Commit 978c0b88 authored Oct 06, 2009 by Paul E. McKenney Committed by Ingo Molnar Oct 07, 2009

rcu: Place root rcu_node structure in separate lockdep class



Before this patch, all of the rcu_node structures were in the same lockdep
class, so that lockdep would complain when rcu_preempt_offline_tasks()
acquired the root rcu_node structure's lock while holding one of the leaf
rcu_nodes' locks.

This patch changes rcu_init_one() to use a separate
spin_lock_init() for the root rcu_node structure's lock than is
used for that of all of the rest of the rcu_node structures, which
puts the root rcu_node structure's lock in its own lockdep class.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <12548908983277-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent e74f4c45

kernel/rcutree.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -1647,6 +1647,7 @@ 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);
		rnp->gpnum = 0;
		rnp->qsmask = 0;
		@@ -1670,6 +1671,7 @@ 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);
		}

		/*

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