Messages in this thread | | | Date | Thu, 28 Jul 2022 12:48:23 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH] irqdomain: Fix mapping-creation race |
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On Thu, 28 Jul 2022 10:27:10 +0100, Johan Hovold <johan+linaro@kernel.org> wrote: > > Parallel probing (e.g. due to asynchronous probing) of devices that share > interrupts can currently result in two mappings for the same hardware > interrupt to be created.
And I thought nobody would be using shared interrupts anymore. Turns out people are still building braindead HW... :-/
> > Add a serialising mapping mutex so that looking for an existing mapping > before creating a new one is done atomically. > > Note that serialising the lookup and creation in > irq_create_mapping_affinity() would have been enough to prevent the > duplicate mapping, but that could instead cause > irq_create_fwspec_mapping() to fail when there is a race. > > Fixes: 765230b5f084 ("driver-core: add asynchronous probing support for drivers") > Fixes: b62b2cf5759b ("irqdomain: Fix handling of type settings for existing mappings") > Cc: Dmitry Torokhov <dtor@chromium.org> > Cc: Jon Hunter <jonathanh@nvidia.com> > Signed-off-by: Johan Hovold <johan+linaro@kernel.org> > --- > kernel/irq/irqdomain.c | 46 +++++++++++++++++++++++++++++++----------- > 1 file changed, 34 insertions(+), 12 deletions(-) > > diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c > index 8fe1da9614ee..d263a7dd4170 100644 > --- a/kernel/irq/irqdomain.c > +++ b/kernel/irq/irqdomain.c > @@ -22,6 +22,7 @@ > > static LIST_HEAD(irq_domain_list); > static DEFINE_MUTEX(irq_domain_mutex); > +static DEFINE_MUTEX(irq_mapping_mutex);
I'd really like to avoid a global mutex. At the very least this should be a per-domain mutex, otherwise this will serialise a lot more than what is needed.
> > static struct irq_domain *irq_default_domain; > > @@ -669,7 +670,7 @@ EXPORT_SYMBOL_GPL(irq_create_direct_mapping); > #endif > > /** > - * irq_create_mapping_affinity() - Map a hardware interrupt into linux irq space > + * __irq_create_mapping_affinity() - Map a hardware interrupt into linux irq space > * @domain: domain owning this hardware interrupt or NULL for default domain > * @hwirq: hardware irq number in that domain space > * @affinity: irq affinity > @@ -679,9 +680,9 @@ EXPORT_SYMBOL_GPL(irq_create_direct_mapping); > * If the sense/trigger is to be specified, set_irq_type() should be called > * on the number returned from that call. > */
This comment should be moved to the exported function, instead of documenting something that nobody can call...
> -unsigned int irq_create_mapping_affinity(struct irq_domain *domain, > - irq_hw_number_t hwirq, > - const struct irq_affinity_desc *affinity) > +static unsigned int __irq_create_mapping_affinity(struct irq_domain *domain, > + irq_hw_number_t hwirq, > + const struct irq_affinity_desc *affinity) > { > struct device_node *of_node; > int virq; > @@ -724,6 +725,19 @@ unsigned int irq_create_mapping_affinity(struct irq_domain *domain, > > return virq; > } > + > +unsigned int irq_create_mapping_affinity(struct irq_domain *domain, > + irq_hw_number_t hwirq, > + const struct irq_affinity_desc *affinity) > +{ > + unsigned int virq; > + > + mutex_lock(&irq_mapping_mutex); > + virq = __irq_create_mapping_affinity(domain, hwirq, affinity); > + mutex_unlock(&irq_mapping_mutex); > + > + return virq; > +} > EXPORT_SYMBOL_GPL(irq_create_mapping_affinity); > > static int irq_domain_translate(struct irq_domain *d, > @@ -789,6 +803,8 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec) > if (WARN_ON(type & ~IRQ_TYPE_SENSE_MASK)) > type &= IRQ_TYPE_SENSE_MASK; > > + mutex_lock(&irq_mapping_mutex); > + > /* > * If we've already configured this interrupt, > * don't do it again, or hell will break loose. > @@ -801,7 +817,7 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec) > * interrupt number. > */ > if (type == IRQ_TYPE_NONE || type == irq_get_trigger_type(virq)) > - return virq; > + goto out; > > /* > * If the trigger type has not been set yet, then set > @@ -810,26 +826,26 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec) > if (irq_get_trigger_type(virq) == IRQ_TYPE_NONE) { > irq_data = irq_get_irq_data(virq); > if (!irq_data) > - return 0; > + goto err; > > irqd_set_trigger_type(irq_data, type); > - return virq; > + goto out; > } > > pr_warn("type mismatch, failed to map hwirq-%lu for %s!\n", > hwirq, of_node_full_name(to_of_node(fwspec->fwnode))); > - return 0; > + goto err; > } > > if (irq_domain_is_hierarchy(domain)) { > virq = irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, fwspec); > if (virq <= 0) > - return 0; > + goto err; > } else { > /* Create mapping */ > - virq = irq_create_mapping(domain, hwirq); > + virq = __irq_create_mapping_affinity(domain, hwirq, NULL);
This rechecks for the existence of the mapping. Surely we can do a bit better by rejigging this (admittedly bitrotting) code.
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
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