1 files changed, 17 insertions, 1 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index d8024192c73b..b4efb9e36680 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -676,7 +676,23 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
         struct rcu_node *rnp = rcu_get_root(rsp);
 
         if (!cpu_needs_another_gp(rsp, rdp)) {
-                spin_unlock_irqrestore(&rnp->lock, flags);
+                if (rnp->completed == rsp->completed) {
+                        spin_unlock_irqrestore(&rnp->lock, flags);
+                        return;
+                }
+                spin_unlock(&rnp->lock);         /* irqs remain disabled. */
+
+                /*
+                 * Propagate new ->completed value to rcu_node structures
+                 * so that other CPUs don't have to wait until the start
+                 * of the next grace period to process their callbacks.
+                 */
+                rcu_for_each_node_breadth_first(rsp, rnp) {
+                        spin_lock(&rnp->lock);   /* irqs already disabled. */
+                        rnp->completed = rsp->completed;
+                        spin_unlock(&rnp->lock); /* irqs remain disabled. */
+                }
+                local_irq_restore(flags);
                 return;
         }