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

From: Frederic Weisbecker
Date: Mon Aug 15 2011 - 11:53:58 EST

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@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxxx>
Cc: Avi Kivity <avi@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx>
Cc: Paul E . McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Paul Menage <menage@xxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Stephen Hemminger <shemminger@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Tim Pepper <lnxninja@xxxxxxxxxxxxxxxxxx>
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)


+static void cpuset_update_rcu_cpu(int cpu)
+ unsigned long flags;
+ local_irq_save(flags);
+ if (cpuset_cpu_adaptive_nohz(cpu))
+ smp_cpuset_update_nohz(cpu);
+ local_irq_restore(flags);
* 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;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/