue, 23 Jul 2013 09:56:33 -0400 Date: Tue, 23 Jul 2013 09:56:22 -0400 From: Don Zickus To: Michal Hocko Cc: linux-kernel@vger.kernel.org, Andrew Morton , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar Subject: Re: [RFC 1/2] watchdog: update watchdog attributes atomically Message-ID: <20130723135622.GG126784@redhat.com> References: <1374224699-13255-1-git-send-email-mhocko@suse.cz> <20130719161047.GN126784@redhat.com> <20130719163323.GB9759@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130719163323.GB9759@dhcp22.suse.cz> 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 On Fri, Jul 19, 2013 at 06:33:23PM +0200, Michal Hocko wrote: > On Fri 19-07-13 12:10:48, Don Zickus wrote: > > On Fri, Jul 19, 2013 at 11:04:58AM +0200, Michal Hocko wrote: > > > proc_dowatchdog doesn't synchronize multiple callers which > > > might lead to confusion when two parallel callers might confuse > > > watchdog_enable_all_cpus resp. watchdog_disable_all_cpus (e.g. watchdog > > > gets enabled even if watchdog_thresh was set to 0 already). > > > > > > This patch adds a local mutex which synchronizes callers to the sysctl > > > handler. > > > > Looks fine by me, except one little nitpick.. > > > > > > > > Signed-off-by: Michal Hocko > > > --- > > > kernel/watchdog.c | 7 +++++-- > > > 1 file changed, 5 insertions(+), 2 deletions(-) > > > > > > diff --git a/kernel/watchdog.c b/kernel/watchdog.c > > > index 1241d8c..2d64c02 100644 > > > --- a/kernel/watchdog.c > > > +++ b/kernel/watchdog.c > > > @@ -520,13 +520,15 @@ int proc_dowatchdog(struct ctl_table *table, int write, > > > void __user *buffer, size_t *lenp, loff_t *ppos) > > > { > > > int err, old_thresh, old_enabled; > > > + static DEFINE_MUTEX(watchdog_proc_mutex); > > > > Should we just make this global instead of hiding it as a static inside a > > function. I don't know the kernel rules for deciding which approach makes > > sense. I know it is the same result in either case... > > I've hidden it into the function to discourage from abusing it for > something else and because the usage is nicely focused in this > function. But I have no problem to pull it out. I understand what you are saying. I just remember in the past being asked not to do that, which is why I had the question. I guess we can leave it as is. Cheers, Don