alistair23-linux/kernel/irq/cpuhotplug.c

/*
 * Generic cpu hotunplug interrupt migration code copied from the
 * arch/arm implementation
 *
 * Copyright (C) Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
#include <linux/interrupt.h>
#include <linux/ratelimit.h>
#include <linux/irq.h>

#include "internals.h"

/* For !GENERIC_IRQ_EFFECTIVE_AFF_MASK this looks at general affinity mask */
static inline bool irq_needs_fixup(struct irq_data *d)
{
	const struct cpumask *m = irq_data_get_effective_affinity_mask(d);

	return cpumask_test_cpu(smp_processor_id(), m);
}

static bool migrate_one_irq(struct irq_desc *desc)
{
	struct irq_data *d = irq_desc_get_irq_data(desc);
	struct irq_chip *chip = irq_data_get_irq_chip(d);
	bool maskchip = !irq_can_move_pcntxt(d) && !irqd_irq_masked(d);
	const struct cpumask *affinity;
	bool brokeaff = false;
	int err;

	/*
	 * IRQ chip might be already torn down, but the irq descriptor is
	 * still in the radix tree. Also if the chip has no affinity setter,
	 * nothing can be done here.
	 */
	if (!chip || !chip->irq_set_affinity) {
		pr_debug("IRQ %u: Unable to migrate away\n", d->irq);
		return false;
	}

	/*
	 * No move required, if:
	 * - Interrupt is per cpu
	 * - Interrupt is not started
	 * - Affinity mask does not include this CPU.
	 *
	 * Note: Do not check desc->action as this might be a chained
	 * interrupt.
	 */
	if (irqd_is_per_cpu(d) || !irqd_is_started(d) || !irq_needs_fixup(d)) {
		/*
		 * If an irq move is pending, abort it if the dying CPU is
		 * the sole target.
		 */
		irq_fixup_move_pending(desc, false);
		return false;
	}

	/*
	 * Complete an eventually pending irq move cleanup. If this
	 * interrupt was moved in hard irq context, then the vectors need
	 * to be cleaned up. It can't wait until this interrupt actually
	 * happens and this CPU was involved.
	 */
	irq_force_complete_move(desc);

	/*
	 * If there is a setaffinity pending, then try to reuse the pending
	 * mask, so the last change of the affinity does not get lost. If
	 * there is no move pending or the pending mask does not contain
	 * any online CPU, use the current affinity mask.
	 */
	if (irq_fixup_move_pending(desc, true))
		affinity = irq_desc_get_pending_mask(desc);
	else
		affinity = irq_data_get_affinity_mask(d);

	/* Mask the chip for interrupts which cannot move in process context */
	if (maskchip && chip->irq_mask)
		chip->irq_mask(d);

	if (cpumask_any_and(affinity, cpu_online_mask) >= nr_cpu_ids) {
		affinity = cpu_online_mask;
		brokeaff = true;
	}

	err = irq_do_set_affinity(d, affinity, true);
	if (err) {
		pr_warn_ratelimited("IRQ%u: set affinity failed(%d).\n",
				    d->irq, err);
		brokeaff = false;
	}

	if (maskchip && chip->irq_unmask)
		chip->irq_unmask(d);

	return brokeaff;
}

/**
 * irq_migrate_all_off_this_cpu - Migrate irqs away from offline cpu
 *
 * The current CPU has been marked offline.  Migrate IRQs off this CPU.
 * If the affinity settings do not allow other CPUs, force them onto any
 * available CPU.
 *
 * Note: we must iterate over all IRQs, whether they have an attached
 * action structure or not, as we need to get chained interrupts too.
 */
void irq_migrate_all_off_this_cpu(void)
{
	struct irq_desc *desc;
	unsigned int irq;

	for_each_active_irq(irq) {
		bool affinity_broken;

		desc = irq_to_desc(irq);
		raw_spin_lock(&desc->lock);
		affinity_broken = migrate_one_irq(desc);
		raw_spin_unlock(&desc->lock);

		if (affinity_broken) {
			pr_warn_ratelimited("IRQ %u: no longer affine to CPU%u\n",
					    irq, smp_processor_id());
		}
	}
}