[tip:core/urgent] rcu: Fix local_irq_disable() CONFIG_PROVE_RCU=y false positives

[tip-bot for Lai Jiangshan <laijs@cn.fujitsu.com>]

Commit-ID:  0cff810f54b3b52075c27f7a7021d5b195264b6c
Gitweb:     http://git.kernel.org/tip/0cff810f54b3b52075c27f7a7021d5b195264b6c
Author:     Lai Jiangshan <laijs@cn.fujitsu.com>
AuthorDate: Thu, 18 Mar 2010 12:25:33 -0700
Committer:  Ingo Molnar <mingo@elte.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@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
Cc: eric.dumazet@gmail.com
LKML-Reference: <1268940334-10892-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.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)