rcu: Let the world know when RCU adjusts its geometry

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@linux.vnet.ibm.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 518e08428b2e..30499508c72e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3391,6 +3391,8 @@ 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