From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754735AbbFQJl1 (ORCPT ); Wed, 17 Jun 2015 05:41:27 -0400 Received: from mail-wg0-f51.google.com ([74.125.82.51]:35743 "EHLO mail-wg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020AbbFQJlT (ORCPT ); Wed, 17 Jun 2015 05:41:19 -0400 Date: Wed, 17 Jun 2015 11:41:14 +0200 From: Ingo Molnar To: Andy Lutomirski , "Paul E. McKenney" Cc: x86@kernel.org, linux-kernel@vger.kernel.org, =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker , Rik van Riel , Oleg Nesterov , Denys Vlasenko , Borislav Petkov , Kees Cook , Brian Gerst Subject: Re: [RFC/INCOMPLETE 01/13] context_tracking: Add context_tracking_assert_state Message-ID: <20150617094114.GA3940@gmail.com> References: <1d95640676a92a5ff7382e9c87517c12ea23ccd9.1434485184.git.luto@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1d95640676a92a5ff7382e9c87517c12ea23ccd9.1434485184.git.luto@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Andy Lutomirski wrote: > This will let us sprinkle sanity checks around the kernel without > making too much of a mess. > > Signed-off-by: Andy Lutomirski > --- > include/linux/context_tracking.h | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h > index 2821838256b4..0fbea4b152e1 100644 > --- a/include/linux/context_tracking.h > +++ b/include/linux/context_tracking.h > @@ -57,6 +57,13 @@ static inline void context_tracking_task_switch(struct task_struct *prev, > if (context_tracking_is_enabled()) > __context_tracking_task_switch(prev, next); > } > + > +static inline void context_tracking_assert_state(enum ctx_state state) > +{ > + rcu_lockdep_assert(!context_tracking_is_enabled() || > + this_cpu_read(context_tracking.state) == state, > + "context tracking state was wrong"); > +} Please don't introduce assert() style debug check interfaces! (And RCU should be fixed too I suspect.) They are absolutely horrible on the brain when mixed with WARN_ON() interfaces, which are the dominant runtime check interface in the kernel. Instead make it something like: #define ct_state() (this_cpu_read(context_tracking.state)) #define CT_WARN_ON(cond) \ WARN_ON(context_tracking_is_enabled() && (cond)) and then the debug checks can be written as: CT_WARN_ON(ct_state() != CONTEXT_KERNEL); This is IMHO _far_ more readable than: context_tracking_assert_state(CONTEXT_KERNEL); ok? (Assuming people will accept 'ct/CT' as an abbreviation for context tracking.) Thanks, Ingo