From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751285Ab3HTSix (ORCPT ); Tue, 20 Aug 2013 14:38:53 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:58999 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827Ab3HTSiw (ORCPT ); Tue, 20 Aug 2013 14:38:52 -0400 Date: Tue, 20 Aug 2013 11:38:43 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, 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: <20130820183843.GK29406@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130818022453.GA3475@linux.vnet.ibm.com> <1376967074-32530-1-git-send-email-paulmck@linux.vnet.ibm.com> <52133EBF.3020605@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52133EBF.3020605@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13082018-5518-0000-0000-000011593387 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 20, 2013 at 06:02:39PM +0800, Lai Jiangshan wrote: > On 08/20/2013 10:51 AM, 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 > > [ paulmck: Banish mid-function ifdef, more or less per Josh Triplett. ] > > --- > > kernel/rcutorture.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 45 insertions(+) > > > > diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c > > index 3d936f0f..f5cf2bb 100644 > > --- a/kernel/rcutorture.c > > +++ b/kernel/rcutorture.c > > @@ -66,6 +66,7 @@ static int fqs_duration; /* Duration of bursts (us), 0 to disable. */ > > static int fqs_holdoff; /* Hold time within burst (us). */ > > static int fqs_stutter = 3; /* Wait time between bursts (s). */ > > static int n_barrier_cbs; /* Number of callbacks to test RCU barriers. */ > > +static int object_debug; /* Test object-debug double call_rcu()?. */ > > static int onoff_interval; /* Wait time between CPU hotplugs, 0=disable. */ > > static int onoff_holdoff; /* Seconds after boot before CPU hotplugs. */ > > static int shutdown_secs; /* Shutdown time (s). <=0 for no shutdown. */ > > @@ -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"); > > module_param(onoff_interval, int, 0444); > > MODULE_PARM_DESC(onoff_interval, "Time between CPU hotplugs (s), 0=disable"); > > module_param(onoff_holdoff, int, 0444); > > @@ -1934,6 +1937,46 @@ rcu_torture_cleanup(void) > > rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); > > } > > > > +#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD > > +static void rcu_torture_leak_cb(struct rcu_head *rhp) > > +{ > > +} > > + > > +static void rcu_torture_err_cb(struct rcu_head *rhp) > > +{ > > + /* This -might- happen due to race conditions, but is unlikely. */ > > + pr_alert("rcutorture: duplicated callback was invoked.\n"); > > +} > > +#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ > > + > > +/* > > + * Verify that double-free causes debug-objects to complain, but only > > + * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. Otherwise, say that the test > > + * cannot be carried out. > > + */ > > +static void rcu_test_debug_objects(void) > > +{ > > +#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. */ > > you can use rcu_read_lock() directly. I could do that as well, but it doesn't do everything that local_irq_disable() does. Right, which means that my comment is bad. Fixing both, thank you! > > + call_rcu(&rh1, rcu_torture_leak_cb); /* start grace period. */ And the one above cannot start a grace period due to irqs being enabled. Which is -almost- always OK, but... > > + call_rcu(&rh2, rcu_torture_err_cb); And this one should invoke rcu_torture_leak_cb instead of rcu_torture_err_cb(). Just results in a confusing error message, but... OK, a few more fixes, then! > > + 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: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n"); > > +#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ > > +} The result is as follows. Better? Thanx, Paul #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD static void rcu_torture_leak_cb(struct rcu_head *rhp) { } static void rcu_torture_err_cb(struct rcu_head *rhp) { /* * This -might- happen due to race conditions, but is unlikely. * The scenario that leads to this happening is that the * first of the pair of duplicate callbacks is queued, * someone else starts a grace period that includes that * callback, then the second of the pair must wait for the * next grace period. Unlikely, but can happen. If it * does happen, the debug-objects subsystem won't have splatted. */ pr_alert("rcutorture: duplicated callback was invoked.\n"); } #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ /* * Verify that double-free causes debug-objects to complain, but only * if CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. Otherwise, say that the test * cannot be carried out. */ static void rcu_test_debug_objects(void) { #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"); preempt_disable(); /* Prevent preemption from interrupting test. */ rcu_read_lock(); /* Make it impossible to finish a grace period. */ call_rcu(&rh1, rcu_torture_leak_cb); /* Start grace period. */ local_irq_disable(); /* Make it harder to start a new grace period. */ call_rcu(&rh2, rcu_torture_leak_cb); call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */ local_irq_enable(); rcu_read_unlock(); preempt_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: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n"); #endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */ } > > + > > static int __init > > rcu_torture_init(void) > > { > > @@ -2163,6 +2206,8 @@ rcu_torture_init(void) > > firsterr = retval; > > goto unwind; > > } > > + if (object_debug) > > + rcu_test_debug_objects(); > > rcutorture_record_test_transition(); > > mutex_unlock(&fullstop_mutex); > > return 0; >