linux-kernel - [PATCH tip/core/rcu 6/7] rcu: Kick rcuo kthreads after their CPU goes offline

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Message-Id: <1414534982-29203-6-git-send-email-paulmck@linux.vnet.ibm.com>
Date:	Tue, 28 Oct 2014 15:23:01 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...nel.org, laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	dvhart@...ux.intel.com, fweisbec@...il.com, oleg@...hat.com,
	bobby.prani@...il.com,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 6/7] rcu: Kick rcuo kthreads after their CPU goes offline

From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>

If a no-CBs CPU were to post an RCU callback with interrupts disabled
after it entered the idle loop for the last time, there might be no
deferred wakeup for the corresponding rcuo kthreads.  This commit
therefore adds a set of calls to do_nocb_deferred_wakeup() after the
CPU has gone completely offline.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/tree.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 9e3c20f117cd..07bf4aa68d50 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3497,8 +3497,10 @@ static int rcu_cpu_notify(struct notifier_block *self,
 	case CPU_DEAD_FROZEN:
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
-		for_each_rcu_flavor(rsp)
+		for_each_rcu_flavor(rsp) {
 			rcu_cleanup_dead_cpu(cpu, rsp);
+			do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));
+		}
 		break;
 	default:
 		break;
-- 
1.8.1.5

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