[PATCH 21/32] rcu: Restart the tick on non-responding adaptive nohz CPUs

Frederic Weisbecker
2011-08-15T15:53:55Z

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: Andrew Morton <akpm@linux-foundation.org>
Cc: Anton Blanchard <anton@au1.ibm.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Pepper <lnxninja@linux.vnet.ibm.com>
---
kernel/rcutree.c | 17 +++++++++++++++++
1 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 0009bfc..d496c70 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"

@@ -295,6 +296,20 @@ 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.
@@ -317,6 +332,8 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp)
return 1;
}

+ cpuset_update_rcu_cpu(rdp->cpu);
+
/* If preemptible RCU, no point in sending reschedule IPI. */
if (rdp->preemptible)
return 0;
--
1.7.5.4