nohz: Ensure full dynticks CPUs are RCU nocbs

We need full dynticks CPU to also be RCU nocb so
that we don't have to keep the tick to handle RCU
callbacks.

Make sure the range passed to nohz_full= boot
parameter is a subset of rcu_nocbs=

The CPUs that fail to meet this requirement will be
excluded from the nohz_full range. This is checked
early in boot time, before any CPU has the opportunity
to stop its tick.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index f5ab50235cba..1d4ceff793a4 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1695,7 +1695,7 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
                           struct rcu_node *rnp, struct rcu_data *rdp)
 {
         /* No-CBs CPUs do not have orphanable callbacks. */
-        if (is_nocb_cpu(rdp->cpu))
+        if (rcu_is_nocb_cpu(rdp->cpu))
                 return;
 
         /*
@@ -2757,10 +2757,10 @@ static void _rcu_barrier(struct rcu_state *rsp)
          * corresponding CPU's preceding callbacks have been invoked.
          */
         for_each_possible_cpu(cpu) {
-                if (!cpu_online(cpu) && !is_nocb_cpu(cpu))
+                if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu))
                         continue;
                 rdp = per_cpu_ptr(rsp->rda, cpu);
-                if (is_nocb_cpu(cpu)) {
+                if (rcu_is_nocb_cpu(cpu)) {
                         _rcu_barrier_trace(rsp, "OnlineNoCB", cpu,
                                            rsp->n_barrier_done);
                         atomic_inc(&rsp->barrier_cpu_count);