sched/nohz: Convert to hotplug state machine

Install the callbacks via the state machine.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: rt@linuxtronix.de
Link: http://lkml.kernel.org/r/20161117183541.8588-14-bigeasy@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3bcb61b52f6cab66caae86f9c4311a5fc54524a2..71496a20e67015d9cd3d57da393c97384c048bba 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -390,24 +390,16 @@ static int __init tick_nohz_full_setup(char *str)
 }
 __setup("nohz_full=", tick_nohz_full_setup);
 
-static int tick_nohz_cpu_down_callback(struct notifier_block *nfb,
-                                      unsigned long action,
-                                      void *hcpu)
+static int tick_nohz_cpu_down(unsigned int cpu)
 {
-       unsigned int cpu = (unsigned long)hcpu;
-
-       switch (action & ~CPU_TASKS_FROZEN) {
-       case CPU_DOWN_PREPARE:
-               /*
-                * The boot CPU handles housekeeping duty (unbound timers,
-                * workqueues, timekeeping, ...) on behalf of full dynticks
-                * CPUs. It must remain online when nohz full is enabled.
-                */
-               if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
-                       return NOTIFY_BAD;
-               break;
-       }
-       return NOTIFY_OK;
+       /*
+        * The boot CPU handles housekeeping duty (unbound timers,
+        * workqueues, timekeeping, ...) on behalf of full dynticks
+        * CPUs. It must remain online when nohz full is enabled.
+        */
+       if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
+               return -EBUSY;
+       return 0;
 }
 
 static int tick_nohz_init_all(void)
@@ -428,7 +420,7 @@ static int tick_nohz_init_all(void)
 
 void __init tick_nohz_init(void)
 {
-       int cpu;
+       int cpu, ret;
 
        if (!tick_nohz_full_running) {
                if (tick_nohz_init_all() < 0)
@@ -469,7 +461,10 @@ void __init tick_nohz_init(void)
        for_each_cpu(cpu, tick_nohz_full_mask)
                context_tracking_cpu_set(cpu);
 
-       cpu_notifier(tick_nohz_cpu_down_callback, 0);
+       ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+                                       "kernel/nohz:predown", NULL,
+                                       tick_nohz_cpu_down);
+       WARN_ON(ret < 0);
        pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
                cpumask_pr_args(tick_nohz_full_mask));