From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750779Ab3HSETv (ORCPT ); Mon, 19 Aug 2013 00:19:51 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:49208 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732Ab3HSETo (ORCPT ); Mon, 19 Aug 2013 00:19:44 -0400 X-Originating-IP: 50.43.39.152 Date: Sun, 18 Aug 2013 21:19:25 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, Mathieu Desnoyers , Sedat Dilek , Davidlohr Bueso , Rik van Riel , Linus Torvalds Subject: Re: [PATCH tip/core/rcu 1/5] rcu: Add duplicate-callback tests to rcutorture Message-ID: <20130819041925.GA12202@leaf> References: <20130818022453.GA3475@linux.vnet.ibm.com> <1376792717-3755-1-git-send-email-paulmck@linux.vnet.ibm.com> <20130818025420.GC28923@leaf> <20130819035528.GD29406@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130819035528.GD29406@linux.vnet.ibm.com> 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 Sun, Aug 18, 2013 at 08:55:28PM -0700, Paul E. McKenney wrote: > On Sat, Aug 17, 2013 at 07:54:20PM -0700, Josh Triplett wrote: > > On Sat, Aug 17, 2013 at 07:25:13PM -0700, Paul E. McKenney wrote: > > > From: "Paul E. McKenney" > > > > > > This commit adds a object_debug option to rcutorture to allow the > > > debug-object-based checks for duplicate call_rcu() invocations to > > > be deterministically tested. > > > > > > Signed-off-by: Paul E. McKenney > > > Cc: Mathieu Desnoyers > > > Cc: Sedat Dilek > > > Cc: Davidlohr Bueso > > > Cc: Rik van Riel > > > Cc: Thomas Gleixner > > > Cc: Linus Torvalds > > > Tested-by: Sedat Dilek > > > > Two comments below; with those fixed, > > Reviewed-by: Josh Triplett > > > > > --- > > > @@ -100,6 +101,8 @@ module_param(fqs_stutter, int, 0444); > > > MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)"); > > > module_param(n_barrier_cbs, int, 0444); > > > MODULE_PARM_DESC(n_barrier_cbs, "# of callbacks/kthreads for barrier testing"); > > > +module_param(object_debug, int, 0444); > > > +MODULE_PARM_DESC(object_debug, "Enable debug-object double call_rcu() testing"); > > > > modules-next has a change to ignore and warn about > > unknown module parameters. Thus, I'd suggest wrapping the ifdef around > > this module parameter, so it doesn't exist at all without > > CONFIG_DEBUG_OBJECTS_RCU_HEAD. > > > > Alternatively, consider providing the test unconditionally, and just > > printing a big warning message saying that it's going to cause > > corruption in the !CONFIG_DEBUG_OBJECTS_RCU_HEAD case. > > I currently do something like the above. The module parameter > is defined unconditionally, but the actual tests are under #ifdef > CONFIG_DEBUG_OBJECTS_RCU_HEAD. If you specify object_debug for a > !CONFIG_DEBUG_OBJECTS_RCU_HEAD kernel, the pr_alert() below happens, > and the test is omitted, thus avoiding the list corruption. > > Seem reasonable? That's exactly the bit I was commenting on. I'm saying that you should either make the test unconditional (perhaps with a warning saying it's about to cause list corruption), or you should compile out the module parameter as well and then you don't need the pr_alert (since current kernels will emit a warning when you pass a non-existent module parameter). Personally, I'd go with the latter. - Josh Triplett