rcu: Assume rcu_init() is called before smp

The rcu_init() function is called way before SMP is initialized and
therefore only the boot CPU should be online at this stage.

Simplify the boot per-cpu initialization accordingly.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Uladzislau Rezki <uladzislau.rezki@sony.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a4b8189455d5eca9694101d779346a269597994b..e6a9e5744e45c20a7350bb29393427de2b1222b5 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4782,7 +4782,7 @@ static void __init kfree_rcu_batch_init(void)
 
 void __init rcu_init(void)
 {
-       int cpu;
+       int cpu = smp_processor_id();
 
        rcu_early_boot_tests();
 
@@ -4802,11 +4802,10 @@ void __init rcu_init(void)
         * or the scheduler are operational.
         */
        pm_notifier(rcu_pm_notify, 0);
-       for_each_online_cpu(cpu) {
-               rcutree_prepare_cpu(cpu);
-               rcu_cpu_starting(cpu);
-               rcutree_online_cpu(cpu);
-       }
+       WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
+       rcutree_prepare_cpu(cpu);
+       rcu_cpu_starting(cpu);
+       rcutree_online_cpu(cpu);
 
        /* Create workqueue for Tree SRCU and for expedited GPs. */
        rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);