linux-kernel - [PATCH tip/core/rcu 06/16] rcu: Let the world know when RCU adjusts its geometry

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Date:	Fri, 15 Nov 2013 16:23:28 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	sbw@....edu, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 06/16] rcu: Let the world know when RCU adjusts its geometry

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

Some RCU bugs have been specific to the layout of the rcu_node tree,
but RCU will silently adjust the tree at boot time if appropriate.
This obscures valuable debugging information, so print a message when
this happens.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index acbfead2eb82..875f2a0f9d8d 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3378,6 +3378,8 @@ static void __init rcu_init_geometry(void)
 	if (rcu_fanout_leaf == CONFIG_RCU_FANOUT_LEAF &&
 	    nr_cpu_ids == NR_CPUS)
 		return;
+	pr_info("RCU: Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%d\n",
+		rcu_fanout_leaf, nr_cpu_ids);
 
 	/*
 	 * Compute number of nodes that can be handled an rcu_node tree
-- 
1.8.1.5

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