From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750750Ab3HSDzk (ORCPT ); Sun, 18 Aug 2013 23:55:40 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:47978 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750727Ab3HSDzj (ORCPT ); Sun, 18 Aug 2013 23:55:39 -0400 Date: Sun, 18 Aug 2013 20:55:28 -0700 From: "Paul E. McKenney" To: Josh Triplett 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: <20130819035528.GD29406@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130818022453.GA3475@linux.vnet.ibm.com> <1376792717-3755-1-git-send-email-paulmck@linux.vnet.ibm.com> <20130818025420.GC28923@leaf> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130818025420.GC28923@leaf> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13081903-2398-0000-0000-0000019DA1EE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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? > > @@ -2163,6 +2178,28 @@ rcu_torture_init(void) > > firsterr = retval; > > goto unwind; > > } > > + if (object_debug) { > > +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD > > + struct rcu_head rh1; > > + struct rcu_head rh2; > > + > > + init_rcu_head_on_stack(&rh1); > > + init_rcu_head_on_stack(&rh2); > > + pr_alert("rcutorture: WARN: Duplicate call_rcu() test starting.\n"); > > + local_irq_disable(); /* Make it hard to finish grace period. */ > > + call_rcu(&rh1, rcu_torture_leak_cb); /* start grace period. */ > > + call_rcu(&rh2, rcu_torture_err_cb); > > + call_rcu(&rh2, rcu_torture_err_cb); /* duplicate callback. */ > > + local_irq_enable(); > > + rcu_barrier(); > > + pr_alert("rcutorture: WARN: Duplicate call_rcu() test complete.\n"); > > + destroy_rcu_head_on_stack(&rh1); > > + destroy_rcu_head_on_stack(&rh2); > > +#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ > > + pr_alert("rcutorture: !%s, not testing duplicate call_rcu()\n", > > + "CONFIG_DEBUG_OBJECTS_RCU_HEAD"); > > Why put this parameter in a separate string? That makes it harder to > grep for the full error message. (That's assuming you keep the error > message, given the comment above.) Force of habit, fixed. ;-) Thanx, Paul