rcu: Fix comment about _rcu_barrier()/orphanage exclusion

In the old days, _rcu_barrier() acquired ->onofflock to exclude
rcu_send_cbs_to_orphanage(), which allowed the latter to avoid memory
barriers in callback handling.  However, _rcu_barrier() recently started
doing get_online_cpus() to lock out CPU-hotplug operations entirely, which
means that the comment in rcu_send_cbs_to_orphanage() that talks about
->onofflock is now obsolete.  This commit therefore fixes the comment.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 74df86bd9204..ac8aed8ee417 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1581,8 +1581,8 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
 {
         /*
          * Orphan the callbacks.  First adjust the counts.  This is safe
-         * because ->onofflock excludes _rcu_barrier()'s adoption of
-         * the callbacks, thus no memory barrier is required.
+         * because _rcu_barrier() excludes CPU-hotplug operations, so it
+         * cannot be running now.  Thus no memory barrier is required.
          */
         if (rdp->nxtlist != NULL) {
                 rsp->qlen_lazy += rdp->qlen_lazy;