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Date:	Sat, 29 Dec 2012 17:43:04 +0100
From:	Frederic Weisbecker <>
To:	LKML <>
Cc:	Frederic Weisbecker <>,
	Alessio Igor Bogani <>,
	Andrew Morton <>,
	Chris Metcalf <>,
	Christoph Lameter <>,
	Geoff Levand <>,
	Gilad Ben Yossef <>,
	Hakan Akkan <>,
	Ingo Molnar <>,
	"Paul E. McKenney" <>,
	Paul Gortmaker <>,
	Peter Zijlstra <>,
	Steven Rostedt <>,
	Thomas Gleixner <>
Subject: [PATCH 25/27] rcu: Don't keep the tick for RCU while in userspace

If we are interrupting userspace, we don't need to keep
the tick for RCU: quiescent states don't need to be reported
because we soon run in userspace and local callbacks are handled
by the nocb threads.

CHECKME: Do the nocb threads actually handle the global
grace period completion for local callbacks?

Signed-off-by: Frederic Weisbecker <>
Cc: Alessio Igor Bogani <>
Cc: Andrew Morton <>
Cc: Chris Metcalf <>
Cc: Christoph Lameter <>
Cc: Geoff Levand <>
Cc: Gilad Ben Yossef <>
Cc: Hakan Akkan <>
Cc: Ingo Molnar <>
Cc: Paul E. McKenney <>
Cc: Paul Gortmaker <>
Cc: Peter Zijlstra <>
Cc: Steven Rostedt <>
Cc: Thomas Gleixner <>
 kernel/time/tick-sched.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 0e1ebff..76d1b08 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -22,6 +22,7 @@
 #include <linux/module.h>
 #include <linux/irq_work.h>
 #include <linux/posix-timers.h>
+#include <linux/context_tracking.h>
 #include <asm/irq_regs.h>
@@ -604,10 +605,9 @@ static bool can_stop_full_tick(int cpu)
 	 * Keep the tick if we are asked to report a quiescent state.
-	 * This must be further optimized (avoid checks for local callbacks,
-	 * ignore RCU in userspace, etc...
+	 * This must be further optimized (avoid checks for local callbacks)
-	if (rcu_pending(cpu)) {
+	if (!context_tracking_in_user() && rcu_pending(cpu)) {
 		trace_printk("Can't stop: RCU pending\n");
 		return false;

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