lkml.org 
[lkml]   [2012]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 11/32] nohz/cpuset: Don't turn off the tick if rcu needs it
Date
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 <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>
---
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 81c04f4..e06639e 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -184,6 +184,7 @@ 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 6c4a672..e141c7e 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -212,7 +212,6 @@ int rcu_cpu_stall_suppress __read_mostly;
module_param(rcu_cpu_stall_suppress, int, 0644);

static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
-static int rcu_pending(int cpu);

/*
* Return the number of RCU-sched batches processed thus far for debug & stats.
@@ -1915,7 +1914,7 @@ 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)
{
return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
__rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) ||
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 43fa7ac..4f99766 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -506,9 +506,21 @@ 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))
@@ -517,12 +529,14 @@ 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
@@ -852,7 +866,7 @@ void tick_nohz_check_adaptive(void)
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);

if (ts->tick_stopped && !is_idle_task(current)) {
- if (!sched_can_stop_tick())
+ if (!can_stop_adaptive_tick())
tick_nohz_restart_sched_tick();
}
}
--
1.7.5.4


\
 
 \ /
  Last update: 2012-03-21 15:07    [from the cache]
©2003-2011 Jasper Spaans