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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>
This commit is contained in:
Paul E. McKenney 2009-10-06 21:48:18 -07:00 committed by Ingo Molnar
parent e74f4c4564
commit 978c0b8814
1 changed files with 3 additions and 1 deletions
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4
kernel/rcutree.c
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@ -1647,7 +1647,8 @@ 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++) {
spin_lock_init(&rnp->lock);
if (rnp != rcu_get_root(rsp))
spin_lock_init(&rnp->lock);
rnp->gpnum = 0;
rnp->qsmask = 0;
rnp->qsmaskinit = 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);
}
/*