rcu: Account for nocb-CPU callback counts in RCU CPU stall warnings

The RCU CPU stall warnings print an estimate of the total number of
RCU callbacks queued in the system, but this estimate leaves out
the callbacks queued for nocbs CPUs.  This commit therefore introduces
rcu_get_n_cbs_cpu(), which gives an accurate callback estimate for
both nocbs and normal CPUs, and uses this new function as needed.

This commit also introduces a rcu_get_n_cbs_nocb_cpu() helper function
that returns the number of callbacks for nocbs CPUs or zero otherwise,
and also uses this function in place of direct access to ->nocb_q_count
while in the area (fewer characters, you see).

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index c3e2807a834a..a8f82b7dc5e2 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -455,6 +455,7 @@ static void __init rcu_spawn_nocb_kthreads(void);
 static void __init rcu_organize_nocb_kthreads(void);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 static bool init_nocb_callback_list(struct rcu_data *rdp);
+static unsigned long rcu_get_n_cbs_nocb_cpu(struct rcu_data *rdp);
 static void rcu_bind_gp_kthread(void);
 static bool rcu_nohz_full_cpu(void);
 static void rcu_dynticks_task_enter(void);