linux-kernel - [tip:core/urgent] rcu: Fix local_irq_disable() CONFIG_PROVE

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Message-ID: <tip-0cff810f54b3b52075c27f7a7021d5b195264b6c@git.kernel.org>
Date:	Thu, 18 Mar 2010 22:03:35 GMT
From:	tip-bot for Lai Jiangshan <laijs@...fujitsu.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, paulmck@...ux.vnet.ibm.com,
	hpa@...or.com, mingo@...hat.com, tglx@...utronix.de,
	laijs@...fujitsu.com, mingo@...e.hu
Subject: [tip:core/urgent] rcu: Fix local_irq_disable() CONFIG_PROVE_RCU=y false positives

Commit-ID:  0cff810f54b3b52075c27f7a7021d5b195264b6c
Gitweb:     http://git.kernel.org/tip/0cff810f54b3b52075c27f7a7021d5b195264b6c
Author:     Lai Jiangshan <laijs@...fujitsu.com>
AuthorDate: Thu, 18 Mar 2010 12:25:33 -0700
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 18 Mar 2010 21:25:32 +0100

rcu: Fix local_irq_disable() CONFIG_PROVE_RCU=y false positives

It is documented that local_irq_disable() also delimits RCU_SCHED
read-site critical sections.

See the document of synchronize_sched() or
Documentation/RCU/whatisRCU.txt.

So we have to test irqs_disabled() in rcu_read_lock_sched_held().
Otherwise rcu-lockdep brings incorrect complaint.

Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: dipankar@...ibm.com
Cc: mathieu.desnoyers@...ymtl.ca
Cc: josh@...htriplett.org
Cc: dvhltc@...ibm.com
Cc: niv@...ibm.com
Cc: peterz@...radead.org
Cc: rostedt@...dmis.org
Cc: Valdis.Kletnieks@...edu
Cc: dhowells@...hat.com
Cc: eric.dumazet@...il.com
LKML-Reference: <1268940334-10892-1-git-send-email-paulmck@...ux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 include/linux/rcupdate.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index e1bdc4b..872a98e 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -149,7 +149,7 @@ static inline int rcu_read_lock_sched_held(void)
 		return 1;
 	if (debug_locks)
 		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
-	return lockdep_opinion || preempt_count() != 0;
+	return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
 }
 #else /* #ifdef CONFIG_PREEMPT */
 static inline int rcu_read_lock_sched_held(void)
@@ -180,7 +180,7 @@ static inline int rcu_read_lock_bh_held(void)
 #ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)
 {
-	return !rcu_scheduler_active || preempt_count() != 0;
+	return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled();
 }
 #else /* #ifdef CONFIG_PREEMPT */
 static inline int rcu_read_lock_sched_held(void)
--
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