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From: Frederic Weisbecker <fweisbec@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>, linaro-sched-sig@lists.linaro.org
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
        Alessio Igor Bogani <abogani@kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>, Avi Kivity <avi@redhat.com>,
        Chris Metcalf <cmetcalf@tilera.com>, Christoph Lameter <cl@linux.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Geoff Levand <geoff@infradead.org>,
        Gilad Ben Yossef <gilad@benyossef.com>, Ingo Molnar <mingo@kernel.org>,
        Max Krasnyansky <maxk@qualcomm.com>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Stephen Hemminger <shemminger@vyatta.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Sven-Thorsten Dietrich <thebigcorporation@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>, Zen Lin <zen@openhuawei.org>
Subject: [PATCH 16/32] rcu: Restart the tick on non-responding adaptive nohz CPUs
Date: Wed, 21 Mar 2012 14:58:22 +0100
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When a CPU in adaptive nohz mode doesn't respond to complete
a grace period, issue it a specific IPI so that it restarts
the tick and chases a quiescent state.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Zen Lin <zen@openhuawei.org>
---
 kernel/rcutree.c |   17 +++++++++++++++++
 1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e141c7e..3fffc26 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -50,6 +50,7 @@
 #include <linux/wait.h>
 #include <linux/kthread.h>
 #include <linux/prefetch.h>
+#include <linux/cpuset.h>
 
 #include "rcutree.h"
 #include <trace/events/rcu.h>
@@ -302,6 +303,20 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
 
 #ifdef CONFIG_SMP
 
+static void cpuset_update_rcu_cpu(int cpu)
+{
+#ifdef CONFIG_CPUSETS_NO_HZ
+	unsigned long flags;
+
+	local_irq_save(flags);
+
+	if (cpuset_cpu_adaptive_nohz(cpu))
+		smp_cpuset_update_nohz(cpu);
+
+	local_irq_restore(flags);
+#endif
+}
+
 /*
  * If the specified CPU is offline, tell the caller that it is in
  * a quiescent state.  Otherwise, whack it with a reschedule IPI.
@@ -325,6 +340,8 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
 		return 1;
 	}
 
+	cpuset_update_rcu_cpu(rdp->cpu);
+
 	/*
 	 * The CPU is online, so send it a reschedule IPI.  This forces
 	 * it through the scheduler, and (inefficiently) also handles cases
-- 
1.7.5.4