diff options
Diffstat (limited to 'arch/x86/kernel/apic/vector.c')
| -rw-r--r-- | arch/x86/kernel/apic/vector.c | 88 |
1 files changed, 70 insertions, 18 deletions
diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c index 3b670df4b..ad59d70bc 100644 --- a/arch/x86/kernel/apic/vector.c +++ b/arch/x86/kernel/apic/vector.c @@ -213,6 +213,7 @@ update: */ cpumask_and(d->old_domain, d->old_domain, cpu_online_mask); d->move_in_progress = !cpumask_empty(d->old_domain); + d->cfg.old_vector = d->move_in_progress ? d->cfg.vector : 0; d->cfg.vector = vector; cpumask_copy(d->domain, vector_cpumask); success: @@ -655,46 +656,97 @@ void irq_complete_move(struct irq_cfg *cfg) } /* - * Called with @desc->lock held and interrupts disabled. + * Called from fixup_irqs() with @desc->lock held and interrupts disabled. */ void irq_force_complete_move(struct irq_desc *desc) { struct irq_data *irqdata = irq_desc_get_irq_data(desc); struct apic_chip_data *data = apic_chip_data(irqdata); struct irq_cfg *cfg = data ? &data->cfg : NULL; + unsigned int cpu; if (!cfg) return; - __irq_complete_move(cfg, cfg->vector); - /* * This is tricky. If the cleanup of @data->old_domain has not been * done yet, then the following setaffinity call will fail with * -EBUSY. This can leave the interrupt in a stale state. * - * The cleanup cannot make progress because we hold @desc->lock. So in - * case @data->old_domain is not yet cleaned up, we need to drop the - * lock and acquire it again. @desc cannot go away, because the - * hotplug code holds the sparse irq lock. + * All CPUs are stuck in stop machine with interrupts disabled so + * calling __irq_complete_move() would be completely pointless. */ raw_spin_lock(&vector_lock); - /* Clean out all offline cpus (including ourself) first. */ + /* + * Clean out all offline cpus (including the outgoing one) from the + * old_domain mask. + */ cpumask_and(data->old_domain, data->old_domain, cpu_online_mask); - while (!cpumask_empty(data->old_domain)) { + + /* + * If move_in_progress is cleared and the old_domain mask is empty, + * then there is nothing to cleanup. fixup_irqs() will take care of + * the stale vectors on the outgoing cpu. + */ + if (!data->move_in_progress && cpumask_empty(data->old_domain)) { raw_spin_unlock(&vector_lock); - raw_spin_unlock(&desc->lock); - cpu_relax(); - raw_spin_lock(&desc->lock); + return; + } + + /* + * 1) The interrupt is in move_in_progress state. That means that we + * have not seen an interrupt since the io_apic was reprogrammed to + * the new vector. + * + * 2) The interrupt has fired on the new vector, but the cleanup IPIs + * have not been processed yet. + */ + if (data->move_in_progress) { /* - * Reevaluate apic_chip_data. It might have been cleared after - * we dropped @desc->lock. + * In theory there is a race: + * + * set_ioapic(new_vector) <-- Interrupt is raised before update + * is effective, i.e. it's raised on + * the old vector. + * + * So if the target cpu cannot handle that interrupt before + * the old vector is cleaned up, we get a spurious interrupt + * and in the worst case the ioapic irq line becomes stale. + * + * But in case of cpu hotplug this should be a non issue + * because if the affinity update happens right before all + * cpus rendevouz in stop machine, there is no way that the + * interrupt can be blocked on the target cpu because all cpus + * loops first with interrupts enabled in stop machine, so the + * old vector is not yet cleaned up when the interrupt fires. + * + * So the only way to run into this issue is if the delivery + * of the interrupt on the apic/system bus would be delayed + * beyond the point where the target cpu disables interrupts + * in stop machine. I doubt that it can happen, but at least + * there is a theroretical chance. Virtualization might be + * able to expose this, but AFAICT the IOAPIC emulation is not + * as stupid as the real hardware. + * + * Anyway, there is nothing we can do about that at this point + * w/o refactoring the whole fixup_irq() business completely. + * We print at least the irq number and the old vector number, + * so we have the necessary information when a problem in that + * area arises. */ - data = apic_chip_data(irqdata); - if (!data) - return; - raw_spin_lock(&vector_lock); + pr_warn("IRQ fixup: irq %d move in progress, old vector %d\n", + irqdata->irq, cfg->old_vector); } + /* + * If old_domain is not empty, then other cpus still have the irq + * descriptor set in their vector array. Clean it up. + */ + for_each_cpu(cpu, data->old_domain) + per_cpu(vector_irq, cpu)[cfg->old_vector] = VECTOR_UNUSED; + + /* Cleanup the left overs of the (half finished) move */ + cpumask_clear(data->old_domain); + data->move_in_progress = 0; raw_spin_unlock(&vector_lock); } #endif |