cpu hotplug: adjust root-domain->online span in response to hotplug event (393d94d9) · Commits · 戴 / test

We currently set the root-domain online span automatically when the domain is added to the cpu if the cpu is already a member of cpu_online_map. This was done as a hack/bug-fix for s2ram, but it also causes a problem with hotplug CPU_DOWN transitioning. The right way to fix the original problem is to actually respond to CPU_UP events, instead of CPU_ONLINE, which is already too late. This solves the hung reboot regression reported by Andrew Morton and others. Signed-off-by:

Gregory Haskins <ghaskins@novell.com> Acked-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by:

Ingo Molnar <mingo@elte.hu> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

kernel/sched.c

+7 −11

Original line number	Diff line number	Diff line
		@@ -5813,6 +5813,13 @@ 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;
		@@ -5821,15 +5828,6 @@ 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
		@@ -6105,8 +6103,6 @@ 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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