From: Paul Gortmaker <paul.gortmaker@windriver.com>
Date: Thu, 20 Dec 2012 17:35:02 +0000 (-0800)
Subject: rcu: Prevent soft-lockup complaints about no-CBs CPUs
X-Git-Url: http://git.mmlx.us/?a=commitdiff_plain;h=353af9c9a866b07492b15a4efd18ec93123d3a1d;p=linux-edison.git

rcu: Prevent soft-lockup complaints about no-CBs CPUs

The wait_event() at the head of the rcu_nocb_kthread() can result in
soft-lockup complaints if the CPU in question does not register RCU
callbacks for an extended period.  This commit therefore changes
the wait_event() to a wait_event_interruptible().

Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f6e5ec2932b..43dba2d798a 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2366,10 +2366,11 @@ static int rcu_nocb_kthread(void *arg)
 	for (;;) {
 		/* If not polling, wait for next batch of callbacks. */
 		if (!rcu_nocb_poll)
-			wait_event(rdp->nocb_wq, rdp->nocb_head);
+			wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head);
 		list = ACCESS_ONCE(rdp->nocb_head);
 		if (!list) {
 			schedule_timeout_interruptible(1);
+			flush_signals(current);
 			continue;
 		}