linux-kernel - [tip:smp/hotplug] sched/migration: Move CPU

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Date:	Fri, 6 May 2016 06:07:13 -0700
From:	tip-bot for Thomas Gleixner <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	peterz@...radead.org, mingo@...nel.org, tglx@...utronix.de,
	hpa@...or.com, linux-kernel@...r.kernel.org
Subject: [tip:smp/hotplug] sched/migration: Move CPU_ONLINE into scheduler
 state

Commit-ID:  7d97669933eb94245ec9b715753753ec5ca8f646
Gitweb:     http://git.kernel.org/tip/7d97669933eb94245ec9b715753753ec5ca8f646
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 10 Mar 2016 12:54:17 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 6 May 2016 14:58:25 +0200

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@...utronix.de>
Acked-by: Peter Zijlstra <peterz@...radead.org>
Cc: rt@...utronix.de
Link: http://lkml.kernel.org/r/20160310120025.421743581@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/sched/core.c | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 688e8a8..8d8d903 100644
--- 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;
 }