[tip:timers/urgent] tick/broadcast: Make idle check independent from mode and config

[tip-bot for Thomas Gleixner]

Commit-ID:  f32dd117051185da6e923b35491a44d7debeeea5
Gitweb:     http://git.kernel.org/tip/f32dd117051185da6e923b35491a44d7debeeea5
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 7 Jul 2015 16:29:38 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 7 Jul 2015 18:46:47 +0200

tick/broadcast: Make idle check independent from mode and config

Currently the broadcast busy check, which prevents the idle code from
going into deep idle, works only in one shot mode.

If NOHZ and HIGHRES are off (config or command line) there is no
sanity check at all, so under certain conditions cpus are allowed to
go into deep idle, where the local timer stops, and are not woken up
again because there is no broadcast timer installed or a hrtimer based
broadcast device is not evaluated.

Move tick_broadcast_oneshot_control() into the common code and provide
proper subfunctions for the various config combinations.

The common check in tick_broadcast_oneshot_control() is for the C3STOP
misfeature flag of the local clock event device. If its not set, idle
can proceed. If set, further checks are necessary.

Provide checks for the trivial cases:

 - If broadcast is disabled in the config, then return busy

 - If oneshot mode (NOHZ/HIGHES) is disabled in the config, return
   busy if the broadcast device is hrtimer based.

 - If oneshot mode is enabled in the config call the original
   tick_broadcast_oneshot_control() function. That function needs
   extra checks which will be implemented in seperate patches.

[ Split out from a larger combo patch ]

Reported-and-tested-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Suzuki Poulose <Suzuki.Poulose@xxxxxxx>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@xxxxxxx>
Cc: Catalin Marinas <Catalin.Marinas@xxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Link: alpine.DEB.2.11.1507070929360.3916@nanos">http://lkml.kernel.org/r/alpine.DEB.2.11.1507070929360.3916@nanos
---
 include/linux/tick.h         |  4 ----
 kernel/time/tick-broadcast.c | 26 +++++++++++---------------
 kernel/time/tick-common.c    | 21 +++++++++++++++++++++
 kernel/time/tick-sched.h     | 10 ++++++++++
 4 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 3741ba1..6916dcb 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -67,11 +67,7 @@ extern void tick_broadcast_control(enum tick_broadcast_mode mode);
 static inline void tick_broadcast_control(enum tick_broadcast_mode mode) { }
 #endif /* BROADCAST */
 
-#if defined(CONFIG_GENERIC_CLOCKEVENTS_BROADCAST) && defined(CONFIG_TICK_ONESHOT)
 extern int tick_broadcast_oneshot_control(enum tick_broadcast_state state);
-#else
-static inline int tick_broadcast_oneshot_control(enum tick_broadcast_state state) { return 0; }
-#endif
 
 static inline void tick_broadcast_enable(void)
 {
diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
index 9877d0b..ef77b16 100644
--- a/kernel/time/tick-broadcast.c
+++ b/kernel/time/tick-broadcast.c
@@ -685,18 +685,7 @@ static void broadcast_shutdown_local(struct clock_event_device *bc,
 	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 }
 
-/**
- * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
- * @state:	The target state (enter/exit)
- *
- * The system enters/leaves a state, where affected devices might stop
- * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
- *
- * Called with interrupts disabled, so clockevents_lock is not
- * required here because the local clock event device cannot go away
- * under us.
- */
-int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 {
 	struct clock_event_device *bc, *dev;
 	struct tick_device *td;
@@ -717,9 +706,6 @@ int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 	td = this_cpu_ptr(&tick_cpu_device);
 	dev = td->evtdev;
 
-	if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
-		return 0;
-
 	raw_spin_lock(&tick_broadcast_lock);
 	bc = tick_broadcast_device.evtdev;
 	cpu = smp_processor_id();
@@ -961,6 +947,16 @@ bool tick_broadcast_oneshot_available(void)
 	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
 }
 
+#else
+int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct clock_event_device *bc = tick_broadcast_device.evtdev;
+
+	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
+		return -EBUSY;
+
+	return 0;
+}
 #endif
 
 void __init tick_broadcast_init(void)
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 76446cb..55e13ef 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -343,6 +343,27 @@ out_bc:
 	tick_install_broadcast_device(newdev);
 }
 
+/**
+ * tick_broadcast_oneshot_control - Enter/exit broadcast oneshot mode
+ * @state:	The target state (enter/exit)
+ *
+ * The system enters/leaves a state, where affected devices might stop
+ * Returns 0 on success, -EBUSY if the cpu is used to broadcast wakeups.
+ *
+ * Called with interrupts disabled, so clockevents_lock is not
+ * required here because the local clock event device cannot go away
+ * under us.
+ */
+int tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+
+	if (!(td->evtdev->features & CLOCK_EVT_FEAT_C3STOP))
+		return 0;
+
+	return __tick_broadcast_oneshot_control(state);
+}
+
 #ifdef CONFIG_HOTPLUG_CPU
 /*
  * Transfer the do_timer job away from a dying cpu.
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 42fdf49..a4a8d4e 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -71,4 +71,14 @@ extern void tick_cancel_sched_timer(int cpu);
 static inline void tick_cancel_sched_timer(int cpu) { }
 #endif
 
+#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
+extern int __tick_broadcast_oneshot_control(enum tick_broadcast_state state);
+#else
+static inline int
+__tick_broadcast_oneshot_control(enum tick_broadcast_state state)
+{
+	return -EBUSY;
+}
+#endif
+
 #endif
--
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