Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754057Ab1BWRtP (ORCPT ); Wed, 23 Feb 2011 12:49:15 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:51706 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752695Ab1BWRtO (ORCPT ); Wed, 23 Feb 2011 12:49:14 -0500 Date: Wed, 23 Feb 2011 09:49:02 -0800 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: Steven Rostedt , linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com Subject: Re: [PATCH] debug rcu head support !PREEMPT config Message-ID: <20110223174902.GN2163@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110223013917.GA20996@linux.vnet.ibm.com> <1298425183-21265-5-git-send-email-paulmck@linux.vnet.ibm.com> <1298431409.7666.76.camel@gandalf.stny.rr.com> <1298472914.7666.85.camel@gandalf.stny.rr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3414 Lines: 85 On Wed, Feb 23, 2011 at 10:13:19AM -0500, Mathieu Desnoyers wrote: > Remove DEBUG_RCU_HEAD dependency on PREEMPT config. Handle the unability to > detect if within a RCU read-side critical section by never performing any > attempt to recover from a failure situation in the fixup handlers. Just print > the warnings. > > This patch is only compile-tested. Queued with mods due to skew, thank you Mathieu! Thanx, Paul > Signed-off-by: Mathieu Desnoyers > --- > kernel/rcupdate.c | 17 +++++++++++++++++ > lib/Kconfig.debug | 2 +- > 2 files changed, 18 insertions(+), 1 deletion(-) > > Index: linux-2.6-lttng/lib/Kconfig.debug > =================================================================== > --- linux-2.6-lttng.orig/lib/Kconfig.debug > +++ linux-2.6-lttng/lib/Kconfig.debug > @@ -313,7 +313,7 @@ config DEBUG_OBJECTS_WORK > > config DEBUG_OBJECTS_RCU_HEAD > bool "Debug RCU callbacks objects" > - depends on DEBUG_OBJECTS && PREEMPT > + depends on DEBUG_OBJECTS > help > Enable this to turn on debugging of RCU list heads (call_rcu() usage). > > Index: linux-2.6-lttng/kernel/rcupdate.c > =================================================================== > --- linux-2.6-lttng.orig/kernel/rcupdate.c > +++ linux-2.6-lttng/kernel/rcupdate.c > @@ -142,7 +142,14 @@ static int rcuhead_fixup_init(void *addr > * Ensure that queued callbacks are all executed. > * If we detect that we are nested in a RCU read-side critical > * section, we should simply fail, otherwise we would deadlock. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > +#ifndef CONFIG_PREEMPT > + WARN_ON(1); > + return 0; > +#endif > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > irqs_disabled()) { > WARN_ON(1); > @@ -184,7 +191,14 @@ static int rcuhead_fixup_activate(void * > * Ensure that queued callbacks are all executed. > * If we detect that we are nested in a RCU read-side critical > * section, we should simply fail, otherwise we would deadlock. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > +#ifndef CONFIG_PREEMPT > + WARN_ON(1); > + return 0; > +#endif > if (rcu_preempt_depth() != 0 || preempt_count() != 0 || > irqs_disabled()) { > WARN_ON(1); > @@ -214,6 +228,9 @@ static int rcuhead_fixup_free(void *addr > * Ensure that queued callbacks are all executed. > * If we detect that we are nested in a RCU read-side critical > * section, we should simply fail, otherwise we would deadlock. > + * In !PREEMPT configurations, there is no way to tell if we are > + * in a RCU read-side critical section or not, so we never > + * attempt any fixup and just print a warning. > */ > #ifndef CONFIG_PREEMPT > WARN_ON(1); > -- > Mathieu Desnoyers > Operating System Efficiency R&D Consultant > EfficiOS Inc. > http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/