Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753160Ab1BWPNY (ORCPT ); Wed, 23 Feb 2011 10:13:24 -0500 Received: from blu0-omc1-s13.blu0.hotmail.com ([65.55.116.24]:49357 "EHLO blu0-omc1-s13.blu0.hotmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751704Ab1BWPNX (ORCPT ); Wed, 23 Feb 2011 10:13:23 -0500 X-Originating-IP: [174.91.193.52] X-Originating-Email: [pdumas9@sympatico.ca] Message-ID: Date: Wed, 23 Feb 2011 10:13:19 -0500 From: Mathieu Desnoyers To: Steven Rostedt , "Paul E. McKenney" CC: 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: [PATCH] debug rcu head support !PREEMPT config 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-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1298472914.7666.85.camel@gandalf.stny.rr.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 10:12:19 up 322 days, 1:01, 6 users, load average: 1.69, 1.66, 1.54 User-Agent: Mutt/1.5.18 (2008-05-17) X-OriginalArrivalTime: 23 Feb 2011 15:13:23.0141 (UTC) FILETIME=[36512F50:01CBD36C] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3131 Lines: 80 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. 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/