rcu: Consolidate offline-CPU callback initialization

Currently, both rcu_cleanup_dead_cpu() and rcu_send_cbs_to_orphanage()
initialize the outgoing CPU's callback list.  However, only
rcu_cleanup_dead_cpu() invokes rcu_send_cbs_to_orphanage(), and
it does so unconditionally, which means that only one of these
initializations is required.  This commit therefore consolidates the
callback-list initialization with the rest of the callback handling in
rcu_send_cbs_to_orphanage().

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

1 files changed, 5 insertions, 4 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 48d640ca1a05..8e020c59ecfd 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2256,8 +2256,12 @@ rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp,
                 rsp->orphan_donetail = rdp->nxttail[RCU_DONE_TAIL];
         }
 
-        /* Finally, initialize the rcu_data structure's list to empty.  */
+        /*
+         * Finally, initialize the rcu_data structure's list to empty and
+         * disallow further callbacks on this CPU.
+         */
         init_callback_list(rdp);
+        rdp->nxttail[RCU_NEXT_TAIL] = NULL;
 }
 
 /*
@@ -2398,9 +2402,6 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
         WARN_ONCE(rdp->qlen != 0 || rdp->nxtlist != NULL,
                   "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, nxtlist=%p\n",
                   cpu, rdp->qlen, rdp->nxtlist);
-        init_callback_list(rdp);
-        /* Disallow further callbacks on this CPU. */
-        rdp->nxttail[RCU_NEXT_TAIL] = NULL;
         mutex_unlock(&rsp->onoff_mutex);
 }