linux-kernel - [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu

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Date:	Sun, 25 Oct 2009 19:03:55 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...ymtl.ca,
	josh@...htriplett.org, dvhltc@...ibm.com, niv@...ibm.com,
	tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
	Valdis.Kletnieks@...edu, dhowells@...hat.com, avi@...hat.com,
	mtosatti@...hat.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 6/6] rcu: Simplify creating of lockdep class for root rcu_node

From: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Use lockdep_set_class() to simplify the code and to avoid any additional
overhead in the !LOCKDEP case.

Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcutree.c |    5 ++---
 kernel/rcutree.h |    2 ++
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ddbf111..f57c32e 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1666,8 +1666,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
 		cpustride *= rsp->levelspread[i];
 		rnp = rsp->level[i];
 		for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
-			if (rnp != rcu_get_root(rsp))
-				spin_lock_init(&rnp->lock);
+			spin_lock_init(&rnp->lock);
 			rnp->gpnum = 0;
 			rnp->qsmask = 0;
 			rnp->qsmaskinit = 0;
@@ -1690,7 +1689,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
 			INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
 		}
 	}
-	spin_lock_init(&rcu_get_root(rsp)->lock);
+	lockdep_set_class(&rcu_get_root(rsp)->lock, &rcu_root_class);
 }
 
 /*
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 599161f..e091b30 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -296,6 +296,8 @@ DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
 
 #else /* #ifdef RCU_TREE_NONCORE */
 
+static struct lock_class_key rcu_root_class;
+
 /* Forward declarations for rcutree_plugin.h */
 static inline void rcu_bootup_announce(void);
 long rcu_batches_completed(void);
-- 
1.5.2.5

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