Re: [PATCH v6 3/6] irqdomain: Add irq_domain_{push,pop}_irq() functions.

[Linus Walleij]

Sorry for top posting but we need to loop in Bjorn Helgass and the
linux-pci mailing list on this patch, at least so they see it, and can
recognize similar cases in the future.

(The patch set if very nice.)

Yours,
Linus Walleij

On Tue, Apr 11, 2017 at 7:21 PM, David Daney <david.daney@xxxxxxxxxx> wrote:
> For an already existing irqdomain hierarchy, as might be obtained via
> a call to pci_enable_msix_range(), a PCI driver wishing to add an
> additional irqdomain to the hierarchy needs to be able to insert the
> irqdomain to that already initialized hierarchy.  Calling
> irq_domain_create_hierarchy() allows the new irqdomain to be created,
> but no existing code allows for initializing the associated irq_data.
>
> Add a couple of helper functions (irq_domain_push_irq() and
> irq_domain_pop_irq()) to initialize the irq_data for the new
> irqdomain added to an existing hierarchy.
>
> Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> ---
>  include/linux/irqdomain.h |   3 +
>  kernel/irq/irqdomain.c    | 178 ++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 181 insertions(+)
>
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 9f36160..0316846 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -425,6 +425,9 @@ extern void irq_domain_free_irqs_common(struct irq_domain *domain,
>  extern void irq_domain_free_irqs_top(struct irq_domain *domain,
>                                      unsigned int virq, unsigned int nr_irqs);
>
> +extern int irq_domain_push_irq(struct irq_domain *domain, int virq, void *arg);
> +extern int irq_domain_pop_irq(struct irq_domain *domain, int virq);
> +
>  extern int irq_domain_alloc_irqs_parent(struct irq_domain *domain,
>                                         unsigned int irq_base,
>                                         unsigned int nr_irqs, void *arg);
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index 31805f2..ea9d30d 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -1304,6 +1304,184 @@ int __irq_domain_alloc_irqs(struct irq_domain *domain, int irq_base,
>         return ret;
>  }
>
> +/* The irq_data was moved, fix the revmap to refer to the new location */
> +static void irq_domain_fix_revmap(struct irq_data *d)
> +{
> +       void **slot;
> +
> +       if (d->hwirq < d->domain->revmap_size)
> +               return; /* Not using radix tree. */
> +
> +       /* Fix up the revmap. */
> +       mutex_lock(&revmap_trees_mutex);
> +       slot = radix_tree_lookup_slot(&d->domain->revmap_tree, d->hwirq);
> +       if (slot)
> +               radix_tree_replace_slot(&d->domain->revmap_tree, slot, d);
> +       mutex_unlock(&revmap_trees_mutex);
> +}
> +
> +/**
> + * irq_domain_push_irq() - Push a domain in to the top of a hierarchy.
> + * @domain:    Domain to push.
> + * @virq:      Irq to push the domain in to.
> + * @arg:       Passed to the irq_domain_ops alloc() function.
> + *
> + * For an already existing irqdomain hierarchy, as might be obtained
> + * via a call to pci_enable_msix(), add an additional domain to the
> + * head of the processing chain.  Must be called before request_irq()
> + * has been called.
> + */
> +int irq_domain_push_irq(struct irq_domain *domain, int virq, void *arg)
> +{
> +       struct irq_data *child_irq_data;
> +       struct irq_data *root_irq_data = irq_get_irq_data(virq);
> +       struct irq_desc *desc;
> +       int rv = 0;
> +
> +       /*
> +        * Check that no action has been set, which indicates the virq
> +        * is in a state where this function doesn't have to deal with
> +        * races between interrupt handling and maintaining the
> +        * hierarchy.  This will catch gross misuse.  Attempting to
> +        * make the check race free would require holding locks across
> +        * calls to struct irq_domain_ops->alloc(), which could lead
> +        * to deadlock, so we just do a simple check before starting.
> +        */
> +       desc = irq_to_desc(virq);
> +       if (!desc)
> +               return -EINVAL;
> +       if (WARN_ON(desc->action))
> +               return -EBUSY;
> +
> +       if (domain == NULL)
> +               return -EINVAL;
> +
> +       if (WARN_ON(!domain->ops->alloc))
> +               return -EINVAL;
> +
> +       if (!root_irq_data)
> +               return -EINVAL;
> +
> +       child_irq_data = kzalloc_node(sizeof(*child_irq_data), GFP_KERNEL,
> +                                     irq_data_get_node(root_irq_data));
> +       if (!child_irq_data)
> +               return -ENOMEM;
> +
> +       mutex_lock(&irq_domain_mutex);
> +
> +       /* Copy the original irq_data. */
> +       *child_irq_data = *root_irq_data;
> +
> +       irq_domain_fix_revmap(child_irq_data);
> +
> +       /*
> +        * Overwrite the root_irq_data, which is embedded in struct
> +        * irq_desc, with values for this domain.
> +        */
> +       root_irq_data->parent_data = child_irq_data;
> +       root_irq_data->domain = domain;
> +       root_irq_data->mask = 0;
> +       root_irq_data->hwirq = 0;
> +       root_irq_data->chip = NULL;
> +       root_irq_data->chip_data = NULL;
> +       rv = domain->ops->alloc(domain, virq, 1, arg);
> +       if (rv) {
> +               /* Restore the original irq_data. */
> +               *root_irq_data = *child_irq_data;
> +               irq_domain_fix_revmap(root_irq_data);
> +               goto error;
> +       }
> +
> +       if (root_irq_data->hwirq < domain->revmap_size) {
> +               domain->linear_revmap[root_irq_data->hwirq] = virq;
> +       } else {
> +               mutex_lock(&revmap_trees_mutex);
> +               radix_tree_insert(&domain->revmap_tree,
> +                                 root_irq_data->hwirq, root_irq_data);
> +               mutex_unlock(&revmap_trees_mutex);
> +       }
> +error:
> +       mutex_unlock(&irq_domain_mutex);
> +
> +       return rv;
> +}
> +EXPORT_SYMBOL_GPL(irq_domain_push_irq);
> +
> +/**
> + * irq_domain_pop_irq() - Remove a domain from the top of a hierarchy.
> + * @domain:    Domain to remove.
> + * @virq:      Irq to remove the domain from.
> + *
> + * Undo the effects of a call to irq_domain_push_irq().  Must be
> + * called either before request_irq() or after free_irq().
> + */
> +int irq_domain_pop_irq(struct irq_domain *domain, int virq)
> +{
> +       struct irq_data *root_irq_data = irq_get_irq_data(virq);
> +       struct irq_data *child_irq_data;
> +       struct irq_data *tmp_irq_data;
> +       struct irq_desc *desc;
> +
> +       /*
> +        * Check that no action is set, which indicates the virq is in
> +        * a state where this function doesn't have to deal with races
> +        * between interrupt handling and maintaining the hierarchy.
> +        * This will catch gross misuse.  Attempting to make the check
> +        * race free would require holding locks across calls to
> +        * struct irq_domain_ops->free(), which could lead to
> +        * deadlock, so we just do a simple check before starting.
> +        */
> +       desc = irq_to_desc(virq);
> +       if (!desc)
> +               return -EINVAL;
> +       if (WARN_ON(desc->action))
> +               return -EBUSY;
> +
> +       if (domain == NULL)
> +               return -EINVAL;
> +
> +       if (!root_irq_data)
> +               return -EINVAL;
> +
> +       tmp_irq_data = irq_domain_get_irq_data(domain, virq);
> +
> +       /* We can only "pop" if this domain is at the top of the list */
> +       if (WARN_ON(root_irq_data != tmp_irq_data))
> +               return -EINVAL;
> +
> +       if (WARN_ON(root_irq_data->domain != domain))
> +               return -EINVAL;
> +
> +       child_irq_data = root_irq_data->parent_data;
> +       if (WARN_ON(!child_irq_data))
> +               return -EINVAL;
> +
> +       mutex_lock(&irq_domain_mutex);
> +
> +       root_irq_data->parent_data = NULL;
> +
> +       if (root_irq_data->hwirq >= domain->revmap_size) {
> +               mutex_lock(&revmap_trees_mutex);
> +               radix_tree_delete(&domain->revmap_tree, root_irq_data->hwirq);
> +               mutex_unlock(&revmap_trees_mutex);
> +       }
> +
> +       if (domain->ops->free)
> +               domain->ops->free(domain, virq, 1);
> +
> +       /* Restore the original irq_data. */
> +       *root_irq_data = *child_irq_data;
> +
> +       irq_domain_fix_revmap(root_irq_data);
> +
> +       mutex_unlock(&irq_domain_mutex);
> +
> +       kfree(child_irq_data);
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(irq_domain_pop_irq);
> +
>  /**
>   * irq_domain_free_irqs - Free IRQ number and associated data structures
>   * @virq:      base IRQ number
> --
> 1.8.3.1
>