From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753500Ab0CATEO (ORCPT ); Mon, 1 Mar 2010 14:04:14 -0500 Received: from e8.ny.us.ibm.com ([32.97.182.138]:39409 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752003Ab0CATEL (ORCPT ); Mon, 1 Mar 2010 14:04:11 -0500 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, "Paul E. McKenney" Subject: [PATCH RFC tip/core/rcu 1/2] rcu: suppress RCU lockdep warnings during early boot Date: Mon, 1 Mar 2010 11:03:53 -0800 Message-Id: <1267470234-27150-1-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.6.6 In-Reply-To: <20100301190329.GA26892@linux.vnet.ibm.com> References: <20100301190329.GA26892@linux.vnet.ibm.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org RCU is used during very early boot, before RCU and lockdep have been initialized. So make the underlying primitives (rcu_read_lock_held(), rcu_read_lock_bh_held(), rcu_read_lock_sched_held(), and rcu_dereference_check()) check for early boot via the rcu_scheduler_active flag. This will suppress false positives. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 26 +++++++++++++++++--------- 1 files changed, 17 insertions(+), 9 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index c843736..af51d5f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -104,12 +104,14 @@ extern struct lockdep_map rcu_sched_lock_map; * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ static inline int rcu_read_lock_held(void) { - if (debug_locks) - return lock_is_held(&rcu_lock_map); - return 1; + if (!rcu_scheduler_active || !debug_locks) + return 1; + return lock_is_held(&rcu_lock_map); } /** @@ -119,12 +121,14 @@ static inline int rcu_read_lock_held(void) * an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING, * this assumes we are in an RCU-bh read-side critical section unless it can * prove otherwise. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ static inline int rcu_read_lock_bh_held(void) { - if (debug_locks) - return lock_is_held(&rcu_bh_lock_map); - return 1; + if (!rcu_scheduler_active || !debug_locks) + return 1; + return lock_is_held(&rcu_bh_lock_map); } /** @@ -135,14 +139,18 @@ static inline int rcu_read_lock_bh_held(void) * this assumes we are in an RCU-sched read-side critical section unless it * can prove otherwise. Note that disabling of preemption (including * disabling irqs) counts as an RCU-sched read-side critical section. + * + * Check rcu_scheduler_active to prevent false positives during boot. */ static inline int rcu_read_lock_sched_held(void) { int lockdep_opinion = 0; + if (!rcu_scheduler_active || !debug_locks) + return 1; if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active; + return lockdep_opinion || preempt_count() != 0; } #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -166,7 +174,7 @@ static inline int rcu_read_lock_bh_held(void) static inline int rcu_read_lock_sched_held(void) { - return preempt_count() != 0 || !rcu_scheduler_active; + return !rcu_scheduler_active || preempt_count() != 0; } #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -184,7 +192,7 @@ static inline int rcu_read_lock_sched_held(void) */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_locks && !(c)) \ + if (rcu_scheduler_active && debug_locks && !(c)) \ lockdep_rcu_dereference(__FILE__, __LINE__); \ rcu_dereference_raw(p); \ }) -- 1.6.6