From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756135Ab0ECSxf (ORCPT ); Mon, 3 May 2010 14:53:35 -0400 Received: from e2.ny.us.ibm.com ([32.97.182.142]:40164 "EHLO e2.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754117Ab0ECSx1 (ORCPT ); Mon, 3 May 2010 14:53:27 -0400 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, "Paul E. McKenney" Subject: [PATCH tip/core/urgent 01/10] rcu: v2: optionally leave lockdep enabled after RCU lockdep splat Date: Mon, 3 May 2010 11:53:10 -0700 Message-Id: <1272912799-17859-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.0 In-Reply-To: <20100503185253.GA17672@linux.vnet.ibm.com> References: <20100503185253.GA17672@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Lai Jiangshan There is no need to disable lockdep after an RCU lockdep splat, so remove the debug_lockdeps_off() from lockdep_rcu_dereference(). To avoid repeated lockdep splats, use a static variable in the inlined rcu_dereference_check() and rcu_dereference_protected() macros so that a given instance splats only once, but so that multiple instances can be detected per boot. This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY, which is disabled by default. Requested-by: Eric Paris Signed-off-by: Lai Jiangshan Tested-by: Eric Paris Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 15 +++++++++++---- kernel/lockdep.c | 2 ++ lib/Kconfig.debug | 12 ++++++++++++ 3 files changed, 25 insertions(+), 4 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 07db2fe..ec9ab49 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -190,6 +190,15 @@ static inline int rcu_read_lock_sched_held(void) #ifdef CONFIG_PROVE_RCU +#define __do_rcu_dereference_check(c) \ + do { \ + static bool __warned; \ + if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ + __warned = true; \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + } \ + } while (0) + /** * rcu_dereference_check - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing @@ -219,8 +228,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ rcu_dereference_raw(p); \ }) @@ -237,8 +245,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_protected(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ (p); \ }) diff --git a/kernel/lockdep.c b/kernel/lockdep.c index 2594e1c..73747b7 100644 --- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -3801,8 +3801,10 @@ void lockdep_rcu_dereference(const char *file, const int line) { struct task_struct *curr = current; +#ifndef CONFIG_PROVE_RCU_REPEATEDLY if (!debug_locks_off()) return; +#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */ printk("\n===================================================\n"); printk( "[ INFO: suspicious rcu_dereference_check() usage. ]\n"); printk( "---------------------------------------------------\n"); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 935248b..94090b4 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -512,6 +512,18 @@ config PROVE_RCU Say N if you are unsure. +config PROVE_RCU_REPEATEDLY + bool "RCU debugging: don't disable PROVE_RCU on first splat" + depends on PROVE_RCU + default n + help + By itself, PROVE_RCU will disable checking upon issuing the + first warning (or "splat"). This feature prevents such + disabling, allowing multiple RCU-lockdep warnings to be printed + on a single reboot. + + Say N if you are unsure. + config LOCKDEP bool depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT -- 1.7.0