Merge pull request #46 from toradex/4.9-2.3.x-imx

4.9 2.3.x imx

1 files changed, 14 insertions, 6 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d1a02877a42c..d0b113de3316 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1718,15 +1718,23 @@ 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.
+ * Awaken the grace-period kthread.  Don't do a self-awaken (unless in
+ * an interrupt or softirq handler), 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.  If all those checks are passed, track some
+ * debug information and awaken.
+ *
+ * So why do the self-wakeup when in an interrupt or softirq handler
+ * in the grace-period kthread's context?  Because the kthread might have
+ * been interrupted just as it was going to sleep, and just after the final
+ * pre-sleep check of the awaken condition.  In this case, a wakeup really
+ * is required, and is therefore supplied.
  */
 static void rcu_gp_kthread_wake(struct rcu_state *rsp)
 {
-	if (current == rsp->gp_kthread ||
+	if ((current == rsp->gp_kthread &&
+	     !in_interrupt() && !in_serving_softirq()) ||
 	    !READ_ONCE(rsp->gp_flags) ||
 	    !rsp->gp_kthread)
 		return;