clockevents: Make tick handover explicit

clockevents_notify() is a leftover from the early design of the
clockevents facility. It's really not a notification mechanism,
it's a multiplex call. We are way better off to have explicit
calls instead of this monstrosity.

Split out the tick_handover call and invoke it explicitely from
the hotplug code. Temporary solution will be cleaned up in later
patches.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ Rebase ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/1658173.RkEEILFiQZ@vostro.rjw.lan
Signed-off-by: Ingo Molnar <mingo@kernel.org>

7 files changed, 10 insertions, 13 deletions

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index f97f498a5d10..f4bde22f8a05 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -11,7 +11,6 @@
 /* Clock event notification values */
 enum clock_event_nofitiers {
         CLOCK_EVT_NOTIFY_ADD,
-        CLOCK_EVT_NOTIFY_CPU_DYING,
         CLOCK_EVT_NOTIFY_CPU_DEAD,
 };
 
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 6119321fc3be..2c68fa3b9436 100644
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -19,12 +19,14 @@ extern void tick_unfreeze(void);
 extern void tick_suspend_local(void);
 /* Should be core only, but XEN resume magic and ARM BL switcher require it */
 extern void tick_resume_local(void);
+extern void tick_handover_do_timer(void);
 #else /* CONFIG_GENERIC_CLOCKEVENTS */
 static inline void tick_init(void) { }
 static inline void tick_freeze(void) { }
 static inline void tick_unfreeze(void) { }
 static inline void tick_suspend_local(void) { }
 static inline void tick_resume_local(void) { }
+static inline void tick_handover_do_timer(void) { }
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
 
 #ifdef CONFIG_TICK_ONESHOT
diff --git a/kernel/cpu.c b/kernel/cpu.c
index af5db20e5803..eba7eaa1341d 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -339,6 +339,8 @@ static int __ref take_cpu_down(void *_param)
                 return err;
 
         cpu_notify(CPU_DYING | param->mod, param->hcpu);
+        /* Give up timekeeping duties */
+        tick_handover_do_timer();
         /* Park the stopper thread */
         kthread_park(current);
         return 0;
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index be9abf32c0b9..88fb3b96c7cc 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -655,10 +655,6 @@ int clockevents_notify(unsigned long reason, void *arg)
         raw_spin_lock_irqsave(&clockevents_lock, flags);
 
         switch (reason) {
-        case CLOCK_EVT_NOTIFY_CPU_DYING:
-                tick_handover_do_timer(arg);
-                break;
-
         case CLOCK_EVT_NOTIFY_CPU_DEAD:
                 tick_shutdown_broadcast_oneshot(arg);
                 tick_shutdown_broadcast(arg);
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 721d29b99d10..6a7a64ec7d1b 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1707,10 +1707,6 @@ static int hrtimer_cpu_notify(struct notifier_block *self,
                 break;
 
 #ifdef CONFIG_HOTPLUG_CPU
-        case CPU_DYING:
-        case CPU_DYING_FROZEN:
-                clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DYING, &scpu);
-                break;
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
         {
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index e28ba5c044c5..055c868f3ec9 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -332,20 +332,23 @@ out_bc:
         tick_install_broadcast_device(newdev);
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
 /*
  * Transfer the do_timer job away from a dying cpu.
  *
- * Called with interrupts disabled.
+ * Called with interrupts disabled. Not locking required. If
+ * tick_do_timer_cpu is owned by this cpu, nothing can change it.
  */
-void tick_handover_do_timer(int *cpup)
+void tick_handover_do_timer(void)
 {
-        if (*cpup == tick_do_timer_cpu) {
+        if (tick_do_timer_cpu == smp_processor_id()) {
                 int cpu = cpumask_first(cpu_online_mask);
 
                 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
                         TICK_DO_TIMER_NONE;
         }
 }
+#endif
 
 /*
  * Shutdown an event device on a given cpu:
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 0266f9dbd114..aabcb5d00cf2 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -20,7 +20,6 @@ extern int tick_do_timer_cpu __read_mostly;
 extern void tick_setup_periodic(struct clock_event_device *dev, int broadcast);
 extern void tick_handle_periodic(struct clock_event_device *dev);
 extern void tick_check_new_device(struct clock_event_device *dev);
-extern void tick_handover_do_timer(int *cpup);
 extern void tick_shutdown(unsigned int *cpup);
 extern void tick_suspend(void);
 extern void tick_resume(void);