X-Git-Url: http://review.tizen.org/git/?a=blobdiff_plain;f=kernel%2Frcu%2Ftree.c;h=6705d947ef14ff7fbbf28e0be24e4727face8c4e;hb=42d49f4525661181162386eea643275a5de10b59;hp=b3d116cd072d7bd24803a52c8d6b478930bd6b8b;hpb=3962dfbe22a8d65e4162354cc859440293d85524;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index b3d116c..6705d94 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1228,6 +1228,22 @@ static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
 }
 
 /*
+ * Awaken the grace-period kthread for the specified flavor of RCU.
+ * Don't do a self-awaken, and don't bother awakening when there is
+ * nothing for the grace-period kthread to do (as in several CPUs
+ * raced to awaken, and we lost), and finally don't try to awaken
+ * a kthread that has not yet been created.
+ */
+static void rcu_gp_kthread_wake(struct rcu_state *rsp)
+{
+	if (current == rsp->gp_kthread ||
+	    !ACCESS_ONCE(rsp->gp_flags) ||
+	    !rsp->gp_kthread)
+		return;
+	wake_up(&rsp->gp_wq);
+}
+
+/*
  * If there is room, assign a ->completed number to any callbacks on
  * this CPU that have not already been assigned.  Also accelerate any
  * callbacks that were previously assigned a ->completed number that has
@@ -1670,7 +1686,7 @@ static void rsp_wakeup(struct irq_work *work)
 	struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
 
 	/* Wake up rcu_gp_kthread() to start the grace period. */
-	wake_up(&rsp->gp_wq);
+	rcu_gp_kthread_wake(rsp);
 }
 
 /*
@@ -1746,7 +1762,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
 {
 	WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
 	raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
-	wake_up(&rsp->gp_wq);  /* Memory barrier implied by wake_up() path. */
+	rcu_gp_kthread_wake(rsp);
 }
 
 /*
@@ -2322,7 +2338,7 @@ static void force_quiescent_state(struct rcu_state *rsp)
 	}
 	rsp->gp_flags |= RCU_GP_FLAG_FQS;
 	raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
-	wake_up(&rsp->gp_wq);  /* Memory barrier implied by wake_up() path. */
+	rcu_gp_kthread_wake(rsp);
 }
 
 /*