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>

1 files changed, 14 insertions, 19 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 3bcb61b52f6c..71496a20e670 100644
--- 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));