linux-kernel - [RFC PATCH 4/8] nohz: Add API to check tick state

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Message-Id: <1350750167-14263-5-git-send-email-fweisbec@gmail.com>
Date:	Sat, 20 Oct 2012 12:22:43 -0400
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [RFC PATCH 4/8] nohz: Add API to check tick state

We need some quick way to check if the CPU has stopped
its tick. This will be useful to implement the printk tick
using the irq work subsystem.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 include/linux/tick.h     |   17 ++++++++++++++++-
 kernel/time/tick-sched.c |    2 +-
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index f37fceb..2307dd3 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -8,6 +8,8 @@
 
 #include <linux/clockchips.h>
 #include <linux/irqflags.h>
+#include <linux/percpu.h>
+#include <linux/hrtimer.h>
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 
@@ -122,13 +124,26 @@ static inline int tick_oneshot_mode_active(void) { return 0; }
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
 
 # ifdef CONFIG_NO_HZ
+DECLARE_PER_CPU(struct tick_sched, tick_cpu_sched);
+
+static inline int tick_nohz_tick_stopped(void)
+{
+	return __this_cpu_read(tick_cpu_sched.tick_stopped);
+}
+
 extern void tick_nohz_idle_enter(void);
 extern void tick_nohz_idle_exit(void);
 extern void tick_nohz_irq_exit(void);
 extern ktime_t tick_nohz_get_sleep_length(void);
 extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);
 extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);
-# else
+
+# else /* !CONFIG_NO_HZ */
+static inline int tick_nohz_tick_stopped(void)
+{
+	return 0;
+}
+
 static inline void tick_nohz_idle_enter(void) { }
 static inline void tick_nohz_idle_exit(void) { }
 
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f423bdd..ccc1971 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -28,7 +28,7 @@
 /*
  * Per cpu nohz control structure
  */
-static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
+DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
 
 /*
  * The time, when the last jiffy update happened. Protected by xtime_lock.
-- 
1.7.5.4

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