clocksource/dummy_timer: Convert to hotplug state machine

Install the callbacks via the state machine and let the core invoke
the callbacks on the already online CPUs.

Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160713153336.130385842@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 6 insertions, 30 deletions

diff --git a/drivers/clocksource/dummy_timer.c b/drivers/clocksource/dummy_timer.c
index 776b6c86dcd5..89f1c2edbe02 100644
--- a/drivers/clocksource/dummy_timer.c
+++ b/drivers/clocksource/dummy_timer.c
@@ -16,10 +16,9 @@
 
 static DEFINE_PER_CPU(struct clock_event_device, dummy_timer_evt);
 
-static void dummy_timer_setup(void)
+static int dummy_timer_starting_cpu(unsigned int cpu)
 {
-        int cpu = smp_processor_id();
-        struct clock_event_device *evt = raw_cpu_ptr(&dummy_timer_evt);
+        struct clock_event_device *evt = per_cpu_ptr(&dummy_timer_evt, cpu);
 
         evt->name       = "dummy_timer";
         evt->features   = CLOCK_EVT_FEAT_PERIODIC |
@@ -29,36 +28,13 @@ static void dummy_timer_setup(void)
         evt->cpumask    = cpumask_of(cpu);
 
         clockevents_register_device(evt);
+        return 0;
 }
 
-static int dummy_timer_cpu_notify(struct notifier_block *self,
-                                      unsigned long action, void *hcpu)
-{
-        if ((action & ~CPU_TASKS_FROZEN) == CPU_STARTING)
-                dummy_timer_setup();
-
-        return NOTIFY_OK;
-}
-
-static struct notifier_block dummy_timer_cpu_nb = {
-        .notifier_call = dummy_timer_cpu_notify,
-};
-
 static int __init dummy_timer_register(void)
 {
-        int err = 0;
-
-        cpu_notifier_register_begin();
-        err = __register_cpu_notifier(&dummy_timer_cpu_nb);
-        if (err)
-                goto out;
-
-        /* We won't get a call on the boot CPU, so register immediately */
-        if (num_possible_cpus() > 1)
-                dummy_timer_setup();
-
-out:
-        cpu_notifier_register_done();
-        return err;
+        return cpuhp_setup_state(CPUHP_AP_DUMMY_TIMER_STARTING,
+                                 "AP_DUMMY_TIMER_STARTING",
+                                 dummy_timer_starting_cpu, NULL);
 }
 early_initcall(dummy_timer_register);