sched/migration: Move CPU_ONLINE into scheduler state

The alleged requirement that the migration notifier has a lower priority than
perf is completely undocumented and there is no indication at all that this is
true. perf does not even handle the CPU_ONLINE notification and perf really
has nothing to do with migration.

Move the CPU_ONLINE code into the sched_activate_cpu() state callback.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: rt@linutronix.de
Link: http://lkml.kernel.org/r/20160310120025.421743581@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 688e8a8..8d8d903 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5424,17 +5424,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
 
        switch (action & ~CPU_TASKS_FROZEN) {
 
-       case CPU_ONLINE:
-               /* Update our root-domain */
-               raw_spin_lock_irqsave(&rq->lock, flags);
-               if (rq->rd) {
-                       BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
-
-                       set_rq_online(rq);
-               }
-               raw_spin_unlock_irqrestore(&rq->lock, flags);
-               break;
-
 #ifdef CONFIG_HOTPLUG_CPU
        case CPU_DYING:
                sched_ttwu_pending();
@@ -7090,12 +7079,34 @@ static int cpuset_cpu_inactive(unsigned int cpu)
 
 int sched_cpu_activate(unsigned int cpu)
 {
+       struct rq *rq = cpu_rq(cpu);
+       unsigned long flags;
+
        set_cpu_active(cpu, true);
 
        if (sched_smp_initialized) {
                sched_domains_numa_masks_set(cpu);
                cpuset_cpu_active();
        }
+
+       /*
+        * Put the rq online, if not already. This happens:
+        *
+        * 1) In the early boot process, because we build the real domains
+        *    after all cpus have been brought up.
+        *
+        * 2) At runtime, if cpuset_cpu_active() fails to rebuild the
+        *    domains.
+        */
+       raw_spin_lock_irqsave(&rq->lock, flags);
+       if (rq->rd) {
+               BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span));
+               set_rq_online(rq);
+       }
+       raw_spin_unlock_irqrestore(&rq->lock, flags);
+
+       update_max_interval();
+
        return 0;
 }