[tip:core/urgent] rcu: Make RCU lockdep check the lockdep_recursion variable

[tip-bot for Paul E. McKenney]

Commit-ID:  bc293d62b26ec590afc90a9e0a31c45d355b7bd8
Gitweb:     http://git.kernel.org/tip/bc293d62b26ec590afc90a9e0a31c45d355b7bd8
Author:     Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Thu, 15 Apr 2010 12:50:39 -0700
Committer:  Ingo Molnar <mingo@xxxxxxx>
CommitDate: Mon, 19 Apr 2010 08:37:19 +0200

rcu: Make RCU lockdep check the lockdep_recursion variable

The lockdep facility temporarily disables lockdep checking by
incrementing the current->lockdep_recursion variable.  Such
disabling happens in NMIs and in other situations where lockdep
might expect to recurse on itself.

This patch therefore checks current->lockdep_recursion, disabling RCU
lockdep splats when this variable is non-zero.  In addition, this patch
removes the "likely()", as suggested by Lai Jiangshan.

Reported-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Reported-by: David Miller <davem@xxxxxxxxxxxxx>
Tested-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: laijs@xxxxxxxxxxxxxx
Cc: dipankar@xxxxxxxxxx
Cc: mathieu.desnoyers@xxxxxxxxxx
Cc: josh@xxxxxxxxxxxxxxxx
Cc: dvhltc@xxxxxxxxxx
Cc: niv@xxxxxxxxxx
Cc: peterz@xxxxxxxxxxxxx
Cc: rostedt@xxxxxxxxxxx
Cc: Valdis.Kletnieks@xxxxxx
Cc: dhowells@xxxxxxxxxx
Cc: eric.dumazet@xxxxxxxxx
LKML-Reference: <20100415195039.GA22623@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 include/linux/rcupdate.h |    5 +----
 kernel/rcupdate.c        |    7 +++++++
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 9f1ddfe..07db2fe 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -101,10 +101,7 @@ extern struct lockdep_map rcu_sched_lock_map;
 # define rcu_read_release_sched() \
 		lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
 
-static inline int debug_lockdep_rcu_enabled(void)
-{
-	return likely(rcu_scheduler_active && debug_locks);
-}
+extern int debug_lockdep_rcu_enabled(void);
 
 /**
  * rcu_read_lock_held - might we be in RCU read-side critical section?
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index 63fe254..03a7ea1 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -69,6 +69,13 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
 
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 
+int debug_lockdep_rcu_enabled(void)
+{
+	return rcu_scheduler_active && debug_locks &&
+	       current->lockdep_recursion == 0;
+}
+EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
+
 /**
  * rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
  *
--
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