[tip:core/rcu] rcu: Add comment to the last sleep in the rcu tasks loop

["tip-bot for Steven Rostedt (VMware)" <tipbot@zytor.com>]

Commit-ID:  cd23ac8ddb7be993f88bee893b89a8b4971c3651
Gitweb:     https://git.kernel.org/tip/cd23ac8ddb7be993f88bee893b89a8b4971c3651
Author:     Steven Rostedt (VMware) <rostedt@goodmis.org>
AuthorDate: Thu, 24 May 2018 18:58:16 -0400
Committer:  Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CommitDate: Thu, 12 Jul 2018 15:39:21 -0700

rcu: Add comment to the last sleep in the rcu tasks loop

At the end of rcu_tasks_kthread() there's a lonely
schedule_timeout_uninterruptible() call with no apparent rationale for
its existence. But there is. It is to keep the thread from going into
a tight loop if there's some anomaly. That really needs a comment.

Link: http://lkml.kernel.org/r/20180524223839.GU3803@linux.vnet.ibm.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/rcu/update.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4c7c49c106ee..39cb23d22109 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -814,6 +814,7 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 			list = next;
 			cond_resched();
 		}
+		/* Paranoid sleep to keep this from entering a tight loop */
 		schedule_timeout_uninterruptible(HZ/10);
 	}
 }