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Subject[PATCH 11/32] rcu: Restart the tick on non-responding adaptive nohz CPUs
From: Frederic Weisbecker <fweisbec@gmail.com>

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: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
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>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/rcutree.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 0dca81f..21664a3 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -53,6 +53,7 @@
#include <linux/delay.h>
#include <linux/stop_machine.h>
#include <linux/random.h>
+#include <linux/cpuset.h>

#include "rcutree.h"
#include <trace/events/rcu.h>
@@ -798,6 +799,20 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp)
return (rdp->dynticks_snap & 0x1) == 0;
}

+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
+}
+
/*
* Return true if the specified CPU has passed through a quiescent
* state by virtue of being in or having passed through an dynticks
@@ -845,6 +860,9 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
rdp->offline_fqs++;
return 1;
}
+
+ cpuset_update_rcu_cpu(rdp->cpu);
+
return 0;
}

--
1.7.10.4



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