From: Frederic Weisbecker <fweis...@gmail.com>
If RCU is waiting for the current CPU to complete a grace
period, don't turn off the tick. Unlike dynctik-idle, we
are not necessarily going to enter into rcu extended quiescent
state, so we may need to keep the tick to note current CPU's
quiescent states.
[added build fix from Zen Lin]
Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
Cc: Alessio Igor Bogani <abog...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Avi Kivity <a...@redhat.com>
Cc: Chris Metcalf <cmetc...@tilera.com>
Cc: Christoph Lameter <c...@linux.com>
Cc: Daniel Lezcano <daniel.lezc...@linaro.org>
Cc: Geoff Levand <ge...@infradead.org>
Cc: Gilad Ben Yossef <gi...@benyossef.com>
Cc: Hakan Akkan <hakanak...@gmail.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Kevin Hilman <khil...@ti.com>
Cc: Max Krasnyansky <m...@qualcomm.com>
Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephen Hemminger <shemmin...@vyatta.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporat...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Signed-off-by: Steven Rostedt <rost...@goodmis.org>
---
include/linux/rcupdate.h | 1 +
kernel/rcutree.c | 3 +--
kernel/time/tick-sched.c | 22 ++++++++++++++++++----
3 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 7c968e4..9804c3a 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -186,6 +186,7 @@ static inline int rcu_preempt_depth(void)
extern void rcu_sched_qs(int cpu);
extern void rcu_bh_qs(int cpu);
extern void rcu_check_callbacks(int cpu, int user);
+extern int rcu_pending(int cpu);
struct notifier_block;
extern void rcu_idle_enter(void);
extern void rcu_idle_exit(void);
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 74df86b..0dca81f 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -234,7 +234,6 @@ module_param(jiffies_till_next_fqs, ulong, 0644);
static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
static void force_quiescent_state(struct rcu_state *rsp);
-static int rcu_pending(int cpu);
/*
* Return the number of RCU-sched batches processed thus far for debug & stats.
@@ -2429,7 +2428,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct
rcu_data *rdp)
* by the current CPU, returning 1 if so. This function is part of the
* RCU implementation; it is -not- an exported member of the RCU API.
*/
-static int rcu_pending(int cpu)
+int rcu_pending(int cpu)
{
struct rcu_state *rsp;
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 35047b2..de3c8fe 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -512,9 +512,21 @@ void tick_nohz_idle_enter(void)
local_irq_enable();
}
+#ifdef CONFIG_CPUSETS_NO_HZ
+static bool can_stop_adaptive_tick(void)
+{
+ if (!sched_can_stop_tick())
+ return false;
+
+ /* Is there a grace period to complete ? */
+ if (rcu_pending(smp_processor_id()))
+ return false;
+
+ return true;
+}
+
static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts)
{
-#ifdef CONFIG_CPUSETS_NO_HZ
int cpu = smp_processor_id();
if (!cpuset_adaptive_nohz() || is_idle_task(current))
@@ -523,12 +535,14 @@ static void tick_nohz_cpuset_stop_tick(struct tick_sched
*ts)
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
return;
- if (!sched_can_stop_tick())
+ if (!can_stop_adaptive_tick())
return;
tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
-#endif
}
+#else
+static void tick_nohz_cpuset_stop_tick(struct tick_sched *ts) { }
+#endif
/**
* tick_nohz_irq_exit - update next tick event from interrupt exit
@@ -860,7 +874,7 @@ void tick_nohz_check_adaptive(void)
if (cpuset_adaptive_nohz()) {
if (ts->tick_stopped && !is_idle_task(current)) {
- if (!sched_can_stop_tick())
+ if (!can_stop_adaptive_tick())
tick_nohz_restart_sched_tick();
}
}
--
1.7.10.4
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