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Subject[PATCH 16/32] rcu: Restart the tick on non-responding adaptive nohz CPUs
Date
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


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