timer: Further simplify the SMP and HOTPLUG logic

Remove one CONFIG_HOTPLUG_CPU #ifdef in trade for introducing one
CONFIG_SMP #ifdef.

The CONFIG_SMP ifdef avoids declaring the per-CPU __tvec_bases storage
on UP systems since they already have boot_tvec_bases.

Also (re)add a runtime check on the base alignment -- for the paranoid
amongst us :-)

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/fdd2d35e169bdc554ffa3fe77f77716298c75ada.1427814611.git.viresh.kumar@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 15 insertions, 8 deletions

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 1feb9c7035c0..2ece3aa5069c 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -101,7 +101,6 @@ struct tvec_base {
  */
 struct tvec_base boot_tvec_bases;
 EXPORT_SYMBOL(boot_tvec_bases);
-static DEFINE_PER_CPU(struct tvec_base, __tvec_bases);
 
 static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
 
@@ -1038,6 +1037,8 @@ int try_to_del_timer_sync(struct timer_list *timer)
 EXPORT_SYMBOL(try_to_del_timer_sync);
 
 #ifdef CONFIG_SMP
+static DEFINE_PER_CPU(struct tvec_base, __tvec_bases);
+
 /**
  * del_timer_sync - deactivate a timer and wait for the handler to finish.
  * @timer: the timer to be deactivated
@@ -1591,12 +1592,10 @@ static void migrate_timers(int cpu)
         spin_unlock_irq(&new_base->lock);
         put_cpu_var(tvec_bases);
 }
-#endif /* CONFIG_HOTPLUG_CPU */
 
 static int timer_cpu_notify(struct notifier_block *self,
                                 unsigned long action, void *hcpu)
 {
-#ifdef CONFIG_HOTPLUG_CPU
         switch (action) {
         case CPU_DEAD:
         case CPU_DEAD_FROZEN:
@@ -1605,18 +1604,24 @@ static int timer_cpu_notify(struct notifier_block *self,
         default:
                 break;
         }
-#endif
+
         return NOTIFY_OK;
 }
 
-static struct notifier_block timers_nb = {
-        .notifier_call  = timer_cpu_notify,
-};
+static inline void timer_register_cpu_notifier(void)
+{
+        cpu_notifier(timer_cpu_notify, 0);
+}
+#else
+static inline void timer_register_cpu_notifier(void) { }
+#endif /* CONFIG_HOTPLUG_CPU */
 
 static void __init init_timer_cpu(struct tvec_base *base, int cpu)
 {
         int j;
 
+        BUG_ON(base != tbase_get_base(base));
+
         base->cpu = cpu;
         per_cpu(tvec_bases, cpu) = base;
         spin_lock_init(&base->lock);
@@ -1643,8 +1648,10 @@ static void __init init_timer_cpus(void)
         for_each_possible_cpu(cpu) {
                 if (cpu == local_cpu)
                         base = &boot_tvec_bases;
+#ifdef CONFIG_SMP
                 else
                         base = per_cpu_ptr(&__tvec_bases, cpu);
+#endif
 
                 init_timer_cpu(base, cpu);
         }
@@ -1657,7 +1664,7 @@ void __init init_timers(void)
 
         init_timer_cpus();
         init_timer_stats();
-        register_cpu_notifier(&timers_nb);
+        timer_register_cpu_notifier();
         open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
 }