[PATCH 1/2] Revert "cpu hotplug: adjust root-domain->online span inresponse to hotplug

[Gregory Haskins]

event"

This reverts commit 393d94d98b19089ec172566e23557997931b137e.

I submitted 393d94d98b1 to -mm and sched-devel, and then quickly realized
it was flawed.  However, the patch was already "in flight" and made it
to Linus' tree and is in .25-rc5.  So this patch reverts the
original/flawed fix, and the patch that follows has the updated version.

Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
Cc: Gautham R Shenoy <ego@xxxxxxxxxx>
Cc: "Siddha, Suresh B" <suresh.b.siddha@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 kernel/sched.c |   18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index b02e4fc..52b9867 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5813,13 +5813,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
 		/* Must be high prio: stop_machine expects to yield to it. */
 		rq = task_rq_lock(p, &flags);
 		__setscheduler(rq, p, SCHED_FIFO, MAX_RT_PRIO-1);
-
-		/* Update our root-domain */
-		if (rq->rd) {
-			BUG_ON(!cpu_isset(cpu, rq->rd->span));
-			cpu_set(cpu, rq->rd->online);
-		}
-
 		task_rq_unlock(rq, &flags);
 		cpu_rq(cpu)->migration_thread = p;
 		break;
@@ -5828,6 +5821,15 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
 	case CPU_ONLINE_FROZEN:
 		/* Strictly unnecessary, as first user will wake it. */
 		wake_up_process(cpu_rq(cpu)->migration_thread);
+
+		/* Update our root-domain */
+		rq = cpu_rq(cpu);
+		spin_lock_irqsave(&rq->lock, flags);
+		if (rq->rd) {
+			BUG_ON(!cpu_isset(cpu, rq->rd->span));
+			cpu_set(cpu, rq->rd->online);
+		}
+		spin_unlock_irqrestore(&rq->lock, flags);
 		break;
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -6103,6 +6105,8 @@ static void rq_attach_root(struct rq *rq, struct root_domain *rd)
 	rq->rd = rd;
 
 	cpu_set(rq->cpu, rd->span);
+	if (cpu_isset(rq->cpu, cpu_online_map))
+		cpu_set(rq->cpu, rd->online);
 
 	for (class = sched_class_highest; class; class = class->next) {
 		if (class->join_domain)

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